Association between Dietary Nitrate, Nitrite Intake, and Site-Specific Cancer Risk: A Systematic Review and Meta-Analysis

Plant proteins: are they a good alternative to animal proteins in older people?

PURPOSE OF REVIEW

This review provides the latest insight into the impact of consuming plant-based protein for older people.

RECENT FINDINGS

According to the latest data, a healthy diet rich in plant-based-protein-rich-food could promote healthy aging. This health effect is partly because of the amino acid composition of proteins, as well as to the important constituents such as fiber and bioactive compounds found in the matrix. Furthermore, even though animal protein is more effective at stimulating muscle protein synthesis, a high consumption of plant protein (beyond 31 g/day) appears to enhance physical performance and reduce the risk of frailty in older individuals.

SUMMARY

Recent literature highlights numerous health benefits for older people associated with a substantial intake of plant-based vs. animal-based protein, both in preventing and mitigating chronic age-related diseases and reducing the risk of all-cause mortality. However, a high intake of plant-based protein-rich products could pose risks of malnutrition and fiber-related intestinal intolerances. Further research is needed to assess the risk-benefit ratio of a high consumption of plant proteins in older individuals before we can make robust recommendations on how far animal proteins can be healthfully replaced with plant proteins.

Beet supplementation mitigates post-exercise inflammation

Objectives

This study investigated the efficacy of a mixed beet-based supplement (BEET) versus placebo (PL) in countering inflammation during recovery from 2.25 h of intensive cycling in 20 male and female cyclists. A multi-omics approach was used that included untargeted proteomics and a targeted oxylipin panel.

Methods

A randomized, placebo-controlled, double-blind, crossover design was used with two 2-week supplementation periods and a 2-week washout period. Supplementation periods were followed by a 2.25 h cycling bout at close to 70%VO2max. The BEET supplement provided 212 mg of nitrates per day, 200 mg caffeine from green tea extract, 44 mg vitamin C from Camu Camu berry, B-vitamins from quinoa sprouts (40% Daily Value for thiamin, riboflavin, niacin, and vitamin B6), and 2.5 g of a mushroom blend containing Cordyceps sinensis and Inonotus obliquus. Six blood samples were collected before and after supplementation (overnight fasted state), immediately post-exercise, and at 1.5 h-, 3 h-, and 24 h-post-exercise.

Results

The 2.25 h cycling bout increased plasma levels of 41 of 67 oxylipins detected. BEET supplementation significantly increased plasma nitrate (NO3 -) and nitrite (NO2 -) (sum, NO3 - + NO2 -) concentrations (interaction effect, p < 0.001) and two anti-inflammatory oxylipins [18-hydroxyeicosapentaenoic acid (18-HEPE) and 4-hydroxy-docosahexanoic acid (4-HDoHE)]. The untargeted proteomics analysis identified 616 proteins (458 across all times points), and 2-way ANOVA revealed a cluster of 45 proteins that were decreased and a cluster of 21 that were increased in the BEET versus PL trials. Functional enrichment supported significant BEET-related reductions in inflammation-related proteins including several proteins related to complement activation, the acute phase response, and immune cell adhesion, migration, and differentiation.

Discussion

Intake of a BEET-based supplement during a 2-week period was linked to higher plasma levels of NO3 - + NO2 -, elevated post-exercise levels of two anti-inflammatory oxylipins, and a significant decrease in a cluster of proteins involved in complement activation and inflammation. These data support that 2-weeks intake of nitrate from a mixed beet-based supplement moderated protein biomarkers of exercise-induced inflammation in athletes.

The Nitrate-Nitrite-Nitric Oxide Pathway: Potential Role in Mitigating Oxidative Stress in Hypertensive Disorders of Pregnancy

Hypertensive diseases of pregnancy (HDPs) represent a global clinical challenge, affecting 5-10% of women and leading to complications for both maternal well-being and fetal development. At the heart of these complications is endothelial dysfunction, with oxidative stress emerging as a pivotal causative factor. The reduction in nitric oxide (NO) bioavailability is a vital indicator of this dysfunction, culminating in blood pressure dysregulation. In the therapeutic context, although antihypertensive medications are commonly used, they come with inherent concerns related to maternal-fetal safety, and a percentage of women do not respond to these therapies. Therefore, alternative strategies that directly address the pathophysiology of HDPs are required. This article focuses on the potential of the nitrate-nitrite-NO pathway, abundantly present in dark leafy greens and beetroot, as an alternative approach to treating HDPs. The objective of this review is to discuss the prospective antioxidant role of nitrate. We hope our discussion paves the way for using nitrate to improve endothelial dysfunction and control oxidative stress, offering a potential therapy for managing HDPs.

Formation and prediction of heterocyclic amines and N-nitrosamines in smoked sausages using back propagation artificial neural network

BACKGROUND

Heterocyclic amines (HAs) and N-nitrosamines (NAs) are formed easily during the thermal processing of food, and epidemiological studies have demonstrated that consuming HAs and NAs increases the risk of cancer. However, there are few studies on the application of back propagation artificial neural network (BP-ANN) models to simultaneously predict the content of HAs and NAs in sausages. This study aimed to investigate the effects of cooking time and temperature, smoking time and temperature, and fat-to-lean ratio on the formation of HAs and NAs in smoked sausages, and to predict their total content based on the BP-ANN model.

RESULTS

With an increase in processing time, processing temperature and fat ratio, the content of HAs and NAs in smoked sausages increased significantly, while the content of HA precursors and nitrite residues decreased significantly. The optimal network topology of the BP-ANN model was 5-11-2, the correlation coefficient values for training, validation, testing and all datasets were 0.99228, 0.99785, 0.99520 and 0.99369, respectively, and the mean squared error value of the best validation performance was 0.11326. The bias factor and the accuracy factor were within acceptable limits, and the predicted values approximated the true values, indicating that the model has good predictive performance.

CONCLUSION

The contents of HAs and NAs in smoked sausages were significantly influenced by the cooking conditions, smoking conditions and fat ratio. The BP-ANN model has high application value in predicting the contents of HAs and NAs in sausages, which provides a theoretical basis for the suppression of carcinogen formation. © 2024 Society of Chemical Industry.

N-Nitrosamines: a potential hazard in processed meat products

Nitrite, nitrate, and their salts are added to processed meat products to improve color, flavor, and shelf life and to lower the microbial burden. N-Nitrosamine compounds are formed when nitrosing agents (such as secondary nitrosamines) in meat products interact with nitrites and nitrates that have been added to the meat. With the consumption of such meat products, nitrosation reactions occur in the human body and N-nitrosamine formation occurs in the gastrointestinal tract. Despite the benefits nitrites and nitrates have on food, their tendency to create nitrosamines and an increase in the body's nitrous amine load presents health risks. The inclusion of nitrosamine compounds in possible and probable carcinogen classes according to the International Agency for Research on Cancer requires a re-examination of the literature review on processed meat products. This article evaluates the connections between various cancer types and nitrosamines found in processed meat products. © 2023 Society of Chemical Industry.

YTHDF1 mediates N-methyl-N-nitrosourea-induced gastric carcinogenesis by controlling HSPH1 translation

YT521-B homology (YTH) domain family (YTHDF) proteins serve as readers that directly recognise m6A modifications. In this study, we aim to probe the role of YTHDF1 in environmental carcinogen-induced malignant transformation of gastric cells and gastric cancer (GC) carcinogenesis. We established a long-term low-dose MNU-induced malignant transformation model in gastric epithelial cells. In vivo and in vitro experiments were conducted to validate the malignant phenotype and characterise the roles of YTHDF1 and its downstream genes in malignant transformation cells. Additionally, we explored downstream m6A modification targets of YTHDF1 using RNA-sequencing, RNA immunoprecipitation, and proteomics analyses, and conducted validation experiments in cell experiments and clinical samples. Long-term low-dose exposure of MNU converted normal Gges-1 cells into malignant cells. YTHDF1 mRNA and protein expression are increased in MNU-induced malignant cells (p<0.001). Meanwhile, YTHDF1 knockdown inhibits the malignant potential of MNU-treated cells (p<0.01). YTHDF1 knockdown specifically suppresses HSPH1 protein, but not RNA levels. RIP-qPCR validates HSPH1 is the target of YTHDF1 (p<0.01). HSPH1 knockdown impairs the malignant potential of MNU-induced transformed cells. The increased expression of the key regulatory factor YTHDF1 in MNU-induced gastric carcinogenesis affects malignant transformation and tumorigenesis by regulating the translation of downstream HSPH1. These findings provide new potential targets for preventing and treating environmental chemical-induced gastric carcinogenesis.

Polycyclic Aromatic Hydrocarbons and Pancreatic Cancer: An Analysis of the Blood Biomarker, r-1,t-2,3,c-4-Tetrahydroxy-1,2,3,4-tetrahydrophenanthrene and Selected Metabolism Gene SNPs

Exposure to polycyclic aromatic hydrocarbons (PAHs), byproducts of incomplete combustion, and their effects on the development of cancer are still being evaluated. Recent studies have analyzed the relationship between PAHs and tobacco or dietary intake in the form of processed foods and smoked/well-done meats. This study aims to assess the association of a blood biomarker and metabolite of PAHs, r-1,t-2,3,c-4-tetrahydroxy-1,2,3,4-tetrahydrophenanthrene (PheT), dietary intake, selected metabolism SNPs, and pancreatic cancer. Demographics, food-frequency data, SNPs, treatment history, and levels of PheT in plasma were determined from 400 participants (202 cases and 198 controls) and evaluated based on pancreatic adenocarcinoma diagnosis. Demographic and dietary variables were selected based on previously published literature indicating association with pancreatic cancer. A multiple regression model combined the significant demographic and food items with SNPs. Final multivariate logistic regression significant factors (p-value < 0.05) associated with pancreatic cancer included: Type 2 Diabetes [OR = 6.26 (95% CI = 2.83, 14.46)], PheT [1.03 (1.02, 1.05)], very well-done red meat [0.90 (0.83, 0.96)], fruit/vegetable servings [1.35 (1.06, 1.73)], recessive (rs12203582) [4.11 (1.77, 9.91)], recessive (rs56679) [0.2 (0.06, 0.85)], overdominant (rs3784605) [3.14 (1.69, 6.01)], and overdominant (rs721430) [0.39 (0.19, 0.76)]. Of note, by design, the level of smoking did not differ between our cases and controls. This study does not provide strong evidence that PheT is a biomarker of pancreatic cancer susceptibility independent of dietary intake and select metabolism SNPs among a nonsmoking population.

Dietary Nitrate from Plant Foods: A Conditionally Essential Nutrient for Cardiovascular Health

Under specific conditions, such as catabolic stress or systemic inflammation, endogenous nutrient production becomes insufficient and exogenous supplementation (for example, through dietary intake) is required. Herein, we propose consideration of a dietary nitrate from plant foods as a conditionally essential nutrient for cardiovascular health based on its role in nitric oxide homeostasis. Nitrate derived from plant foods may function as a conditionally essential nutrient, whereas nitrate obtained from other dietary sources, such as drinking water and cured/processed meats, warrants separate consideration because of the associated health risks. We have surveyed the literature and summarized epidemiological evidence regarding the effect of dietary nitrate on cardiovascular disease and risk factors. Meta-analyses and population-based observational studies have consistently demonstrated an inverse association of dietary nitrate with blood pressure and cardiovascular disease outcomes. Considering the available evidence, we suggest 2 different approaches to providing dietary guidance on nitrate from plant-based dietary sources as a nutrient: the Dietary Reference Intakes developed by the National Academies of Sciences, Engineering, and Medicine, and the dietary guidelines evaluated by the Academy of Nutrition and Dietetics. Ultimately, this proposal underscores the need for food-based dietary guidelines to capture the complex and context-dependent relationships between nutrients, particularly dietary nitrate, and health.

Disturbances in Nitric Oxide Cycle and Related Molecular Pathways in Clear Cell Renal Cell Carcinoma

It is important to note that maintaining adequate levels of nitric oxide (NO), the turnover, and the oxidation level of nitrogen are essential for the optimal progression of cellular processes, and alterations in the NO cycle indicate a crucial step in the onset and progression of multiple diseases. Cellular accumulation of NO and reactive nitrogen species in many types of tumour cells is expressed by an increased susceptibility to oxidative stress in the tumour microenvironment. Clear cell renal cell carcinoma (ccRCC) is a progressive metabolic disease in which tumour cells can adapt to metabolic reprogramming to enhance NO production in the tumour space. Understanding the factors governing NO biosynthesis metabolites in ccRCC represents a relevant, valuable approach to studying NO-based anticancer therapy. Exploring the molecular processes mediated by NO, related disturbances in molecular pathways, and NO-mediated signalling pathways in ccRCC could have significant therapeutic implications in managing and treating this condition.

From nitrate to NO: potential effects of nitrate-reducing bacteria on systemic health and disease

Current research has described improving multisystem disease and organ function through dietary nitrate (DN) supplementation. They have provided some evidence that these floras with nitrate (NO3-) reductase are mediators of the underlying mechanism. Symbiotic bacteria with nitrate reductase activity (NRA) are found in the human digestive tract, including the mouth, esophagus and gastrointestinal tract (GT). Nitrate in food can be converted to nitrite under the tongue or in the stomach by these symbiotic bacteria. Then, nitrite is transformed to nitric oxide (NO) by non-enzymatic synthesis. NO is currently recognized as a potent bioactive agent with biological activities, such as vasodilation, regulation of cardiomyocyte function, neurotransmission, suppression of platelet agglutination, and prevention of vascular smooth muscle cell proliferation. NO also can be produced through the conventional L-arginine-NO synthase (L-NOS) pathway, whereas endogenous NO production by L-arginine is inhibited under hypoxia-ischemia or disease conditions. In contrast, exogenous NO3-/NO2-/NO activity is enhanced and becomes a practical supplemental pathway for NO in the body, playing an essential role in various physiological activities. Moreover, many diseases (such as metabolic or geriatric diseases) are primarily associated with disorders of endogenous NO synthesis, and NO generation from the exogenous NO3-/NO2-/NO route can partially alleviate the disease progression. The imbalance of NO in the body may be one of the potential mechanisms of disease development. Therefore, the impact of these floras with nitrate reductase on host systemic health through exogenous NO3-/NO2-/NO pathway production of NO or direct regulation of floras ecological balance is essential (e.g., regulation of body homeostasis, amelioration of diseases, etc.). This review summarizes the bacteria with nitrate reductase in humans, emphasizing the relationship between the metabolic processes of this microflora and host systemic health and disease. The potential effects of nitrate reduction bacteria on human health and disease were also highlighted in disease models from different human systems, including digestive, cardiovascular, endocrine, nervous, respiratory, and urinary systems, providing innovative ideas for future disease diagnosis and treatment based on nitrate reduction bacteria.

Novel strategies for controlling nitrite content in prepared dishes: Current status, potential benefits, limitations and future challenges

Sodium nitrite is commonly used as a multifunctional curing ingredient in the processing of prepared dishes, especially meat products, to impart unique color, flavor and to prolong the shelf life of such products. However, the use of sodium nitrite in the meat industry has been controversial due to potential health risks. Finding suitable substitutes for sodium nitrite and controlling nitrite residue have been a major challenge faced by the meat processing industry. This paper summarizes possible factors affecting the variation of nitrite content in the processing of prepared dishes. New strategies for controlling nitrite residues in meat dishes, including natural pre-converted nitrite, plant extracts, irradiation, non-thermal plasma and high hydrostatic pressure (HHP), are discussed in detail. The advantages and limitations of these strategies are also summarized. Raw materials, cooking techniques, packaging methods, and storage conditions all affect the content of nitrite in the prepared dishes. The use of vegetable pre-conversion nitrite and the addition of plant extracts can help reduce nitrite residues in meat products and meet the consumer demand for clean labeled meat products. Atmospheric pressure plasma, as a non-thermal pasteurization and curing process, is a promising meat processing technology. HHP has good bactericidal effect and is suitable for hurdle technology to limit the amount of sodium nitrite added. This review is intended to provide insights for the control of nitrite in the modern production of prepared dishes.

Highly Sensitive Graphene-Based Electrochemical Sensor for Nitrite Assay in Waters

The importance of nitrite ions has long been recognized due to their extensive use in environmental chemistry and public health. The growing use of nitrogen fertilizers and additives containing nitrite in processed food items has increased exposure and, as a result, generated concerns about potential harmful health consequences. This work presents the development of an electrochemical sensor based on graphene/glassy carbon electrode (EGr/GC) with applicability in trace level detection of nitrite in water samples. According to the structural characterization of the exfoliated material, it appears as a mixture of graphene oxide (GO; 21.53%), few-layers graphene (FLG; 73.25%) and multi-layers graphene (MLG; 5.22%) and exhibits remarkable enhanced sensing response towards nitrite compared to the bare electrode (three orders of magnitude higher). The EGr/GC sensor demonstrated a linear range between 3 × 10^-7 and 10^-3 M for square wave voltammetry (SWV) and between 3 × 10^-7 and 4 × 10^-4 M for amperometry (AMP), with a low limit of detection LOD (9.9 × 10^-8 M). Excellent operational stability, repeatability and interference-capability were displayed by the modified electrode. Furthermore, the practical applicability of the sensor was tested in commercially available waters with excellent results.

Caloric Restriction (CR) Plus High-Nitrate Beetroot Juice Does Not Amplify CR-Induced Metabolic Adaptation and Improves Vascular and Cognitive Functions in Overweight Adults: A 14-Day Pilot Randomised Trial

Caloric restriction (CR) and dietary nitrate supplementation are nutritional interventions with pleiotropic physiological functions. This pilot study investigates the combined effects of CR and nitrate-rich beetroot juice (BRJ) on metabolic, vascular, and cognitive functions in overweight and obese middle-aged and older adults. This was a two-arm, parallel randomized clinical trial including 29 participants allocated to CR + BRJ (n = 15) or CR alone (n = 14) for 14 days. Body composition, resting energy expenditure (REE), and hand-grip strength were measured. Resting blood pressure (BP) and microvascular endothelial function were measured, and Trail-Making Test A and B were used to assess cognitive function. Salivary nitrate and nitrite, and urinary nitrate and 8-isoprostane concentrations were measured. Changes in body composition, REE, and systolic and diastolic BP were similar between the two interventions (p > 0.05). The CR + BRJ intervention produced greater changes in average microvascular flux (p = 0.03), NO-dependent endothelial activity (p = 0.02), and TMT-B cognitive scores (p = 0.012) compared to CR alone. Changes in urinary 8-isoprostane were greater in the CR + BRJ group (p = 0.02), and they were inversely associated with changes in average microvascular flux (r = -0.53, p = 0.003). These preliminary findings suggest that greater effects on vascular and cognitive functions could be achieved by combining CR with dietary nitrate supplementation.

Associations of thiocyanate, nitrate, and perchlorate exposure with dyslipidemia: a cross-sectional, population-based analysis

The aim of this study was to assess the associations of urinary thiocyanate, nitrate, and perchlorate concentrations with dyslipidemia, individually and in combination, which has not previously been studied. Data from the 2001-2002 and 2005-2016 National Health and Nutrition Examination Surveys (NHANES) were analyzed in this cross-sectional study. The dependent variables were continuous serum lipid variables (triglycerides [TG], total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], non-HDL-C, and apolipoprotein B [Apo B]) and binary serum lipid variables, with the latter reflecting dyslipidemia (elevated TG, ≥ 150 mg/dL; elevated TC, ≥ 200 mg/dL; elevated LDL-C, ≥ 130 mg/dL; lowered HDL-C, < 40 mg/dL in men and < 5 0 mg/dL in women; elevated non-HDL-C, ≥ 160 mg/dL; and elevated Apo B, ≥ 130 mg/dL). Multivariate logistic, linear, and weighted quantile sum (WQS) regression analyses were used to explore the associations of thiocyanate, nitrate, and perchlorate with the continuous and binary serum lipid variables. The linearity of the associations with the binary serum lipid variables was assessed using restricted cubic spline (RCS) regression. A total of 15,563 adults were included in the analysis. The multivariate linear and logistic regression analyses showed that thiocyanate was positively associated with multiple continuous (TG, TC, LDL-C, non-HDL-C, and Apo B, but not HDL-C) and binary (elevated TG, TC, LDL-C, and non-HDL-C) serum lipid variables, whereas perchlorate was negatively associated with elevated LDL-C. Multivariate RCS logistic regression revealed a linear dose-response relationship between thiocyanate and elevated TG, TC, LDL-C, non-HDL-C, and Apo B, but a nonlinear relationship with lowered HDL-C (inflection point = 1.622 mg/L). WQS regression showed that a mixture of thiocyanate, nitrate, and perchlorate was positively associated with all binary serum lipid variables except for Apo B. Our findings indicate that urinary thiocyanate, nitrate, and perchlorate concentrations, individually and in combination, were associated with dyslipidemia.

Adherence to Mediterranean Diet and Risk of Pancreatic Cancer: Systematic Review and Meta-Analysis

Pancreatic cancer (PC) represents the 6th cause of cancer death. Although the aetiology of PC is not completely understood, numerous risk factors have been identified in association with this cancer, among them diet. However, little is known about the association between the Mediterranean Diet (MedDiet) and the risk of PC. For this reason, we conducted a systematic review with meta-analysis according to the PRISMA guidelines, searching on three databases (PubMed/MEDLINE, Scopus, and EMBASE). The protocol was registered in PROSPERO. Both fixed and random effect models were performed. The Effect size was reported as a hazard ratio (HR) with a 95% Confidence Interval (CI). A total of eight articles were included. The methodological quality of the included meta-analyses was high. Our results show that a higher adherence to the MedDiet is associated with a lower risk of PC [HR:0.82 (0.76-0.88) p < 0.001, based on 1,301,320 subjects]. The results were also confirmed in sensitivity and subgroups analyses (avoidance of potential overlapping effects, type of tools used to assess dietary intake and the diagnosis of PC, prevalence and incidence of PC risk, country where the studies took place, sex, and cancer site). Promoting a higher adherence to the MedDiet could be an effective approach to reduce the risk of PC.

Association of urinary nitrate with diabetes complication and disease-specific mortality among adults with hyperglycemia

BACKGROUND

The hyperglycemia condition disrupts the metabolism of nitrate/nitrite and nitric oxide, and dietary nitrate intake can restore nitric oxide homeostasis. This study aims to examine whether urinary nitrate is associated with diabetes complications and long-term survival among people with hyperglycemia.

METHODS

A total of 6208 people with hyperglycemia who participated in the National Health and Nutrition Examination Survey from 2005 to 2014 were enrolled. Diabetes complications included congestive heart failure, coronary heart disease, angina, stroke, myocardial infarction, diabetic retinopathy, and nephropathy. Mortality wasobtained from the National Death Index until 2015. Urinary nitrate was measured by ion chromatography coupled with electrospray tandem mass spectrometry, which was log-transformed and categized into tertiles. Logistic regression models and cox proportional hazards models were respectively performed to assess the association of urinary nitrate with the risk of diabetes complications and disease-specific mortalities.

RESULTS

After adjustment for potential confounders including urinary perchlorate and thiocyanate, compared with the participants in the lowest tertile of nitrate, the participants in the highest tertile had lower risks of congestive heart failure(odd-ratio[OR] = 0.41, 95%CI:0.27-0.60) and diabetic nephropathy(OR = 0.50, 95%CI: 0.41-0.62). Meanwhile, during a total follow-up of 41,463 person-year, the participants in the highest tertile had lower mortality risk of all-cause(hazard-ratio[HR] = 0.78, 95%CI:0.62-0.97), cardiovascular disease(CVD)(HR = 0.56, 95%CI:0.37-0.84) and diabetes(HR = 0.47, 95%CI:0.24-0.90), which showed dose-dependent linear relationships(P for non-linearity > 0.05). Moreover, no association between nitrate and cancer mortality was observed(HR = 1.13, 95%CI:0.71-1.80).

CONCLUSIONS

Higher urinary nitrate is associated with lower risk of congestive heart failure and diabetic nephropathy, and lower risk of all-cause, CVD, and diabetes mortalities. These findings indicated that inorganic nitrate supplementation can be considered as a supplementary treatment for people with hyperglycemia.

Association between vitamins and risk of brain tumors: A systematic review and dose-response meta-analysis of observational studies

Background

Brain tumor is one of the important causes of cancer mortality, and the prognosis is poor. Therefore, early prevention of brain tumors is the key to reducing mortality due to brain tumors.

Objective

This review aims to quantitatively evaluate the association between vitamins and brain tumors by meta-analysis.

Methods

We searched articles on PubMed, Cochrane Library, Web of Science, and Embase databases from inception to 19 December 2021. According to heterogeneity, the fixed-effects model or random-effects model was selected to obtain the relative risk of the merger. Based on the methods described by Greenland and Longnecker, we explored the dose-response relationship between vitamins and the risk of brain tumors. Subgroup analysis, sensitivity analysis, and publication bias were also used for the analysis.

Results

The study reviewed 23 articles, including 1,347,426 controls and 6,449 brain tumor patients. This study included vitamin intake and circulating concentration. For intake, it mainly included vitamin A, vitamin B, vitamin C, vitamin E, β-carotene, and folate. For circulating concentrations, it mainly included vitamin E and vitamin D in the serum (25-hydroxyvitamin D and α-tocopherol). For vitamin intake, compared with the lowest intakes, the highest intakes of vitamin C (RR = 0.81, 95%CI:0.66–0.99, I² = 54.7%, P_{for heterogeneity} = 0.007), β-carotene (RR = 0.78, 95%CI:0.66–0.93, I² = 0, P_{for heterogeneity} = 0.460), and folate (RR = 0.66, 95%CI:0.55–0.80, I² = 0, P_{for heterogeneity} = 0.661) significantly reduced the risk of brain tumors. For serum vitamins, compared with the lowest concentrations, the highest concentrations of serum α-tocopherol (RR = 0.61, 95%CI:0.44–0.86, I² = 0, P_{for heterogeneity} = 0.656) significantly reduced the risk of brain tumors. The results of the dose-response relationship showed that increasing the intake of 100 μg folate per day reduced the risk of brain tumors by 7% (P_{−nonlinearity} = 0.534, RR = 0.93, 95%CI:0.90–0.96).

Conclusion

Our analysis suggests that the intake of vitamin C, β-carotene, and folate can reduce the risk of brain tumors, while high serum α-tocopherol concentration also has a protective effect on brain tumors. Therefore, vitamins may provide new ideas for the prevention of brain tumors.

Systematic Review Registration

PROSPERO, identifier CRD42022300683.

Association Between Dietary Nitrite intake and Glioma Risk: A Systematic Review and Dose-Response Meta-Analysis of Observational Studies

Background

Nitrite and nitrate intake through food and water may be an important risk factor for many cancers, including glioma. However, the association of nitrite and nitrate with glioma is unclear.

Objective

This review aimed to quantitatively assess the effects of nitrite and nitrate on glioma by meta-analysis.

Methods

A literature search was conducted for available articles published in English using the databases of Embase, Web of Science, PubMed, Medline, and the Cochrane Library up to 24 March 2022. According to heterogeneity, the fixed-effects or random-effects model was selected to obtain the merger’s relative risk (RR). Based on the methods described by Greenland and Longnecker, we explored the dose-response relationship between nitrite/nitrate and the risk of glioma. Subgroup analysis, sensitivity analysis, and publication bias tests were also used.

Results

This study reviewed 17 articles, including 812,107 participants and 4,574 cases. For glioma in adults, compared with the lowest intakes, the highest intakes of nitrite significantly increased the risk of glioma (RR=1.26, 95% confidence interval (95%CI):1.09-1.47). For brain tumors in children, compared with the lowest intakes, the highest intakes of nitrate significantly increased the risk of brain tumors (RR=1.27, 95%CI:1.06-1.52). The results of subgroup and sensitivity analyses remained unchanged. In the dose-response relationship, per 1 mg/day increase in nitrite intake increased the risk of glioma by 14% (RR=1.14, 95%CI:1.01-1.27).

Conclusions

Our analysis suggests that nitrite increases the risk of glioma in adults, while nitrate increases the risk of brain tumors in children. Therefore, the effects of nitrite and nitrate on glioma cannot be ignored.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42022320295.

Perchlorate, nitrate, and thiocyanate: Environmental relevant NIS-inhibitors pollutants and their impact on thyroid function and human health

Thyroid disruptors are found in food, atmosphere, soil, and water. These contaminants interfere with the thyroid function through the impairment of thyroid hormone synthesis, plasma transport, peripheral metabolism, transport into the target cells, and thyroid hormone action. It is well known that iodide uptake mediated by the sodium-iodide symporter (NIS) is the first limiting step involved in thyroid hormones production. Therefore, it has been described that several thyroid disruptors interfere with the thyroid function through the regulation of NIS expression and/or activity. Perchlorate, nitrate, and thiocyanate competitively inhibit the NIS-mediated iodide uptake. These contaminants are mainly found in food, water and in the smoke of cigarettes. Although the impact of the human exposure to these anions is highly controversial, some studies indicated their deleterious effects in the thyroid function, especially in individuals living in iodine deficient areas. Considering the critical role of thyroid function and the production of thyroid hormones for growth, metabolism, and development, this review summarizes the impact of the exposure to these NIS-inhibitors on thyroid function and their consequences for human health.