Prospective study of meat intake and dietary nitrates, nitrites, and nitrosamines and risk of adult glioma

Associations between dietary antioxidant vitamins and risk of glioma: an updated systematic review and meta-analysis of observational studies

Background

Epidemiological studies investigating the potential associations between antioxidant vitamins intake and risk of glioma have yielded inconsistent results. To address this, we carried out a systematic review and updated meta-analysis to explore the relationship between dietary antioxidant vitamins intake and risk of glioma.

Methods

We comprehensively searched electronic databases including PubMed, Web of Science, Embase, Scopus, China National Knowledge Infrastructure (CNKI) and Wan fang Data from their inception to March 2024. We employed fixed-effects or random-effects models to estimate the pooled relative risks (RRs) and 95% confidence intervals (CIs) for the associations between dietary antioxidant vitamins intake and risk of glioma. Publication bias was assessed through the visual inspection of the funnel plots and quantified by the Begg's and Egger's tests. Heterogeneity across studies was assessed using the Cochran's Q test and I-square (I2). Additionally, subgroup and sensitivity analyses were performed to explore potential sources of heterogeneity and evaluate the robustness of the results.

Results

Overall, a total of 15 articles involving 3,608 glioma cases and 771,930 participants were included in the final analysis. The pooled analyses revealed that the highest intake of vitamin C significantly reduced the risk of glioma (RR = 0.78; 95%CI: 0.63-0.96; P = 0.022), compared to the lowest intake. However, no significant associations were observed between vitamin A and vitamin E intake and the risk of glioma (P>0.05). Subgroup analyses revealed the inverse association between vitamin C intake and risk of glioma in the population-based case-control studies (RR = 0.82; 95%CI: 0.68-1.00, P = 0.049) and study quality <7(RR = 0.52, 95%CI: 0.29-0.92, P = 0.025).

Conclusion

Our findings show that higher intake of vitamin C is strongly associated with a reduced risk of glioma, although a dose-response relationship was not evident. Future large-scale prospective studies are warranted to confirm these findings.

Efficient nitrate and Cr(VI) removal by denitrifier: The mechanism of S. oneidensis MR-1 promoting electron production, transportation and consumption

When Cr(VI) and nitrate coexist, the efficiency of both bio-denitrification and Cr(VI) bio-reduction is poor because chromate hinders bacterial normal functions (i.e., electron production, transportation and consumption). Moreover, under anaerobic condition, the method about efficient nitrate and Cr(VI) removal remained unclear. In this paper, the addition of Shewanella oneidensis MR-1 to promote the electron production, transportation and consumption of denitrifier and cause an increase in the removal of nitrate and Cr(VI). The efficiency of nitrate and Cr(VI) removal accomplished by P. denitrificans as a used model denitrifier increased respectively from 51.3% to 96.1% and 34.3% to 99.8% after S. oneidensis MR-1 addition. The mechanism investigations revealed that P. denitrificans provided S. oneidensis MR-1 with lactate, which was utilized to secreted riboflavin and phenazine by S. oneidensis MR-1. The riboflavin served as coenzymes of cellular reductants (i.e., thioredoxin and glutathione) in P. denitrificans, which created favorable intracellular microenvironment conditions for electron generation. Meanwhile, phenazine promoted biofilm formation, which increased the adsorption of Cr(VI) on the cell surface and accelerated the Cr(VI) reduction by membrane bound chromate reductases thereby reducing damage to other enzymes respectively. Overall, this strategy reduced the negative effect of chromate, thus improved the generation, transportation, and consumption of electrons. SYNOPSIS: The presence of S. oneidensis MR-1 facilitated nitrate and Cr(VI) removal by P. denitrificans through decreasing the negative effect of chromate due to the metabolites' secretion.

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.

EFSA Panel on Contaminants in the Food Chain (EFSA CONTAM Panel), Schrenk D, Bignami M, Bodin L, Chipman JK, del Mazo J, Hogstrand C, (Ron) Hoogenboom L, Leblanc J, Nebbia CS, Nielsen E, Ntzani E, Petersen A, Sand S, Schwerdtle T, Vleminckx C, Wallace H, Romualdo B, Cristina F, Stephen H, Marco I, Mosbach‐Schulz O, Riolo F, Christodoulidou A, Grasl‐Kraupp B. Risk assessment of N-nitrosamines in food

EFSA was asked for a scientific opinion on the risks to public health related to the presence of N-nitrosamines (N-NAs) in food. The risk assessment was confined to those 10 carcinogenic N-NAs occurring in food (TCNAs), i.e. NDMA, NMEA, NDEA, NDPA, NDBA, NMA, NSAR, NMOR, NPIP and NPYR. N-NAs are genotoxic and induce liver tumours in rodents. The in vivo data available to derive potency factors are limited, and therefore, equal potency of TCNAs was assumed. The lower confidence limit of the benchmark dose at 10% (BMDL10) was 10 μg/kg body weight (bw) per day, derived from the incidence of rat liver tumours (benign and malignant) induced by NDEA and used in a margin of exposure (MOE) approach. Analytical results on the occurrence of N-NAs were extracted from the EFSA occurrence database (n = 2,817) and the literature (n = 4,003). Occurrence data were available for five food categories across TCNAs. Dietary exposure was assessed for two scenarios, excluding (scenario 1) and including (scenario 2) cooked unprocessed meat and fish. TCNAs exposure ranged from 0 to 208.9 ng/kg bw per day across surveys, age groups and scenarios. 'Meat and meat products' is the main food category contributing to TCNA exposure. MOEs ranged from 3,337 to 48 at the P95 exposure excluding some infant surveys with P95 exposure equal to zero. Two major uncertainties were (i) the high number of left censored data and (ii) the lack of data on important food categories. The CONTAM Panel concluded that the MOE for TCNAs at the P95 exposure is highly likely (98-100% certain) to be less than 10,000 for all age groups, which raises a health concern.

Highly Selective and Sensitive Detection of Nitrite Ion by an Unusual Nitration of a Fluorescent Benzimidazole

Nitrite (NO₂^-) is a physiologically significant anion having implications for cellular signaling. Here we report our serendipitous discovery of highly selective fluorescence-based nitrite sensing using a benzimidazole which stems from hitherto-unknown direct nitration of a benzimidazole using sodium nitrite. Using one- and two-dimensional NMR techniques, we elucidate the chemical structures of the new nitrated benzimidazoles and show differences in the nitration products using conventional nitration with nitric acid. We also show its utility in robust sensing of nitrite-containing samples.

Ion-selective electrodes based on laser-induced graphene as an alternative method for nitrite monitoring

Nitrite is an important food additive for cured meats; however, high nitrite levels pose adverse health effects to humans. Hence, monitoring nitrite concentration is critical to comply with limits imposed by regulatory agencies. Laser-induced graphene (LIG) has proven to be a scalable manufacturing alternative to produce high-performance electrochemical transducers for sensors. Herein, we expand upon initial LIG studies by fabricating hydrophilic and hydrophobic LIG that are subsequently converted into ion-selective sensors to monitor nitrite in food samples with comparable performance to the standard photometric method (Griess method). The hydrophobic LIG resulted in an ion-selective electrode with improved potential stability due partly to a decrease in the water layer between the electrode and the nitrite poly(vinyl) chloride-based ion-selective membrane. These resultant nitrite ion-selective sensors displayed Nernstian response behavior with a sensitivity of 59.5 mV dec-1, a detection limit of 0.3 ± 0.1 mg L-1 (mean ± standard deviation), and a broad linear sensing range from 10-5 to 10-1 M, which was significantly larger than currently published nitrite methods. Nitrite levels were determined directly in food extract samples of sausage, ham, and bacon for 5 min. These sensor metrics are significant as regulatory agencies limit nitrite levels up to 200 mg L-1 in finished products to reduce the potential formation of nitrosamine (carcinogenic compound). These results demonstrate the versatility of LIG as a platform for ion-selective-LIG sensors and simple, efficient, and scalable electrochemical sensing in general while demonstrating a promising alternative to monitor nitrite levels in food products ensuring regulatory compliance.

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.

Epidemiology of Glioblastoma Multiforme-Literature Review

Glioblastoma multiforme (GBM) is one of the most aggressive malignancies, with a median overall survival of approximately 15 months. In this review, we analyze the pathogenesis of GBM, as well as epidemiological data, by age, gender, and tumor location. The data indicate that GBM is the higher-grade primary brain tumor and is significantly more common in men. The risk of being diagnosed with glioma increases with age, and median survival remains low, despite medical advances. In addition, it is difficult to determine clearly how GBM is influenced by stimulants, certain medications (e.g., NSAIDs), cell phone use, and exposure to heavy metals.

Dietary Factors and Risk of Glioma in Adults: A Systematic Review and Dose-Response Meta-Analysis of Observational Studies

Background

Gliomas are the most common primary intracranial tumors in adults. Inappropriate dietary habits are thought to be a risk factor for most human cancer, and glioma is no exception. However, the effect of dietary factors on glioma is not clear.

Objective

This review aims to quantitatively evaluate the association between various dietary intakes and glioma using a meta-analysis.

Methods

We searched articles on PubMed, the Cochrane Library, the Web of Science, and EMBASE from their inception until October 11, 2021. According to heterogeneity, the fixed-effects or random-effects model was selected to obtain the relative risk (RR) of merger. Based on the methods described by Greenland and Longnecker, we explored the dose-response relationship between dietary intakes and the risk of glioma. Subgroup analysis, sensitivity analysis, and publication bias were also used.

Results

This study reviewed 33 articles, including 3,606,015 controls and 8,831 patients with glioma. This study included 12 food groups. Compared with the lowest intakes, the highest intakes of tea (RR = 0.82, 95%CI:0.71–0.93), total vegetables (RR = 0.84, 95%CI: 0.70–1.00), green vegetables (RR = 0.80, 95%CI: 0.66–0.98), and orange vegetables (RR = 0.79, 95%CI: 0.66–0.96) significantly reduced the risk of glioma, while the highest intakes of grains (RR = 1.39, 95%CI: 1.16–1.66), processed meats (RR = 1.19, 95%CI: 1.00–1.42), and processed fish (RR = 1.37, 95%CI: 1.03–1.84) significantly increased the risk of glioma. The results of subgroup and sensitivity analyses remained unchanged. In the dose-response relationship, only tea was statistically significant. Taking an extra cup of tea every day reduced the risk of glioma by 4%.

Conclusions

Our analysis suggests that the intakes of tea, total vegetables, green vegetables, and orange vegetables may reduce the risk of glioma, while the intakes of grains, processed meats, and processed fish may increase the risk of glioma. Therefore, the effect of dietary factors on glioma should not be ignored.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/, CRD42022296658.

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

BACKGROUND

People consume nitrates, nitrites, nitrosamines, and NOCs compounds primarily through processed food. Many studies have yielded inconclusive results regarding the association between cancer and dietary intakes of nitrates and nitrites. This study aimed to quantify these associations across the reported literature thus far.

METHODS

We performed a systematic review following PRISMA and MOOSE guidelines. A literature search was performed using Web of Science, Embase, PubMed, the Cochrane library, and google scholar up to January 2020. STATA version 12.0 was used to conduct meta-regression and a two-stage meta-analysis.

RESULTS

A total of 41 articles with 13 different cancer sites were used for analysis. Of these 13 cancer types/sites, meta-regression analysis showed that bladder and stomach cancer risk was greater, and that pancreatic cancer risk was lower with increasing nitrite intakes. Kidney and bladder cancer risk were both lower with increasing nitrate intakes. When comparing highest to lowest (reference) categories of intake, meta-analysis of studies showed that high nitrate intake was associated with an increased risk of thyroid cancer (OR = 1.40, 95% CI: 1.02, 1.77). When pooling all intake categories and comparing against the lowest (reference) category, higher nitrite intake was associated with an increased risk of glioma (OR = 1.12, 95% CI: 1.03, 1.22). No other associations between cancer risk and dietary intakes of nitrates or nitrites were observed.

CONCLUSION

This study showed varied associations between site-specific cancer risks and dietary intakes of nitrate and nitrite. Glioma, bladder, and stomach cancer risks were higher and pancreatic cancer risk was lower with higher nitrite intakes, and thyroid cancer risk was higher and kidney cancer risk lower with higher nitrate intakes. These data suggest type- and site-specific effects of cancer risk, including protective effects, from dietary intakes of nitrate and nitrite.

The Epidemiology of Central Nervous System Tumors

This article reviews the current epidemiology of central nervous system tumors. Population-level basic epidemiology, nationally and internationally, and current understanding of germline genetic risk are discussed, with a focus on known and well-studied risk factors related to the etiology of central nervous system tumors.

An insight into the risk factors of brain tumors and their therapeutic interventions

Brain tumors are an abnormal growth of cells in the brain, also known as multifactorial groups of neoplasm. Incidence rates of brain tumors increase rapidly, and it has become a leading cause of tumor related deaths globally. Several factors have potential risks for intracranial neoplasm. To date, the International Agency for Research on Cancer has classified the ionizing radiation and the N-nitroso compounds as established carcinogens and probable carcinogens respectively. Diagnosis of brain tumors is based on histopathology and suitable imaging techniques. Labeled amino acids and fluorodeoxyglucose with or without contrast-enhanced MRI are used for the evaluation of tumor traces. T2-weighted MRI is an advanced diagnostic implementation, used for the detection of low-grade gliomas. Treatment decisions are based on tumor size, location, type, patient's age and health status. Conventional therapeutic approaches for tumor treatment are surgery, radiotherapy and chemotherapy. While the novel strategies may include targeted therapy, electric field treatments and vaccine therapy. Inhibition of cyclin-dependent kinase inhibitors is an attractive tumor mitigation strategy for advanced-stage cancers; in the future, it may prove to be a useful targeted therapy. The blood-brain barrier poses a major hurdle in the transport of therapeutics towards brain tissues. Moreover, nanomedicine has gained a vital role in cancer therapy. Nano drug delivery system such as liposomal drug delivery has been widely used in the cancer treatment. Liposome encapsulated drugs have improved therapeutic efficacy than free drugs. Numerous treatment therapies for brain tumors are in advanced clinical research.

Consumption of red meat and processed meat and cancer incidence: a systematic review and meta-analysis of prospective studies

Red meat and processed meat consumption has been hypothesized to increase risk of cancer, but the evidence is inconsistent. We performed a systematic review and meta-analysis of prospective studies to summarize the evidence of associations between consumption of red meat (unprocessed), processed meat, and total red and processed meat with the incidence of various cancer types. We searched in MEDLINE and EMBASE databases through December 2020. Using a random-effect meta-analysis, we calculated the pooled relative risk (RR) and 95% confidence intervals (CI) of the highest versus the lowest category of red meat, processed meat, and total red and processed meat consumption in relation to incidence of various cancers. We identified 148 published articles. Red meat consumption was significantly associated with greater risk of breast cancer (RR = 1.09; 95% CI = 1.03-1.15), endometrial cancer (RR = 1.25; 95% CI = 1.01-1.56), colorectal cancer (RR = 1.10; 95% CI = 1.03-1.17), colon cancer (RR = 1.17; 95% CI = 1.09-1.25), rectal cancer (RR = 1.22; 95% CI = 1.01-1.46), lung cancer (RR = 1.26; 95% CI = 1.09-1.44), and hepatocellular carcinoma (RR = 1.22; 95% CI = 1.01-1.46). Processed meat consumption was significantly associated with a 6% greater breast cancer risk, an 18% greater colorectal cancer risk, a 21% greater colon cancer risk, a 22% greater rectal cancer risk, and a 12% greater lung cancer risk. Total red and processed meat consumption was significantly associated with greater risk of colorectal cancer (RR = 1.17; 95% CI = 1.08-1.26), colon cancer (RR = 1.21; 95% CI = 1.09-1.34), rectal cancer (RR = 1.26; 95% CI = 1.09-1.45), lung cancer (RR = 1.20; 95% CI = 1.09-1.33), and renal cell cancer (RR = 1.19; 95% CI = 1.04-1.37). This comprehensive systematic review and meta-analysis study showed that high red meat intake was positively associated with risk of breast cancer, endometrial cancer, colorectal cancer, colon cancer, rectal cancer, lung cancer, and hepatocellular carcinoma, and high processed meat intake was positively associated with risk of breast, colorectal, colon, rectal, and lung cancers. Higher risk of colorectal, colon, rectal, lung, and renal cell cancers were also observed with high total red and processed meat consumption.

A Case-Control Study on Dietary Acid Load in Relation to Glioma

Limited data are available linking dietary factors to glioma. The current study was conducted to investigate the association between Dietary Acid Load (DAL) and odds of glioma in Iranian adults. This case-control study was done on 128 newly diagnosed patients with glioma and 256 healthy controls in Tehran, Iran. A validated detailed food frequency questionnaire (FFQ) was used to assess dietary intakes of participants. DAL was estimated using the protein to potassium ratio (Pro: K). Glioma was diagnosed based on pathological tests. A detailed questionnaire including several non-dietary confounders was also completed. Participants in the highest tertile of DAL score had a non-significant higher odds of glioma as compared to those in the lowest tertile (OR: 1.50; 95% CI: 0.88-2.57), which remained after controlling for some potential confounders (OR: 1.66; 0.70-3.91). After further adjustment for dietary intakes of meats and processed meats, legumes and nuts, fruits, salt tea, and coffee, those in the top tertile of DAL score were significantly more likely to have glioma than those in the bottom tertile (OR: 3.09; 95% CI: 1.06, 8.99; P = 0.03). This association was also reached following further adjustment for BMI (OR: 3.05; 95% CI: 1.04, 8.91; P = 0.03). We found a significant positive association between dietary acid load, as estimated by Prot:K ratio, and odds of glioma among adults. Further studies, in particular prospective cohorts with long-term follow up, are required to confirm these findings.

Differential exposure to N-ethyl N-nitrosourea during pregnancy is relevant to the induction of glioma and PNSTs in the brain

Exposure to N-nitroso compounds (NOCs) during pregnancy has been associated with an increase in brain tumors in the progeny. This study investigated the brain tumorigenic effect of N-ethyl N-nitrosourea (ENU) after differential exposure of rats during pregnancy. Sprague Dawley rats were exposed to a single dose of ENU (80 mg/kg) in three different circumstances: 1) at first, second or third week of gestation; 2) at the 15th embryonic day (E15) in consecutive litters and 3) at E15 in three successive generations. Location and characterization of the offspring's brain tumors were performed by magnetic resonance imaging and histopathological studies. Finally, tumor incidence and latency and the animals' survival were recorded. ENU-exposure in the last two weeks of pregnancy induced intracranial tumors in over 70% of the offspring rats, these being mainly gliomas with some peripheral nerve sheath tumors (PNSTs). Tumors appeared in young adults; glioma-like small multifocal neoplasias converged on large glioblastomas in senescence and PNSTs in the sheath of the trigeminal nerve, extending to cover the brain convexity. ENU-exposure at E15 in subsequent pregnancies lead to an increase in glioma and PNST incidence. However, consecutive generational ENU-exposure (E15) decreased the animals' survival due to an early onset of both types of tumors. Moreover, PNST presented an inheritable component because progeny, which were not themselves exposed to ENU but whose progenitors were, developed PNSTs. Our results suggest that repeated exposure to ENU later in pregnancy and in successive generations favours the development of intracranial gliomas and PNSTs in the offspring.

Adherence to the Mediterranean dietary pattern in relation to glioma: A case-control study

BACKGROUND

Although Mediterranean diet (MD) was associated with a lower risk of mortality and cancer, no data are available investigating the association between adherence to the MD and risk of glioma.

METHODS

In this case-control study, we enrolled a total of 128 newly diagnosed patients with glioma, confirmed by pathological assessment, and 256 hospital-based controls from 2009 to 2011 in Tehran, Iran. A valid and reliable Block-format food frequency questionnaire (FFQ) was used to assess dietary intakes. Adherence to the MD was examined using the scoring method suggested by Trichopoulou et al. Logistic regression was used to examine the associations of interest.

RESULTS

After controlling for age, sex, and energy intake, participants in the highest tertile of MD score had not significantly lower odds of glioma than those in the lowest tertile (OR: 0.58, 95% CI: 0.32-1.03, P_trend = 0.06). However, after taking other potential confounders into account, individuals with the greatest adherence to the MD score were 74% less likely to have glioma than those with the lowest adherence (OR: 0.26, 95% CI: 0.12-0.55, P_trend < 0.001). Additional adjustments for dietary intakes and BMI did not significantly alter this association (OR: 0.36, 95% CI: 0.16-0.78, P_trend = 0.009; OR: 0.36, 95% CI: 0.16-0.78, P_trend = 0.01, respectively).

CONCLUSION

We found that adherence to the MD was associated with a lower likelihood of having glioma. Prospective cohort studies are needed to further examine these findings.

Risk factors for childhood and adult primary brain tumors

Primary brain tumors account for ~1% of new cancer cases and ~2% of cancer deaths in the United States; however, they are the most commonly occurring solid tumors in children. These tumors are very heterogeneous and can be broadly classified into malignant and benign (or non-malignant), and specific histologies vary in frequency by age, sex, and race/ethnicity. Epidemiological studies have explored numerous potential risk factors, and thus far the only validated associations for brain tumors are ionizing radiation (which increases risk in both adults and children) and history of allergies (which decreases risk in adults). Studies of genetic risk factors have identified 32 germline variants associated with increased risk for these tumors in adults (25 in glioma, 2 in meningioma, 3 in pituitary adenoma, and 2 in primary CNS lymphoma), and further studies are currently under way for other histologic subtypes, as well as for various childhood brain tumors. While identifying risk factors for these tumors is difficult due to their rarity, many existing datasets can be leveraged for future discoveries in multi-institutional collaborations. Many institutions are continuing to develop large clinical databases including pre-diagnostic risk factor data, and developments in molecular characterization of tumor subtypes continue to allow for investigation of more refined phenotypes. Key Point 1. Brain tumors are a heterogeneous group of tumors that vary significantly in incidence by age, sex, and race/ethnicity.2. The only well-validated risk factors for brain tumors are ionizing radiation (which increases risk in adults and children) and history of allergies (which decreases risk).3. Genome-wide association studies have identified 32 histology-specific inherited genetic variants associated with increased risk of these tumors.

Reeves G, Floud S, Balkwill A, Bradbury K, Liao LM, Freedman ND, Beral V, Sweetland S, The Million Women Study, the NIH-AARP study, and the PLCO study. Diet and risk of glioma: combined analysis of 3 large prospective studies in the UK and USA

BACKGROUND

Available evidence on diet and glioma risk comes mainly from studies with retrospective collection of dietary data. To minimize possible differential dietary recall between those with and without glioma, we present findings from 3 large prospective studies.

METHODS

Participants included 692 176 from the UK Million Women Study, 470 780 from the US National Institutes of Health-AARP study, and 99 148 from the US Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Cox regression yielded study-specific adjusted relative risks for glioma in relation to 15 food groups, 14 nutrients, and 3 dietary patterns, which were combined, weighted by inverse variances of the relative risks. Separate analyses by <5 and ≥5 years follow-up assessed potential biases related to changes of diet before glioma diagnosis.

RESULTS

The 1 262 104 participants (mean age, 60.6 y [SD 5.5] at baseline) were followed for 15.4 million person-years (mean 12.2 y/participant), during which 2313 incident gliomas occurred, at mean age 68.2 (SD 6.4). Overall, there was weak evidence for increased glioma risks associated with increasing intakes of total fruit, citrus fruit, and fiber and healthy dietary patterns, but these associations were generally null after excluding the first 5 years of follow-up. There was little evidence for heterogeneity of results by study or by sex.

CONCLUSIONS

The largest prospective evidence to date suggests little, if any, association between major food groups, nutrients, or common healthy dietary patterns and glioma incidence. With the statistical power of this study and the comprehensive nature of the investigation here, it seems unlikely we have overlooked major effects of diet on risk of glioma that would be of public health concern.

Dietary insulin index and insulin load in relation to glioma: findings from a case-control study

BACKGROUND

Although hyperinsulinemia is assumed to be involved in brain carcinogenesis, data on the link between dietary insulin index (DII) and dietary insulin load (DIL) and risk of glioma are lacking.

OBJECTIVE

The current study aimed to investigate the relation between DII and DIL and risk of glioma in a case-control study among Iranian adults.

METHODS

In this hospital-based case-control study, 128 pathologically confirmed cases of glioma and 256 age and sex-matched controls were enrolled. Dietary intakes of study participants were assessed using a validated Block-format 123-item semi-quantitative FFQ. DII and DIL were computed using a published food insulin index (FII) data.

RESULTS

A significant positive association was found between DIL and glioma (OR: 3.56; 95% CI: 1.85-6.58, P < 0.001); such that after controlling for potential confounders, participants in the highest quartile of DIL had 2.95 times greater odds of glioma than those in the lowest quartile (OR: 2.95; 95% CI: 1.40-6.24, P_trend=0.006). Furthermore, we observed a significant positive association between DII and glioma (OR: 2.65; 95% CI: 1.43-4.93, P_trend= 0.001). This association remained significant even after considering energy intake (OR: 2.66; 95% CI: 1.43-4.95, P_trend = 0.001). However, when further potential confounders were taken into account, this relationship became non-significant (OR: 1.87; 95% CI: 0.92-3.80, P_trend = 0.03), despite a significant trend of increased odds ratios (P = 0.03).

CONCLUSIONS

In conclusion, we found a significant positive association between DIL and odds of glioma. DII was not significantly associated with odds of glioma after controlling for confounders.

A case–control study on dietary quality indices and glioma

No study is available that has assessed the association of dietary diversity score (DDS) and alternative healthy eating index (AHEI) with glioma. The present study aimed to assess this association in Iranian adults. Overall, 128 pathologically confirmed cases of glioma were enrolled from hospitals and 256 age- and sex-matched controls were recruited from other wards of the hospital between 2009 and 2011. Dietary assessment was done using a validated block-format 123-item semi-quantitative FFQ. Dietary indices including DDS and AHEI-2010 were constructed according to standard methods. After controlling for potential confounders, a significant inverse association was found between DDS and risk of glioma (OR 0·42, 95 % CI 0·19, 0·94). Such finding was also seen when further adjustment was made for BMI; such that participants in the highest quartile of DDS were 56 % less likely to have glioma compared with those in the lowest quartile (OR 0·44, 95 % CI, 0·20, 0·97). In addition, a significant inverse association was found between adherence to AHEI and glioma; such that in the fully adjusted model, participants in the fourth quartile of AHEI had 74 % lower risk of glioma compared with those in the first quartile (OR 0·26, 95 % CI 0·12, 0·56). In conclusion, we found that greater adherence to the healthy, as measured by AHEI, and diverse, as measured by DDS, diets was associated with decreased odds of glioma.

The association between the dietary inflammatory index and glioma: A case-control study

BACKGROUND & AIMS

Dietary inflammatory potential has been associated with several cancers. However, the relationship between the dietary inflammatory index (DII®) and glioma is not clear. The aim of this study was to examine DII in relation to glioma.

METHODS

In a hospital-based case-control study, we selected 128 newly-diagnosed cases of glioma and 256 controls. Cases were medically confirmed glioma patients, with no history of other cancers. A validated food frequency questionnaire was used to assess diet. DII scores were calculated based on the quantity of dietary components with inflammatory or anti-inflammatory potential. We used conditional logistic regression models to examine the association between the DII and glioma.

RESULT

Study participants were on average 43 years old and predominantly male (58%). After controlling for age, sex and energy intake, individuals in the highest quartile of DII had 87% (95% CI: 1.00-3.47) increased risk of glioma compared to those in the lowest quartile. Additional adjustment for environmental confounders strengthened the relationship; participants with the greatest DII scores had approximately 2.1 times (95% CI: 1.06, 3.83) increased odds of glioma than those with the lowest intake scores. The association was not substantially altered by further adjustment for BMI (2.76; 1.15-6.60).

CONCLUSION

In conclusion, diets with high anti-inflammatory and low inflammatory nutrient contents are recommended to prevent glioma.

Use of Mendelian andomization for dentifying isk actors for rain umors

Gliomas are a group of primary brain tumors, the most common and aggressive subtype of which is glioblastoma. Glioblastoma has a median survival of just 15 months after diagnosis. Only previous exposure to ionizing radiation and particular inherited genetic syndromes are accepted risk factors for glioma; the vast majority of cases are thought to occur spontaneously. Previous observational studies have described associations between several risk factors and glioma, but studies are often conflicting and whether these associations reflect true casual relationships is unclear because observational studies may be susceptible to confounding, measurement error and reverse causation. Mendelian randomization (MR) is a form of instrumental variable analysis that can be used to provide supporting evidence for causal relationships between exposures (e.g., risk factors) and outcomes (e.g., disease onset). MR utilizes genetic variants, such as single nucleotide polymorphisms (SNPs), that are robustly associated with an exposure to determine whether there is a causal effect of the exposure on the outcome. MR is less susceptible to confounding, reverse causation and measurement errors as it is based on the random inheritance during conception of genetic variants that can be relatively accurately measured. In previous studies, MR has implicated a genetically predicted increase in telomere length with an increased risk of glioma, and found little evidence that obesity related factors, vitamin D or atopy are causal in glioma risk. In this review, we describe MR and its potential use to discover and validate novel risk factors, mechanistic factors, and therapeutic targets in glioma.

Assessment of dietary nitrate intake in humans: a systematic review

Background

The nitrate content of foods and water is highly variable, which has implications for the compilation of food-composition databases and assessment of dietary nitrate intake.

Objective

A systematic review was conducted to ascertain the dietary assessment methods used and to provide estimates of daily nitrate intake in humans.

Design

Relevant articles were identified by a systematic search of 3 electronic databases (PubMed, Web of Science, and Embase) from inception until February 2018. Observational studies conducted in adult populations and reporting information on dietary assessment methods and daily nitrate intake were included. Ecological analyses were conducted to explore the association of nitrate intake with indexes of economic development [Gross Domestic Product (GDP) and KOF Index of Globalization].

Results

A total of 55 articles were included. Forty-two studies investigated associations between nitrate intake and disease risk; 36 (87%) of these studies examined the association between nitrate intake and cancer risk, whereas only 6 studies explored the association of nitrate intake with the risk of diabetes, glaucoma, kidney failure, hypertension, and atherosclerotic vascular disease. The majority of studies used food-frequency questionnaires to assess nitrate intake (n = 43). The median daily nitrate intakes in healthy and patient populations were 108 and 110 mg/d, respectively. We found a significant inverse correlation of nitrate intake with GDP (r = -0.46, P < 0.001) and KOF index (r = -0.31, P = 0.002).

Conclusions

The median estimated daily nitrate intakes by healthy and patient populations were similar, and these values were below the safe upper intake of daily intake (3.7 mg nitrate ion/kg body weight). However, there is considerable heterogeneity in the application of food-composition tables, which may have implications for the accuracy of estimated daily nitrate intake. The association between nitrate intake and risk of cardiometabolic diseases needs further investigation. The protocol for this systematic review has been registered in the PROSPERO database (https://www.crd.york.ac.uk/prospero; CRD number: 42017060354).

Meat and haem iron intake in relation to glioma in the European Prospective Investigation into Cancer and Nutrition study

Diets high in red or processed meat have been associated positively with some cancers, and several possible underlying mechanisms have been proposed, including iron-related pathways. However, the role of meat intake in adult glioma risk has yielded conflicting findings because of small sample sizes and heterogeneous tumour classifications. The aim of this study was to examine red meat, processed meat and iron intake in relation to glioma risk in the European Prospective Investigation into Cancer and Nutrition study. In this prospective cohort study, 408 751 individuals from nine European countries completed demographic and dietary questionnaires at recruitment. Multivariable Cox proportional hazards models were used to examine intake of red meat, processed meat, total dietary iron and haem iron in relation to incident glioma. During an average follow-up of 14.1 years, 688 incident glioma cases were diagnosed. There was no evidence that any of the meat variables (red, processed meat or subtypes of meat) or iron (total or haem) were associated with glioma; results were unchanged when the first 2 years of follow-up were excluded. This study suggests that there is no association between meat or iron intake and adult glioma. This is the largest prospective analysis of meat and iron in relation to glioma and as such provides a substantial contribution to a limited and inconsistent literature.

Allergic conditions and risk of glioma and meningioma in the CERENAT case-control study

Inverse association between allergic conditions and glioma risk has been consistently reported in epidemiological studies with little attention paid to potential environmental confounders; the association with meningioma risk is less consistent. We examined the association between allergy history and risk of glioma and meningioma in adults using data from the CERENAT (CEREbral tumors: a NATional study) multicenter case-control study carried out in 4 areas in France in 2004-2010. Participants' histories of doctor-diagnosed allergic asthma, eczema, rhinitis/hay fever and other allergic conditions were collected at onset through a detailed questionnaire delivered in a face-to-face interview. Conditional logistic regression for matched sets was adjusted for participants' educational level and mobile phone use. A total of 273 glioma cases, 218 meningioma cases and 982 matched controls selected from the local electoral rolls were analyzed. A significant inverse association was found between glioma and a history of any allergy (OR 0.52, 95% CI 0.36-0.75), with a dose-effect relationship with the number of allergic conditions reported (p-trend = 0.001) and a particularly strong association with hay fever/allergic rhinitis (OR 0.46, 95% CI 0.30-0.72). Interestingly, associations with glioma risk were more pronounced in women. For meningioma, no association was observed with overall or specific allergic conditions. Our findings confirmed the inverse association between allergic conditions and glioma risk but questioned the role of allergy in meningioma risk. Future research is needed to clarify the biological mechanism of overall allergy and allergic rhinitis on glioma and to confirm the different effect by gender.

Association between dietary nitrate and nitrite intake and sitespecific cancer risk: evidence from observational studies

Epidemiological studies have reported inconsistent findings on the association between dietary nitrate and nitrite intake and cancer risk. We performed a meta-analysis of epidemiological studies to summarize available evidence on the association between dietary nitrate and nitrite intake and cancer risk from published prospective and case-control studies. PubMed database was searched to identify eligible publications through April 30^th, 2016. Study-specific relative risks (RRs) with corresponding 95% confidence interval (CI) from individual studies were pooled by using random- or fixed- model, and heterogeneity and publication bias analyses were conducted.

Data from 62 observational studies, 49 studies for nitrates and 51 studies for nitrites, including a total of 60,627 cancer cases were analyzed. Comparing the highest vs. lowest levels, dietary nitrate intake was inversely associated with gastric cancer risk (RR = 0.78; 95%CI = 0.67-0.91) with moderate heterogeneity (I² = 42.3%). In contrast, dietary nitrite intake was positively associated with adult glioma and thyroid cancer risk with pooled RR of 1.21 (95%CI = 1.03-1.42) and 1.52 (95%CI = 1.12-2.05), respectively. No significant associations were found between dietary nitrate/nitrite and cancers of the breast, bladder, colorectal, esophagus, renal cell, non-Hodgkin lymphoma, ovarian, and pancreas. The present meta-analysis provided modest evidence that positive associations of dietary nitrate and negative associations of dietary nitrite with certain cancers.

Metabolomic screening of pre-diagnostic serum samples identifies association between α- and γ-tocopherols and glioblastoma risk

Glioblastoma is associated with poor prognosis with a median survival of one year. High doses of ionizing radiation is the only established exogenous risk factor. To explore new potential biological risk factors for glioblastoma, we investigated alterations in metabolite concentrations in pre-diagnosed serum samples from glioblastoma patients diagnosed up to 22 years after sample collection, and undiseased controls. The study points out a latent biomarker for future glioblastoma consisting of nine metabolites (γ-tocopherol, α-tocopherol, erythritol, erythronic acid, myo-inositol, cystine, 2-keto-L-gluconic acid, hypoxanthine and xanthine) involved in antioxidant metabolism. We detected significantly higher serum concentrations of α-tocopherol (p=0.0018) and γ-tocopherol (p=0.0009) in future glioblastoma cases. Compared to their matched controls, the cases showed a significant average fold increase of α- and γ-tocopherol levels: 1.2 for α-T (p=0.018) and 1.6 for γ-T (p=0.003). These tocopherol levels were associated with a glioblastoma odds ratio of 1.7 (α-T, 95% CI:1.0-3.0) and 2.1 (γ-T, 95% CI:1.2-3.8). Our exploratory metabolomics study detected elevated serum levels of a panel of molecules with antioxidant properties as well as oxidative stress generated compounds. Additional studies are necessary to confirm the association between the observed serum metabolite pattern and future glioblastoma development.

Health risk factors associated with meat, fruit and vegetable consumption in cohort studies: A comprehensive meta-analysis

The aim of this study was to perform a meta-analysis to test the association between red, processed, and total meat, as well as fruit and vegetable consumption, and selected health risk factors, including body weight status, smoking habit, physical activity level, level of education, and alcohol drinking in cohort studies on non-communicable disease. A systematic search of electronic databases was performed to identify relevant articles published up to March 2017. In a two-stage approach, frequency-weighted linear regression coefficients were first calculated for each variable, and then combined across studies through meta-regression. Ninety-eight studies including 20 on red meat, 6 on processed meat, 12 on total meat, 37 on fruit and vegetable combined, 21 on fruit and 24 on vegetable consumption were analyzed. Intake of red meat was positively associated with BMI, percentage of overweight and obese, low physical activity, and current and ever smoking and inversely associated with percentage of non-smokers and high physically active individuals. Similar associations were found for red meat were found, although based on fewer data. Intake of fruits and vegetables was positively associated with prevalence of non-smokers, high education and high physical activity, and similar results were found when examining fruit and vegetable consumption separately. Stratification by geographical area revealed that some associations were stronger in US rather than European or Asian cohorts. In conclusions, the distribution of health risk factors associated with high meat and fruit/vegetable consumption may differ from those of low-consumers. Some of these differences may mediate, confound, or modify the relation between diet and non-communicable disease risk.

Re-evaluation of sodium nitrate (E 251) and potassium nitrate (E 252) as food additives

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provided a scientific opinion re-evaluating the safety of sodium nitrate (E 251) and potassium nitrate (E 252) when used as food additives. The current acceptable daily intakes (ADIs) for nitrate of 3.7 mg/kg body weight (bw) per day were established by the SCF (1997) and JECFA (2002). The available data did not indicate genotoxic potential for sodium and potassium nitrate. The carcinogenicity studies in mice and rats were negative. The Panel considered the derivation of an ADI for nitrate based on the formation of methaemoglobin, following the conversion of nitrate, excreted in the saliva, to nitrite. However, there were large variations in the data on the nitrate-to-nitrite conversion in the saliva in humans. Therefore, the Panel considered that it was not possible to derive a single value of the ADI from the available data. The Panel noticed that even using the highest nitrate-to-nitrite conversion factor the methaemoglobin levels produced due to nitrite obtained from this conversion would not be clinically significant and would result to a theoretically estimated endogenous N-nitroso compounds (ENOC) production at levels which would be of low concern. Hence, and despite the uncertainty associated with the ADI established by the SCF, the Panel concluded that currently there was insufficient evidence to withdraw this ADI. The exposure to nitrate solely from its use as a food additive was estimated to be less than 5% of the overall exposure to nitrate in food based on a refined estimated exposure scenario. This exposure did not exceed the current ADI (SCF, 1997). However, if all sources of exposure to dietary nitrate are considered (food additive, natural presence and contamination), the ADI would be exceeded for all age groups at the mean and the highest exposure.

Re-evaluation of potassium nitrite (E 249) and sodium nitrite (E 250) as food additives

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provided a scientific opinion re-evaluating the safety of potassium nitrite (E 249) and sodium nitrite (E 250) when used as food additives. The ADIs established by the SCF (1997) and by JECFA (2002) for nitrite were 0-0.06 and 0-0.07 mg/kg bw per day, respectively. The available information did not indicate in vivo genotoxic potential for sodium and potassium nitrite. Overall, an ADI for nitrite per se could be derived from the available repeated dose toxicity studies in animals, also considering the negative carcinogenicity results. The Panel concluded that an increased methaemoglobin level, observed in human and animals, was a relevant effect for the derivation of the ADI. The Panel, using a BMD approach, derived an ADI of 0.07 mg nitrite ion/kg bw per day. The exposure to nitrite resulting from its use as food additive did not exceed this ADI for the general population, except for a slight exceedance in children at the highest percentile. The Panel assessed the endogenous formation of nitrosamines from nitrites based on the theoretical calculation of the NDMA produced upon ingestion of nitrites at the ADI and estimated a MoE > 10,000. The Panel estimated the MoE to exogenous nitrosamines in meat products to be < 10,000 in all age groups at high level exposure. Based on the results of a systematic review, it was not possible to clearly discern nitrosamines produced from the nitrite added at the authorised levels, from those found in the food matrix without addition of external nitrite. In epidemiological studies there was some evidence to link (i) dietary nitrite and gastric cancers and (ii) the combination of nitrite plus nitrate from processed meat and colorectal cancers. There was evidence to link preformed NDMA and colorectal cancers.

Migraine Triggers and Oxidative Stress: A Narrative Review and Synthesis

BACKGROUND

Blau theorized that migraine triggers are exposures that in higher amounts would damage the brain. The recent discovery that the TRPA1 ion channel transduces oxidative stress and triggers neurogenic inflammation suggests that oxidative stress may be the common denominator underlying migraine triggers.

OBJECTIVE

The aim of this review is to present and discuss the available literature on the capacity of common migraine triggers to generate oxidative stress in the brain.

METHODS

A Medline search was conducted crossing the terms "oxidative stress" and "brain" with "alcohol," "dehydration," "water deprivation," "monosodium glutamate," "aspartame," "tyramine," "phenylethylamine," "dietary nitrates," "nitrosamines," "noise," "weather," "air pollutants," "hypoglycemia," "hypoxia," "infection," "estrogen," "circadian," "sleep deprivation," "information processing," "psychosocial stress," or "nitroglycerin and tolerance." "Flavonoids" was crossed with "prooxidant." The reference lists of the resulting articles were examined for further relevant studies. The focus was on empirical studies, in vitro and of animals, of individual triggers, indicating whether and/or by what mechanism they can generate oxidative stress.

RESULTS

In all cases except pericranial pain, common migraine triggers are capable of generating oxidative stress. Depending on the trigger, mechanisms include a high rate of energy production by the mitochondria, toxicity or altered membrane properties of the mitochondria, calcium overload and excitotoxicity, neuroinflammation and activation of microglia, and activation of neuronal nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. For some triggers, oxidants also arise as a byproduct of monoamine oxidase or cytochrome P450 processing, or from uncoupling of nitric oxide synthase.

CONCLUSIONS

Oxidative stress is a plausible unifying principle behind the types of migraine triggers encountered in clinical practice. The possible implications for prevention and for understanding the nature of the migraine attack are discussed.

Red and processed meat consumption and risk of glioma in adults: A systematic review and meta-analysis of observational studies

BACKGROUND

These findings from several observational studies, investigated the association between red meat consumption and gliomas, were inconsistent. We conducted a systematic review and meta-analysis of observational studies to summarize available date on the relation between meat intake and risk of glioma.

MATERIALS AND METHODS

A systematic literature search of relevant reports published until May 2014 of the PubMed/Medline, ISI Web of Knowledge, Excerpta Medica database, Ovid database, Google Scholar, and Scopus databases was conducted. From 723 articles yielded in the preliminary literature search, data from eighteen publications (14 case-control, three cohort, and one nested case-control study) on unprocessed red meat, processed meat, and/or total red meat consumption in relation to glioma in adults were included in the analysis. Quality assessment of studies was performed. Random effects model was used to conduct the meta-analysis.

RESULTS

We found a positive significant association between unprocessed red meat intake and risk of glioma (relative risk [RR] = 1.30; 95% confidence interval [CI]: 1.08-1.58) after excluding three studies with uncertain type of brain cancer. This analysis included only one cohort study which revealed no relation between unprocessed red meat intake and glioma (RR = 1.75; 95% CI: 0.35-8.77). Consumption of processed meats was not related to increased risk of glioma in population-based case-control studies (RR = 1.26; 95% CI: 1.05-1.51) and reduced risk in hospital-based case-controls (RR = 0.79; 95% CI: 0.65-0.97). No significant association was seen between processed red meat intake and risk of glioma in cohort studies (RR: 1.08; 95% CI: 0.84-1.37). Total red meat consumption was not associated with risk of adult glioma in case-control or cohort studies.

CONCLUSION

In this meta-analysis of 18 observational studies, we found a modest positive association between unprocessed red meat intake and risk of gliomas based almost entirely on case-control studies. Processed red meat was overall not associated with risk of gliomas in case-control or cohort studies.

Is dietary nitrate/nitrite exposure a risk factor for development of thyroid abnormality? A systematic review and meta-analysis

The potential effects of inorganic nitrate/nitrite on global health are a much debated issue. In addition to possible methemoglobinemia and carcinogenic properties, anti-thyroid effects of nitrate/nitrite have been suggested. Considering the growing significance of nitrate/nitrite and since there is no comprehensive review in data available, clarifying the effect of nitrate/nitrite on thyroid disorder outcomes is essential. Therefore, we conducted this systematic review of experimental and clinical studies, and a meta-analysis of relevant cohort and cross-sectional studies investigating the association of nitrate/nitrite exposure and thyroid function. Most animal studies show that high exposure (~10-600 times of acceptable daily intake) to nitrate/nitrite induces anti-thyroid effects, including decreased serum level of thyroid hormones and histomorphological changes in thyroid gland; however no similar observations have been documented in humans. Based on our meta-analysis, no significant association was observed between nitrate exposure and the risk of thyroid cancer, hyper- and hypothyroidism; findings from three cohort studies however showed a significant association between higher exposure to nitrite and the risk of thyroid cancer (risk = 1.48, 95% confidence interval = 1.09-2.02, P = 0.012). Additional research is needed to clarify the association between nitrate/nitrite exposures and both thyroid function and cancer.

Association between Vitamin C Intake and Glioma Risk: Evidence from a Meta-Analysis

Background: The field of quantifying the association between the intake of vitamin C and risk of glioma still has conflicts. Thus, we performed a comprehensive meta-analysis to test the hypothesis that a high intake of vitamin C may be a protective effect on glioma risk. Methods: Pertinent studies were identified by a search in PubMed and Web of Knowledge up to June 2014. The random-effect model was used to combine study-specific results. Publication bias was estimated using Begg' funnel plot and Egger's regression asymmetry test. Results: Thirteen articles with 15 studies (2 cohort study and 13 case-control studies) involving 3,409 glioma cases about vitamin C intake and glioma risk were used in this meta-analysis. The combined relative risks (RRs) of glioma associated with vitamin C intake was 0.86 (95% CIs = 0.75-0.99). Overall, significant protective associations were also found in the American population (RRs = 0.85, 95% CIs = 0.73-0.98) and case-control studies (RRs = 0.80, 95% CIs = 0.69-0.93). No publication bias was found. Conclusions: Our analysis indicated that vitamin C intake might decrease the risk of glioma, especially among the Americans.

Nitrate in drinking water and bladder cancer risk in Spain

BACKGROUND

Nitrate is a widespread contaminant in drinking water and ingested nitrate under conditions resulting in endogenous nitrosation is suspected to be carcinogenic. However, the suggested association between nitrate in drinking water and bladder cancer remains inconsistent. We evaluated the long-term exposure to drinking water nitrate as a risk factor for bladder cancer, considering endogenous nitrosation modifiers and other covariables.

METHODS

We conducted a hospital-based case-control study of bladder cancer in Spain (1998-2001). Residential histories and water consumption information were ascertained through personal interviews. Historical nitrate levels (1940-2000) were estimated in study municipalities based on monitoring records and water source. Residential histories of study subjects were linked with nitrate estimates by year and municipality to calculate individual exposure from age 18 to recruitment. We calculated odds ratios (OR) and 95% confidence intervals (CI) for bladder cancer among 531 cases and 556 controls with reliable interviews and nitrate exposure information covering at least 70% of years from age 18 to interview.

RESULTS

Average residential levels ranged from 2.1mg/L to 12.0mg/L among regions. Adjusted OR (95%CI) for average residential levels relative to ≤ 5 mg/L were 1.2 (0.7-2.0) for >5-10mg/L and 1.1 (0.6-1.9) for >10mg/L. The OR for subjects with longest exposure duration (>20 years) to highest levels (>9.5mg/L) was 1.4 (0.9-2.3). Stratification by intake of vitamin C, vitamin E, meat, and gastric ulcer diagnosis did not modify these results. A non-significant negative association was found with waterborne ingested nitrate with an OR of 0.7 (0.4-1.0) for >8 vs. ≤ 4 mg/day. Adjustment for several covariables showed similar results to crude analyses.

CONCLUSION

Bladder cancer risk was inconsistently associated with chronic exposure to drinking water nitrate at levels below the current regulatory limit. Elevated risk is suggested only among subjects with longest exposure duration to the highest levels. No evidence of interaction with endogenous nitrosation modifiers was observed.

Vitamin E intake is not associated with glioma risk: evidence from a meta-analysis

BACKGROUND

Epidemiological studies evaluating the association between vitamin E intake and glioma risk have produced inconsistent results. Thus, we conducted a meta-analysis to summarize the evidence from epidemiological studies of vitamin E intake with the risk of glioma.

METHODS

Pertinent studies were identified by a search in pubmed and web of knowledge up to August 2014. The random-effect model was used to combine the results. Publication bias was estimated using the Egger's regression asymmetry test.

RESULTS

Twelve studies including 3180 glioma cases about vitamin E intake with the risk of glioma were included in this meta-analysis. The combined relative risk (RR) of glioma associated with vitamin E intake was 0.88 (95% CI = 0.69-1.12). The association was significant neither in the case-control studies nor in the cohort studies. No publication biases were found.

CONCLUSIONS

Our analysis indicated that vitamin E intake is not associated with the risk of glioma.

Nitrate and nitrite in the diet: how to assess their benefit and risk for human health

Nitrate is a natural constituent of the human diet and an approved food additive. It can be partially converted to nitrogen monoxide, which induces vasodilation and thereby decreases blood pressure. This effect is associated with a reduced risk regarding cardiovascular disease, myocardial infarction, and stroke. Moreover, dietary nitrate has been associated with beneficial effects in patients with gastric ulcer, renal failure, or metabolic syndrome. Recent studies indicate that such beneficial health effects due to dietary nitrate may be achievable at intake levels resulting from the daily consumption of nitrate-rich vegetables. N-nitroso compounds are endogenously formed in humans. However, their relevance for human health has not been adequately explored up to now. Nitrate and nitrite are per se not carcinogenic, but under conditions that result in endogenous nitrosation, it cannot be excluded that ingested nitrate and nitrite may lead to an increased cancer risk and may probably be carcinogenic to humans. In this review, the known beneficial and detrimental health effects related to dietary nitrate/nitrite intake are described and the identified gaps in knowledge as well as the research needs required to perform a reliable benefit/risk assessment in terms of long-term human health consequences due to dietary nitrate/nitrite intake are presented.

Early life exposures and the risk of adult glioma

Exposure to common infections in early life may stimulate immune development and reduce the risk for developing cancer. Birth order and family size are proxies for the timing of exposure to childhood infections with several studies showing a reduced risk of glioma associated with a higher order of birth (and presumed younger age at infection). The aim of this study was to examine whether birth order, family size, and other early life exposures are associated with the risk of glioma in adults using data collected in a large clinic-based US case-control study including 889 glioma cases and 903 community controls. A structured interviewer-administered questionnaire was used to collect information on family structure, childhood exposures and other potential risk factors. Logistic regression was used to calculate odds ratios (OR) and corresponding 95% confidence intervals (CI) for the association between early life factors and glioma risk. Persons having any siblings were at significantly lower risk for glioma when compared to those reporting no siblings (OR=0.64; 95% CI 0.44-0.93; p=0.020). Compared to first-borns, individuals with older siblings had a significantly lower risk (OR=0.75; 95% CI 0.61-0.91; p=0.004). Birth weight, having been breast fed in infancy, and season of birth were not associated with glioma risk. The current findings lend further support to a growing body of evidence that early exposure to childhood infections reduces the risk of glioma onset in children and adults.

A meta-analysis of alcohol consumption and the risk of brain tumours

BACKGROUND

Alcohol is capable of traversing the blood-brain barrier and is thus a possible risk factor for brain cancer. Several epidemiological studies have been published on the issue, a number of those during recent years, with inconsistent findings.

MATERIALS AND METHODS

We performed a systematic literature search in the Medline and EMBASE databases. We found a total of 19 studies providing risk estimates for total alcohol or specific alcoholic beverages. Pooled estimates of the relative risks (RR) and 95% confidence intervals (CI) were calculated using random-effects models.

RESULTS

The pooled RR of brain cancer for alcohol drinkers versus non-drinkers was 0.97 (95% CI 0.82-1.15; based on 12 studies). Moderate (<2 drinks/day) and heavy alcohol drinkers had RRs of 1.01 (95% CI 0.81-1.25) and 1.35 (95% CI 0.85-2.15), respectively. With reference to specific alcoholic beverages, the RRs were 1.01 (95% CI 0.70-1.48) for wine, 0.96 (95% CI 0.82-1.12) for beer, and 1.20 (95% CI 1.01-1.42) for spirit consumption. The RRs for drinkers versus non-drinkers were 0.93 (95% CI 0.81-1.07) for glioma and 0.71 (95% CI 0.45-1.12) for meningioma.

CONCLUSIONS

Alcohol drinking does not appear to be associated with adult brain cancer, though a potential effect of high doses deserves further study.

Brain cancer in workers employed at a specialty chemical research facility

ABSTRACT This study evaluated unique exposures and their relationship to brain cancer mortality in employees of a specialty chemical research facility. Following an exposure assessment that concerned compounds distinct to this facility, the authors conducted a cohort mortality study of 5,284 workers to assess mortality in reference to the general population and a nested case-control study to evaluate brain cancer risk associated with specific jobs and unique chemical exposures. Four hundred eighty-six deaths, including 14 brain cancer deaths, were identified. Overall mortality was lower than expected. Brain cancer mortality was elevated (standardized mortality ratio [SMR] = 2.02, 95% confidence interval [CI] = 1.11-3.40). Exposures to 5 specific chemical categories were assessed. Exploration of work history and the specific chemical exposures did not explain the brain cancer cases. No clear occupational etiology was identified.

Dietary components related to N-nitroso compound formation: a prospective study of adult glioma

BACKGROUND

N-nitroso compounds (NOC) are found in processed meat and are formed endogenously from intake of nitrite and nitrate. Endogenous NOC formation is antagonized by nitrosation inhibitors in fruit and vegetables (e.g., vitamin C) and promoted by heme in red meat. It has been hypothesized that a diet resulting in high exposure to NOCs increases adult glioma risk.

METHODS

Using proportional hazards models, we tested this hypothesis among 545,770 participants in the prospective NIH-AARP Diet and Health Study, which assessed dietary intake at baseline (1995-1996) with a comprehensive food frequency questionnaire, and at ages 12 to 13 years with an abbreviated food frequency questionnaire.

RESULTS

During follow-up through 2003, 585 participants were diagnosed with glioma. We found no significant trends in glioma risk for consumption of processed or red meat, nitrate, or vitamin C or E. We found significant positive trends for nitrite intake from plant sources (hazard ratio for quintile 5 versus quintile 1, 1.59; 95% confidence interval, 1.20-2.10; P for trend = 0.028) and, unexpectedly, for fruit and vegetable intake (hazard ratio, 1.42; 95% confidence interval, 1.08-1.86; P for trend = 0.0081). Examination of interactions between dietary intakes (e.g., nitrite and vitamin C) and a limited analysis of diet at ages 12 to 13 years provided no support for the NOC hypothesis.

CONCLUSIONS

Our results suggest that consumption of processed or red meat, nitrite, or nitrate does not increase adult glioma risk, and that consumption of fruit and vegetables, vitamin C, or vitamin E does not reduce risk.

IMPACT

Our results, in agreement with the only previous prospective analysis, cast doubt on the NOC hypothesis in relation to dietary intake and adult glioma risk.