Oral magnesium and vitamin C supplements in asthma: a parallel group randomized placebo-controlled trial

The Role of Vitamins in the Pathogenesis of Asthma

Vitamins play a crucial role in the proper functioning of organisms. Disturbances of their levels, seen as deficiency or excess, enhance the development of various diseases, including those of the cardiovascular, immune, or respiratory systems. The present paper aims to summarize the role of vitamins in one of the most common diseases of the respiratory system, asthma. This narrative review describes the influence of vitamins on asthma and its main symptoms such as bronchial hyperreactivity, airway inflammation, oxidative stress, and airway remodeling, as well as the correlation between vitamin intake and levels and the risk of asthma in both pre- and postnatal life.

The effects of vitamin C on respiratory, allergic and immunological diseases: an experimental and clinical-based review

Vitamin C is used in modern medicine supplements for treatment of various disorders associated with oxidative stress, inflammation and immune dysregulation. In this review article, experimental and clinical results regarding the effects of vitamin C on respiratory immunologic, and allergic diseases are reviewed. Various databases and appropriate keywords are used to search the effect of vitamin C on respiratory diseases until the end of May 2022. Books, theses and articles were included. These studies assessed the effects of vitamin C on respiratory disorders including asthma, chronic obstructive pulmonary disease (COPD), lung infection and lung cancer. Vitamin C showed relaxant effect on tracheal smooth muscle via various mechanisms. The preventive effects of vitamin C were mediated by antioxidant, immunomodulatory and anti-inflammatory mechanisms in the experimental animal models of different respiratory diseases. Some clinical studies also indicated the effect of vitamin C on lung cancer and lung infections. Therefore, vitamin C could be used a preventive and/or relieving therapy in respiratory diseases.

Oxidative stress stimulation leads to cell-specific oxidant and antioxidant responses in airway resident and inflammatory cells

AIMS

The imbalance between reactive oxygen species (ROS) and the antioxidant response has been linked to various airway diseases, including asthma. However, knowledge on cell-specific responses of the airway resident and inflammatory cells against increased oxidant stress is very limited. We aim to better understand the cell-specific antioxidant response that contributes to the pathophysiology of lung disease in response to oxidative stress.

MATERIALS AND METHODS

The human cell lines of epithelial, fibroblast, endothelial, monocyte, eosinophil and neutrophil were incubated with tert-butyl hydroperoxide (tBHP) or cigarette smoke condensate (CSC). Following stimulation, cell viability, total oxidant and antioxidant activity were assessed in both residential and inflammatory cells. Human Oxidative Stress Plus RT² Profiler PCR array was used to determine 84 gene expression differences in oxidant and antioxidant pathways following oxidant stimulus in all cells.

KEY FINDINGS

We showed that various cell types respond differently to oxidative stress inducers, with distinct gene expression and oxidant-antioxidant generation. Most importantly, eosinophils increased the activity of all main antioxidant enzymes in response to both oxidants. Monocytes, on the other hand, showed no change in response to each stimulation, whereas neutrophils only increased their CAT activity in response to both stimuli. The increase in NRF2-regulated genes HSPA1A, HMOX1 and DUSP1 after both tBHP and CSC in epithelial cells and fibroblasts indicates Nfr2 pathway activation.

SIGNIFICANCE

This study advances our knowledge of the molecular and cellular mechanisms of cell-specific antioxidant response upon exposure to oxidative stress. Additionally, our observations imply that the eosinophils' distinct biological response may be utilized for endotype-based cell-targeted antioxidant therapy.

The protective effect of butylated hydroxytoluene and 3-hydroxytyrosol on food allergy in mice

OBJECTIVE

To test the effect of two dietary antioxidants: butylated hydroxytoluene (BHT) and 3-hydroxytyrosol (3-HT) in experimental food allergy.

METHODS

BALB/c mice maintained on control diet or diet with BHT or 3-HT were sensitized with ovalbumin (OVA) or saline through transdermal exposure. Plasma OVA-specific IgE (OVA-IgE) and IgG1 (OVA-IgG1) antibody levels were determined using ELISA. Sensitized mice were challenged by oral gavage with OVA. Rectal temperature (RT) was measured before and after challenge. Mast cell degranulation was quantified by measuring the plasma levels of mouse mucosal mast cell protease-1 (mMCP-1). Flow cytometry was carried out to evaluate the percentage Th2 cells from the spleen.

RESULTS

Mice on either a 3-HT or BHT diet showed a significantly decreased IgE response to OVA sensitization and less severe anaphylaxis, as evidenced by a diminished drop in body temperature, attenuated clinical signs, a more rapid recovery and decreased mast cell degranulation (as determined by lower plasma mMCP-1 levels).

CONCLUSION

The present study indicates two dietary antioxidants: BHT and 3-HT may be protective against experimental food allergy. These results suggest 3-HT and BHT could potentially be useful for prevention of food allergy.

Mediterranean-Type Diets as a Protective Factor for Asthma and Atopy

We are currently riding the second wave of the allergy epidemic, which is ongoing in affluent societies, but now also affecting developing countries. This increase in the prevalence of atopy/asthma in the Western world has coincided with a rapid improvement in living conditions and radical changes in lifestyle, suggesting that this upward trend in allergic manifestations may be associated with cultural and environmental factors. Diet is a prominent environmental exposure that has undergone major changes, with a substantial increase in the consumption of processed foods, all across the globe. On this basis, the potential effects of dietary habits on atopy and asthma have been researched rigorously, but even with a considerable body of evidence, clear associations are far from established. Many factors converge to obscure the potential relationship, including methodological, pathophysiological and cultural differences. To date, the most commonly researched, and highly promising, candidate for exerting a protective effect is the so-called Mediterranean diet (MedDi). This dietary pattern has been the subject of investigation since the mid twentieth century, and the evidence regarding its beneficial health effects is overwhelming, although data on a correlation between MedDi and the incidence and severity of asthma and atopy are inconclusive. As the prevalence of asthma appears to be lower in some Mediterranean populations, it can be speculated that the MedDi dietary pattern could indeed have a place in a preventive strategy for asthma/atopy. This is a review of the current evidence of the associations between the constituents of the MedDi and asthma/atopy, with emphasis on the pathophysiological links between MedDi and disease outcomes and the research pitfalls and methodological caveats which may hinder identification of causality. MedDi, as a dietary pattern, rather than short-term supplementation or excessive focus on single nutrient effects, may be a rational option for preventive intervention against atopy and asthma.

Nutrition in Asthma

An emerging body of evidence suggests that diet plays an important role in both the development and management of asthma. The relationship between dietary intake and asthma risk has been explored in epidemiological studies, though intervention trials examining the effects of nutrient intake and dietary patterns on asthma management are scarce. Evidence for diets high in fruits and vegetables, antioxidants, omega-3 fatty acids and soluble fiber such as the Mediterranean diet is conflicting. However, some studies suggest that these diets may reduce the risk of asthma, particularly in young children, and could have positive effects on disease management. In contrast, a Westernized dietary pattern, high in saturated fatty acids, refined grains, and sugars may promote an inflammatory environment resulting in the onset of disease and worsening of asthma outcomes. This review will summarize the state of the evidence for the impact of whole dietary patterns, as well as individual nutrients on the prevalence and management of asthma.

Clinical trial on the effects of oral magnesium supplementation in stable-phase COPD patients

Background and aims

COPD is a common chronic condition in older age that impacts on daily activities and quality of life. Previous studies suggest that magnesium deficit in COPD patients affects bronco-obstruction, inflammation, and physical performance. We investigated whether oral magnesium supplementation in stable-phase COPD patients improves lung function, physical performance, and quality of life.

Methods

We conducted a double-blind randomized-controlled clinical study with 49 participants divided into two groups: one given 300 mg/day of magnesium citrate (n = 25) and the other one sachet/day of a placebo (n = 24). The following parameters were assessed at baseline and after 3 and 6 months: lung function (spirometry), physical performance (handgrip strength, lower limb strength, six-minute walk test), inflammation (e.g., C-reactive protein, CRP), disease-related symptoms, and quality of life (St George’s Respiratory Questionnaire, EuroQoL-5D, the Modified British Medical Research Council Questionnaire).

Results

Linear mixed models revealed significantly lower CRP values in the intervention group than in the placebo group at the 6 month follow-up (β = − 3.2, 95% CI − 6.0, − 0.4, p = 0.03). Moreover, the maximum work for flexion tended to increase in both groups between the 3 and the 6 month assessments, especially in the placebo group. No significant differences within and between groups over the study period were observed for the other parameters tested.

Conclusions

Although the established minimum sample size was not reached, our results suggests that oral magnesium supplementation may have a potential anti-inflammatory role. On the other hand, it does not seem to substantially influence lung function, physical performance, and quality of life in COPD patients.

Trial registration

The study is registered in clinicaltrial.gov (Trial Registration: NCT02680769, 13 June 2016, retrospectively registered).

Supplementary Information

The online version contains supplementary material available at 10.1007/s40520-021-01921-z.

Effect of ascorbic acid supplementation on pulmonary functions in healthy adults: a randomized controlled pilot study

OBJECTIVES

The fact that oxidative stress plays an important role in the pathogenesis of various pulmonary diseases is supported by the beneficial effect of antioxidants. It is also well known that an altered oxidant-antioxidant balance after the age of 35 years increases the susceptibility to develop obstructive lung diseases later in life. Given this, the present study was designed to evaluate the effect of antioxidant supplementation on lung functions in healthy adults after the age of 35 years.

METHODS

Persons of age ≥35 years (n=45) were randomized into three arms (each comprising 15 participants) to receive either no intervention (NI arm), ascorbic acid 250 mg daily (AA250 arm), or ascorbic acid 500 mg daily (AA500 arm) for 6 weeks. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, and peak expiratory flow (PEF) were measured at baseline and 6 weeks. Persons of age group (20-30 years) were also enrolled in the study to compare their lung functions and cardiovascular parameters at baseline with those ≥35 years of age. All the adverse events experienced by participants were recorded.

RESULTS

Baseline pulmonary functions were found to be comparable among the three study arms and compared to ≥35 years age group, these parameters were found to be better in the younger age group (20-30 years). Most of the pulmonary functions were comparable among the three study arms at 6 weeks. A significant improvement in PEF and % predicted PEF was noted in AA250 arm when compared to baseline values (p=0.049 and 0.026, respectively) and in participants with normal pulmonary functions when compared to those with reduced functions at baseline (p=0.059 and p=0.037).

CONCLUSIONS

Although ascorbic acid did not affect most of the pulmonary functions in healthy adults, it improved PEF and % predicted PEF at a daily dose of 250 mg. In this regard, it was found effective in individuals with normal pulmonary indices at baseline.

Immunomodulatory Role of Nutrients: How Can Pulmonary Dysfunctions Improve?

Nutrition is an important tool that can be used to modulate the immune response during infectious diseases. In addition, through diet, important substrates are acquired for the biosynthesis of regulatory molecules in the immune response, influencing the progression and treatment of chronic lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD). In this way, nutrition can promote lung health status. A range of nutrients, such as vitamins (A, C, D, and E), minerals (zinc, selenium, iron, and magnesium), flavonoids and fatty acids, play important roles in reducing the risk of pulmonary chronic diseases and viral infections. Through their antioxidant and anti-inflammatory effects, nutrients are associated with better lung function and a lower risk of complications since they can decrease the harmful effects from the immune system during the inflammatory response. In addition, bioactive compounds can even contribute to epigenetic changes, including histone deacetylase (HDAC) modifications that inhibit the transcription of proinflammatory cytokines, which can contribute to the maintenance of homeostasis in the context of infections and chronic inflammatory diseases. These nutrients also play an important role in activating immune responses against pathogens, which can help the immune system during infections. Here, we provide an updated overview of the roles played by dietary factors and how they can affect respiratory health. Therefore, we will show the anti-inflammatory role of flavonoids, fatty acids, vitamins and microbiota, important for the control of chronic inflammatory diseases and allergies, in addition to the antiviral role of vitamins, flavonoids, and minerals during pulmonary viral infections, addressing the mechanisms involved in each function. These mechanisms are interesting in the discussion of perspectives associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its pulmonary complications since patients with severe disease have vitamins deficiency, especially vitamin D. In addition, researches with the use of flavonoids have been shown to decrease viral replication in vitro. This way, a full understanding of dietary influences can improve the lung health of patients.

Exogenous oxidative stress suppresses IL-33 -driven proliferation programming in group 2 innate lymphoid cells

Although exogenous oxidative stress has been suggested to promote the pathogenesis of airway inflammation, previous trials using conventional antioxidant therapy in asthma have been largely ineffective, suggesting the complex roles of oxidative stress in the regulation of airway inflammation and of its critical mediating lymphocyte populations. Group 2 innate lymphoid cells (ILC2s) proliferate and induce eosinophilia in response to tissue alarminsin the early phase of airway inflammation. We previously showed that IL-33 -induced endogenous reactive oxygen species is required for optimal metabolic activation of ILC2 functions, however, the role of exogenous oxidative stress in regulating ILC2 functions has not been investigated. Here, we found that exogenous oxidative stress induced by injection of ROS -generating reagent alleviated IL-33 -triggered ILC2 response and inflammation both in the airway and in the liver. Exogenous oxidative stress in ILC2s also compromised IL-33 -mediated accumulation of these cells, as well as subsequent recruitment of eosinophils, after adoptive transferring into ILC2 deficient hosts. Mechanistically, exogenous oxidative stress in ILC2s compromised the proliferation program, while preserving the expression levels of effector molecules in ILC2s. Impaired proliferation under exogenous oxidative stress led to reduced numbers of ILC2s, and an overall decrease in ILC2 response to IL-33 stimulation. Collectively, these data indicate that exogenous oxidative stress suppresses the proliferation program in ILC2s and alleviates IL-33 -triggered inflammation, suggesting that therapeutic induction of oxidative stress might alleviate ILC2 -mediated inflammation in the airway, and possibly also in other organs.

The Effect of Broccoli Sprout Extract on Seasonal Grass Pollen-Induced Allergic Rhinitis

Patients exposed to pollutants are more likely to suffer from allergic rhinitis and may benefit from antioxidant treatment. Our study determined if patients diagnosed with grass-induced allergic rhinitis could benefit from broccoli sprout extract (BSE) supplementation. In total, 47 patients were confirmed with grass-induced allergic rhinitis and randomized to one of four groups: group 1 (nasal steroid spray + BSE), group 2 (nasal steroid spray + placebo tablet), group 3 (saline nasal spray + BSE) and group 4 (saline nasal spray + placebo tablet). Peak Nasal Inspiratory Flow (PNIF), Total Nasal Symptoms Scores (TNSS) and nasal mucus cytokine levels were analyzed in samples collected before and after the 3-week intervention. Comparing before and after the intervention, PNIF improved significantly when comparing Groups 1 and 2, vs. placebo, at various time points (p ≤ 0.05 at 5, 15, 60 and 240 min) following nasal challenge, while TNSS was only statistically significant at 5 (p = 0.03), 15 (p = 0.057) and 30 (p = 0.05) minutes. There were no statistically significant differences in various cytokine markers before and after the intervention. Combining nasal corticosteroid with BSE led to the most significant improvement in objective measures.

The role of oral magnesium supplements for the management of stable bronchial asthma: a systematic review and meta-analysis

Asthma is a chronic lung disease characterized by airway inflammation and hyper-responsiveness of airway smooth muscles. There is growing evidence that magnesium may have a role in managing asthma through its dual effect as an anti-inflammatory and bronchodilating agent. To assess the efficacy of oral magnesium supplements in chronic asthmatic patients. In addition to searching through Clinicaltrials.gov/ and references for oral magnesium supplement studies, we performed a database search in Medline, CINAHL, CENTRAL, and Embase. We contacted the authors of the included trials to ask for additional information. We included randomized controlled trials that compared oral magnesium supplements versus placebo, in addition to standard asthma treatment in mild-moderate asthmatic adults and children (older than 6 years). Two reviewers independently performed the study selection, data abstraction, and the assessment of the risk of bias. Eight trials at moderate risk of bias enrolling a total of 917 patients were included. Oral magnesium improved FEV1 at week 8 (5.69 (L/min); 95% CI: 1.92, 9.46; I²: 45%). There was no significant improvement in FEV1 at other follow up periods. There was no significant change in FVC, Methacholine challenge test, the frequency of bronchodilator use, or symptoms score. There were no data on mortality or quality of life. Oral magnesium supplements may lead to improvement in FEV1 that was only demonstrated at eight weeks; but no effect on any other outcome. Until future evidence emerges, oral magnesium cannot be recommended as adjuvants to standard treatment for mild to moderate asthmatic individuals.

Dietary patterns and respiratory health in adults from nine European countries-Evidence from the GA2 LEN study

BACKGROUND

Dietary patterns defined using principal component analysis (PCA) offer an alternative to the analysis of individual foods and nutrients and have been linked with asthma and allergic disease. However, results have not been reproducible in different settings.

OBJECTIVE

To identify dietary patterns common to different European countries and examine their associations with asthma and allergic symptoms.

METHODS

In sixteen study centers in nine European countries, 3206 individuals aged 15-77 years completed a common, internationally validated, food frequency questionnaire and a respiratory symptoms questionnaire. The outcomes of interest were current asthma, asthma symptoms score (derived based on responses to 5 asthma symptom-related questions), atopy (positive skin prick test). Spirometry was used to estimate forced expiratory volume in 1 second (FEV₁ ), forced vital capacity (FVC), the FEV₁ /FVC, spirometric restriction (FVC below the lower limit of normal (<LLN)) and FEV₁ /FVC < LLN. A novel meta-analytic approach was used to identify dietary patterns using PCA and to examine associations with asthma and allergic symptoms.

RESULTS

Two dietary patterns emerged, generally correlating with the same foods in different countries: one associated with intake of animal proteins and carbohydrates; the other with fruit and vegetables. There was evidence that the former pattern was associated with a higher asthma score (RR 1.63, 95% CI: 1.33-2.01), current asthma (RR 2.03, 95% CI: 1.52-2.71), wheeze (RR 1.84, 95% CI: 1.30-2.60), atopic status (RR 1.68, 95% CI: 1.16-2.44) and with decreased lung function, including an FVC <LLN (RR 4.57, 95% CI: 2.27-9.21).

CONCLUSIONS AND CLINICAL RELEVANCE

Our findings suggest an increase in sensitisation to common allergens, an increase in asthma symptoms, and a reduction in lung function in those eating a diet rich in animal proteins and carbohydrates. We found little evidence of an association between these outcomes and eating a diet rich in fruits and vegetables.

Diet effects in the asthma treatment: A systematic review

INTRODUCTION

Obesity in asthmatic patients has important relationships with asthma control, pulmonary function, and quality of life. The objective of this study was to conduct a systematic review of the literature on the effect of diet on asthma management in adults.

METHODS

We searched PubMed, Embase, and Scopus (January 1948-October 2014) for randomized clinical trials that evaluated the effects of diet in adults with asthma.

RESULTS

Of 12,215 studies identified, 21 were included. A reduction in weight of at least 7.5% from baseline as a result of caloric restriction can be beneficial for improving disease control, quality of life, and pulmonary function in obese patients with asthma. A dietary pattern rich in foods with potential antioxidant effect had an impact in improving asthma control, but with little clinical significance. Studies involving antioxidant supplementation showed improvements in asthma control with magnesium supplementation and less decline in lung function with vitamin C supplementation. Studies of fatty acid supplementation demonstrated effects on weight loss and improvement of asthma control and lung function. Studies of supplementation with propolis and caffeine reported significant increases in FEV1. Conversely, studies of high dietary salt intake reported greater declines in lung function.

CONCLUSIONS

The evidence shows that, for obese adults with asthma, the best dietary intervention seems to be caloric restriction, regardless of specific dietary components.

Diet and Asthma: Is It Time to Adapt Our Message?

Asthma is a chronic respiratory disorder which is associated with airway inflammation. Environmental factors, in association with genetic susceptibility, play a critical role in asthma pathophysiology. Inhaled allergens, smoke exposure, indoor and outdoor air pollution are common triggers of asthma symptoms. Although the role of diet has clearly established mechanisms in diseases such as cardiovascular disease, type 2 diabetes, and cancer, it is not commonly identified as a causal factor in asthma. However, some dietary patterns, such as the Western diet, which includes a high intake of refined grains, processed and red meats, and desserts, have pro-inflammatory effects. On the contrary, the Mediterranean diet, with high intake of fruits and vegetables has anti-inflammatory properties. The influence of food on asthma outcomes is of growing interest, but dietary habits of asthma patients are not commonly investigated in clinical practice. In this review, we focus on the impact of diet on asthma risk and asthma control. We also detail the influence of diet on obese patients with asthma.

Diet Hypotheses in Light of the Microbiota Revolution: New Perspectives

From an evolutionary standpoint, allergy has only recently emerged as a significant health problem. Various hypotheses were proposed to explain this, but they all indicated the importance of rapid lifestyle changes, which occurred in industrialized countries in the last few decades. In this review, we discuss evidence from epidemiological and experimental studies that indicate changes in dietary habits may have played an important role in this phenomenon. Based on the example of dietary fiber, we discuss molecular mechanisms behind this and point towards the importance of diet-induced changes in the microbiota. Finally, we reason that future studies unraveling mechanisms governing these changes, along with the development of better tools to manipulate microbiota composition in individuals will be crucial for the design of novel strategies to combat numerous inflammatory disorders, including atopic diseases.

The effect of dietary components on inflammatory lung diseases - a literature review

Anti-inflammatory treatment in chronic inflammatory lung diseases usually involves glucocorticosteroids. With patients suffering from serious side effects or becoming resistant, specific nutrients, that are suggested to positively influence disease progression, can be considered as new treatment options. The dietary inflammatory index is used to calculate effects of dietary components on inflammation and lung function to identify most potent dietary components, based on 162 articles. The positive effects of n-3 PUFAs and vitamin E on lung function can at least partially be explained by their anti-inflammatory effect. Many other dietary components showed only small or no effects on inflammation and/or lung function, although the number of weighted studies was often too small for a reliable assessment. Optimal beneficial dietary elements might reduce the required amounts of anti-inflammatory treatments, thereby decreasing both side effects and development of resistance as to improve quality of life of patients suffering from chronic inflammatory lung diseases.

A systematic review and meta-analysis of complementary and alternative medicine in asthma

Asthma is a chronic, inflammatory lung disease affecting around 235 million people worldwide. Conventional medications in asthma are not curative and patients have significant concerns regarding their side-effects. Consequently, many asthma patients turn to complementary and alternative medicine (CAM) for a more holistic approach to care. We systematically reviewed the available evidence on the effectiveness of CAM in the management of asthma in adults.We searched the MEDLINE, EMBASE, CINAHL, AMED and Cochrane databases for randomised controlled trials published in English between 1990 and 2016 investigating the effectiveness of oral or topical CAM in asthmatic adults. The quality of the studies was assessed using the Cochrane Risk of Bias Assessment Tool.In all, 23 eligible trials were identified covering 19 different CAMs. Overall, there was limited evidence on the effectiveness of CAM in adult asthma as most CAMs were only assessed in a single trial. CAMs with multiple trials provided null or inconsistent results. Many of the trials were rated as having high risk of bias.The existing evidence is insufficient to recommend any of the oral and topical CAMs in the management of asthma in adults.

Evaluation of the PPAR-γ Agonist Pioglitazone in Mild Asthma: A Double-Blind Randomized Controlled Trial

Background

Peroxisome proliferator-activated receptor gamma (PPAR-γ) is a nuclear receptor that modulates inflammation in models of asthma. To determine whether pioglitazone improves measures of asthma control and airway inflammation, we performed a single-center randomized, double-blind, placebo-controlled, parallel-group trial.

Methods

Sixty-eight participants with mild asthma were randomized to 12 weeks pioglitazone (30 mg for 4 weeks, then 45 mg for 8 weeks) or placebo. The primary outcome was the adjusted mean forced expiratory volume in one second (FEV₁) at 12 weeks. The secondary outcomes were mean peak expiratory flow (PEF), scores on the Juniper Asthma Control Questionnaire (ACQ) and Asthma Quality of Life Questionnaire (AQLQ), fractional exhaled nitric oxide (FeNO), bronchial hyperresponsiveness (PD₂₀), induced sputum counts, and sputum supernatant interferon gamma-inducible protein-10 (IP-10), vascular endothelial growth factor (VEGF), monocyte chemotactic protein-1 (MCP-1), and eosinophil cationic protein (ECP) levels. Study recruitment was closed early after considering the European Medicines Agency’s reports of a potential increased risk of bladder cancer with pioglitazone treatment. Fifty-five cases were included in the full analysis (FA) and 52 in the per-protocol (PP) analysis.

Results

There was no difference in the adjusted FEV₁ at 12 weeks (-0.014 L, 95% confidence interval [CI] -0.15 to 0.12, p = 0.84) or in any of the secondary outcomes in the FA. The PP analysis replicated the FA, with the exception of a lower evening PEF in the pioglitazone group (-21 L/min, 95% CI -39 to -4, p = 0.02).

Conclusions

We found no evidence that treatment with 12 weeks of pioglitazone improved asthma control or airway inflammation in mild asthma.

Trial Registration

ClinicalTrials.gov NCT01134835

Pilot randomised trial of a healthy eating behavioural intervention in uncontrolled asthma

Rigorous research on the benefit of healthy eating patterns for asthma control is lacking.We randomised 90 adults with objectively confirmed uncontrolled asthma and a low-quality diet (Dietary Approaches to Stop Hypertension (DASH) scores <6 out of 9) to a 6-month DASH behavioural intervention (n=46) or usual-care control (n=44). Intention-to-treat analyses used repeated-measures mixed models.Participants were middle-aged, 67% female and multiethnic. Compared with controls, intervention participants improved on DASH scores (mean change (95% CI) 0.6 (0, 1.1) versus -0.3 (-0.8, 0.2); difference 0.8 (0.2, 1.5)) and the primary outcome, Asthma Control Questionnaire scores (-0.2 (-0.5, 0) versus 0 (-0.3, 0.3); difference -0.2 (-0.5, 0.1)) at 6 months. The mean group differences in changes in Mini Asthma Quality of Life Questionnaire overall and subdomain scores consistently favoured the intervention over the control group: overall 0.4 (95% CI 0, 0.8), symptoms 0.5 (0, 0.9), environment 0.4 (-0.1, 1.0), emotions 0.4 (-0.2, 0.9) and activities 0.3 (0, 0.7). These differences were modest, but potentially clinical significant.The DASH behavioural intervention improved diet quality with promising clinical benefits for better asthma control and functional status among adults with uncontrolled asthma. A full-scale efficacy trial is warranted.

Cyclic nitroxide radicals attenuate inflammation and Hyper-responsiveness in a mouse model of allergic asthma

The effects of stable cyclic nitroxide radicals have been extensively investigated both in vivo and in vitro demonstrating anti-inflammatory, radioprotective, anti-mutagenic, age-retardant, hypotensive, anti-cancer and anti-teratogenic activities. Yet, these stable radicals have not been evaluated in asthma and other airway inflammatory disorders. The present study investigated the effect of 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl (TPL) and 3-carbamoyl-proxyl (3-CP) in a mouse model of ovalbumin (OVA)-induced allergic asthma. Both 3-CP and TPL were non-toxic when administered either orally (1% w/w nitroxide-containing chow) or via intraperitoneal (IP) injection (∼300 mg/kg). Feeding the mice orally demonstrated that 3-CP was more effective than TPL in reducing inflammatory cell recruitment into the airway and in suppressing airway hyper-responsiveness (AHR) in OVA-challenged mice. To characterize the optimal time-window of intervention and mode of drug administration, 3-CP was given orally during allergen sensitization, during allergen challenge or during both sensitization and challenge stages, and via IP injection or intranasal instillation for 3 days during the challenge period. 3-CP given via all modes of delivery markedly inhibited OVA-induced airway inflammation, expression of cytokines, AHR and protein nitration of the lung tissue. Oral administration during the entire experiment was the most efficient delivery of 3-CP and was more effective than dexamethasone a potent corticosteroid used for asthma treatment. Under a similar administration regimen (IP injection before the OVA challenge), the effect of 3-CP was similar to that of dexamethasone and even greater on AHR and protein nitration. The protective effect of the nitroxides, which preferentially react with free radicals, in suppressing the increase of main asthmatic inflammatory markers substantiate the key role played by reactive oxygen and nitrogen species in the molecular mechanism of asthma. The present results demonstrate the therapeutic potential of nitroxides for the treatment of asthma.

Pharmacotherapy of critical asthma syndrome: current and emerging therapies

The critical asthma syndrome (CAS) encompasses the most severe, persistent, refractory asthma patients for the clinician to manage. Personalized pharmacotherapy is necessary to prevent the next acute severe asthma exacerbation, not just the control of symptoms. The 2007 National Asthma Education and Prevention Program Expert Panel 3 provides guidelines for the treatment of uncontrolled asthma. The patient's response to recommended pharmacotherapy is highly variable which risks poor asthma control leading to frequent exacerbations that can deteriorate into CAS. Controlling asthma symptoms and preventing acute exacerbations may be two separate clinical activities with their own unique demands. Clinicians must be prepared to use the entire spectrum of asthma medications available but must concurrently be aware of potential drug toxicities some of which can paradoxically worsen asthma control. Medications normally prescribed for COPD can potentially be useful in the CAS patient, particularly those with asthma-COPD overlap syndrome. Immunomodulation with drugs like omalizumab in IgE-mediated asthma syndromes is one important approach. New and emerging drugs address unique aspects of airway inflammation and biology but at a significant financial cost. The pharmacology and toxicities of the agents that may be used in the treatment of CAS to control asthma symptoms and prevent severe exacerbations are reviewed.

What have studies of non-industrialized countries told us about the cause of allergic disease?

The increase in allergic diseases that was observed in countries that had experienced rapid economic growth since the mid-20th century initiated a search for environmental exposures that may explain these phenomena that continues to the present day. Societies that are in the earlier stages of the process of industrialization provide an opportunity to compare the initial stages of economic development and the lifestyle changes that may accompany this, with other communities whose way of life may not have changed appreciably for centuries. These studies have consistently demonstrated higher levels of allergic disease in the relatively affluent populations compared with those who maintain a more traditional lifestyle. Environmental changes that have emerged from these studies that may modify the risk of allergic disease include microbial exposures including parasite infection, pollution, diet and obesity. In addition, food and drug allergies represent a neglected area of research in these countries that may be causing a relatively high burden of disease.

Effect of a soy isoflavone supplement on lung function and clinical outcomes in patients with poorly controlled asthma: a randomized clinical trial

IMPORTANCE

Soy isoflavone supplements are used to treat several chronic diseases, although the data supporting their use are limited. Some data suggest that supplementation with soy isoflavone may be an effective treatment for patients with poor asthma control.

OBJECTIVE

To determine whether a soy isoflavone supplement improves asthma control in adolescent and adult patients with poorly controlled disease.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, randomized, double-blind, placebo-controlled trial conducted between May 2010 and August 2012 at 19 adult and pediatric pulmonary and allergy centers in the American Lung Association Asthma Clinical Research Centers network. Three hundred eighty-six adults and children aged 12 years or older with symptomatic asthma while taking a controller medicine and low dietary soy intake were randomized, and 345 (89%) completed spirometry at week 24.

INTERVENTIONS

Participants were randomly assigned to receive soy isoflavone supplement containing 100 mg of total isoflavones (n=193) or matching placebo (n=193) in 2 divided doses administered daily for 24 weeks.

MAIN OUTCOMES AND MEASURES

The primary outcome measure was change in forced expiratory volume in the first second (FEV1) at 24 weeks. Secondary outcome measures were symptoms, episodes of poor asthma control, Asthma Control Test score (range, 5-25; higher scores indicate better control), and systemic and airway biomarkers of inflammation.

RESULTS

Mean changes in prebronchodilator FEV1 over 24 weeks were 0.03 L (95% CI, -0.01 to 0.08 L) in the placebo group and 0.01 L (95% CI, -0.07 to 0.07 L) in the soy isoflavone group, which were not significantly different (P = .36). Mean changes in symptom scores on the Asthma Control Test (placebo, 1.98 [95% CI, 1.42-2.54] vs soy isoflavones, 2.20 [95% CI, 1.53-2.87]; positive values indicate a reduction in symptoms), number of episodes of poor asthma control (placebo, 3.3 [95% CI, 2.7-4.1] vs soy isoflavones, 3.0 [95% CI, 2.4-3.7]), and changes in exhaled nitric oxide (placebo, -3.48 ppb [95% CI, -5.99 to -0.97 ppb] vs soy isoflavones, 1.39 ppb [95% CI, -1.73 to 4.51 ppb]) did not significantly improve more with the soy isoflavone supplement than with placebo. Mean plasma genistein level increased from 4.87 ng/mL to 37.67 ng/mL (P < .001) in participants receiving the supplement.

CONCLUSIONS AND RELEVANCE

Among adults and children aged 12 years or older with poorly controlled asthma while taking a controller medication, use of a soy isoflavone supplement, compared with placebo, did not result in improved lung function or clinical outcomes. These findings suggest that this supplement should not be used for patients with poorly controlled asthma.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01052116.

Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE)

An increasing recognition has emerged of the complexities of the global health agenda—specifically, the collision of infections and noncommunicable diseases and the dual burden of over- and undernutrition. Of particular practical concern are both 1) the need for a better understanding of the bidirectional relations between nutritional status and the development and function of the immune and inflammatory response and 2) the specific impact of the inflammatory response on the selection, use, and interpretation of nutrient biomarkers. The goal of the Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE) is to provide guidance for those users represented by the global food and nutrition enterprise. These include researchers (bench and clinical), clinicians providing care/treatment, those developing and evaluating programs/interventions at scale, and those responsible for generating evidence-based policy. The INSPIRE process included convening 5 thematic working groups (WGs) charged with developing summary reports around the following issues: 1) basic overview of the interactions between nutrition, immune function, and the inflammatory response; 2) examination of the evidence regarding the impact of nutrition on immune function and inflammation; 3) evaluation of the impact of inflammation and clinical conditions (acute and chronic) on nutrition; 4) examination of existing and potential new approaches to account for the impact of inflammation on biomarker interpretation and use; and 5) the presentation of new approaches to the study of these relations. Each WG was tasked with synthesizing a summary of the evidence for each of these topics and delineating the remaining gaps in our knowledge. This review consists of a summary of the INSPIRE workshop and the WG deliberations.

Anti-oxidant N-acetylcysteine diminishes diesel exhaust-induced increased airway responsiveness in person with airway hyper-reactivity

BACKGROUND

Inhalation of diesel exhaust (DE) at moderate concentrations causes increased airway responsiveness in asthmatics and increased airway resistance in both healthy and asthmatic subjects, but the effect of baseline airway responsiveness and anti-oxidant supplementation on this dynamic is unknown.

OBJECTIVES

We aimed to determine if changes in airway responsiveness due to DE are attenuated by thiol anti-oxidant supplementation, particularly in those with underlying airway hyper-responsiveness.

METHODS

Participants took N-acetylcysteine (600 mg) or placebo capsules three times daily for 6 days. On the last of these 6 days, participants were exposed for 2 h to either filtered air (FA) or DE (300 μg/m(3) of particulate matter smaller than 2.5 microns). Twenty-six non-smokers were studied under each of three experimental conditions (filtered air with placebo, diesel exhaust with placebo, and diesel exhaust with N-acetylcysteine) using a randomized, double-blind, crossover design, with a 2-week washout between conditions. Methacholine challenge was performed pre-exposure (baseline airway responsiveness) and post-exposure (effect of exposure).

RESULTS

Anti-oxidant supplementation reduced baseline airway responsiveness in hyper-responsive individuals by 20% (p = 0.001). In hyper-responsive individuals, airway responsiveness increased 42% following DE compared with FA (p = 0.03) and this increase was abrogated with anti-oxidant supplementation (diesel exhaust with N-acetylcysteine vs. filtered air with placebo, p = 0.85).

CONCLUSIONS

Anti-oxidant (N-acetylcysteine) supplementation protects against increased airway responsiveness associated with DE inhalation and reduces need for supplement bronchodilators in those with baseline airway hyper-responsiveness. Individuals with variants in genes of oxidative stress metabolism when exposed to DE are protected from increases in airway responsiveness if taking anti-oxidant supplementation.

The effect of vitamin C on bronchoconstriction and respiratory symptoms caused by exercise: a review and statistical analysis

Physical activity increases oxidative stress and therefore the antioxidant effects of vitamin C administration might become evident in people undertaking vigorous exercise. Vitamin C is involved in the metabolism of histamine, prostaglandins, and cysteinyl leukotrienes, all of which appear to be mediators in the pathogenesis of exercise-induced bronchoconstriction (EIB). Three studies assessing the effect of vitamin C on patients with EIB were subjected to a meta-analysis and revealed that vitamin C reduced postexercise FEV1 decline by 48% (95% CI: 33% to 64%). The correlation between postexercise FEV1 decline and respiratory symptoms associated with exercise is poor, yet symptoms are the most relevant to patients. Five other studies examined subjects who were under short-term, heavy physical stress and revealed that vitamin C reduced the incidence of respiratory symptoms by 52% (95% CI: 36% to 65%). Another trial reported that vitamin C halved the duration of the respiratory symptoms in male adolescent competitive swimmers. Although FEV1 is the standard outcome for assessing EIB, other outcomes may provide additional information. In particular, the mean postexercise decline of FEF50 is twice the decline of FEV1. Schachter and Schlesinger (1982) reported the effect of vitamin C on exercise-induced FEF60 levels in 12 patients suffering from EIB and their data are analyzed in this paper. The postexercise FEF60 decline was greater than 60% for five participants and such a dramatic decline indicates that the absolute postexercise FEF60 level becomes an important outcome in its own right. Vitamin C increased postexercise FEF60 levels by 50% to 150% in those five participants, but had no significant effect in the other seven participants. Thus, future research on the effects of vitamin C on EIB should not be restricted to measuring only FEV1. Vitamin C is inexpensive and safe, and further study on those people who have EIB or respiratory symptoms associated with exercise is warranted.

Intranasal administration of a combination of choline chloride, vitamin C, and selenium attenuates the allergic effect in a mouse model of airway disease

Respiratory allergic disease is an inflammatory condition accompanied by oxidative stress. Supplementation of an anti-inflammatory agent with antioxidants may have a therapeutic effect. In this study, the effects of choline chloride in combination with antioxidants were evaluated via the intranasal route in a mouse model of allergic airway disease. Balb/c mice were sensitized on days 0, 7, and 14 and challenged on days 25-30 with cockroach extract (CE) and with a booster challenge on day 38. They were treated with choline chloride (ChCl; 1mg/kg), vitamin C (Vit C; 308.33 mg/kg), and selenium (Se; 1mg/kg) alone or in combination via the intranasal route on days 31, 33, 35, 37, and 39. The mice were sacrificed on day 40 to collect blood, bronchoalveolar lavage fluid, lungs, and spleen. Mice immunized with CE showed a significant increase in airway hyperresponsiveness (AHR), lung inflammation, Th2 cytokines, and the oxidative stress markers intracellular reactive oxygen species and 8-isoprostanes compared to the phosphate-buffered saline control group. A significant decrease was observed in these parameters with all the treatments (p<0.01). The highest decrease was noticed in the ChCl+Vit C+Se-treated group, with AHR decreased to the normal level. This group also showed the highest decrease in airway inflammation (p<0.001), IL-4 and IL-5 (p<0.001), IgE and IgG1 (p<0.001), NF-κB (p<0.001), and 8-isoprostane levels (p<0.001). Glutathione peroxidase activity, which was decreased significantly in CE-immunized mice, was restored to normal levels in this group (p<0.001). IL-10 level was decreased in CE-immunized mice and was restored to normal by combination treatment. The combination treatment induced FOXP3(+) cells in splenocyte culture, responsible for the upregulation of IL-10. In conclusion, the combination of choline chloride, vitamin C, and selenium via the intranasal route reduces AHR, inflammation, and oxidative stress, probably by causing IL-10 production by FOXP3(+) cells, and possesses therapeutic potential against allergic airway disease.

Vitamins C and E for asthma and exercise-induced bronchoconstriction

BACKGROUND

The association between dietary antioxidants and asthma or exercise-induced bronchoconstriction (EIB) is not fully understood. Vitamin C and vitamin E are natural antioxidants that are predominantly present in fruits and vegetables; inadequate vitamin E intake is associated with airway inflammation. It has been postulated that the combination may be more beneficial than either single antioxidant for people with asthma and exercise-induced bronchoconstriction.

OBJECTIVES

To assess the effects of supplementation of vitamins C and E versus placebo (or no vitamin C and E supplementation) on exacerbations and health-related quality of life (HRQL) in adults and children with chronic asthma. To also examine the potential effects of vitamins C and E on exercise-induced bronchoconstriction in people with asthma and in people without a diagnosis of asthma who experience symptoms only on exercise.

SEARCH METHODS

Trials were identified from the Cochrane Airways Review Group Specialised Register and from trial registry websites. Searches were conducted in September 2013.

SELECTION CRITERIA

We included randomised controlled trials of adults and children with a diagnosis of asthma. We separately considered trials in which participants had received a diagnosis of exercise-induced bronchoconstriction (or exercise-induced asthma). Trials comparing vitamin C and E supplementation versus placebo were included. We included trials in which asthma management for treatment and control groups included similar background therapy. Short-term use of vitamins C and E at the time of exacerbation or for cold symptoms in people with asthma is outside the scope of this review.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of potential studies and subsequently screened full-text study reports for inclusion. We used standard methods as expected by The Cochrane Collaboration.

MAIN RESULTS

It was not possible to aggregate the five included studies (214 participants). Four studies (206 participants) addressed the question of whether differences in outcomes were seen when vitamin C and E supplementation versus placebo was provided for participants with asthma, and only one of those studies (160 children) included a paediatric population; the remaining three studies included a combined total of just 46 adults. An additional study considered the question of whether differences in outcomes were noted when vitamin C and E supplementation was compared with placebo for exercise-induced asthma; this trial included only eight participants. The randomisation process of the trials were unclear leading us to downgrade the quality of the evidence. Four of the studies were double blind while the other study was single blind.None of these studies provided data on our two prespecified primary outcome measures: exacerbations and HRQL. Lung function data obtained from the studies were inconclusive. The only studies that provided any suggestion of an effect, and only with some outcomes, were the paediatric study, especially for children with moderate to severe asthma, and the small study on exercise-induced asthma. Even so, this evidence was judged to be at moderate/low quality. Only one study contributed data on asthma symptoms and adverse events, reporting no evidence of an effect of the intervention for symptoms and that one participant in the treatment group dropped out due to cystitis.

AUTHORS' CONCLUSIONS

It is not possible to draw firm conclusions from this review with respect to the comparison of vitamin C and E supplementation versus placebo in the management of asthma or exercise-induced bronchoconstriction. We found only one study relevant to exercise-induced bronchoconstriction; most included participants came from studies designed to assess the effect of vitamin supplementation on the impact of atmospheric pollutants (such as ozone). Evidence is lacking on the comparison of vitamin C and E supplementation versus placebo for asthma with respect to outcomes such as HRQL and exacerbations, which were not addressed by any of the included studies.When compared with lung function tests alone, HRQL scores and exacerbation frequency are better indicators of the severity of asthma, its impact on daily activities and its response to treatment in a patient population. These end points are well recognised in good quality studies of asthma management. However, clinical studies of vitamins C and E in the management of asthma using these important end points of exacerbations and effects on quality of life are not available, and evidence is insufficient to support robust conclusions on the role of vitamin C and E supplementation in asthma and exercise-induced breathlessness.

Effects of antioxidant supplements and nutrients on patients with asthma and allergies

Asthma and allergic diseases have become a worldwide public health concern because of their increased prevalence. Despite decades of research on risk factors, the causes of these disorders are poorly understood. They are thought to develop through complex interactions between genetic and environmental factors. Because pulmonary and systemic oxidative stress increase inflammatory responses relevant to asthma and allergy, dietary or vitamin supplementation with antioxidants (a broad and varied category) has been proposed as an approach to reducing asthma incidence or morbidity. Meta-analyses of observational epidemiologic studies of variable methodological quality suggest associations of relatively low dietary intake of antioxidants and higher asthma and allergy prevalence. However, there have been few longitudinal studies of maternal or child dietary or vitamin/supplement antioxidant intake and asthma/allergy development. Moreover, there are no clinical trial data to support the use of dietary antioxidants or supplements to prevent asthma or allergy. A few small clinical trials suggest that specific antioxidants from diet or vitamin supplements might improve asthma control or lung function in asthmatic children or adults. Studies suggest that responses to antioxidants might be modified by life stage, genetic susceptibility, and environmental sources of oxidative stress. Large trials of antioxidant vitamin supplementation to prevent cancer suggest an increase in overall mortality with antioxidant vitamin supplementation, at least in populations with sufficient dietary antioxidant intake. This cautionary experience suggests that future trials to assess whether antioxidants reduce asthma incidence or improve asthma control should focus on supplementation of dietary sources of antioxidants. The potential benefits and risks of trials of vitamin supplements might be considered in special situations in which vulnerable populations have marked deficiency in dietary antioxidants, poor access to dietary antioxidants, and high exposure to environmental sources of oxidants.

Vitamin C and common cold-induced asthma: a systematic review and statistical analysis

BACKGROUND

Asthma exacerbations are often induced by the common cold, which, in turn, can be alleviated by vitamin C.

OBJECTIVE

To investigate whether vitamin C administration influences common cold-induced asthma.

METHODS

Systematic review and statistical analysis of the identified trials. Medline, Scopus and Cochrane Central were searched for studies that give information on the effects of vitamin C on common cold-induced asthma. All clinically relevant outcomes related to asthma were included in this review. The estimates of vitamin C effect and their confidence intervals [CI] were calculated for the included studies.

RESULTS

Three studies that were relevant for examining the role of vitamin C on common cold-induced asthma were identified. The three studies had a total of 79 participants. Two studies were randomized double-blind placebo-controlled trials. A study in Nigeria on asthmatics whose asthma attacks were precipitated by respiratory infections found that 1 g/day vitamin C decreased the occurrence of asthma attacks by 78% (95% CI: 19% to 94%). A cross-over study in former East-Germany on patients who had infection-related asthma found that 5 g/day vitamin C decreased the proportion of participants who had bronchial hypersensitivity to histamine by 52 percentage points (95% CI: 25 to 71). The third study did not use a placebo. Administration of a single dose of 1 gram of vitamin C to Italian non-asthmatic common cold patients increased the provocative concentration of histamine (PC20) 3.2-fold (95% CI: 2.0 to 5.1), but the vitamin C effect was significantly less when the same participants did not suffer from the common cold.

CONCLUSIONS

The three reviewed studies differed substantially in their methods, settings and outcomes. Each of them found benefits from the administration of vitamin C; either against asthma attacks or against bronchial hypersensitivity, the latter of which is a characteristic of asthma. Given the evidence suggesting that vitamin C alleviates common cold symptoms and the findings of this systematic review, it may be reasonable for asthmatic patients to test vitamin C on an individual basis, if they have exacerbations of asthma caused by respiratory infections. More research on the role of vitamin C on common cold-induced asthma is needed.

Deficiency of gp91phox inhibits allergic airway inflammation

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, a multienzyme complex, is the major source for production of reactive oxygen species (ROS). ROS are increased in allergic diseases, such as asthma, but the role of ROS in disease pathogenesis remains uncertain. We hypothesized that mice unable to generate ROS via the NADPH oxidase pathway would have decreased allergic airway inflammation. To test this hypothesis, we studied gp91phox(-/-) mice in a model of allergic airway inflammation after sensitization and challenge with ovalbumin. Serum, bronchoalveolar lavage fluid, and lungs were then examined for evidence of allergic inflammation. We found that mice lacking a functional NADPH oxidase complex had significantly decreased ROS production and allergic airway inflammation, compared with wild-type (WT) control animals. To determine the mechanism by which allergic inflammation was inhibited by gp91phox deficiency, we cultured bone marrow-derived dendritic cells from WT and gp91phox(-/-) mice and activated them with LPS. IL-12 expression was significantly increased in the gp91phox(-/-) bone marrow-derived dendritic cells, suggesting that the cytokine profile produced in the absence of gp91phox enhanced the conditions leading to T helper (Th) type 1 differentiation, while inhibiting Th2 polarization. Splenocytes from sensitized gp91phox(-/-) animals produced significantly less IL-13 in response to ovalbumin challenge in vitro compared with splenocytes from sensitized WT mice, suggesting that NADPH oxidase promotes allergic sensitization. In contrast, inflammatory cytokines produced by T cells cultured from WT and gp91phox(-/-) mice under Th0, Th1, Th2, and Th17 conditions were not significantly different. This study demonstrates the importance of NADPH oxidase activity and ROS production in a murine model of asthma.

WITHDRAWN: Vitamin C supplementation for asthma

This Cochrane Review was withdrawn from publication on 23 October 2013 by the Co‐ordinating Editor of the Cochrane Airways Group with the agreement of the authors. The Cochrane Review has been replaced by two new Cochrane Reviews with updated methods:

Milan SJ, Hart A, Wilkinson M. Vitamin C for asthma and exercise‐induced bronchoconstriction. Cochrane Database of Systematic Reviews 2013, Issue 10. Art. No.: CD010391. DOI: 10.1002/14651858.CD010391.pub2. Wilkinson M, Hart A, Milan SJ, Sugumar K. Vitamins C and E for asthma and exercise‐induced bronchoconstriction. Cochrane Database of Systematic Reviews 2014, Issue 6. Art. No.: CD010749. DOI: 10.1002/14651858.CD010749.pub2.

A previous version of this review, published on 21 January 2009, received comments from H. Hemilä (Department of Public Health, University of Helsinki, Helsinki, Finland). In response to this feedback the review was updated and published on 20 June 2012 PMID: 19160185], as follows: (1) removed three instances of reporting of baseline lung function values; and (2) deleted statistical data from a trial that only reported data on participants who benefited from treatment.

The parts of the review affected by these changes are the section on Effects of interventions, the first paragraph of the Discussion section, and Data and Analyses Table 1: Oral vitamin C vs placebo (single‐dose studies).

The uncorrected version of the review (published 21 January 2009) is no longer available in the Cochrane Database of Systematic Reviews , but can be accessed via PubMed Central: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6176494/ .

This statement was revised on 29 October 2018 to clarify the reason for withdrawing the review, provide information about previous amendments to the review, and include a link to the 2009 publication in PubMed Central.

The editorial group responsible for this previously published document have withdrawn it from publication.

Vitamin C for asthma and exercise-induced bronchoconstriction

BACKGROUND

Dietary antioxidants, such as vitamin C, in the epithelial lining and lining fluids of the lung may be beneficial in the reduction of oxidative damage (Arab 2002). They may therefore be of benefit in reducing symptoms of inflammatory airway conditions such as asthma, and may also be beneficial in reducing exercise-induced bronchoconstriction, which is a well-recognised feature of asthma and is considered a marker of airways inflammation. However, the association between dietary antioxidants and asthma severity or exercise-induced bronchoconstriction is not fully understood.

OBJECTIVES

To examine the effects of vitamin C supplementation on exacerbations and health-related quality of life (HRQL) in adults and children with asthma or exercise-induced bronchoconstriction compared to placebo or no vitamin C.

SEARCH METHODS

We identified trials from the Cochrane Airways Group's Specialised Register (CAGR). The Register contains trial reports identified through systematic searches of a number of bibliographic databases, and handsearching of journals and meeting abstracts. We also searched trial registry websites. The searches were conducted in December 2012.

SELECTION CRITERIA

We included randomised controlled trials (RCTs). We included both adults and children with a diagnosis of asthma. In separate analyses we considered trials with a diagnosis of exercise-induced bronchoconstriction (or exercise-induced asthma). We included trials comparing vitamin C supplementation with placebo, or vitamin C supplementation with no supplementation. We included trials where the asthma management of both treatment and control groups provided similar background therapy. The primary focus of the review is on daily vitamin C supplementation to prevent exacerbations and improve HRQL. The short-term use of vitamin C at the time of exacerbations or for cold symptoms in people with asthma are outside the scope of this review.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts of potential studies, and subsequently screened full text study reports for inclusion. We used standard methods expected by The Cochrane Collaboration.

MAIN RESULTS

A total of 11 trials with 419 participants met our inclusion criteria. In 10 studies the participants were adults and only one was in children. Reporting of study design was inadequate to determine risk of bias for most of the studies and poor availability of data for our key outcomes may indicate some selective outcome reporting. Four studies were parallel-group and the remainder were cross-over studies. Eight studies included people with asthma and three studies included 40 participants with exercise-induced asthma. Five studies reported results using single-dose regimes prior to bronchial challenges or exercise tests. There was marked heterogeneity in vitamin C dosage regimes used in the selected studies, compounding the difficulties in carrying out meaningful analyses.One study on 201 adults with asthma reported no significant difference in our primary outcome, health-related quality of life (HRQL), and overall the quality of this evidence was low. There were no data available to evaluate the effects of vitamin C supplementation on our other primary outcome, exacerbations in adults. One small study reported data on asthma exacerbations in children and there were no exacerbations in either the vitamin C or placebo groups (very low quality evidence). In another study conducted in 41 adults, exacerbations were not defined according to our criteria and the data were not available in a format suitable for evaluation by our methods. Lung function and symptoms data were contributed by single studies. We rated the quality of this evidence as moderate, but further research is required to assess any clinical implications that may be related to the changes in these parameters. In each of these outcomes there was no significant difference between vitamin C and placebo. No adverse events at all were reported; again this is very low quality evidence.Studies in exercise-induced bronchoconstriction suggested some improvement in lung function measures with vitamin C supplementation, but theses studies were few and very small, with limited data and we judged the quality of the evidence to be low.

AUTHORS' CONCLUSIONS

Currently, evidence is not available to provide a robust assessment on the use of vitamin C in the management of asthma or exercise-induced bronchoconstriction. Further research is very likely to have an important impact on our confidence in the estimates of effect and is likely to change the estimates. There is no indication currently that vitamin C can be recommended as a therapeutic agent in asthma. There was some indication that vitamin C was helpful in exercise-induced breathlessness in terms of lung function and symptoms; however, as these findings were provided only by small studies they are inconclusive. Most published studies to date are too small and inconsistent to provide guidance. Well-designed trials with good quality clinical endpoints, such as exacerbation rates and health-related quality of life scores, are required.

Endocrine disruptors found in food contaminants enhance allergic sensitization through an oxidative stress that promotes the development of allergic airway inflammation

In the past few decades, there has been a significant increase in incidence of allergic diseases. The hygiene hypothesis may provide some clues to explain this rising trend, but it may also be attributable to other environmental factors that exert a proallergic adjuvant effects. However, there is limited information on the risks of developing allergic asthma and related diseases through the ingestion of environmental chemicals found in food contaminants. In the present study, we have shown that oral administration of tributyltin, used as a model environmental chemical, induced oxidative-stress status in the bronchial lymph node, mesenteric lymph node and spleen, but not in the lung, where the initial step of allergic asthma pathogenesis takes place. Mice exposed to tributyltin exhibited heightened Th2 immunity to the allergen with more severe airway inflammation. Tributyltin also induced Treg cells apoptosis preferentially over non-Treg cells. All these effects of tributyltin exposure were canceled by the administration of glutathione monoethyl ester. Meanwhile, tributyltin did not affect airway inflammation of mice transferred with allergen-specific Th2 cells. Collectively, these results suggest that tributyltin exerts its pathological effect during the sensitization phase through oxidative stress that enhances the development of allergic diseases. The current study dissects the pathogenic role of oxidative stress induced by oral exposure to an environmental chemical during the sensitization phase of allergic airway inflammation and would be important for developing therapeutics for prevention of allergic diseases.

Improving asthma during pregnancy with dietary antioxidants: the current evidence

The complication of asthma during pregnancy is associated with a number of poor outcomes for the mother and fetus. This may be partially driven by increased oxidative stress induced by the combination of asthma and pregnancy. Asthma is a chronic inflammatory disease of the airways associated with systemic inflammation and oxidative stress, which contributes to worsening asthma symptoms. Pregnancy alone also intensifies oxidative stress through the systemic generation of excess reactive oxidative species (ROS). Antioxidants combat the damaging effects of ROS; yet antioxidant defenses are reduced in asthma. Diet and nutrition have been postulated as potential factors to combat the damaging effects of asthma. In particular, dietary antioxidants may play a role in alleviating the heightened oxidative stress in asthma. Although there are some observational and interventional studies that have shown protective effects of antioxidants in asthma, assessment of antioxidants in pregnancy are limited and there are no antioxidant intervention studies in asthmatic pregnancies on asthma outcomes. The aims of this paper are to (i) review the relationships between oxidative stress and dietary antioxidants in adults with asthma and asthma during pregnancy, and (ii) provide the rationale for which dietary management strategies, specifically increased dietary antioxidants, might positively impact maternal asthma outcomes. Improving asthma control through a holistic antioxidant dietary approach might be valuable in reducing asthma exacerbations and improving asthma management during pregnancy, subsequently impacting perinatal health.

Oxidative stress and antioxidant deficiencies in asthma: potential modification by diet

The lungs of asthmatic patients are exposed to oxidative stress due to the generation of reactive oxygen and nitrogen species as a consequence of chronic airway inflammation. Increased concentrations of NO*, H2O2 and 8-isoprostane have been measured in exhaled breath and induced sputum of asthmatic patients. O2*-, NO*, and halides interact to form highly reactive species such as peroxynitrite and HOBr, which in turn cause nitration and bromination of protein tyrosine residues. Oxidative stress may also reduce glutathione levels and cause inactivation of antioxidant enzymes such as superoxide dismutase, with a consequent increase in apoptosis, shedding of airway epithelial cells and airway remodelling. The oxidant/antioxidant equilibrium in asthmatic patients may be further perturbed by low dietary intakes of the antioxidant vitamins C and E, selenium and flavonoids, with a consequent lowering of the concentrations of these and other non-dietary antioxidants such as bilirubin and albumin in plasma and airway epithelial lining fluid. Although supplementation with vitamins C and E appears to offer protection against the adverse effects of ozone, recent randomised, placebo-controlled trials of vitamin C or E supplements for patients with mild asthma have not shown significant benefits over standard therapy. However, genetic variation in glutathione S-transferase may influence the susceptibility of asthmatic individuals to oxidative stress and the extent to which they are likely to benefit from antioxidant supplementation. Long-term prospective trials are required to determine whether modification of dietary intake will benefit asthma patients and reduce the socio-economic burden of asthma in the community.

Molecular mechanisms of reactive oxygen species-related pulmonary inflammation and asthma

Asthma is a highly relevant disorder that can be induced by many environmental factors such as allergens and pollutants. One of the most critical pathological symptoms of asthma is airway inflammation. In order to identify a cause of respiratory inflammation, we thoroughly examine the unique role of reactive oxygen species (ROS). Evidence supports that the inhalation of aggravating compounds such as allergens can promote the increased generation of ROS. Accordingly, ROS have a proven role in the cellular signaling cascades of many respiratory diseases that cause respiratory inflammation, including asthma. Although there is no known cure for asthma, current treatments effectively lessen the inflammation symptom. Based on the investigations of asthma pathogenesis and the mechanism of ROS formation, we have identified several novel anti-inflammatory therapeutic treatments, shedding light on a fundamental understanding for the cure of this disorder. In this review, we will outline the pathogenesis of asthma and its relationship to ROS, oxidative stress, and pulmonary inflammation.

Antioxidant intake and allergic disease in children

BACKGROUND

Antioxidant intake may reduce the risk of allergic disease by protecting against oxidative tissue damage. Major sources of antioxidants in the Western world are fruits, vegetables (vitamin C, β-carotene, α-tocopherol), meat and milk (selenium, magnesium, zinc). Children may exclude or eat less of some fruits and vegetables due to cross-reactivity between pollen and these foods, complicating assessment of causal relationships.

OBJECTIVE

To investigate the association between dietary antioxidant intake and allergic disease, taking potential reverse causation into account.

METHODS

Data on 2442 8-year-old children from the Swedish birth cohort study BAMSE were analysed. Children with completed parental questionnaires on exposures and health, including a food-frequency questionnaire and who provided a blood sample were included. Associations between antioxidant intake during the past year and current allergic disease were analysed using logistic regression.

RESULTS

An inverse association was observed between intake of β-carotene and rhinitis (OR(adj), highest vs. lowest quartile, 0.67, 95% CI 0.49-0.93). Magnesium intake was inversely related to asthma (OR(adj), 0.65, 95% CI 0.42-1.00) and atopic sensitisation (OR(adj), 0.78, 95% CI 0.61-1.00). Following exclusion of children who avoided certain fruits, vegetables or milk due to allergic symptoms (n = 285), the inverse association remained between magnesium intake and asthma (OR(adj), 0.58, 95% CI 0.35-0.98), whereas all other associations became non-significant.

CONCLUSION AND CLINICAL RELEVANCE

Diet modifications due to allergy may affect the antioxidant intake and needs to be considered when investigating the relationship between diet and allergic disease. Magnesium intake seems to have a protective effect on childhood asthma.

Intravenous and nebulized magnesium sulfate for treating acute asthma in adults and children: a systematic review and meta-analysis

OBJECTIVES

This systematic review and meta-analysis was conducted to estimate the effects of intravenous and nebulized magnesium sulfate on treating adults and children with acute asthma.

METHODS

Electronic literature search and the manual search of key respiratory journals were performed up to October 18, 2011. Randomized controlled trials were included if patients had been treated with intravenous or nebulized magnesium sulfate in combination with β2-agonists and were compared with the use of β2-agonists. Standardized mean differences (SMDs) and the relative risks (RRs) were calculated for pulmonary functions and hospital admission respectively.

RESULTS

25 trials (16 intravenous, 9 nebulized) involving 1754 patients were included. In adults intravenous treatment was associated with a significant effect upon respiratory function (SMD, 0.30; 95% confidence interval (CI), 0.05 to 0.55; p = 0.02) but weak evidence of effect upon hospital admission (RR 0.86,95% CI 0.73 to 1.01; p = 0.06) in adults, and in children with significant effects upon both respiratory function (SMD, 1.94; 95% CI, 0.80 to 3.08; p = 0.0008) and hospital admission (RR, 0.70; 95% CI, 0.54 to 0.91; p = 0.008). Nebulized treatment was associated with significant effects upon respiratory function (SMD, 0.23; 95% CI, 0.06 to 0.41; p = 0.009) and hospital admission (RR, 0.63; 95% CI, 0.43 to 0.92; p = 0.02) in adults.

CONCLUSION

The use of intravenous magnesium sulfate, in addition to β2-agonists and systemic steroids, in the treatment of acute asthma appears to produce benefits with respect to improve pulmonary function and reduce the number of hospital admissions for children, and only improve pulmonary function for adults. However, the use of nebulized magnesium sulfate just appears to produce benefits for adults.

Reduced medication use and improved pulmonary function with supplements containing vegetable and fruit concentrate, fish oil and probiotics in asthmatic school children: a randomised controlled trial

Dietary pattern changes may be one of the key factors associated with increasing asthma prevalence. Observational studies have found negative associations between fruit, vegetable and fish consumption and risk of asthma. Experimental studies have also shown that probiotics can modulate the immune system. However, each dietary component exhibits a modest effect. The objective of the present study was to investigate the joint effect of multiple beneficial dietary components on asthma. We designed a 16-week school-based double-blind placebo-controlled randomised trial. The supplement group received fruit plus vegetable concentrate, fish oil and probiotics (FVFP supplement), while the control group received placebos. A total of 192 asthmatic children aged 10-12 years were recruited from elementary schools in metropolitan Taipei. Pulmonary function, medication usage, Paediatric Asthma Quality of Life Questionnaire (PAQLQ) score and the Childhood Asthma Control Test score were evaluated at baseline, and at weeks 8 and 16. Compared with the placebo group, the supplement group showed significant improvement in pulmonary function parameters (91 v. 178 ml for forced vital capacity (FVC), 40 v. 107 ml for forced expiratory volume in 1 s (FEV1) and 1·6 v. 4·8 % for FEV1:FVC ratio; all P values < 0·01) and had a significantly reduced proportion of those using short-acting inhaled bronchodilators and inhaled corticosteroids. However, the PAQLQ score and the Childhood Asthma Control Test score were not significantly different between the two groups, possibly because the majority of the children were treated routinely. FVFP supplements reduced medication use and improved pulmonary function in asthmatic children. The present study supports an adjuvant intervention with a combination of fruit, vegetable, fish and probiotic foods.

Influence of mediterranean diet on asthma symptoms, lung function, and systemic inflammation: a randomized controlled trial

OBJECTIVE

The rapidly increasing prevalence of asthma in developed countries suggests an environmental cause. The benefits of Mediterranean diet (MD) in cardiovascular disease have been tentatively attributed to its anti-inflammatory properties. Asthma is an inflammatory disease and MD is associated with reduced asthma risk in epidemiological studies, but there are no reported interventional studies of MD in asthma.

METHODS

In this 12-week open-label randomized trial, 38 adults with symptomatic asthma were allocated to high-intervention (HI), low-intervention (LI), and control groups. The first two groups were encouraged to adopt an MD and received multiple consultation sessions with a nutritionist, written advice, and vouchers for the purchase of appropriate foods. Food frequency questionnaires, asthma control questionnaires, asthma-related quality of life questionnaires (AQLQs), and spirometry were completed at the beginning and at the end of the study.

RESULTS

The MDt score increased in the HI group (p < .001), indicating successful alteration of dietary behavior. Statistically, nonsignificant improvements were seen in spirometry and several AQLQ subdomains in the two intervention groups. No changes were seen in the asthma control or in inflammatory markers.

CONCLUSIONS

The trial intervention has successfully altered the dietary behavior among adults with asthma. Small but consistent improvements were seen in quality of life and spirometry among the intervention group. The use of the MD to treat asthma is feasible and warrants evaluation in a larger study, powered to examine clinical endpoints.

Grape seed proanthocyanidin extract attenuates allergic inflammation in murine models of asthma

BACKGROUND

Antioxidants have been suggested to alleviate the pathophysiological features of asthma, and grape seed proanthocyanidin extract (GSPE) has been reported to have powerful antioxidant activity.

PURPOSE

This study was performed to determine whether GSPE has a therapeutic effect on allergic airway inflammation in both acute and chronic murine model of asthma.

METHODS

Acute asthma model was generated by intraperitoneal sensitization of ovalbumin (OVA) with alum followed by aerosolized OVA challenges, whereas chronic asthma model was induced by repeated intranasal challenges of OVA with fungal protease twice a week for 8 weeks. GSPE was administered by either intraperitoneal injection or oral gavage before OVA challenges. Airway hyperresponsiveness (AHR) was measured, and airway inflammation was evaluated by bronchoalveolar lavage (BAL) fluid analysis and histopathological examination of lung tissue. Lung tissue levels of various cytokines, chemokines, and growth factors were analyzed by quantitative polymerase chain reaction and ELISA. Glutathione assay was done to measure oxidative burden in lung tissue.

RESULTS

Compared to untreated asthmatic mice, mice treated with GSPE showed significantly reduced AHR, decreased inflammatory cells in the BAL fluid, reduced lung inflammation, and decreased IL-4, IL-5, IL-13, and eotaxin-1 expression in both acute and chronic asthma models. Moreover, airway subepithelial fibrosis was reduced in the lung tissue of GSPE-treated chronic asthmatic mice compared to untreated asthmatic mice. Reduced to oxidized glutathione (GSH/GSSG) ratio was increased after GSPE treatment in acute asthmatic lung tissue.

CONCLUSION

GSPE effectively suppressed inflammation in both acute and chronic mouse models of asthma, suggesting a potential role of GSPE as a therapeutic agent for asthma.

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

BACKGROUND

Our systematic review has demonstrated that antioxidant supplements may increase mortality. We have now updated this review.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements for prevention of mortality in adults.

SEARCH METHODS

We searched The Cochrane Library, MEDLINE, EMBASE, LILACS, the Science Citation Index Expanded, and Conference Proceedings Citation Index-Science to February 2011. We scanned bibliographies of relevant publications and asked pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included all primary and secondary prevention randomised clinical trials on antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Three authors extracted data. Random-effects and fixed-effect model meta-analyses were conducted. Risk of bias was considered in order to minimise the risk of systematic errors. Trial sequential analyses were conducted to minimise the risk of random errors. Random-effects model meta-regression analyses were performed to assess sources of intertrial heterogeneity.

MAIN RESULTS

Seventy-eight randomised trials with 296,707 participants were included. Fifty-six trials including 244,056 participants had low risk of bias. Twenty-six trials included 215,900 healthy participants. Fifty-two trials included 80,807 participants with various diseases in a stable phase. The mean age was 63 years (range 18 to 103 years). The mean proportion of women was 46%. Of the 78 trials, 46 used the parallel-group design, 30 the factorial design, and 2 the cross-over design. All antioxidants were administered orally, either alone or in combination with vitamins, minerals, or other interventions. The duration of supplementation varied from 28 days to 12 years (mean duration 3 years; median duration 2 years). Overall, the antioxidant supplements had no significant effect on mortality in a random-effects model meta-analysis (21,484 dead/183,749 (11.7%) versus 11,479 dead/112,958 (10.2%); 78 trials, relative risk (RR) 1.02, 95% confidence interval (CI) 0.98 to 1.05) but significantly increased mortality in a fixed-effect model (RR 1.03, 95% CI 1.01 to 1.05). Heterogeneity was low with an I(2)- of 12%. In meta-regression analysis, the risk of bias and type of antioxidant supplement were the only significant predictors of intertrial heterogeneity. Meta-regression analysis did not find a significant difference in the estimated intervention effect in the primary prevention and the secondary prevention trials. In the 56 trials with a low risk of bias, the antioxidant supplements significantly increased mortality (18,833 dead/146,320 (12.9%) versus 10,320 dead/97,736 (10.6%); RR 1.04, 95% CI 1.01 to 1.07). This effect was confirmed by trial sequential analysis. Excluding factorial trials with potential confounding showed that 38 trials with low risk of bias demonstrated a significant increase in mortality (2822 dead/26,903 (10.5%) versus 2473 dead/26,052 (9.5%); RR 1.10, 95% CI 1.05 to 1.15). In trials with low risk of bias, beta-carotene (13,202 dead/96,003 (13.8%) versus 8556 dead/77,003 (11.1%); 26 trials, RR 1.05, 95% CI 1.01 to 1.09) and vitamin E (11,689 dead/97,523 (12.0%) versus 7561 dead/73,721 (10.3%); 46 trials, RR 1.03, 95% CI 1.00 to 1.05) significantly increased mortality, whereas vitamin A (3444 dead/24,596 (14.0%) versus 2249 dead/16,548 (13.6%); 12 trials, RR 1.07, 95% CI 0.97 to 1.18), vitamin C (3637 dead/36,659 (9.9%) versus 2717 dead/29,283 (9.3%); 29 trials, RR 1.02, 95% CI 0.98 to 1.07), and selenium (2670 dead/39,779 (6.7%) versus 1468 dead/22,961 (6.4%); 17 trials, RR 0.97, 95% CI 0.91 to 1.03) did not significantly affect mortality. In univariate meta-regression analysis, the dose of vitamin A was significantly associated with increased mortality (RR 1.0006, 95% CI 1.0002 to 1.001, P = 0.002).

AUTHORS' CONCLUSIONS

We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing.

Oxidative stress in asthma

Asthma is a chronic inflammatory lung disease that results in airflow limitation, hyperreactivity, and airway remodeling. There is strong evidence that an imbalance between the reducing and oxidizing systems favoring a more oxidative state is present in asthma. Endogenous and exogenous reactive oxygen species, such as superoxide anion, hydroxyl radical, hypohalite radical, and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide, peroxynitrite, and nitrite, play a major role in the airway inflammation and are determinants of asthma severity. Asthma is also associated with decreased antioxidant defenses, such as superoxide dismutase, catalase, and glutathione. In this review, we will summarize the current knowledge and discuss the current and future strategies for the modulation of oxidative stress in asthma.

Dietary intake of α-linolenic acid and low ratio of n-6:n-3 PUFA are associated with decreased exhaled NO and improved asthma control

As recently described, adherence to the Mediterranean diet is associated with improved asthma control. However, evidence of how specific nutrients such as fatty acids and antioxidants may affect this relationship remains largely unknown. We aimed to examine the association between dietary intake of fatty acids and antioxidants and asthma control. A cross-sectional study was developed in 174 asthmatics, mean age of 40 (SD 15) years. Dietary intake was obtained by a FFQ, and nutritional content was calculated using Food Processor Plus™ software (ESHA Research, Inc., Salem, OR, USA). Good asthma control was defined by the combination of forced expiratory volume during the first second, exhaled NO (eNO) and Asthma Control Questionnaire (ACQ) score (control: forced expiratory volume in the first second ≥80 %; eNO ≤35 ppb; ACQ <1·0, scale 0-6 score). Multiple linear and logistic regression models were performed to analyse the associations between nutrients and asthma outcomes, adjusting for confounders. A high n-6:n-3 PUFA ratio predicted high eNO, whereas high intakes of n-3 PUFA, a-linolenic acid (ALA) and SFA were associated with low eNO. Odds for controlled asthma improved along with an increased intake of n-3 PUFA (OR 0·14, 95% CI 0·04, 0·45; P for trend=0·001), SFA (OR 0·36, 95% CI 0·13, 0·97; P for trend=0·047) and ALA (OR 0·18, 95% CI 0·06, 0·58; P for trend=0·005). A high n-6:n-3 PUFA ratio increased the odds for uncontrolled asthma (OR 3·69, 95% CI 1·37, 9·94; P for trend=0·009), after adjusting for energy intake, sex, age, education and use of inhaled corticosteroids. Higher intakes of n-3 PUFA, ALA and SFA were associated with good asthma control, while the risk for uncontrolled asthma increased with a higher n-6:n-3 PUFA ratio. The present results introduce a protective effect of ALA in asthma control, independent of marine n-3 fatty acids, and provide a rationale to dietary intervention studies in asthma.

Vitamin C and asthma in children: modification of the effect by age, exposure to dampness and the severity of asthma

BACKGROUND

We previously found a significant benefit of vitamin C supplementation in asthmatic children.

PURPOSE

To test whether the effect of vitamin C on asthma is heterogeneous over the participant population.

METHODS

Egyptian asthmatic children between 7 and 10 years of age (n = 60) were included in the cross-over trial. They were administered 0.2 grams per day of vitamin C and placebo for separate 6-week periods. The variation in the vitamin C effect on two clinically relevant outcomes was analyzed: the childhood asthma control test (C-ACT), which measures the severity of asthma symptoms (the scale ranges from 0 to 27 points, < 20 points indicating unsatisfactory asthma control), and FEV1. We used linear modeling to examine the variation of the vitamin C effect in the subgroups.

RESULTS

The effect of vitamin C on the C-ACT was significantly modified by age and baseline C-ACT levels. In the children aged 7.0-8.2 years with a baseline C-ACT of 18 to 19 points, vitamin C increased the C-ACT score by 4.2 points (95% CI: 3.3-5.3); whereas in the children aged 8.3-10 years who had a baseline C-ACT of 14 to 15 points, vitamin C increased the C-ACT score by only 1.3 points (95% CI: 0.1-2.5). The effect of vitamin C on the FEV1 levels was significantly modified by age and exposure to dampness. In the children aged 7.0-8.2 years with no exposure to dampness, vitamin C increased the FEV1 level by 37% (95% CI: 34-40%), whereas in the children aged 8.3-10 years with exposure to dampness or mold in their bedroom more than one year prior to the study, vitamin C increased the FEV1 level by only 21% (95% CI: 18-25%).

CONCLUSIONS

We found strong evidence that the effect of vitamin C on asthmatic children is heterogeneous. Further research is needed to confirm our findings and identify the groups of children who would receive the greatest benefit from vitamin C supplementation.