Nitrate and nitrite intake and the risk for type 1 diabetes in Finnish children. Childhood Diabetes in Finland Study Group

Dietary nitrate, nitrite, and nitrosamine in association with diabetes: a systematic review and meta-analysis

CONTEXT

Diabetes is a global health concern, and diet is a contributing factor to diabetes. Findings regarding the connection between nitrate, nitrite, and nitrosamine and diabetes risk are inconsistent.

OBJECTIVE

The aim was to examine the effects of these dietary compounds on diabetes risk.

DATA SOURCES

The data were sourced from PubMed, EMBASE, Scopus, and Web of Science until February 28, 2023. Studies that reported individual-level consumption of these compounds were included. Review articles or ecological studies were excluded.

DATA EXTRACTION

The number of events and total observations were recorded.

DATA ANALYSIS

The pooled odds ratio (OR) was calculated and displayed in a forest plot. Subgroup and sensitivity analyses were predefined. A dose-response meta-analysis was conducted to determine the exposure intervals that may increase the risk of disease. Six observational reports that met the inclusion criteria were included, involving 108 615 individuals. Participants in the highest quantile of nitrite intake had a greater risk of diabetes compared with those in the lowest quantile (OR, 1.61; 95% confidence interval [CI], 1.08-2.39; I2 = 74%, P = 0.02). Higher nitrosamine consumption tended to increase diabetes risk (OR, 1.52; 95% CI, 0.76-3.04; I2 = 76%; P = 0.24). The relationship was stronger for type 1 (OR, 1.79; 95% CI, 1.20-2.67; I2 = 58%; P < 0.01) than for type 2 diabetes (OR, 1.42; 95% CI, 0.86-2.37; I2 = 71%; P = 0.17). Additionally, nitrite consumption had a dose-dependent association with both phenotypes. No association was found between diabetes risk and high nitrate intake (OR, 1.01; 95% CI, 0.87-1.18; I2 = 28%; P = 0.87).

CONCLUSION

Attention should be paid to the consumption of nitrite-containing foods.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42023394462 (https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=394462).

Metabolic effects of L-citrulline in type 2 diabetes

The prevalence of type 2 diabetes (T2D) is increasing worldwide. Decreased nitric oxide (NO) bioavailability is involved in the pathophysiology of T2D and its complications. L-citrulline (Cit), a precursor of NO production, has been suggested as a novel therapeutic agent for T2D. Available data from human and animal studies indicate that Cit supplementation in T2D increases circulating levels of Cit and L-arginine while decreasing circulating glucose and free fatty acids and improving dyslipidemia. The underlying mechanisms for these beneficial effects of Cit include increased insulin secretion from the pancreatic β cells, increased glucose uptake by the skeletal muscle, as well as increased lipolysis and β-oxidation, and decreased glyceroneogenesis in the adipose tissue. Thus, Cit has antihyperglycemic, antidyslipidemic, and antioxidant effects and has the potential to be used as a new therapeutic agent in the management of T2D. This review summarizes available literature from human and animal studies to explore the effects of Cit on metabolic parameters in T2D. It also discusses the possible mechanisms underlying Cit-induced improved metabolic parameters in T2D.

Islet autoantibody seroconversion in type-1 diabetes is associated with metagenome-assembled genomes in infant gut microbiomes

The immune system of some genetically susceptible children can be triggered by certain environmental factors to produce islet autoantibodies (IA) against pancreatic β cells, which greatly increases their risk for Type-1 diabetes. An environmental factor under active investigation is the gut microbiome due to its important role in immune system education. Here, we study gut metagenomes that are de-novo-assembled in 887 at-risk children in the Environmental Determinants of Diabetes in the Young (TEDDY) project. Our results reveal a small set of core protein families, present in >50% of the subjects, which account for 64% of the sequencing reads. Time-series binning generates 21,536 high-quality metagenome-assembled genomes (MAGs) from 883 species, including 176 species that hitherto have no MAG representation in previous comprehensive human microbiome surveys. IA seroconversion is positively associated with 2373 MAGs and negatively with 1549 MAGs. Comparative genomics analysis identifies lipopolysaccharides biosynthesis in Bacteroides MAGs and sulfate reduction in Anaerostipes MAGs as functional signatures of MAGs with positive IA-association. The functional signatures in the MAGs with negative IA-association include carbohydrate degradation in lactic acid bacteria MAGs and nitrate reduction in Escherichia MAGs. Overall, our results show a distinct set of gut microorganisms associated with IA seroconversion and uncovered the functional genomics signatures of these IA-associated microorganisms.

Maternal Nitrate and Nitrite Intakes during Pregnancy and Risk of Islet Autoimmunity and Type 1 Diabetes: The DIPP Cohort Study

BACKGROUND

High dietary intake of nitrate and nitrite might increase the risk of type 1 diabetes. To our knowledge, no earlier prospective study has explored whether maternal dietary intake of nitrate and nitrite during pregnancy is associated with the risk of type 1 diabetes in the offspring.

OBJECTIVE

Our aim was to study association between maternal intake of nitrate and nitrite during pregnancy and the risk of islet autoimmunity and type 1 diabetes in the offspring.

DESIGN

Children born between 1997 and 2004 at Oulu and Tampere University Hospitals in Finland and carrying increased human leukocyte antigen (HLA)-conferred risk for type 1 diabetes were followed in the Type 1 Diabetes Prediction and Prevention (DIPP) study from 3 mo of age. Islet autoantibodies were screened at 3- to 12-mo intervals from serum samples. Of 4879 children, 312 developed islet autoimmunity and 178 developed type 1 diabetes during a 15-y follow-up. Maternal intake of nitrate and nitrite during the eighth month of pregnancy was assessed after birth using a validated self-administered FFQ. Cox proportional hazards regression was used for the statistical analyses.

RESULTS

Maternal intake of nitrate and nitrite during pregnancy was not associated with the child's risk of islet autoimmunity [nitrate: HR 0.99 (95% CI: 0.88, 1.11); nitrite: HR 1.03 (95% CI: 0.92, 1.15)] or type 1 diabetes [nitrate: HR 1.02 (95% CI: 0.88, 1.17); nitrite: HR 0.97 (95% CI: 0.83, 1.12)] when adjusted for energy (residual method), sex, HLA risk group, and family history of diabetes. Further adjustment for dietary antioxidants (vitamin C, vitamin E, and selenium) did not change the results.

CONCLUSION

Maternal dietary intake of nitrate or nitrite during pregnancy is not associated with the risk of islet autoimmunity or type 1 diabetes in the offspring genetically at risk for type 1 diabetes.

Consumption of red meat, genetic susceptibility, and risk of LADA and type 2 diabetes

Purpose

Red meat consumption is positively associated with type 1 (T1D) and type 2 (T2D) diabetes. We investigated if red meat consumption increases the risk of latent autoimmune diabetes in adults (LADA) and T2D, and potential interaction with family history of diabetes (FHD), HLA and TCF7L2 genotypes.

Methods

Analyses were based on Swedish case–control data comprising incident cases of LADA (n = 465) and T2D (n = 1528) with matched, population-based controls (n = 1789; n = 1553 in genetic analyses). Multivariable-adjusted ORs in relation to self-reported processed and unprocessed red meat intake were estimated by conditional logistic regression models. Attributable proportion (AP) due to interaction was used to assess departure from additivity of effects.

Results

Consumption of processed red meat was associated with increased risk of LADA (per one servings/day OR 1.27, 95% CI 1.07–1.52), whereas no association was observed for unprocessed red meat. For T2D, there was no association with red meat intake once BMI was taken into account. The combination of high (> 0.3 servings/day vs. less) processed red meat intake and high-risk HLA-DQB1 and -DRB1 genotypes yielded OR 8.05 (95% CI 4.86–13.34) for LADA, with indications of significant interaction (AP 0.53, 95% CI 0.32–0.73). Results were similar for the combination of FHD-T1D and processed red meat. No interaction between processed red meat intake and FHD-T2D or risk variants of TCF7L2 was seen in relation to LADA or T2D.

Conclusion

Consumption of processed but not unprocessed red meat may increase the risk of LADA, especially in individuals with FHD-T1D or high-risk HLA genotypes.

Electronic supplementary material

The online version of this article (10.1007/s00394-020-02285-2) contains supplementary material, which is available to authorized users.

The Association of Maternal Protein Intake during Pregnancy in Humans with Maternal and Offspring Insulin Sensitivity Measures

The purpose of this review is to critically evaluate the studies assessing the relations between protein intake during human pregnancy and insulin sensitivity measures in the mother and offspring, and to get a better understanding of the knowledge gaps that still exist. Overall, there is insufficient evidence to conclude about implications of higher amounts of protein intake during pregnancy on maternal or offspring insulin sensitivity. However, studies show a relation between protein quality and insulin sensitivity, such that animal protein may be associated with negative outcomes and plant protein may be associated with positive insulin sensitivity outcomes. There is an urgent need for standardized studies using comparable terminology to evaluate any potential relations between insulin sensitivity in mothers and offspring and truly low and high maternal protein intake while maintaining eucaloric balance to better inform about optimal protein dosage and quality during this period.

A Joint Modeling Approach for Childhood Meat, Fish and Egg Consumption and the Risk of Advanced Islet Autoimmunity

Several dietary factors have been suspected to play a role in the development of advanced islet autoimmunity (IA) and/or type 1 diabetes (T1D), but the evidence is fragmentary. A prospective population-based cohort of 6081 Finnish newborn infants with HLA-DQB1-conferred susceptibility to T1D was followed up to 15 years of age. Diabetes-associated autoantibodies and diet were assessed at 3- to 12-month intervals. We aimed to study the association between consumption of selected foods and the development of advanced IA longitudinally with Cox regression models (CRM), basic joint models (JM) and joint latent class mixed models (JLCMM). The associations of these foods to T1D risk were also studied to investigate consistency between alternative endpoints. The JM showed a marginal association between meat consumption and advanced IA: the hazard ratio adjusted for selected confounding factors was 1.06 (95% CI: 1.00, 1.12). The JLCMM identified two classes in the consumption trajectories of fish and a marginal protective association for high consumers compared to low consumers: the adjusted hazard ratio was 0.68 (0.44, 1.05). Similar findings were obtained for T1D risk with adjusted hazard ratios of 1.13 (1.02, 1.24) for meat and 0.45 (0.23, 0.86) for fish consumption. Estimates from the CRMs were closer to unity and CIs were narrower compared to the JMs. Findings indicate that intake of meat might be directly and fish inversely associated with the development of advanced IA and T1D, and that disease hazards in longitudinal nutritional epidemiology are more appropriately modeled by joint models than with naive approaches.

Beneficial treatment effects of dietary nitrate supplementation on testicular injury in streptozotocin-induced diabetic male rats

RESEARCH QUESTION

Do low doses of dietary nitrate help to attenuate the progression of diabetic reproductive disorders in streptozotocin-induced diabetic male rats?

DESIGN

Fifty male Wistar rats were divided into five groups: controls receiving distilled water; controls receiving 100 mg/l nitrate in distilled water; diabetic rats receiving distilled water; diabetic rats receiving insulin 2-4 U/day of neutral protamine hagedorn insulin; and diabetic rats receiving 100 mg/l nitrate in distilled water. Diabetes was induced by 45 mg/kg streptozotocin. Nitrate and insulin treatment were started 4 weeks after diabetes induction for 8 weeks. Serum insulin, nitrogen oxide, stereology of testis, apoptosis, sperm parameters, and mRNA expression of Pdcd4, Pacs2, p53 and miR-449a were assessed at the end of the study.

RESULTS

Blood glucose, apoptotic index of seminiferous tubules and expression of p53, Pdcd4, and Pacs2 mRNA were significantly higher in the diabetic rats (P < 0.001). Decreased body weight, serum insulin and nitrogen oxide level, and miR-449a were observed in the diabetic group (P < 0.01 for insulin; P < 0.001 for others). Most sperm parameters and stereological results differed between diabetic and control rats; nitrate recovered almost all these alterations, including dead spermatozoa, sperm motility grade, sperm deformity index, spermatozoa with damaged DNA, malformations in abnormal spermatozoa, total volume of seminiferous tubule, germinal epithelium, capsule, lumen, interstitial tissue, seminiferous tubule diameter, germinal epithelium height, the number of spermatogenic, Sertoli and Leydig cells.

CONCLUSIONS

Treatment with sodium nitrate could modulate apoptosis, which is a major cause of diabetic testicular disorder. These experiments suggest that nitric oxide plays an important role in the function of the reproductive system.

Assessment, mapping, and management of health risk from nitrate accumulation in onion for Iranian population

Excess accumulation of nitrate in vegetable crops is normally related to the excessive use of nitrogen fertilizers applied in agricultural fields. This study was performed to evaluate the level of nitrate concentration in onion production in Isfahan province of Iran and the potential health risks associated with high level of nitrate in this crop, as an example of a case-study. The risk was estimated by using the United States Environmental Protection Agency (USEPA) method and presented as risk maps. Additionally, the impact of an improved fertilizer management practice in selected vulnerable fields for reducing nitrate concentration in onion production was evaluated. For this assessment, four different onion fields in which onion bulb nitrate concentration was higher than the safety level (70 mg kg^-1 FW), provided by Welch (2003) in a survey study, were chosen. The risk maps showed that despite higher risk possibility in adults, in comparison with children, all values were lower than the acceptable level. Further, the split application of nitrogen fertilizers in all fields significantly reduced plant nitrate concentration with no reduction in yield and even observed increase in the overall economic yield production. Therefore, considering crop yields and nitrate accumulation impacts, improved nitrogen management could provide an opportunity to promote onion crop production while reducing negative health effects in high-risk regions in Isfahan province of Iran.

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).

Modified Healthy Eating Index and Incidence of Metabolic Syndrome in Children and Adolescents: Tehran Lipid and Glucose Study

OBJECTIVE

To assess the relationship between modified healthy eating index (mHEI) with the development of metabolic syndrome (MetS) among children and adolescents.

STUDY DESIGN

Dietary data were collected using a food frequency questionnaire among 424 healthy subjects, aged 6-18 years. The components of mHEI were grains, vegetables and fruits, dairy, red to white meat ratio, butter, sweet snacks, sweetened beverages, salty snacks, and fast food. Multivariable logistic regression models were used to estimate the incidence of MetS after 3.6 years of follow-up in each quartile of the mHEI score, adjusted for baseline age, sex, total energy intake, physical activity, and body mass index.

RESULTS

The mean ± SD age and mHEI scores of participants were 13.6 ± 3.7 years and 55.9 ± 10.0, respectively, at baseline. MetS developed in 11% of the participants at the end of follow-up. After adjustment for confounders, the occurrences of MetS decreased in the highest quartile compared with the lowest quartile of the mHEI score (OR = 0.35, 95% CI 0.13-0.98, P for trend = .025). In addition, higher scores of mHEI components including fruits, salty snacks, and fast food were associated with lower risk of MetS.

CONCLUSIONS

Higher scores of mHEI as an indicator of diet quality may hinder the development of MetS among children and adolescents.

Nitrate induces a type 1 diabetic profile in alligator hatchlings

Type 1 diabetes (T1D) is a chronic autoimmune disease that affects 1 in 300 children by age 18. T1D is caused by inflammation-induced loss of insulin-producing pancreatic beta cells, leading to high blood glucose and a host of downstream complications. Although multiple genes are associated with T1D risk, only 5% of genetically susceptible individuals actually develop clinical disease. Moreover, a growing number of T1D cases occur in geographic clusters and among children with low risk genotypes. These observations suggest that environmental factors contribute to T1D etiology. One potential factor, supported primarily by epidemiological studies, is the presence of nitrate and nitrite in drinking water. To test this hypothesis, female hatchling alligators were exposed to environmentally relevant concentrations of nitrate in their tank water (reference, 10mg/L, or 100mg/L NO₃-N) from hatch through 5 weeks or 5 months of age. At each time point, endpoints related to T1D were investigated: plasma levels of glucose, triglycerides, testosterone, estradiol, and thyroxine; pancreas, fat body, and thyroid weights; weight gain or loss; presence of immune cells in the pancreas; and pancreatic beta cell number, assessed by antibody staining of nkx6.1 protein. Internal dosing of nitrate was confirmed by measuring plasma and urine nitrate levels and whole blood methemoglobin. Cluster analysis indicated that high nitrate exposure (most animals exposed to 100mg/L NO3-N and one alligator exposed to 10mg/L NO3-N) induced a profile of endpoints consistent with early T1D that could be detected after 5 weeks and was more strongly present after 5 months. Our study supports epidemiological data correlating elevated nitrate with T1D onset in humans, and highlights nitrate as a possible environmental contributor to the etiology of T1D, possibly through its role as a nitric oxide precursor.

Red meat, diseases, and healthy alternatives: A critical review

Meat is an important food for human nutrition, by especially providing high-quality protein and also some essential micronutrients, in front iron, zinc, and vitamin B₁₂. However, a high intake of red and processed meat is associated with an increased risk for diseases, especially type 2 diabetes and colorectal cancer, as several epidemiological studies and meta-analyses have shown. This review summarizes meta-analyses of publications studying the association between red and processed meat intake and type 2 diabetes, cardiovascular diseases, colorectal and other cancers, and all-cause mortality. Various potential mechanisms involved in the increased disease risk are discussed. Furthermore, the beneficial effects of healthy alternatives for meat, like fish, nuts, vegetables and fruits, pulses and legumes, whole grains, and dairy products are reviewed by including selected papers and recent meta-analyses.

Is there a role for gut microbiota in type 1 diabetes pathogenesis?

Type 1 diabetes mellitus (T1D) is an autoimmune disease characterized by insufficient insulin production due to the destruction of insulin secreting β-cells in the Langerhans islets. A variety of factors, including chemicals, viruses, commensal bacteria and diet have been proposed to contribute to the risk of developing the disorder. In the last years, gut microbiota has been proposed as a main factor in T1D pathogenesis. Several alterations of gut microbiota composition were described both in animal model and in humans. The decrease of Firmicutes/Bacteroides ratio was the most frequent pattern described, in particular, in human studies. Furthermore, Bacteroides, Clostridium cluster XIVa, Lactobacillus, Bifidobacterium, and Prevotella relative abundances were different in healthy and affected subjects. Dysbiosis would seem to increase intestinal permeability and thus promote the development of a pro-inflammatory niche that stimulates β-cell autoimmunity in predisposed subjects. Preliminary studies on animal models were realized to investigate the role of gut microbiota modulation as therapy or prevention approach in predisposed animals: promising and stimulating results have been reported. Key message Dietary antigens and microbiota-derived products might act as triggers of T1D by causing a pro-inflammatory and metabolic dysfunctional environment.

Nitrate-nitrite-nitrosamines exposure and the risk of type 1 diabetes: A review of current data

The potential toxic effects of nitrate-nitrite-nitrosamine on pancreatic β cell have remained a controversial issue over the past two decades. In this study, we reviewed epidemiological studies investigated the associations between nitrate-nitrite-nitrosamines exposure, from both diet and drinking water to ascertain whether these compounds may contribute to development of type 1 diabetes. To identify relevant studies, a systematic search strategy of PubMed, Scopus, and Science Direct was conducted using queries including the key words “nitrate”, “nitrite”, “nitrosamine” with “type 1 diabetes” or “insulin dependent diabetes mellitus”. All searches were limited to studies published in English. Ecologic surveys, case-control and cohort studies have indicated conflicting results in relation to nitrate-nitrite exposure from drinking water and the risk of type 1 diabetes. A null, sometimes even negative association has been mainly reported in regions with a mean nitrate levels < 25 mg/L in drinking water, while increased risk of type 1 diabetes was observed in those with a maximum nitrate levels > 40-80 mg/L. Limited data are available regarding the potential diabetogenic effect of nitrite from drinking water, although there is evidence indicating dietary nitrite could be a risk factor for development of type 1 diabetes, an effect however that seems to be significant in a higher range of acceptable limit for nitrate/nitrite. Current data regarding dietary exposure of nitrosamine and development of type 1 diabetes is also inconsistent. Considering to an increasing trend of type 1 diabetes mellitus (T1DM) along with an elevated nitrate-nitrite exposure, additional research is critical to clarify potential harmful effects of nitrate-nitrite-nitrosamine exposure on β-cell autoimmunity and the risk of T1DM.

Environmental Risk Factors and Type 1 Diabetes: Past, Present, and Future

Type 1 diabetes is an autoimmune condition that results from the destruction of the insulin-producing beta cells of the pancreas. The excess morbidity and mortality resulting from its complications, coupled with its increasing incidence, emphasize the importance of better understanding the causes of this condition. Over the past several decades, a substantive amount of work has been done and, although many advances have occurred in identifying disease-susceptibility genes, there has been a lag in understanding the environmental triggers. Several putative environmental risk factors have been proposed, including infections, dietary factors, air pollution, vaccines, location of residence, family environment and stress. However, most of these factors have been inconclusive, thus supporting the need for further study into the causes of type 1 diabetes.

Dietary factors in the development of type 1 diabetes

There are several indicators concerning the putative importance of dietary factors during the fetal period lactation, infancy and childhood in the etiology of type 1 diabetes. Among foods, cow's milk consumption has been associated with an increased risk of preclinical and/or clinical type 1 diabetes and sugars with a progression from preclinical to clinical disease. Breast milk, on the other hand, may be protective. Processed foods may be related to a greater risk of type 1 diabetes because they contain higher amounts of advanced glycation end-products. Nitrites or N-nitroso compounds in processed meat products could increase the risk of this disease. Among nutrients, n-3 fatty acids, vitamins D and E, and zinc may protect from preclinical and/or clinical type 1 diabetes. The microbial composition of foods or food's other effects on gut microbiota are receiving increasing attention, also due to their putative role in the development of type 1 diabetes. Still the number of prospective studies in this research field is limited and most of the findings remain to be replicated.

Zebrafish as a Model to Assess the Teratogenic Potential of Nitrite

High nitrate levels in the environment may result in congenital defects or miscarriages in humans. Presumably, this is due to the conversion of nitrate to nitrite by gut and salivary bacteria. However, in other mammalian studies, high nitrite levels do not cause birth defects, although they can lead to poor reproductive outcomes. Thus, the teratogenic potential of nitrite is not clear. It would be useful to have a vertebrate model system to easily assess teratogenic effects of nitrite or any other chemical of interest. Here, we demonstrate the utility of zebrafish (Danio rerio) to screen compounds for toxicity and embryonic defects. Zebrafish embryos are fertilized externally and have rapid development, making them a good model for teratogenic studies. We show that increasing the time of exposure to nitrite negatively affects survival. Increasing the concentration of nitrite also adversely affects survival, whereas nitrate does not. For embryos that survive nitrite exposure, various defects can occur, including pericardial and yolk sac edema, swim bladder noninflation, and craniofacial malformation. Our results indicate that the zebrafish is a convenient system for studying the teratogenic potential of nitrite. This approach can easily be adapted to test other chemicals for their effects on early vertebrate development.

Maternal intake of fatty acids and their food sources during lactation and the risk of preclinical and clinical type 1 diabetes in the offspring

AIMS

We examined maternal dietary intake of fatty acids and foods which are sources of fatty acids during lactation and whether they are associated with the risk of preclinical and clinical type 1 diabetes in the offspring.

METHODS

The subjects comprised a cohort of 2,939 mother-child pairs from the prospective Type 1 Diabetes Prediction and Prevention Study. Composition of maternal diet during the third month of lactation was assessed by a validated food frequency questionnaire. Among the children with HLA-conferred susceptibility to type 1 diabetes, 172 developed preclinical and 81 clinical diabetes. Average follow-up for preclinical type 1 diabetes was 7.5 years (range 0.2-14.0 years) and for clinical type 1 diabetes 7.7 years (0.2-14.0 years).

RESULTS

Maternal intake of fatty acids during lactation was not associated with the risk of type 1 diabetes in the offspring. After adjusting for putative confounders, maternal total consumption of red meat and meat products during lactation was associated both with increased risk for preclinical [hazard ratio (HR) 1.19, 95 % CI 1.02-1.40, p = 0.038] and clinical type 1 diabetes (HR 1.27, 95 % CI 1.06-1.52, p = 0.025). In particular, consumption of processed meat products showed an association with increased risk for type 1 diabetes (HR 1.23, 95 % CI 1.02-1.48, p = 0.045). Maternal use of vegetable oils was associated with increased risk for preclinical type 1 diabetes (HR 1.21, 95 % CI 1.03-1.41, p = 0.023).

CONCLUSIONS

Maternal consumption of red meat, especially processed meat, during lactation may increase the risk of type 1 diabetes.

Beneficial effects of inorganic nitrate/nitrite in type 2 diabetes and its complications

Background and aim

The ability of inorganic nitrate and nitrite to convert to nitric oxide (NO), and some of its properties e.g. regulation of glucose metabolism, vascular homeostasis, and insulin signaling pathway, have recently raised the hypothesis that inorganic nitrate and nitrite could be potential therapeutic agents in type 2 diabetes. In this review, we reviewed experimental and clinical studies investigating the effect of nitrate/nitrite administration on various aspects of type 2 diabetes.

Findings

Studies showed that an altered metabolism of nitrate/nitrite and impaired NO pathway occurs in diabetes which could contribute to its complications. Some important beneficial properties, including regulation of glucose homeostasis and insulin signaling pathway, improvement of insulin resistance and vascular function, hypotensive, hypolipidemic as well as anti-inflammatory and anti-oxidative effects have been observed following administration of inorganic nitrate/nitrite.

Conclusion

It seems that dietary nitrate/nitrite could be a compensatory fuel for a disrupted nitrate/nitrite/NO pathway and related disorders in diabetes. Although some beneficial properties of nitrate/nitrite have been reported by experimental investigations, long-term clinical studies with various doses of inorganic nitrate/nitrite supplementation, are recommended to confirm these effects.

Can exposure to environmental chemicals increase the risk of diabetes type 1 development?

Type 1 diabetes mellitus (T1DM) is an autoimmune disease, where destruction of beta-cells causes insulin deficiency. The incidence of T1DM has increased in the last decades and cannot entirely be explained by genetic predisposition. Several environmental factors are suggested to promote T1DM, like early childhood enteroviral infections and nutritional factors, but the evidence is inconclusive. Prenatal and early life exposure to environmental pollutants like phthalates, bisphenol A, perfluorinated compounds, PCBs, dioxins, toxicants, and air pollutants can have negative effects on the developing immune system, resulting in asthma-like symptoms and increased susceptibility to childhood infections. In this review the associations between environmental chemical exposure and T1DM development is summarized. Although information on environmental chemicals as possible triggers for T1DM is sparse, we conclude that it is plausible that environmental chemicals can contribute to T1DM development via impaired pancreatic beta-cell and immune-cell functions and immunomodulation. Several environmental factors and chemicals could act together to trigger T1DM development in genetically susceptible individuals, possibly via hormonal or epigenetic alterations. Further observational T1DM cohort studies and animal exposure experiments are encouraged.

The role of Toll-like receptors and vitamin D in diabetes mellitus type 1--a review

It is widely accepted that type 1 diabetes mellitus (T1DM) is an autoimmune disease resulting from an interaction between immunologic, genetic and environmental factors. However, the exact mechanism leading to the development of T1DM remains incomplete. There is a large body of evidence pointing towards the important role of toll-like receptor (TLR) activation and vitamin D deficiency in T1DM pathogenesis. In this article, we review the available data on the influence of TLRs' level of activation and vitamin D status on the risk of the development of T1DM in humans and rodent models. We also summarize the current information regarding the interactions between TLRs' level of activation, vitamin D status and various environmental factors, such as enteroviral infections, the gut microbiota and breastfeeding substitution, among others. Our results stipulate that vitamin D seems to protect against T1DM by reducing the TLRs' level of activation.

Prepregnancy low-carbohydrate dietary pattern and risk of gestational diabetes mellitus: a prospective cohort study

BACKGROUND

Low-carbohydrate diets (LCDs) have been vastly popular for weight loss. The association between a low-carbohydrate dietary pattern and risk of gestational diabetes mellitus (GDM) remains unknown.

OBJECTIVE

We aimed to prospectively examine the association of 3 prepregnancy low-carbohydrate dietary patterns with risk of GDM.

DESIGN

We included 21,411 singleton pregnancies in the Nurses' Health Study II. Prepregnancy LCD scores were calculated from validated food-frequency questionnaires, including an overall LCD score on the basis of intakes of carbohydrate, total protein, and total fat; an animal LCD score on the basis of intakes of carbohydrate, animal protein, and animal fat; and a vegetable LCD score on the basis of intakes of carbohydrate, vegetable protein, and vegetable fat. A higher score reflected a higher intake of fat and protein and a lower intake of carbohydrate, and it indicated closer adherence to a low-carbohydrate dietary pattern. RRs and 95% CIs were estimated by using generalized estimating equations with log-binomial models.

RESULTS

We documented 867 incident GDM pregnancies during 10 y follow-up. Multivariable-adjusted RRs (95% CIs) of GDM for comparisons of highest with lowest quartiles were 1.27 (1.06, 1.51) for the overall LCD score (P-trend = 0.03), 1.36 (1.13, 1.64) for the animal LCD score (P-trend = 0.003), and 0.84 (0.69, 1.03) for the vegetable LCD score (P-trend = 0.08). Associations between LCD scores and GDM risk were not significantly modified by age, parity, family history of diabetes, physical activity, or overweight status.

CONCLUSIONS

A prepregnancy low-carbohydrate dietary pattern with high protein and fat from animal-food sources is positively associated with GDM risk, whereas a prepregnancy low-carbohydrate dietary pattern with high protein and fat from vegetable food sources is not associated with the risk. Women of reproductive age who follow a low-carbohydrate dietary pattern may consider consuming vegetable rather than animal sources of protein and fat to minimize their risk of GDM.

Beyond genetics. Influence of dietary factors and gut microbiota on type 1 diabetes

Type 1 diabetes (T1D) is an autoimmune disease ultimately leading to destruction of insulin secreting β-cells in the pancreas. Genetic susceptibility plays an important role in T1D etiology, but even mono-zygotic twins only have a concordance rate of around 50%, underlining that other factors than purely genetic are involved in disease development. Here we review the influence of dietary and environmental factors on T1D development in humans as well as animal models. Even though data are still inconclusive, there are strong indications that gut microbiota dysbiosis plays an important role in T1D development and evidence from animal models suggests that gut microbiota manipulation might prove valuable in future prevention of T1D in genetically susceptible individuals.

High meat consumption is associated with type 1 diabetes mellitus in a Sardinian case-control study

The large worldwide variation in type 1 diabetes incidence and increasing incidence over time points toward important environmental risk factors. Among them, nutrition plays an important role. The objective was to investigate the relationship between type 1 diabetes and nutritional factors in pregnancy and early in life. We carried out, using semi-quantitative food frequency questionnaires, a retrospective case-control study in 298 children of 0-15 years old, 145 of which were affected by type 1 diabetes. The diet of all children and of their mothers during pregnancy and lactation was assessed. In children, a statistically significant dose-response association between type 1 diabetes and the amount of meat consumption was found while no other nutritional factors were associated with the disease. High meat consumption seems to be an important early in life cofactor for type 1 diabetes development, although these findings need to be confirmed in wider prospective follow-up studies.

Unprocessed red and processed meats and risk of coronary artery disease and type 2 diabetes--an updated review of the evidence

Growing evidence suggests that effects of red meat consumption on coronary heart disease (CHD) and type 2 diabetes could vary depending on processing. We reviewed the evidence for effects of unprocessed (fresh/frozen) red and processed (using sodium/other preservatives) meat consumption on CHD and diabetes. In meta-analyses of prospective cohorts, higher risk of CHD is seen with processed meat consumption (RR per 50 g: 1.42, 95 %CI = 1.07-1.89), but a smaller increase or no risk is seen with unprocessed meat consumption. Differences in sodium content (~400 % higher in processed meat) appear to account for about two-thirds of this risk difference. In similar analyses, both unprocessed red and processed meat consumption are associated with incident diabetes, with higher risk per g of processed (RR per 50 g: 1.51, 95 %CI = 1.25-1.83) versus unprocessed (RR per 100 g: 1.19, 95 % CI = 1.04-1.37) meats. Contents of heme iron and dietary cholesterol may partly account for these associations. The overall findings suggest that neither unprocessed red nor processed meat consumption is beneficial for cardiometabolic health, and that clinical and public health guidance should especially prioritize reducing processed meat consumption.

Meat consumption, diabetes, and its complications

Several prospective studies have reported that risk of type 2 diabetes (T2DM) is elevated in meat consumers, especially when processed meats are consumed. Elevated risks of coronary heart disease (CHD) and stroke in meat consumers have also been reported. In this overview, the evidence regarding meat consumption and the risk of diabetes, both type 1 diabetes (T1DM) and T2DM and their macro- and microvascular complications, is reviewed. For T2DM, we performed a new meta-analysis including publications up to October 2012. For T1DM, only a few studies have reported increased risks for meat consumers or for high intake of saturated fatty acids and nitrates and nitrites. For T2DM, CHD, and stroke, the evidence is strongest. Per 100 g of total meat, the pooled relative risk (RR) for T2DM is 1.15 (95 % CI 1.07-1.24), for (unprocessed) red meat 1.13 (95 % CI 1.03-1.23), and for poultry 1.04 (95 % CI 0.99-1.33); per 50 g of processed meat, the pooled RR is 1.32 (95 % CI 1.19-1.48). Hence, the strongest association regarding T2DM is observed for processed (red) meat. A similar observation has been made for CHD. For stroke, however, a recent meta-analysis shows moderately elevated risks for meat consumers, for processed as well as for fresh meats. For the microvascular complications of diabetes, few prospective data were available, but suggestions for elevated risks can be derived from findings on hyperglycemia and hypertension. The results are discussed in the light of the typical nutrients and other compounds present in meat--that is, saturated and trans fatty acids, dietary cholesterol, protein and amino acids, heme-iron, sodium, nitrites and nitrosamines, and advanced glycation end products. In light of these findings, a diet moderate to low in red meat, unprocessed and lean, and prepared at moderate temperatures is probably the best choice from the public health point of view.

Immunobiology of beta-cell destruction

Type 1 diabetes is a chronic disease characterized by severe insulin deficiency and hyperglycemia, due to autoimmune destruction of pancreatic islets of Langerhans. A susceptible genetic background is necessary, but not sufficient, for the development of the disease. Epidemiological and clinical observations underscore the importance of environmental factors as triggers of type 1 diabetes, currently under investigation. Islet-specific autoantibodies precede clinical onset by months to years and are established tools for risk prediction, yet minor players in the pathogenesis of the disease. Many efforts have been made to elucidate disease-relevant defects in the key immune effectors of islet destruction, from the early failure of specific tolerance to the vicious circle of destructive insulitis. However, the events triggering islet autoimmunity as well as the transition to overt diabetes are still largely unknown, making prevention and treatment strategies still a challenge.

Inhibition of toxigenesis of group II (nonproteolytic) Clostridium botulinum type B in meat products by using a reduced level of nitrite

The effect of three different concentrations of sodium nitrite (0, 75, and 120 mg/kg) on growth and toxigenesis of group II (nonproteolytic) Clostridium botulinum type B was studied in Finnish wiener-type sausage, bologna-type sausage, and cooked ham. A low level of inoculum (2.0 log CFU/g) was used for wiener-type sausage and bologna-type sausage, and both low (2.0 log CFU/g) and high (4.0 log CFU/g) levels were used for cooked ham. The products were formulated and processed under simulated commercial conditions and stored at 8°C for 5 weeks. C. botulinum counts were determined in five replicate samples of each nitrite concentration at 1, 3, and 5 weeks after thermal processing. All samples were positive for C. botulinum type B. The highest C. botulinum counts were detected in nitrite-free products. Toxigenesis was observed in nitrite-free products during storage, but products containing either 75 or 120 mg/kg nitrite remained nontoxic during the 5-week study period, suggesting that spores surviving the heat treatment were unable to germinate and develop into a toxic culture in the presence of nitrite. The results suggest that the safety of processed meat products with respect to group II C. botulinum type B can be maintained even with a reduced concentration (75 mg/kg) of sodium nitrite.

Meat consumption and its association with C-reactive protein and incident type 2 diabetes: the Rotterdam Study

OBJECTIVE

To investigate whether intake of different types of meat is associated with circulating C-reactive protein (CRP) and risk of type 2 diabetes in a prospective cohort study.

RESEARCH DESIGN AND METHODS

Our analysis included 4,366 Dutch participants who did not have diabetes at baseline. During a median follow-up period of 12.4 years, 456 diabetes cases were confirmed. Intake of red meat, processed meat, and poultry was derived from a food frequency questionnaire, and their association with serum high-sensitivity CRP was examined cross-sectionally using linear regression models. Their association with risk of type 2 diabetes was examined using multivariate Cox proportional hazards model, including age, sex, family history of diabetes, and lifestyle and dietary factors.

RESULTS

An increment of 50 g of processed meat was associated with increased CRP concentration (β(processed meat) = 0.12; P = 0.01), whereas intake of red meat and poultry was not. When comparing the highest to the lowest category of meat intake with respect to diabetes incidence, the adjusted relative risks were as follows: for red meat (1.42 [95% CI 1.06-1.91]), for processed meat (1.87 [1.26-2.78]), and for poultry (0.95 [0.74-1.22]). Additional analysis showed that the associations were not affected appreciably after inclusion of CRP into the model. After adjustment for BMI, however, the association for red meat attenuated to 1.18 (0.88-1.59).

CONCLUSIONS

Intake of processed meat is associated with higher risk of type 2 diabetes. It appears unlikely that CRP mediates this association.

Epidemiology of environmental exposures and human autoimmune diseases: findings from a National Institute of Environmental Health Sciences Expert Panel Workshop

Autoimmune diseases (AID) are a collection of many complex disorders of unknown etiology resulting in immune responses to self-antigens and are thought to result from interactions between genetic and environmental factors. Here we review the epidemiologic evidence for the role of environmental factors in the development of human AID, the conclusions that can be drawn from the existing data, critical knowledge gaps, and research needed to fill these gaps and to resolve uncertainties. We specifically summarize the state of knowledge and our levels of confidence in the role of specific agents in the development of autoimmune diseases, and we define the areas of greatest impact for future investigations. Among our consensus findings we are confident that: 1) crystalline silica exposure can contribute to the development of several AID; 2) solvent exposure can contribute to the development of systemic sclerosis; 3) smoking can contribute to the development of seropositive rheumatoid arthritis; and 4) an inverse association exists between ultraviolet radiation exposure and the risk of development of multiple sclerosis. We suggest that more studies of phenotypes, genotypes, and multiple exposures are needed. Additional knowledge gaps needing investigation include: defining important windows in the timing of exposures and latencies relating to age, developmental state, and hormonal changes; understanding dose-response relationships; and elucidating mechanisms for disease development. Addressing these essential issues will require more resources to support research, particularly of rare AID, but knowledge of the risks conferred by environmental factors in specific genetic contexts could pave the way for prevention of AID in the future.

Food consumption and advanced β cell autoimmunity in young children with HLA-conferred susceptibility to type 1 diabetes: a nested case-control design

BACKGROUND

Evidence for the role of food consumption during childhood in the development of β cell autoimmunity is scarce and fragmentary.

OBJECTIVE

We set out to study the associations of longitudinal food consumption in children with the development of advanced β cell autoimmunity.

DESIGN

Children with advanced β cell autoimmunity (n = 232) (ie, with repeated positivity for antibodies against islet cells) together with positivity for at least one of the other 3 antibodies analyzed or clinical type 1 diabetes were identified from a prospective birth cohort of 6069 infants with HLA-DQB1-conferred susceptibility to type 1 diabetes who were born in 1996-2004, with the longest follow-up to the age of 11 y. Repeated 3-d food records were completed by the families and daycare personnel. Diabetes-associated autoantibodies and diets were measured at 3-12-mo intervals. Four control subjects, who were matched for birth date, sex, area, and genetic risk, were randomly selected for each case.

RESULTS

In the main food groups, only intakes of cow-milk products (OR: 1.05; 95% CI: 1.00, 1.10) and fruit and berry juices (OR: 1.09; 95% CI: 1.02, 1.12) were significantly, although marginally, associated with advanced β cell autoimmunity. The consumption of fresh milk products and cow milk-based infant formulas was related to the endpoint, whereas no evidence was shown for consumption of sour milk products and cheese. The intake of fat from all milk products and protein from fresh milk products was associated with risk of advanced β cell autoimmunity.

CONCLUSION

Intakes of cow milk and fruit and berry juices could be related to the development of advanced β cell autoimmunity. This trial was registered at clinicaltrials.gov as number NCT00223613.

Type 1 diabetes mellitus and components in drinking water and diet: a population-based, case-control study in Prince Edward Island, Canada

OBJECTIVE

To determine the relationship between the risk of type 1 diabetes (T1D) and daily intake of drinking water and dietary components, including nitrate, nitrite, and nitrosamines, during the year prior to diagnosis.

METHODS

Controls (n = 105) were matched by age at diagnosis and sex to T1D cases (n = 57) newly diagnosed during 2001-2004. Food consumption was assessed using a food frequency questionnaire. Locally available samples of foods were tested for nitrate, nitrite, and nitrosamine concentrations. Water consumption was determined through an additional questionnaire, and water samples were taken from homes and tested for routine chemical components, including nitrate.

RESULTS

After controlling for age, age, sex, and daily energy intake, nitrate intake from food sources showed a non-significant positive trend (odds ratios and 95% confidence intervals for quartiles = 1.00, 1.63 (0.58, 4.63), 1.71 (0.54, 5.40), 3.02 (0.78, 11.74); p for trend = 0.13). Nitrite and nitrosamine intake were not related to T1D risk (p for trend = 0.77 and 0.81, respectively). When food and water components were combined, zinc and calcium intakes were marginally and inversely related to T1D risk (p for trend = 0.07 and 0.06, respectively). After further model adjustment of possible confounders and significant risk factors, an increased intake of caffeine marginally increased the risk of T1D (p = 0.07).

CONCLUSION

Dietary components from both food and water sources may influence the risk of developing T1D in young persons.

Low-carbohydrate diet scores and risk of type 2 diabetes in men

BACKGROUND

Fat and protein sources may influence whether low-carbohydrate diets are associated with type 2 diabetes (T2D).

OBJECTIVE

The objective was to compare the associations of 3 low-carbohydrate diet scores with incident T2D.

DESIGN

A prospective cohort study was conducted in participants from the Health Professionals Follow-Up Study who were free of T2D, cardiovascular disease, or cancer at baseline (n = 40,475) for up to 20 y. Cumulative averages of 3 low-carbohydrate diet scores (high total protein and fat, high animal protein and fat, and high vegetable protein and fat) were calculated every 4 y from food-frequency questionnaires and were associated with incident T2D by using Cox models.

RESULTS

We documented 2689 cases of T2D during follow-up. After adjustments for age, smoking, physical activity, coffee intake, alcohol intake, family history of T2D, total energy intake, and body mass index, the score for high animal protein and fat was associated with an increased risk of T2D [top compared with bottom quintile; hazard ratio (HR): 1.37; 95% CI: 1.20, 1.58; P for trend < 0.01]. Adjustment for red and processed meat attenuated this association (HR: 1.11; 95% CI: 0.95, 1.30; P for trend = 0.20). A high score for vegetable protein and fat was not significantly associated with the risk of T2D overall but was inversely associated with T2D in men aged <65 y (HR: 0.78; 95% CI: 0.66, 0.92; P for trend = 0.01, P for interaction = 0.01).

CONCLUSIONS

A score representing a low-carbohydrate diet high in animal protein and fat was positively associated with the risk of T2D in men. Low-carbohydrate diets should obtain protein and fat from foods other than red and processed meat.

Long-term animal-protein consumption is associated with an increased prevalence of diabetes among the elderly: the Mediterranean Islands (MEDIS) study

AIM

The role of animal-protein consumption on the prevalence of diabetes is not yet fully understood. For this reason, this study investigated the relationship between long-term animal-protein intake and diabetes in elderly individuals with no known cardiovascular disease.

METHODS

During 2005-2007, 1190 men and women, aged 65-100 years, from Cyprus, Mitilini, Samothraki, Cephalonia, Crete, Lemnos, Corfu and Zakynthos were enrolled into the study. Diabetes was defined as fasting blood glucose ≥ 125 mg/dL or the use of antidiabetic medication. All participants were asked about their dietary habits through a semiquantitative food-frequency questionnaire. Assessment of protein and energy intakes was performed using food-composition tables.

RESULTS

After adjusting for age, gender, obesity, history of hypertension, hypercholesterolaemia and dietary habits, a 5% increase in protein intake from meat and meat products was associated with a 34% (OR=1.338, 95% CI: 1.02-1.76) greater likelihood of diabetes, while a 5% increase in total protein intake was associated with a 29% (OR=1.288, 95% CI: 1.00-1.69) greater likelihood of diabetes. No significant associations between diabetes and protein intakes from vegetables and cereals were observed.

CONCLUSION

Animal-protein consumption was associated with a higher prevalence of diabetes among the elderly, whereas protein intakes, especially from plant sources, within the recommended range appear to confer considerable protection. This suggests that reducing or controlling the burden of diabetes through dietary means in the elderly should include monitoring their daily protein intake.

Maternal food consumption during pregnancy and risk of advanced β-cell autoimmunity in the offspring

BACKGROUND

Evidence for a putative role of maternal diet during pregnancy in the development of β-cell autoimmunity in the child is scarce. The authors study the association of food consumption during pregnancy and the development of β-cell autoimmunity in the offspring.

SUBJECTS AND METHODS

A prospective Finnish birth cohort of 4297 infants with human leukocyte antigen (HLA)-DQB1-conferred susceptibility to type 1 diabetes and their mothers. Blood samples were collected from the children at 3-12 months intervals to measure type 1 diabetes-associated antibodies: antibodies against islet cells (ICA), insulin, glutamate dehydroxylase, and islet antigen 2. The mothers completed a validated food frequency questionnaire. The end-point was repeated positivity for ICA together with at least one of the other three antibodies. Piecewise-exponential survival models were used. The effective sample size was 3723, with 138 end-points. The median follow-up time was 4.4 years.

RESULTS

Maternal consumption of butter, low-fat margarines, berries, and coffee were inversely associated with the development of advanced β-cell autoimmunity in the offspring, adjusted for genetic risk group and familial diabetes. These associations for low-fat margarines (use vs. non-use HR 0.60, 95% CI: 0.38-0.93, p = 0.02), berries (continuous variable HR 0.90, 95% CI: 0.83-0.98, p = 0.02) and coffee (highest quarter vs. lowest HR 0.62, 95% CI: 0.40-0.97, p = 0.04), remained significant when adjusting for potential confounding sociodemographic, perinatal, and other dietary factors.

CONCLUSIONS

In this study assessing total food consumption of the mother during pregnancy, only few among the 27 food groups tested were weakly related to the development of advanced β-cell autoimmunity in Finnish children.

Higher protein intake is associated with diabetes risk in South Asian Indians: the Metabolic Syndrome and Atherosclerosis in South Asians Living in America (MASALA) study

OBJECTIVE

Despite a high prevalence of type 2 diabetes in South Asian Indians, the impact of diet in this high-risk ethnic group has not been fully explored. The association of macronutrient intake and diabetes in South Asian Indians was examined in this cross-sectional study.

METHODS

A population-based cohort of 146 South Asian Indians aged 45-79 years without existing cardiovascular disease living in the San Francisco Bay Area was recruited between August 2006 and October 2007. Macronutrient intake was assessed with a food-frequency questionnaire developed and validated in South Asians. Diabetes was defined by use of a hypoglycemic medication, a fasting plasma glucose level > or =126 mg/dL, or a 2-hour post-challenge glucose level > or =200 mg/dL. The association between energy-adjusted macronutrient intake and diabetes was explored using multivariable logistic regression models.

RESULTS

Forty-one (28%) participants had type 2 diabetes; 20 were unaware of this diagnosis and were classified as having diabetes by laboratory testing. In a model fully adjusted for age, sex, waist circumference, and hypertension, there was a 70% increase in the odds of diabetes per standard deviation in gram of protein intake/day (standardized OR 1.70 [95% CI 1.08, 2.68], p = 0.02). There was a trend toward increased protein intake and diabetes in the subset of participants with previously unknown, laboratory-diagnosed diabetes. Results did not vary significantly by sex, body mass index, or dietary pattern.

CONCLUSIONS

Higher level of protein intake was associated with increased odds of diabetes in this cohort of South Asian Indians. Diet may be a modifiable lifestyle factor in this high-risk ethnic group.

Red and processed meat consumption and risk of incident coronary heart disease, stroke, and diabetes mellitus: a systematic review and meta-analysis

BACKGROUND

Meat consumption is inconsistently associated with development of coronary heart disease (CHD), stroke, and diabetes mellitus, limiting quantitative recommendations for consumption levels. Effects of meat intake on these different outcomes, as well as of red versus processed meat, may also vary.

METHODS AND RESULTS

We performed a systematic review and meta-analysis of evidence for relationships of red (unprocessed), processed, and total meat consumption with incident CHD, stroke, and diabetes mellitus. We searched for any cohort study, case-control study, or randomized trial that assessed these exposures and outcomes in generally healthy adults. Of 1598 identified abstracts, 20 studies met inclusion criteria, including 17 prospective cohorts and 3 case-control studies. All data were abstracted independently in duplicate. Random-effects generalized least squares models for trend estimation were used to derive pooled dose-response estimates. The 20 studies included 1 218 380 individuals and 23 889 CHD, 2280 stroke, and 10 797 diabetes mellitus cases. Red meat intake was not associated with CHD (n=4 studies; relative risk per 100-g serving per day=1.00; 95% confidence interval, 0.81 to 1.23; P for heterogeneity=0.36) or diabetes mellitus (n=5; relative risk=1.16; 95% confidence interval, 0.92 to 1.46; P=0.25). Conversely, processed meat intake was associated with 42% higher risk of CHD (n=5; relative risk per 50-g serving per day=1.42; 95% confidence interval, 1.07 to 1.89; P=0.04) and 19% higher risk of diabetes mellitus (n=7; relative risk=1.19; 95% confidence interval, 1.11 to 1.27; P<0.001). Associations were intermediate for total meat intake. Consumption of red and processed meat were not associated with stroke, but only 3 studies evaluated these relationships.

CONCLUSIONS

Consumption of processed meats, but not red meats, is associated with higher incidence of CHD and diabetes mellitus. These results highlight the need for better understanding of potential mechanisms of effects and for particular focus on processed meats for dietary and policy recommendations.

Intake of antioxidant vitamins and trace elements during pregnancy and risk of advanced beta cell autoimmunity in the child

BACKGROUND

Type 1 diabetes may have its origins in the fetal period of life. Free radicals were implicated in the cause of type 1 diabetes. It was hypothesized that antioxidant nutrients could protect against type 1 diabetes.

OBJECTIVE

We assessed whether high maternal intake of selected dietary antioxidants during pregnancy is associated with a reduced risk of advanced beta cell autoimmunity in the child, defined as repeated positivity for islet cell antibodies plus >/=1 other antibody, overt type 1 diabetes, or both.

DESIGN

The study was carried out as part of the population-based birth cohort of the Type 1 Diabetes Prediction and Prevention Project. The data comprised 4297 children with increased genetic susceptibility to type 1 diabetes, born at the University Hospital of Oulu or Tampere, Finland, between October 1997 and December 2002. The children were monitored for diabetes-associated autoantibodies from samples obtained at 3-12-mo intervals. Maternal antioxidant intake during pregnancy was assessed postnatally with a self-administered food-frequency questionnaire, which contained a question about consumption of dietary supplements.

RESULTS

Maternal intake of none of the studied antioxidant nutrients showed association with the risk of advanced beta cell autoimmunity in the child. The hazard ratios, indicating the change in risk per a 2-fold increase in the intake of each antioxidant, were nonsignificant and close to 1.

CONCLUSION

High maternal intake of retinol, beta-carotene, vitamin C, vitamin E, selenium, zinc, or manganese does not protect the child from development of advanced beta cell autoimmunity in early childhood.

Nitrate in community water supplies and risk of childhood type 1 diabetes in Sardinia, Italy

We tested the hypothesis of an association between childhood type 1 diabetes (T1D) risk and nitrate concentration in drinking water in Sardinia, Italy, using Poisson regression analysis. Childhood T1D risk showed an inverse trend with increasing quartile of nitrate level in the total population and among men. A nitrate concentration in drinking water below 10 mg/l is unlikely to account for the spatial variation in childhood T1D incidence.

The association of meat intake and the risk of type 2 diabetes may be modified by body weight

AIM

To investigate the association between meat intake and incidence of type 2 diabetes (type 2 DM) in a large cohort of middle-aged women.

DESIGN, SUBJECTS AND METHODS

Incident cases of type 2 DM were identified during an average of 4.6 years of follow-up in a prospective cohort study of 74,493 middle-aged, Chinese women (mean age +/- SD =51.7+/- 8.97 years). Participants completed in-person interviews that collected information on type 2 DM risk factors such as dietary factors and physical activity in adulthood. Anthropometric indices were measured. Dietary intake was assessed using a validated food frequency questionnaire (FFQ). We included in the current analysis 70,609 women who had no prior history of type 2 DM at study recruitment and who had valid dietary data. The association of type 2 DM with unprocessed meat intake (g/day) and the frequency of consumption of processed meat was evaluated using the Cox model with adjustment for age, kcals/day, body mass index (BMI), waist to hip ratio (WHR), vegetable intake, smoking, alcohol consumption, physical activity, income level, education level, occupation status, and history of hypertension and chronic disease at baseline.

PRINCIPAL RESULTS

We identified 1972 incident cases of type 2 DM during a total of 326,581 person-years of follow up. Intake of unprocessed meat, particularly poultry, was associated with a decrease in the risk of type 2 DM in this cohort. The fully adjusted relative risks (RRs) for quintiles of total unprocessed meat intake were 1.00, 0.78, 0.83, 0.74, and 0.83 (P for trend: <0.01). When the joint effect between meat intake and BMI categories was evaluated, high intake of total unprocessed meat appeared to be associated with an increased risk of type 2 DM among obese women but a reduced risk among lean women (P value for the interaction tests = 0.05). Processed meat consumption was positively associated with the risk of type 2 DM. The adjusted RR was 1.15 (95% 1.01-1.32) in women consuming processed meats compared to those who did not consume processed meats (P=0.04).

CONCLUSIONS

Processed meat intake was positively associated with the risk of type 2 DM. There was an indication that the effect of unprocessed meat intake on type 2 DM may be modified by BMI.

Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems: A global assessment

We provide a global assessment, with detailed multi-scale data, of the ecological and toxicological effects generated by inorganic nitrogen pollution in aquatic ecosystems. Our synthesis of the published scientific literature shows three major environmental problems: (1) it can increase the concentration of hydrogen ions in freshwater ecosystems without much acid-neutralizing capacity, resulting in acidification of those systems; (2) it can stimulate or enhance the development, maintenance and proliferation of primary producers, resulting in eutrophication of aquatic ecosystems; (3) it can reach toxic levels that impair the ability of aquatic animals to survive, grow and reproduce. Inorganic nitrogen pollution of ground and surface waters can also induce adverse effects on human health and economy. Because reductions in SO2 emissions have reduced the atmospheric deposition of H2SO4 across large portions of North America and Europe, while emissions of NOx have gone unchecked, HNO3 is now playing an increasing role in the acidification of freshwater ecosystems. This acidification process has caused several adverse effects on primary and secondary producers, with significant biotic impoverishments, particularly concerning invertebrates and fishes, in many atmospherically acidified lakes and streams. The cultural eutrophication of freshwater, estuarine, and coastal marine ecosystems can cause ecological and toxicological effects that are either directly or indirectly related to the proliferation of primary producers. Extensive kills of both invertebrates and fishes are probably the most dramatic manifestation of hypoxia (or anoxia) in eutrophic and hypereutrophic aquatic ecosystems with low water turnover rates. The decline in dissolved oxygen concentrations can also promote the formation of reduced compounds, such as hydrogen sulphide, resulting in higher adverse (toxic) effects on aquatic animals. Additionally, the occurrence of toxic algae can significantly contribute to the extensive kills of aquatic animals. Cyanobacteria, dinoflagellates and diatoms appear to be major responsible that may be stimulated by inorganic nitrogen pollution. Among the different inorganic nitrogenous compounds (NH4+, NH3, NO2-, HNO2NO3-) that aquatic animals can take up directly from the ambient water, unionized ammonia is the most toxic, while ammonium and nitrate ions are the least toxic. In general, seawater animals seem to be more tolerant to the toxicity of inorganic nitrogenous compounds than freshwater animals, probably because of the ameliorating effect of water salinity (sodium, chloride, calcium and other ions) on the tolerance of aquatic animals. Ingested nitrites and nitrates from polluted drinking waters can induce methemoglobinemia in humans, particularly in young infants, by blocking the oxygen-carrying capacity of hemoglobin. Ingested nitrites and nitrates also have a potential role in developing cancers of the digestive tract through their contribution to the formation of nitrosamines. In addition, some scientific evidences suggest that ingested nitrites and nitrates might result in mutagenicity, teratogenicity and birth defects, contribute to the risks of non-Hodgkin's lymphoma and bladder and ovarian cancers, play a role in the etiology of insulin-dependent diabetes mellitus and in the development of thyroid hypertrophy, or cause spontaneous abortions and respiratory tract infections. Indirect health hazards can occur as a consequence of algal toxins, causing nausea, vomiting, diarrhoea, pneumonia, gastroenteritis, hepatoenteritis, muscular cramps, and several poisoning syndromes (paralytic shellfish poisoning, neurotoxic shellfish poisoning, amnesic shellfish poisoning). Other indirect health hazards can also come from the potential relationship between inorganic nitrogen pollution and human infectious diseases (malaria, cholera). Human sickness and death, extensive kills of aquatic animals, and other negative effects, can have elevated costs on human economy, with the recreation and tourism industry suffering the most important economic impacts, at least locally. It is concluded that levels of total nitrogen lower than 0.5-1.0 mg TN/L could prevent aquatic ecosystems (excluding those ecosystems with naturally high N levels) from developing acidification and eutrophication, at least by inorganic nitrogen pollution. Those relatively low TN levels could also protect aquatic animals against the toxicity of inorganic nitrogenous compounds since, in the absence of eutrophication, surface waters usually present relatively high concentrations of dissolved oxygen, most inorganic reactive nitrogen being in the form of nitrate. Additionally, human health and economy would be safer from the adverse effects of inorganic nitrogen pollution.