Vitamin C in plasma is inversely related to blood pressure and change in blood pressure during the previous year in young Black and White women

Vitamin C: A Comprehensive Review of Its Role in Health, Disease Prevention, and Therapeutic Potential

Since Albert Szent-Györgyi discovered it and it became used in treating scurvy, vitamin C has attracted interest in many studies due to its unique properties. It is an important cofactor in the synthesis of collagen and hormones, and it is involved in immunity, iron absorption, and processes requiring antioxidants. Thus, this review aims to emphasize the importance and usefulness of vitamin C in improving quality of life and preventing various diseases (e.g., chronic diseases, cardiovascular diseases, cancer) but also for its use in treatments against infections, neurodegenerative diseases, and cancer. Although the studies presented provide essential information about the properties of VIC and its beneficial effect on health, some studies contradict these theories. In this respect, further studies on larger samples and over a longer period are needed to demonstrate the therapeutic potential of this nutrient. However, VIC remains a necessary vitamin that should be consumed daily to maintain optimal health and prevent deficiencies that can lead to scurvy and its associated complications.

Genetically Confirmed Optimal Causal Association of Cerebrospinal Fluid Metabolites With Hemorrhagic Stroke

Hemorrhagic stroke (HS) mainly includes intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH), both of which seriously affect the patient's prognosis. Cerebrospinal fluid (CSF) metabolites and HS showed a link in observational studies. However, the causal association between them is not clear. We aimed to establish the optimal causality of CSF metabolites with HS. Mendelian randomization (MR) was employed to identify associations between CSF metabolites and different sources of HS. Univariable MR and false discovery rates (FDR) were used to identify initial causal associations. Linkage disequilibrium score regression determined genetic correlations. Multiple sensitive analyses ensured the reliability of the results. Multivariable MR and MR Bayesian Model Averaging were used to identify the optimal causal associations. The combined effects of metabolites and HS were assessed by meta-analyses. Pathway analyses were performed to identify potential pathways of action. Reverse MR was also conducted to identify reverse causal associations. Finally, Corresponding blood metabolites were used to explore the multiple roles of metabolites. We identified 20 CSF metabolites and six metabolic pathways associated with ICH; 15 CSF metabolites and three metabolic pathways associated with SAH. Nineteen and seven metabolites were causally associated with deep and lobar ICH, respectively. CSF levels of mannose (OR 0.63; 95% CI 0.45-0.88; Pcombined = 0.0059) and N-acetyltaurine (OR 0.68; 95% CI 0.47-0.98; Pcombined = 0.0395) may serve as the optimal exposures for ICH and SAH, respectively. Additionally, CSF ascorbic acid 3-sulfate levels significantly decrease the risk of deep ICH (OR 0.79; 95% CI 0.66-0.94; p = 0.0065; PFDR = 0.091). Supplemental analysis of blood metabolites suggested multiple roles for CSF and blood N-formylanthranilic acid and hippurate. There are significant causal associations between CSF metabolites and HS, which provides a further rationale for the prevention and monitoring of ICH and SAH.

Nutraceuticals as Modulators of Molecular Placental Pathways: Their Potential to Prevent and Support the Treatment of Preeclampsia

Preeclampsia (PE) is a serious condition characterized by new-onset hypertension and proteinuria or organ dysfunction after the 20th week of gestation, making it a leading cause of maternal and fetal mortality worldwide. Despite extensive research, significant gaps remain in understanding the mechanisms underlying PE, contributing to the ineffectiveness of current prevention and treatment strategies. Consequently, premature cesarean sections often become the primary intervention to safeguard maternal and fetal health. Emerging evidence indicates that placental insufficiency, driven by molecular disturbances, plays a central role in the development of PE. Additionally, the maternal microbiome may be implicated in the pathomechanism of preeclampsia by secreting metabolites that influence maternal inflammation and oxidative stress, thereby affecting placental health. Given the limitations of pharmaceuticals during pregnancy due to potential risks to fetal development and concerns about teratogenic effects, nutraceuticals may provide safer alternatives. Nutraceuticals are food products or dietary supplements that offer health benefits beyond basic nutrition, including plant extracts or probiotics. Their historical use in traditional medicine has provided valuable insights into their safety and efficacy, including for pregnant women. This review will examine how the adoption of nutraceuticals can enhance dysregulated placental pathways, potentially offering benefits in the prevention and treatment of preeclampsia.

The Effects of Fenugreek Seed Consumption on Blood Pressure: A Systematic Review and Meta-analysis of Randomized Controlled Trials

INTRODUCTION

Cardiovascular diseases (CVDs) are growing health issues worldwide. Hypertension (HTN) is one of the most common among CVDs in all populations. Fenugreek has recently been the center of multiple investigations.

AIM

In this systematic review and meta-analysis, we aimed at gathering and summing up the existing literature regarding the impact of fenugreek seed on systolic blood pressure (SBP) and diastolic blood pressure (DBP).

METHODS

All major databases (MEDLINE, Cochrane library, EMBASE, and Web of Science) were searched from inception up to 28 June 2022. Relevant randomized controlled trials (RCTs) meeting the inclusion criteria were included and the required data was extracted. The pooled effects were reported as weighted mean differences (WMDs). I-squared test was used to detect between-study heterogeneities. Subgroup analyses were conducted to find sources of heterogeneities. P-values < 0.05 were considered as statistically significant.

RESULTS

Six RCTs including a total of 373 participants were included in the final meta-analysis. Fenugreek seed supplementation significantly reduced SBP (WMD: 3.46 mmHg, 95% CI - 6.33, - 0.59, P=0.018), but not DBP (WMD: 3.19 mmHg; 95% CI, - 5.82 to 12.21, P=0.488). Subgroup analyses showed that fenugreek seed administered in dosages ≥ 15 g/day and durations ≤ 12 weeks significantly reduced SBP and DBP.

CONCLUSION

Supplementation with fenugreek seed, especially in dosages ≥ 15 g/day and durations ≤ 12 weeks, might play a role in reducing SBP, but not DBP. However, further investigations are warranted to ensure the clinical relevance of these findings.

Vitamin C supplementation for diabetes management: A comprehensive narrative review

Growing evidence suggests that vitamin C supplementation may be an effective adjunct therapy in the management of people with diabetes. This paper critically reviews the current evidence on effects of vitamin C supplementation and its potential mechanisms in diabetes management. Evidence from meta-analyses of randomized controlled trials (RCTs) show favourable effects of vitamin C on glycaemic control and blood pressure that may be clinically meaningful, and mixed effects on blood lipids and endothelial function. However, evidence is mostly of low evidence certainty. Emerging evidence is promising for effects of vitamin C supplementation on some diabetes complications, particularly diabetic foot ulcers. However, there is a notable lack of robust and well-designed studies exploring effects of vitamin C as a single compound supplement on diabetes prevention and patient-important outcomes (i.e. prevention and amelioration of diabetes complications). RCTs are also required to investigate potential preventative or ameliorative effects of vitamin C on gestational diabetes outcomes. Oral vitamin C doses of 500-1000 mg per day are potentially effective, safe, and affordable for many individuals with diabetes. However, personalisation of supplementation regimens that consider factors such as vitamin C status, disease status, current glycaemic control, vitamin C intake, redox status, and genotype is important to optimize vitamin C's therapeutic effects safely. Finally, given a high prevalence of vitamin C deficiency in patients with complications, it is recommended that plasma vitamin C concentration be measured and monitored in the clinic setting.

Differential influences of serum vitamin C on blood pressure based on age and sex in normotensive individuals

Aim

Hypertension is among the most prevalent chronic diseases with diverse etiology, affecting over 1 billion people globally. In numerous studies, vitamin C inversely correlated with blood pressure and was suspected to have antihypertensive properties. Currently, there is conflicting evidence regarding the relationship between vitamin C and blood pressure, with most studies being conducted on hypertensive subjects. The principal objective of this project was to investigate the relationship between vitamin C and blood pressure in normotensive adult subjects.

Methods

A total of 2,533 individuals aged 20 years and above were enrolled in the present study from the National Health and Nutrition Examination Survey (NHANES) 2017-2018. Outcome variables were systolic blood pressure (SBP) and diastolic blood pressure (DBP). Serum vitamin C was regarded as an independent variable. EmpowerStats software and R (version 3.4.3) were used to examine the association between vitamin C and SBP or DBP.

Results

Vitamin C was reversely correlated with both SBP (β = −0.02, 95% CI: −0.03 to −0.00, p = 0.0306) and DBP (β = −0.02, 95% CI: −0.04 to −0.01, p = &lt;0.0011) after adjusting all covariates. This reverse relationship may be affected by a number of factors, including a person’s gender, age, race, and ethnicity. A U-shaped association between vitamin C and SBP in females and an inverted one between vitamin C and DBP in males were detected, respectively. We further calculated the inflection points at 90.3 μmol/L for females and 40 μmol/L for males. It is somewhat surprising that a reverse U-shaped distribution between vitamin C and SBP and DBP in people over 50 was detected, and the point of inflection of vitamin C were all located at 40 μmol/L.

Conclusion

Vitamin C was negatively correlated with both SBP and DBP in this cross-sectional analysis. However, a U-shaped relationship and an inverted one were also observed in certain people, which implied that, though vitamin C is considered a vital antioxidant, maintaining vitamin C at appropriate levels may be beneficial according to different populations.

Gamma-glutamyltransferase, arterial remodeling and prehypertension in a healthy population at low cardiometabolic risk

Plasma gamma-glutamyltransferase (GGT) was suggested to reflect the level of systemic oxidative stress. Oxidative stress induces changes in arterial structure and function and contributes to the development of hypertension. Therefore, GGT may be associated with arterial remodeling and blood pressure (BP) increment, even in absence of disease. To test this hypothesis, we evaluated, in 825 healthy subjects at low cardiometabolic risk, the associations of plasma GGT with carotid artery intima-media thickness (IMT), luminal diameter and prehypertension; in 154 subjects was evaluated also the association with aortic stiffness (cfPWV). Associations were controlled for insulin sensitivity, C-reactive protein, and life-style habits. In the main population, BP was remeasured after 3 years. Carotid diameter and cfPWV, but not IMT, were directly and independently related to plasma GGT. Subjects with prehypertension (N = 330) had higher GGT as compared with subjects with normal BP (22 [14] vs 17 [11] IU/L; adjusted P = 0.001), and within prehypertensive subjects, those who developed hypertension during 3 years had higher GGT than those without incident hypertension (27 [16] vs 21 [14] IU/L; adjusted P < 0.05). Within subjects with arterial stiffness measurement, those with prehypertension (N = 79) had higher both GGT and arterial stiffness (25 [14] vs 16 [20] IU/L and 9.11 ± 1.24 vs 7.90 ± 0.94 m/s; adjusted P < 0.01 and <0.05). In the view of previous evidence linking plasma GGT concentration to the level of systemic oxidative stress, our findings suggest a role of oxidative stress in subclinical arterial damage and in prehypertension, even in healthy subjects free of cardiometabolic risk. Arterial organ damage may represent the link between GGT and hypertension.

Nutraceuticals and blood pressure control: a European Society of Hypertension position document

: High-normal blood pressure (BP) is associated with an increased risk of cardiovascular disease, however the cost-benefit ratio of the use of antihypertensive treatment in these patients is not yet clear. Some dietary components and natural products seems to be able to significantly lower BP without significant side effects. The aim of this position document is to highlight which of these products have the most clinically significant antihypertensive action and wheter they could be suggested to patients with high-normal BP. Among foods, beetroot juice has the most covincing evidence of antihypertensive effect. Antioxidant-rich beverages (teas, coffee) could be considered. Among nutrients, magnesium, potassium and vitamin C supplements could improve BP. Among nonnutrient-nutraceuticals, soy isoflavones could be suggested in perimenopausal women, resveratrol in insulin-resistant patients, melatonin in study participants with night hypertension. In any case, the nutracutical approach has never to substitute the drug treatment, when needed.

Vitamin C supplementation improves blood pressure and oxidative stress after acute exercise in patients with poorly controlled type 2 diabetes mellitus: A randomized, placebo-controlled, cross-over study

This study aimed to assess the effect of Vitamin C on blood pressure (BP), and subsequently on oxidative stress and nitric oxide (NO) release, following the low-intensity exercise in the patients. This study included 24 patients with type 2 diabetes mellitus (T2D) (age, 53 ± 7 years; hemoglobin A1c, 10.1% ± 0.9%) randomized into two 6-week daily arms based on the consumption of either placebo or 1000 mg Vitamin C. The crossover trial occurred after a 6-week washout. Before and after both supplementation arms, all patients performed cycling exercise at 33% of peak oxygen consumption for 20 min. BP was measured before, immediately, and 60 min after the exercise. Blood samples were drawn immediately before and after the exercise to determine plasma ascorbate, malondialdehyde (MDA), F₂-isoprostanes (F₂-IsoPs), and NO concentrations. Data showed significant lower BP in the Vitamin C arm when compared with the placebo arm (systolic BP [SBP] P < 0.001 at every time point, diastolic BP [DBP] P < 0.001 except at immediately after exercise, P < 0.05). Plasma ascorbate concentration (P < 0.05 at every time point) and plasma NO (at resting P < 0.001, immediately after exercise P < 0.05) were significantly increased in the Vitamin C arm than in the placebo arm. Plasma MDA (P < 0.05 at every time point) and F₂-IsoPs (P < 0.05 at every time point) concentrations were significantly lower in the Vitamin C arm than in the placebo arm. In addition, data showed significantly lower SBP (P < 0.001 at every time point), DBP (P < 0.001 except at immediately after exercise P < 0.05), plasma MDA (P < 0.001 at every time point), and F₂-IsoPs (P < 0.05 at every time point) at post-supplementation than at pre-supplementation. Besides, there were significantly higher plasma ascorbate (P < 0.05 at every time point) and NO (at rest P < 0.01, immediately after exercise P < 0.05) concentrations at post-supplementation than at pre-supplementation. This is in contrast to the placebo treatment arm which demonstrated no statistical difference in all outcomes throughout the experiment. This study suggests that 6-week Vitamin C supplementation decreased preexercise and postexercise BPs, possibly due to improved oxidative stress and NO release. However, exercise had no effect on any outcome measures.

Vitamin C and Cardiovascular Disease: An Update

The potential beneficial effects of the antioxidant properties of vitamin C have been investigated in a number of pathological conditions. In this review, we assess both clinical and preclinical studies evaluating the role of vitamin C in cardiac and vascular disorders, including coronary heart disease, heart failure, hypertension, and cerebrovascular diseases. Pitfalls and controversies in investigations on vitamin C and cardiovascular disorders are also discussed.

BKCa channel is a molecular target of vitamin C to protect against ischemic brain stroke

Epidemiological studies have demonstrated that vitamin C decreases the risk of stroke, which has generally been ascribed to its function as antioxidant and free radical scavenger. However, whether there is a defined molecular target for vitamin C on stroke is unknown. Utilizing middle cerebral artery occlusion (MCAO) in rats as a model for ischemic stroke, we demonstrated that long-term, low-dose administration of vitamin C prior to MCAO could exert significant neuroprotective effect on the brain damage. The long-term, low-dose vitamin C pretreated rats had decreased brain infarct size and decreased neurological deficit score compared with the vehicle or single high dose pretreated MCAO rats. Furthermore, electrophysiological experiments using patch clamp technique showed that vitamin C increased the whole-cell current of the large-conductance Ca²⁺-activated K⁺ (BK_Ca) channel. Moreover, vitamin C increased the open probability of the channel without change its amplitude. Importantly, blockade of the BK_Ca channels abolished the neuroprotective effect of vitamin C on MCAO. Therefore, this study shows that long-term, low-dose pretreatment with vitamin C could reduce MCAO-induced brain damage through activation of the BK_Ca channels, suggesting that the BK_Ca channel is a molecular target of vitamin C on stroke.

Cohort study of microelement status in "healthy" population of Russian megapolis

The aim of the study was at the cohort assessment of microelement status in large city residents classified as “apparently healthy people”. The population study included 2,025 randomly selected middle-aged (2045 years) persons without chronic diseases or acute infectious pathologies. The set of subjects was standardized by age and gender. A blood sample was taken once from each person to determine concentrations of microelements. The level of peripheral blood microelements were determined by atomic absorption spectrometry using «Shimadzu AA7000» device (Japan). The study of a large population of city residents demonstrated inhomogeneity in their microelement status. Deficit conditions were found for a number of values, including concentrations of potassium, sodium, nickel, stibium, chromium and cadmium. At the same time, there are large proportions of persons with low plasma concentrations of copper and even lower plasma concentrations of zinc and magnesium. On the contrary, 42% of the persons show high concentrations of lithium. Such disturbances of microelement homeostasis (pre-pathological condition) make it necessary to perform targeted correction for the purpose of preventing the development of pathological conditions associated with microelement deficiencies.

Obesity, cardiovascular disease, and role of vitamin C on inflammation: a review of facts and underlying mechanisms

Obesity means the accumulation of excessive fat that may interfere with the maintenance of optimal state of health. Obesity causes cardiac and vascular disease through well-known mediators such as hypertension, type-2 diabetes mellitus, and dyslipidemia, but there are evidences for other mediators such as chronic inflammation, oxidative stress, and thrombosis. The decreased levels of antioxidants factors and nitric oxide predispose to further cardiovascular adverse events. To reduce the risks, antioxidants can help by neutralizing the free radicals and protecting from damage by donating electrons. Having the capacity, vitamin C protects from oxidative stress, prevention of non-enzymatic glycosylation of proteins, and enhances arterial dilation through its effect on nitric oxide release. It also decreases lipid peroxidation, and alleviates inflammation. The anti-inflammatory property of vitamin C could be attributed to ability to modulate the NF-_kB DNA binding activity and down-regulation in the hepatic mRNA expression for the interleukins and tumor factors.

Food and plant bioactives for reducing cardiometabolic disease risk: an evidence based approach

Nutraceuticals active on the main cardiovascular disease risk factors.

Relationships between micronutrient losses in sweat and blood pressure among heat-exposed steelworkers

We aimed to examine the effect of micronutrient losses through sweat on blood pressure (BP) among heat-exposed steelworkers. A total of 224 heat-exposed male steelworkers from an ironworks facility were evaluated in July 2012. We measured the Wet Bulb Globe Temperature Index to evaluate the level of heat stress in the workplace. We collected sweat from the workers during an eight-hour work, and then we measured the micronutrients in the sweat. We also measured the BP of each worker. The results revealed that vitamin C, potassium, and calcium losses in sweat were positively correlated with systolic (SBP) and diastolic (DBP) blood pressure (all P<0.05). A linear stepwise regression analysis revealed that potassium, and calcium losses in sweat adversely affected SBP and DBP (all P<0.05). An analysis of covariance showed that SBP increased when potassium or calcium losses in sweat were >900 mg, or >100 mg, respectively. Further, DBP increased when potassium or calcium losses in sweat were >600 mg or >130 mg, respectively. Therefore, vitamin C, potassium, and calcium losses in sweat may adversely effect BP. To help steelworkers maintain healthy BP, facilities with high temperatures should try to lower environmental temperatures to reduce vitamin C, potassium, and calcium losses in sweat. Additionally, heat-exposed steelworkers may need to increase their dietary intakes of vitamin C, potassium, and calcium. Further research is needed to confirm these findings and support these recommendations.

Nutraceuticals with a clinically detectable blood pressure-lowering effect: a review of available randomized clinical trials and their meta-analyses

AIMS

The aim of the present study was to review and comment on the available evidence on nutraceuticals with a clinically demonstrable blood pressure (BP)-lowering effect.

METHODS

We reviewed studies published in the English language from 1990 to 2015 on dietary supplements or nutraceuticals claiming to show an effect on human BP. An initial list of possibly effective agents and studies was obtained from the online reference, the Natural Medicine Comprehensive Database. Using PubMed, we searched agents identified from this list using the MeSH terms 'hypertension', 'blood pressure', 'dietary supplement' and 'nutraceuticals', alone and in combination. We then focused our attention on meta-analyses and randomized clinical trials.

RESULTS

Beyond the well-known effects on BP of the Dietary Approaches to Stop Hypertension (DASH) and the Mediterranean diet, a large number of studies have investigated the possible BP-lowering effect of different dietary supplements and nutraceuticals, most of which are antioxidant agents with a high tolerability and safety profile. In particular, a relatively large body of evidence supports the use of potassium, magnesium, L-arginine, vitamin C, cocoa flavonoids, beetroot juice, coenzyme Q10, controlled-release melatonin and aged garlic extract. The antihypertensive effect of all these nutraceuticals seems to be dose related and the overall tolerability is good.

CONCLUSION

Some nutraceuticals might have a positive impact on BP in humans. Further clinical research is needed, to identify from the available active nutraceuticals those with the best cost-effectiveness and risk-benefit ratio for widespread and long-term use in the general population with a low-added cardiovascular risk related to uncomplicated hypertension.

Plasma Ascorbic Acid, A Priori Diet Quality Score, and Incident Hypertension: A Prospective Cohort Study

Vitamin C may reduce risk of hypertension, either in itself or by marking a healthy diet pattern. We assessed whether plasma ascorbic acid and the a priori diet quality score relate to incident hypertension and whether they explain each other's predictive abilities. Data were from 2884 black and white adults (43% black, mean age 35 years) initially hypertension-free in the Coronary Artery Risk Development in Young Adults Study (study year 10, 1995-1996). Plasma ascorbic acid was assessed at year 10 and the diet quality score at year 7. Eight-hundred-and-forty cases of hypertension were documented between years 10 and 25. After multiple adjustments, each 12-point (1 SD) higher diet quality score at year 7 related to mean 3.7 μmol/L (95% CI 2.9 to 4.6) higher plasma ascorbic acid at year 10. In separate multiple-adjusted Cox regression models, the hazard ratio of hypertension per 19.6-μmol/L (1 SD) higher ascorbic acid was 0.85 (95% CI 0.79-0.92) and per 12-points higher diet score 0.86 (95% CI 0.79-0.94). These hazard ratios changed little with mutual adjustment of ascorbic acid and diet quality score for each other, or when adjusted for anthropometric variables, diabetes, and systolic blood pressure at year 10. Intake of dietary vitamin C and several food groups high in vitamin C content were inversely related to hypertension, whereas supplemental vitamin C was not. In conclusion, plasma ascorbic acid and the a priori diet quality score independently predict hypertension. This suggests that hypertension risk is reduced by improving overall diet quality and/or vitamin C status. The inverse association seen for dietary but not for supplemental vitamin C suggests that vitamin C status is preferably improved by eating foods rich in vitamin C, in addition to not smoking and other dietary habits that prevent ascorbic acid from depletion.

Nutraceuticals and Blood Pressure Control: Results from Clinical Trials and Meta-Analyses

Beyond the well-known effects on blood pressure (BP) of the dietary approaches to stop hypertension (DASH) and the Mediterranean diets, a large number of studies has investigated the possible BP lowering effect of different dietary supplements and nutraceuticals, the most part of them being antioxidant agents with a high tolerability and safety profile. In particular relatively large body of evidence support the use of potassium, L-arginine, vitamin C, cocoa flavonoids, beetroot juice, coenzyme Q10, controlled-release melatonin, and aged garlic extract. However there is a need for data about the long-term safety of a large part of the above discussed products. Moreover further clinical research is advisable to identify between the available active nutraceuticals those with the best cost-effectiveness and risk-benefit ratio for a large use in general population with low-added cardiovascular risk related to uncomplicated hypertension.

Dietary patterns and physical inactivity, two contributing factors to the double burden of malnutrition among adults in Burkina Faso, West Africa

A population-based cross-sectional study was carried out in the northern neighbourhoods of Ouagadougou (Burkina Faso), to examine the relationship of nutritional deficiencies and cardiometabolic risk factors (CMRF) with lifestyle in adults. We randomly selected 330 households stratified by income tertile. In each income stratum, 110 individuals aged 25-60 years and having lived in Ouagadougou for at least 6 months were randomly selected. We performed anthropometric, dietary intake and physical activity measurements, and blood sample collection. Cluster analysis of dietary intake identified two dietary patterns: 'urban' (29 % of subjects) and 'traditional' (71 %). The 'urban' cluster exhibited a higher intake of fat and sugar, whereas a higher intake of plant protein, complex carbohydrate and fibre was observed in the 'traditional' pattern. Female sex, low income and lack of education were associated with the 'traditional' cluster, as well as Fe and vitamin A deficiency. CMRF prevalence (abdominal obesity, hypertension, hyperglycaemia, dyslipidaemia) was similar in both clusters. Subjects in the 'traditional' cluster spent more time in physical activity and had less sedentary time than those in the 'urban' cluster. 'Traditional' dietary pattern, low income, female sex and sedentary time were significant contributing factors to the double burden of malnutrition. The rapid nutrition transition is reflected in this co-occurrence of CMRF and nutritional deficiencies. This stresses the need for prevention strategies addressing both ends of the nutrition spectrum.

Translation and validation of the dietary approaches to stop hypertension for koreans intervention: culturally tailored dietary guidelines for Korean Americans with high blood pressure

BACKGROUND

Lifestyle modification strategies such as adoption of the Dietary Approaches to Stop Hypertension (DASH) diet are now recognized as an integral part of high blood pressure (HBP) management. Although the high prevalence of HBP among Korean Americans (KAs) is well documented, few dietary interventions have been implemented in this population, in part because of a lack of culturally relevant nutrition education guidelines. Translating and testing the efficacy of culturally relevant dietary recommendations using a well-established dietary guideline such as DASH are imperative for promoting better cardiovascular health for this high-risk cultural group.

OBJECTIVE

The aims of this study were to systematically translate and validate a culturally modified DASH for Koreans (K-DASH) and obtain preliminary evidence of efficacy.

METHODS

A 2-step approach of intervention translation and efficacy testing, together with close adherence to principles of community-based participatory research, was used to maximize community input. A 1-group pre-post design with 24-hour urine and 24-hour ambulatory blood pressure monitoring comparisons was used to test the initial feasibility and efficacy of the K-DASH intervention.

RESULTS

A total of 28 KAs with HBP participated in a 10-week dietary intervention consisting of group education sessions and individual counseling. Both systolic blood pressure and diastolic blood pressure, as measured by ambulatory blood pressure monitoring, were significantly decreased at postintervention evaluation (systolic blood pressure, -4.5 mm Hg; diastolic blood pressure, -2.6 mm Hg; P < .05). Serum low-density lipoprotein cholesterol was significantly decreased (-7.3 mg/dL; P < .05). Serum potassium and ascorbic acid levels were also improved in the reference range. Urine potassium level was significantly increased, supporting increased fruit and vegetable consumption.

CONCLUSION

This pilot study has (a) demonstrated that a cultural adaptation of DASH using community-based participatory research methodology produced a culturally relevant and efficacious dietary intervention for the KAs with HBP and (b) provided strong preliminary evidence for the efficacy of the K-DASH intervention in reducing HBP in hypertensive KAs.

The role of nutrition and nutraceutical supplements in the treatment of hypertension

Vascular biology, endothelial and vascular smooth muscle and cardiac dysfunction play a primary role in the initiation and perpetuation of hypertension, cardiovascular disease and target organ damage. Nutrient-gene interactions and epigenetics are predominant factors in promoting beneficial or detrimental effects in cardiovascular health and hypertension. Macronutrients and micronutrients can prevent, control and treat hypertension through numerous mechanisms related to vascular biology. Oxidative stress, inflammation and autoimmune dysfunction initiate and propagate hypertension and cardiovascular disease. There is a role for the selected use of single and component nutraceutical supplements, vitamins, antioxidants and minerals in the treatment of hypertension based on scientifically controlled studies which complement optimal nutrition, coupled with other lifestyle modifications.

Evidence of clinically relevant efficacy for dietary supplements and nutraceuticals

Beyond the well-known effects on blood pressure (BP) of the DASH and the Mediterranean diets, a large number of studies have investigated the possible a BP-lowering effect from different dietary supplements and nutraceuticals, mostly antioxidant agents with a high tolerability and safety profile. In particular, a relatively large body of evidence support the use of potassium, L-arginine, vitamin C, cocoa flavonoids, coenzyme Q10, controlled-release melatonin, and aged garlic extract. However there is a need for data about the long-term safety of a large part of these products. Moreover, further clinical research is advisable to identify between the available active nutraceuticals and those with the best cost-effectiveness and risk-benefit ratio for widespread use in a general population with low added cardiovascular risk related to uncomplicated hypertension.

Vitamin C intake, circulating vitamin C and risk of stroke: a meta-analysis of prospective studies

Background

Though vitamin C supplementation has shown no observed effects on stroke prevention in several clinical trials, uncertainty remains as to whether long‐term, low‐dose intake influences the development of stroke among general populations. Furthermore, the association between circulating vitamin C and the risk of stroke is also unclear. For further clarification of these issues, we conducted a meta‐analysis of prospective studies.

Methods and Results

PubMed and EMBASE databases were searched, and the bibliographies of the retrieved articles were also reviewed to identify eligible studies. Summary relative risk (RRs) with corresponding 95% confidence intervals (CIs) were computed with a random‐effects model. The summary RR for the high‐versus‐low categories was 0.81 (95% CI: 0.74 to 0.90) for dietary vitamin C intake (11 studies), and 0.62 (95% CI: 0.49 to 0.79) for circulating vitamin C (6 studies). The summary RR for each 100 mg/day increment in dietary vitamin C was 0.83 (95% CI: 0.75 to 0.93) (10 studies), and for each 20 μmol/L increment in circulating vitamin C was 0.81 (95% CI: 0.75 to 0.88) (5 studies). Few studies reported results for vitamin C supplements (RR for high‐versus‐low intake=0.83, 95% CI: 0.62 to 1.10, 3 studies).

Conclusions

This meta‐analysis suggests significant inverse relationships between dietary vitamin C intake, circulating vitamin C, and risk of stroke.

The double burden of malnutrition and cardiometabolic risk widens the gender and socio-economic health gap: a study among adults in Burkina Faso (West Africa)

OBJECTIVE

To document the double burden of malnutrition and cardiometabolic risk factors (CMRF) in adults and its occurrence according to different sociodemographic parameters.

DESIGN

Population-based cross-sectional observational study. We first randomly selected 330 households stratified by tertile of the income levels proxy as low, middle and high income.

SETTING

Northern district of Ouagadougou, the capital city of Burkina Faso.

SUBJECTS

In each income stratum, 110 individuals aged 25-60 years and who had lived permanently in Ouagadougou for at least 6 months were randomly selected, followed with collection of anthropometric, socio-economic and clinical data, and blood samples.

RESULTS

The overall obesity/overweight prevalence was 24.2 % and it was twice as high in women as in men (34.1 % v. 15.5 %, P < 0.001). Hypertension, hyperglycaemia and low HDL cholesterol prevalence was 21.9 %, 22.3 % and 30.0 %, respectively, without gender difference. The prevalence of the metabolic syndrome was 10.3 %. Iron depletion and vitamin A deficiency affected 15.7 % and 25.7 % of participants, respectively, with higher rates in women. Coexistence of at least one nutritional deficiency and one CMRF was observed in 23.5 % of participants, and this 'double burden' was significantly higher in women than in men (30.4 % v. 16.1 %, P = 0.008) and in the low income group.

CONCLUSIONS

CMRF are becoming a leading nutritional problem in adults of Ouagadougou, while nutritional deficiencies persist. The double nutritional burden exacerbates health inequities and calls for action addressing both malnutrition and nutrition-related chronic diseases.

Authors' perspective: What is the optimum intake of vitamin C in humans?

The recommended dietary allowance (RDA) of vitamin C has traditionally been based on the prevention of the vitamin C deficiency disease, scurvy. While higher intakes of vitamin C may exert additional health benefits, the limited Phase III randomized placebo-controlled trials (RCTs) of vitamin C supplementation have not found consistent benefit with respect to chronic disease prevention. To date, this has precluded upward adjustments of the current RDA. Here we argue that Phase III RCTs-designed principally to test the safety and efficacy of pharmaceutical drugs-are ill suited to assess the health benefits of essential nutrients; and the currently available scientific evidence is sufficient to determine the optimum intake of vitamin C in humans. This evidence establishes biological plausibility and mechanisms of action for vitamin C in the primary prevention of coronary heart disease, stroke, and cancer; and is buttressed by consistent data from prospective cohort studies based on blood analysis or dietary intake and well-designed Phase II RCTs. These RCTs show that vitamin C supplementation lowers hypertension, endothelial dysfunction, chronic inflammation, and Helicobacter pylori infection, which are independent risk factors of cardiovascular diseases and certain cancers. Furthermore, vitamin C acts as a biological antioxidant that can lower elevated levels of oxidative stress, which also may contribute to chronic disease prevention. Based on the combined evidence from human metabolic, pharmacokinetic, and observational studies and Phase II RCTs, we conclude that 200 mg per day is the optimum dietary intake of vitamin C for the majority of the adult population to maximize the vitamin's potential health benefits with the least risk of inadequacy or adverse health effects.

Vitamin C activation of the biosynthesis of epoxyeicosatrienoic acids

The cardiovascular effects of vitamin C (VitC) could be mediated by epoxyeicosatrienoic acids (EETs). We aimed to study the mechanism of VitC-dependent microsomal formation of cis- and trans-EETs and the regulation of EET levels in rat isolated perfused kidneys and in vivo. VitC biphasically stimulated rat kidney microsomal cis- and trans-EET formation in a ratio of 1:2, involving the participation of lipid hydroperoxides (LOOHs), Fe²⁺, and cytochrome P450 (CYP). Levels of LOOHs correlated with microsomal EET production. LOOH stimulation of CYP isoforms resulted in preferred trans-over cis-EET formation from arachidonic acid and was associated with the cleavage of LOOHs, which indicated a CYP peroxygenase activity. EETs contributed to VitC-induced vasodilator responses in rat isolated perfused kidneys. VitC (1 mg/ml) given in the drinking water for 9 days doubled rat urinary EET excretion, increased plasma levels of EETs, mostly trans-EETs, by 40%, and reduced plasma levels of 20-hydroxyeicosatetraenoic acid. Depletion of VitC in brain cortex and kidney tissues by more than 20- and 50-fold, respectively, in gulonolactone oxidase-knockout mice was associated with mild increases in tissue EETs. These data suggest that LOOHs are a determinant factor for EET formation in vivo in which VitC exerts a key regulatory effect. VitC-activated CYP peroxygenase activity may represent a CYP interaction with lipoxygenases and cyclooxygenases to mediate the cardiovascular effects of VitC via formation of EETs.

Association between plasma vitamin C concentrations and blood pressure in the European prospective investigation into cancer-Norfolk population-based study

The effect of fruit and vegetable consumption and blood pressure is unclear. A population-based cross-sectional study was conducted in 20 926 men and women aged 40 to 79 years participating in the European Prospective Investigation Into Cancer-Norfolk who completed a health questionnaire and attended a clinic from 1993 to 1997. The relationship between plasma vitamin C concentrations, as an indicator of fruit and vegetable intake, and systolic BP was examined. The magnitude of their association was assessed using dichotomized values of high (≥140 mm Hg) and low (<140 mm Hg) systolic blood pressure. A total of 20 926 participants (46% men; mean [SD] 58.5 years [9.2 years]) were included after excluding participants with any missing data for variables of interest. People with high vitamin C concentrations had lower clinic blood pressure. The likelihood of having high blood pressure was 22% lower (odds ratio: 0.78 [95% CI: 0.71 to 0.86]) for those who were in the top quartiles of plasma vitamin C levels compared with the bottom quartiles after adjusting for age, sex, body mass index, cholesterol, prevalent medical conditions, smoking, physical activity, alcohol consumption, social class, education, use of vitamin C-containing supplement, and antihypertensive medication. Sex-specific analysis, as well as repeated analysis after exclusion of people who used vitamin C-containing supplements or who were taking antihypertensive medication, did not alter the results. There appears to be a strong association between vitamin C concentrations, an indicator of fruit and vegetable consumption, and a lower level of blood pressure. This may provide further evidence for health benefits of dietary patterns with higher fruit and vegetable consumption.

Nutrition transition among adolescents of a south-Mediterranean country: dietary patterns, association with socio-economic factors, overweight and blood pressure. A cross-sectional study in Tunisia

BACKGROUND

The increase in the burden of chronic diseases linked to the nutrition transition and associated dietary and lifestyle changes is of growing concern in south and east Mediterranean countries and adolescents are at the forefront of these changes. This study assessed dietary intake and association with socio-economic factors and health outcomes among adolescents in Tunisia.

METHODS

Cross-sectional survey (year 2005); 1019 subjects 15-19 y. from a clustered random sample. Dietary intake was assessed by a validated semi-quantitative frequency questionnaire (134 items) as was physical activity; the Diet Quality Index International measured diet quality; dietary patterns were derived by multiple correspondence analysis from intakes of 43 food groups. Body Mass Index (BMI) ≥ 85th and 95th percentile defined overweight and obesity. Waist Circumference (WC) assessed abdominal fat. High blood pressure was systolic (SBP) or diastolic blood pressure (DBP) ≥ 90th of the international reference for 15-17 y., and SBP/DBP ≥ 120/80 mm Hg for 18-19 y.

RESULTS

Energy intake levels were quite high, especially for females. The macro-nutrient structure was close to recommendations but only 38% had a satisfactory diet quality. A main traditional to modern dietary gradient, linked to urbanisation and increased economic level, featured an increasing consumption of white bread, dairy products, sugars, added fats and fruits and decreasing consumption of oils, grains, legumes and vegetables; regarding nutrients this modern diet score featured a decreasing relationship with total fat and an increase of calcium intake, but with an increase of energy, sugars and saturated fat, while vitamin C, potassium and fibre decreased. Adjusted for age, energy and physical activity, this modern pattern was associated with increased overweight in males (2nd vs. 1st tertile: Prevalence Odds-Ratio (POR) = 4.0[1.7-9.3], 3rd vs. 1st: POR = 3.3[1.3-8.7]) and a higher WC. Adjusting also for BMI and WC, among females, it was associated with decreased prevalence of high blood pressure (2nd vs. 1st tertile: POR = 0.5[0.3-0.8], 3rd vs. 1st tertile: POR = 0.4[0.2-0.8]).

CONCLUSION

The dietary intake contrasts among Tunisian adolescents, linked to socio-economic differentials are characteristic of a nutrition transition situation. The observed gradient of modernisation of dietary intake features associations with several nutrients involving a higher risk of chronic diseases but might have not only negative characteristics regarding health outcomes.

Vitamin C nutriture in newly diagnosed diabetes

This study was performed to investigate the relationship between serum L-ascorbic acid, vitamin C intake, and diabetes in a nested case-control study. A cross-sectional survey of diet and health was conducted in 2,048 adults with an age of 30 y or older in Yonchon County, Korea. An oral glucose tolerance test was administered to all participants. One hundred cases of newly diagnosed diabetes were identified. Two healthy controls for each case matched with age, gender, drinking status, and smoking status were selected among the survey participants. L-Ascorbic acid levels were analyzed in fasting serum samples and one 24-h dietary recall was performed. Dietary vitamin C intake of persons with diabetes was 50.1±47.6 mg/d and that of controls was 55.1±41.1 mg/d. People with diabetes (22.3±16.8 µmol/L) have lower serum ascorbic acid levels than their controls (26.3±17.0 µmol/L) and the difference was significant by paired t-test (p<0.01). The association between diabetes and serum ascorbic acid level was still significant in non-smokers (24.2±17.8 µmol/L for the diabetes group and 29.5±16.7 µmol/L for the control group, p<0.01) but not in smokers (19.4±15.7 µmol/L for the diabetes group and 21.2±16.0 µmol/L for the control group). Our results suggest that diabetes and smoking interactively affect serum ascorbic acid levels. Since this population had poor nutritional status of vitamin C, further investigation of association between serum ascorbic acid level and diabetes and smoking by the level of vitamin C consumption is warranted.

The Role of Antioxidant Vitamins in Cardiovascular Disease

Objective:

To review the current data on the role of antioxidant vitamins in cardiovascular disease.

Data Sources:

Articles were obtained from a MEDLINE search covering all years. Terms used in the search included combinations of antioxidant, vitamin, vitamin E, vitamin C, beta-carotene, and cardiovascular disease. Reference lists from articles were examined for additional references.

Study Selection and Data Extraction:

Randomized clinical trials were selected and evaluated for study design and data obtained. Observational studies, meta-analyses, and basic science articles were also reviewed for background.

Data Synthesis:

The use of dietary supplements, including vitamins, minerals, and herbal products, is common among patients in the US. Vitamin E, vitamin C, and beta-carotene are all supplements with reported antioxidant activity. Because oxidative stress has been implicated in the development of cardiovascular disease, there has been significant research at the basic science level as well as observational studies and randomized placebo-controlled trials examining the potential impact of vitamin E, vitamin C, and beta-carotene in the prevention and treatment of cardiovascular disease. While basic science data and data from observational studies have identified benefit from antioxidant vitamin supplementation, randomized clinical trials have failed to support a role for antioxidant vitamin supplementation in the prevention or treatment of cardiovascular disease.

Conclusions:

Data from randomized clinical trials do not support the use of antioxidant vitamins in cardiovascular disease. Therefore, antioxidant vitamins should not be recommended to patients for prevention or treatment of cardiovascular disease.

Haptoglobin genotype modifies the association between dietary vitamin C and serum ascorbic acid deficiency

BACKGROUND

Haptoglobin (which is encoded by the Hp gene) is a hemoglobin-binding protein that has antioxidant properties and a common polymorphism that consists of 2 structurally different alleles: Hp1 and Hp2. The capacity of Hp2 to inhibit oxidation and vitamin C depletion is less than that of Hp1, but the influence on vitamin C requirements remains unknown.

OBJECTIVE

This study aimed to determine whether the Hp polymorphism modifies the association between dietary vitamin C and serum ascorbic acid deficiency (<11 μmol/L).

DESIGN

Nonsmoking men and women (n = 1046) between 20 and 29 y of age participated in the Toronto Nutrigenomics and Health Study. Blood samples were collected after the subjects had fasted overnight to determine serum ascorbic acid concentrations by HPLC and for genotyping. A 196-item food-frequency questionnaire was used to estimate vitamin C intake.

RESULTS

A gene-diet interaction on serum ascorbic acid was observed (P = 0.02). The overall odds ratio (95% CI) for serum ascorbic acid deficiency was 2.84 (1.73, 4.65) for subjects who did not meet the Recommended Dietary Allowance for vitamin C compared with those who did. The corresponding odds ratios were 4.77 (2.36, 9.65) for the Hp2-2 genotype and 1.69 (0.80, 3.63) for carriers of the Hp1 allele.

CONCLUSIONS

Individuals with the Hp2-2 genotype had an increased risk of deficiency if they did not meet the Recommended Dietary Allowance for vitamin C, whereas carriers of the Hp1 allele did not. The findings suggest that the greater antioxidant capacity of Hp1 might spare serum ascorbic acid.

Dietary fiber and serum 16α-hydroxyestrone, an estrogen metabolite associated with lower systolic blood pressure

OBJECTIVE

We recently identified an inverse relation between systolic blood pressure (SBP) and serum 16α-hydroxyestrone, a metabolite of 17β-estradiol, in postmenopausal women. Formation of 16α-hydroxyestrone is catalyzed primarily by CYP1A2, a cytochrome P450 enzyme. The objective of this study was to evaluate the relations between known modifiers of CYP1A2 activity and serum 16α-hydroxyestrone in postmenopausal women. We hypothesized that fruits, vegetables, and grains, which contain more soluble fiber (a known inducer of CYP1A2) as a proportion of total fiber, would be more positively associated with serum 16α-hydroxyestrone than legumes, which contain less soluble fiber as a proportion of total fiber.

METHODS

Serum from a population-based sample of 42 postmenopausal women 55 to 69 y of age living in Cook County, Illinois, was assayed for 16α-hydroxyestrone using mass spectrometry. Ordinal logistic regression was used to evaluate the cross-sectional relation between dietary fiber and serum 16α-hydroxyestrone after adjusting for multiple covariates.

RESULTS

Compared with dietary fiber from legumes, dietary fiber from fruits and vegetables was associated with a greater log odds (B=0.201, P=0.036) of having higher serum concentrations of 16α-hydroxyestrone. The log odds of having higher serum concentrations of 16α-hydroxyestrone was also lower in African-American women (B=-2.300, P=0.030) compared with white women.

CONCLUSION

These results are consistent with previous studies demonstrating a negative relation between SBP and dietary fruits and vegetables and a positive relation between African-American race and SBP. Further research is needed regarding dietary factors that may influence the serum concentration of 16α-hydroxyestrone.

Nutrition and nutraceutical supplements in the treatment of hypertension

Macronutrient and micronutrient deficiencies are very common in the general population, and may be even more common in patients with hypertension and cardiovascular disease due to genetic and environmental causes, and prescription drug use. Vascular biology assumes a pivotal role in the initiation and perpetuation of hypertension and target organ damage sequelae. Endothelial activation, oxidative stress and vascular smooth muscle dysfunction (hypertrophy, hyperplasia and remodeling) are initial events that initiate hypertension. Nutrient-gene interactions determine a broad array of phenotypic consequences such as vascular problems and hypertension. Optimal nutrition, nutraceuticals, vitamins, antioxidants, minerals, weight loss, exercise, smoking cessation, and moderate restriction of alcohol and caffeine, in addition to other lifestyle modifications, can prevent, delay the onset, reduce the severity, treat and control hypertension in many patients. An integrative approach combining these lifestyle suggestions with the correct pharmacologic treatment will best achieve new goal blood pressure levels, reduce cardiovascular risk factors, improve vascular health, reduce target organ damage, including coronary heart disease, stroke, congestive heart failure and renal disease, and reduce healthcare expenditure. The expanded scientific roles for nutraceutical supplements will be discussed in relation to the prevention and treatment of essential hypertension and cardiovascular diseases.

The role of cellular micronutrient analysis, nutraceuticals, vitamins, antioxidants and minerals in the prevention and treatment of hypertension and cardiovascular disease

Macronutrient and micronutrient deficiencies are very common in the general population and may be even more common in patients with hypertension and cardiovascular disease due to genetic, environmental causes and prescription drug use. The Hypertension Institute in Nashville, TN, has evaluated micronutrient deficiencies and oxidation status, in a group of hypertensive versus normotensive patients. There are significant differences in numerous intracellular micronutrients and oxidation status between these two groups. Replacement of the micronutrient deficiencies, as well as high-dose therapy of selected nutraceuticals in combination with optimal diet, exercise and weight management resulted in control of blood pressure to goal levels in 62% of the hypertensive population (as defined by JNC 7) over a period of 6 months with complete tapering and discontinuation of antihypertensive drugs. These deficiencies will have an enormous impact on present and future cardiovascular health and outcomes such as hypertension, myocardial infarction, stroke and renal disease and overall health costs. It is estimated that the annual savings in drug costs alone for the treatment of hypertension could be as much as US$10 billion. Diagnosis and treatment of these nutrient deficiencies and improvement in oxidation status using functional intracellular assessments will reduce blood pressure, improve vascular health, endothelial dysfunction, vascular biology and cardiovascular events. Vascular biology assumes a pivotal role in the initiation and perpetuation of hypertension and target organ damage sequelae. Endothelial activation, oxidative stress, inflammation and vascular smooth muscle dysfunction are initial events that start hypertension. Nutrient-gene interactions determine a broad array of phenotypic consequences such as vascular problems and hypertension. Optimal nutrition, nutraceuticals, vitamins, antioxidants, minerals, weight loss, exercise, smoking cessation and moderate restriction of alcohol and caffeine in addition to other lifestyle modifications can prevent and control hypertension in many patients. An integrative approach combining these lifestyle suggestions with the correct pharmacologic treatment will best achieve new goal blood pressure levels, reduce cardiovascular risk factors, improve vascular biology and vascular health, reduce cardiovascular target organ damage and reduce healthcare expenditure. The expanded scientific roles for nutraceutical supplements are discussed in relation to the prevention and treatment of essential hypertension and cardiovascular diseases with emphasis on mechanisms of action and clinical integration with drug therapy with hypertension guidelines. It is the purpose of this paper to review only the hypertension clinical trials that have evaluated the clinical use and efficacy of nutrition, weight loss, exercise and selected nutritional supplements, vitamins, minerals and antioxidants. Numerous clinical trials have evaluated the use of nutritional supplements such as beta carotene, selenium, vitamin C and vitamin E in the prevention of coronary heart disease and stroke yielding conflicting results (positive, neutral and negative). In many of these clinical trials there are enormous clinical design problems, methodologic flaws, varied patient population, variable dose and type of vitamin use, improper selection of vitamin used and many other issues that make the studies difficult to interpret. It is beyond the scope of this paper to review these trials. The reader is referred to the vast literature on this subject.

Functional genetic variants of glutathione S-transferase protect against serum ascorbic acid deficiency

BACKGROUND

Glutathione S-transferases (GSTs) are detoxifying enzymes that contribute to the glutathione-ascorbic acid (vitamin C) antioxidant cycle.

OBJECTIVE

The objective was to determine whether GST genotypes modify the association between dietary vitamin C and serum ascorbic acid.

DESIGN

Nonsmoking men and women (n = 905) between 20 and 29 y of age were participants in the Toronto Nutrigenomics and Health Study. Overnight fasting blood samples were collected to determine serum ascorbic acid concentrations by HPLC and to genotype for deletion polymorphisms in GSTM1 and GSTT1 and an Ile105Val substitution in GSTP1. A 196-item food-frequency questionnaire was used to estimate vitamin C intake.

RESULTS

A gene-diet interaction on serum ascorbic acid was observed for GSTM1 (P = 0.04) and GSTT1 (P = 0.01) but not for GSTP1 (P = 0.83). The odds ratio (95% CI) for serum ascorbic acid deficiency (<11 micromol/L) was 3.20 (1.88, 5.44) for subjects who did not meet the Recommended Dietary Allowance of vitamin C compared with those who did. The corresponding odds ratios (95% CIs) were 2.17 (1.10, 4.28) and 12.28 (4.26, 33.42), respectively, for individuals with the GSTT1*1/*1 +*1/*0 (functional) and GSTT1*0/*0 (null) genotypes and 2.29 (0.96, 5.45) and 4.03 (2.01, 8.09), respectively, for the GSTM1*1/*1+GSTM1*1/*0 and GSTM1*0/*0 genotypes.

CONCLUSIONS

The recommended intake of vitamin C protects against serum ascorbic acid deficiency, regardless of genotype. Individuals with GST null genotypes had an increased risk of deficiency if they did not meet the Recommended Dietary Allowance for vitamin C, which suggests that the GST enzymes protect against serum ascorbic acid deficiency when dietary vitamin C is insufficient.

Vitamin C deficiency in a population of young Canadian adults

A cross-sectional study of the 979 nonsmoking women and men aged 20-29 years who participated in the Toronto Nutrigenomics and Health Study from 2004 to 2008 was conducted to determine the prevalence of serum ascorbic acid (vitamin C) deficiency and its association with markers of chronic disease in a population of young Canadian adults. High performance liquid chromatography was used to determine serum ascorbic acid concentrations from overnight fasting blood samples. A 1-month, 196-item food frequency questionnaire was used to assess dietary intakes. Results showed that 53% of subjects had adequate, 33% had suboptimal, and 14% had deficient levels of serum ascorbic acid. Subjects with deficiency had significantly higher measurements of mean C-reactive protein, waist circumference, body mass index, and blood pressure than did subjects with adequate levels of serum ascorbic acid. The odds ratio for serum ascorbic acid deficiency was 3.43 (95% confidence interval: 2.14, 5.50) for subjects who reported not meeting the recommended daily intake of vitamin C compared with those who did. Results suggest that 1 of 7 young adults has serum ascorbic acid deficiency, in part, because of unmet recommended dietary intakes. Furthermore, serum ascorbic acid deficiency is associated with elevated markers of chronic disease in this population of young adults, which may have long-term adverse health consequences.