Dietary iron intake and blood donations in relation to risk of type 2 diabetes in men: a prospective cohort study

Associations of dietary total, heme, non-heme iron intake with diabetes, CVD, and all-cause mortality in men and women with diabetes

Background

Iron metabolism disorders significantly increase the risk of diabetes and its related complications by inducing oxidative stress, inflammation, insulin resistance, and disturbances in glucose and lipid metabolism. However, whether dietary iron intake can influence progression of diabetes remains unclear. The present study aims to investigate the relationship between total iron, heme iron, and non-heme iron intake and diabetes, CVD, and all-cause mortality among men and women with diabetes in the U.S. population.

Methods

A total of 4416 adults with diabetes(2415 men and 2001 women) from the NHANES 2003-2014 were enrolled. Dietary information was collected by 24-h dietary recall during two nonconsecutive days. Dietary total iron intake was measured based on the dietary survey. Dietary heme iron intake was calculated based on its proportion in dietary total iron intake from each food. non-heme iron is the difference between total iron and heme iron. Diabetes, CVD, and all-cause mortality status were identified as main outcomes. Cox models and RCS analysis were performed to estimate the hazard ratios and 95%CIs.

Results

For men, the participants with a higher dietary heme iron intake were associated with higher risks of CVD (HRheme iron = 1.61,95%CI:1.03-2.51) and all-cause mortality (HRheme iron = 1.42,95%CI:1.10-1.83). For women, participants in the highest quartile of dietary total/heme/non-heme iron intake had a higher diabetes mortality risk ((HRtotal iron = 2.33,95%CI:1.24-4.38; HRheme iron = 1.87,95%CI:1.00-3.49; HRnon-heme iron = 2.28,95%CI:1.19-4.39), compared to those in the lowest quartile. Additionally, the dose-response curve for the relationship between dietary non-heme iron intake and CVD mortality followed a reverse J-shape in women with diabetes.

Conclusions

Higher dietary heme iron intake was associated with an increased CVD mortality risk in both men and women with diabetes. Additionally, higher dietary total, heme, and non-heme iron intake was linked to an increased risk of diabetes mortality among women with diabetes. Therefore, women with diabetes should pay more attention on the overconsumption of any type of dietary iron.

Adherence to the dietary approaches to stop hypertension diet reduces the risk of diabetes mellitus: a systematic review and dose-response meta-analysis

BACKGROUND

Despite several epidemiological studies reporting a significant association between adherence to the Dietary Approaches to Stop Hypertension (DASH) diet and the risk of diabetes mellitus, the results remain controversial. In this systematic review and meta-analysis, we aimed to summarize the existing evidence from published observational studies and evaluate the dose-response relationship between adherence to the DASH diet and diabetes mellitus risk.

METHODS

We performed a systematic search for relevant articles published up to September 2023 using electronic databases of PubMed, Embase, Scopus, and China National Knowledge Infrastructure (CNKI). A random-effects model was applied to calculate the combined relative risks (RR) with 95% confidence intervals (CIs) for the highest compared to the lowest categories of DASH score in relation to diabetes mellitus risk. Heterogeneity among the included studies was assessed using the Cochran's Q test and I-squared (I2) statistic. Literature search, study selection, data extraction, and quality assessment were performed by two independent reviewers.

RESULTS

Fifteen studies involving 557,475 participants and 57,064 diabetes mellitus cases were eligible for our analyses. Pooled analyses from included studies showed that high adherence to the DASH diet was significantly associated with a reduced risk of diabetes mellitus (RR: 0.82; 95% CI: 0.76-0.90, P < 0.001). Moreover, the dose-response meta-analysis revealed a linear trend between adherence to the DASH diet and diabetes mellitus (RR:0.99; 95%CI: 0.97-1.02, Pdose-response = 0.546, Pnonlinearity = 0.701). Subgroup analyses further revealed a significant inverse association between adherence to the DASH diet and diabetes mellitus risk in case-control studies (RR: 0.65; 95%CI: 0.29-1.43, P < 0.001), with a marginal inverse association in cohort studies (RR:0.83; 95%CI: 0.76-0.91, P < 0.001). Additionally, we conducted analyses separately by comparison and found a significant inverse association between DASH diet and diabetes mellitus risk in T3 vs T1 comparison studies (RR = 0.74; 95%CI: 0.64-0.86, P = 0.012).

CONCLUSION

The findings of this study demonstrate a protective association between adherence to the DASH diet and risk of diabetes mellitus. However, further prospective cohort studies and randomized controlled trials are needed to validate these findings.

Integration of epidemiological and blood biomarker analysis links haem iron intake to increased type 2 diabetes risk

Dietary haem iron intake is linked to an increased risk of type 2 diabetes (T2D), but the underlying plasma biomarkers are not well understood. We analysed data from 204,615 participants (79% females) in three large US cohorts over up to 36 years, examining the associations between iron intake and T2D risk. We also assessed plasma metabolic biomarkers and metabolomic profiles in subsets of 37,544 (82% females) and 9,024 (84% females) participants, respectively. Here we show that haem iron intake but not non-haem iron is associated with a higher T2D risk, with a multivariable-adjusted hazard ratio of 1.26 (95% confidence interval 1.20-1.33; P for trend <0.001) comparing the highest to the lowest quintiles. Haem iron accounts for significant proportions of the T2D risk linked to unprocessed red meat and specific dietary patterns. Increased haem iron intake correlates with unfavourable plasma profiles of insulinaemia, lipids, inflammation and T2D-linked metabolites. We also identify metabolites, including L-valine and uric acid, potentially mediating the haem iron-T2D relationship, highlighting their pivotal role in T2D pathogenesis.

Dietary iron intake predicts all-cause and cardiovascular mortality in patients with diabetes

BACKGROUND

Limited data exists on the link between dietary iron intake and mortality in diabetes. Our investigation aimed to explore how dietary iron intake correlates with overall and cause-specific mortality in diabetic individuals.

METHODS

This analysis encompassed 5970 participants with diabetes from the National Health and Nutrition Examination Survey spanning 1999 to 2014. Baseline data were collected through surveys and examinations, with mortality status tracked via National Death Index records until December 31, 2015. Cox proportional hazard models were utilized to calculate hazard ratios (HR) and 95% confidence intervals (CI) for mortality from various causes, including cardiovascular disease (CVD) and cancer.

RESULTS

The average iron intake among the cohort was 14.1 ± 7.4 mg daily, with an average participant age of 61.3 and 3059 (51.3%) male adults. Over 41,425 person-years of follow-up, 1497 deaths were recorded. Following adjustments for multiple variables, an iron intake between 11.1 and 14.4 mg was associated with the lowest risk of all-cause mortality (HR 0.83 [0.70, 0.99], P < 0.05) compared to the reference group (<8.3 mg). Analysis of dose-response curves revealed an L-shaped pattern in men and a J-shaped pattern in women concerning the relationship between iron intake and all-cause mortality.

CONCLUSIONS

Our findings suggest a nonlinear association between dietary iron intake and all-cause mortality in individuals with diabetes. Specifically, higher iron intake may increase all-cause mortality risk in men, while potentially exert a protective effect in women.

Ferroptosis-A Shared Mechanism for Parkinson's Disease and Type 2 Diabetes

Type 2 diabetes (T2D) and Parkinson's disease (PD) are the two most frequent age-related chronic diseases. There are many similarities between the two diseases: both are chronic diseases; both are the result of a decrease in a specific substance-insulin in T2D and dopamine in PD; and both are caused by the destruction of specific cells-beta pancreatic cells in T2D and dopaminergic neurons in PD. Recent epidemiological and experimental studies have found that there are common underlying mechanisms in the pathophysiology of T2D and PD: chronic inflammation, mitochondrial dysfunction, impaired protein handling and ferroptosis. Epidemiological research has indicated that there is a higher risk of PD in individuals with T2D. Moreover, clinical studies have observed that the symptoms of Parkinson's disease worsen significantly after the onset of T2D. This article provides an up-to-date review on the intricate interplay between oxidative stress, reactive oxygen species (ROS) and ferroptosis in PD and T2D. By understanding the shared molecular pathways and how they can be modulated, we can develop more effective therapies, or we can repurpose existing drugs to improve patient outcomes in both disorders.

Scientific opinion on the tolerable upper intake level for iron

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the tolerable upper intake level (UL) for iron. Systematic reviews were conducted to identify evidence regarding high iron intakes and risk of chronic diseases, adverse gastrointestinal effects and adverse effects of iron supplementation in infancy, young childhood and pregnancy. It is established that systemic iron overload leads to organ toxicity, but no UL could be established. The only indicator for which a dose-response could be established was black stools, which reflect the presence of large amounts of unabsorbed iron in the gut. This is a conservative endpoint among the chain of events that may lead to systemic iron overload but is not adverse per se. Based on interventions in which black stools did not occur at supplemental iron intakes of 20-25 mg/day (added to a background intake of 15 mg/day), a safe level of intake for iron of 40 mg/day for adults (including pregnant and lactating women) was established. Using allometric scaling (body weight0.75), this value was scaled down to children and adolescents and safe levels of intakes between 10 mg/day (1-3 years) and 35 mg/day (15-17 years) were derived. For infants 7-11 months of age who have a higher iron requirement than young children, allometric scaling was applied to the supplemental iron intakes (i.e. 25 mg/day) and resulted in a safe level of supplemental iron intake of 5 mg/day. This value was extended to 4-6 month-old infants and refers to iron intakes from fortified foods and food supplements, not from infant and follow-on formulae. The application of the safe level of intake is more limited than a UL because the intake level at which the risk of adverse effects starts to increase is not defined.

Antioxidant Minerals Modified the Association between Iron and Type 2 Diabetes in a Chinese Population

Inconsistent findings exist regarding the relationship between heme iron intake and type 2 diabetes (T2D) among Western and Eastern populations. Easterners tend to consume a plant-based diet which is abundant in antioxidant minerals. To examine the hypothesis that antioxidant mineral may modify the relationship between iron and T2D, we performed a case-control study by measuring the serum mineral levels in 2198 Chinese subjects. A total of 2113 T2D patients and 2458 controls were invited; 502 T2D patients and 1696 controls were finally analyzed. In the total population, high serum iron showed a positive association with T2D odds (odds ratio [OR] = 1.27 [1.04, 1.55]); high magnesium (OR = 0.18 [0.14, 0.22]), copper (OR = 0.27 [0.21, 0.33]), zinc (OR = 0.37 [0.30, 0.46]), chromium (OR = 0.61 [0.50, 0.74]), or selenium concentrations (OR = 0.39 [0.31, 0.48]) were inversely associated with T2D odds. In contrast, in individuals with higher magnesium (>2673.2 µg/dL), zinc (>136.7 µg/dL), copper (>132.1 µg/dL), chromium (>14.0 µg/dL), or selenium concentrations (>16.8 µg/dL), serum iron displayed no association with T2D (p > 0.05). Serum copper and magnesium were significant modifiers of the association between iron and T2D in individuals with different physiological status (p < 0.05). Our findings support the idea that consuming a diet rich in antioxidant minerals is an effective approach for preventing T2D.

Iron, glucose and fat metabolism and obesity: an intertwined relationship

A bidirectional relationship exists between adipose tissue metabolism and iron regulation. Total body fat, fat distribution and exercise influence iron status and components of the iron-regulatory pathway, including hepcidin and erythroferrone. Conversely, whole body and tissue iron stores associate with fat mass and distribution and glucose and lipid metabolism in adipose tissue, liver, and muscle. Manipulation of the iron-regulatory proteins erythroferrone and erythropoietin affects glucose and lipid metabolism. Several lines of evidence suggest that iron accumulation and metabolism may play a role in the development of metabolic diseases including obesity, type 2 diabetes, hyperlipidaemia and non-alcoholic fatty liver disease. In this review we summarise the current understanding of the relationship between iron homoeostasis and metabolic disease.

Iron deficiency and iron overload in men and woman of reproductive age, and pregnant women

Iron is an essential micronutrient for human biology and health, but high iron levels can be dangerous. Both iron deficiency and iron overload have been linked to reproductive health. This review summarizes the effects of iron deficiency and iron overload on men of reproductive age, women of reproductive age, and pregnant women. In addition, appropriate iron levels and the need for iron and nutritional supplements at different stages of life and pregnancy are discussed. In general, men should be aware of the risk of iron overload at any stage of life; women should take appropriate iron supplements before menopause; postmenopausal women should pay attention to the risk of iron overload; and pregnant women should receive reasonable iron supplementation in middle and late pregnancy. By summarizing evidence on the relationship between iron and reproductive health, this review aims to promote the development of strategies to optimize reproductive capacity from the perspective of nutrition. However, additional detailed experimental investigations and clinical studies are needed to assess the underlying causes and mechanisms of the observed associations between iron and reproductive health.

Habitual Tea Consumption Increases the Incidence of Metabolic Syndrome in Middle-Aged and Older Individuals

In middle-aged and elderly individuals, the relationship between tea consumption and incident metabolic syndrome (MetS) is still unclear. Therefore, this study intends to figure out the relationship between tea-drinking frequency and MetS in rural middle-aged and older Chinese residents. In the Northeast China Rural Cardiovascular Health Study, 3632 middle-aged or older individuals (mean age 57 ± 8, 55.2% men) without MetS were included at baseline during 2012–2013 and were followed up on between 2015–2017. Participants showing differential tea consumption frequency were divided into the following classes: non-habitual tea drinkers, occasional tea drinkers, 1–2 times/day drinkers, and ≥3 times/day drinkers. Data showed that non-habitual tea drinking was more common among women. The frequency of tea consumption was higher in ethnic groups other than Han and among singles, as well as in concurrent smokers and drinkers and individuals with primary or lower educational status. The increasing tea consumption was in line with baseline elevations in body mass index, systolic and diastolic blood pressure, high-density lipoprotein cholesterol (HDL-C), and AST/ALT ratio. Multivariate logistic regression analysis confirmed that occasional tea drinking increased the incidence of low HDL-C [OR (95% CI): 1.268 (1.015, 1.584)], high waist circumference [OR (95% CI): 1.336 (1.102, 1.621)], and MetS [OR (95% CI): 1.284 (1.050, 1.570)]. In addition, 1–2 times/day tea drinking increased the cumulative incidence of high TG [OR (95% CI): 1.296 (1.040, 1.616)], high waist circumference [OR (95% CI): 1.296 (1.044, 1.609)] and MetS [OR (95% CI): 1.376 (1.030, 1.760)]. We demonstrated that regular tea consumption is correlated with a greater incidence of metabolic disorders and MetS. Our findings may help clarify the contradictory association reported between tea drinking and MetS development in middle-aged and older residents of rural China.

The Relationship between Dietary Patterns and High Blood Glucose among Adults Based on Structural Equation Modelling

The aim of this study was to examine the association between dietary patterns and high blood glucose in Jiangsu province of China by using structural equation modelling (SEqM). Methods: Participants in this cross-sectional study were recruited through the 2015 Chinese Adult Chronic Disease and Nutrition Surveillance Program in Jiangsu province using a multistage stratified cluster random sampling method. Dietary patterns were defined by exploratory factor analysis (EFA). Confirmatory factor analysis (CFA) was used to test the fitness of EFA. SEqM was used to investigate the association between dietary patterns and high blood glucose. Results: After exclusion, 3137 participants with complete information were analysed for this study. The prevalence of high blood glucose was 9.3% and 8.1% in males and females, respectively. Two dietary patterns: the modern dietary pattern (i.e., high in red meats and its products, vegetables, seafood, condiments, fungi and algae, main grains and poultry; low in other grains, tubers and preserves), and the fruit−milk dietary pattern (i.e., high in milk and its products, fruits, eggs, nuts and seeds and pastry snacks, but low in vegetable oils) were established. Modern dietary pattern was found to be positively associated with high blood glucose in adults in Jiangsu province (multivariate logistic regression: OR = 1.561, 95% CI: 1.025~2.379; SEqM: β = 0.127, p < 0.05). Conclusion: The modern dietary pattern—high intake of red meats—was significantly associated with high blood glucose among adults in Jiangsu province of China, while the fruit−milk dietary pattern was not significantly associated with high blood glucose.

Association between dietary patterns and glycaemic control in a middle-aged Chinese population

OBJECTIVE

The present work was performed to analyse the association of dietary patterns with glycaemic control (Hb A1c < 7 %) in a large group of Chinese adults aged between 45 and 59 years.

DESIGN

Habitual dietary intakes in the preceding 12 months were assessed by well-trained interviewers using a validated semi-quantitative FFQ. Factor analysis with principal component method was used to obtain the dietary patterns, and the associations between dietary patterns and glycaemic control were determined using multivariable logistic regression models. Poor glycaemic control was defined as HbA1c ≥ 7·0.

SETTING

Despite decades of research, data on the relationship between dietary patterns and glycaemic control (HbA1c < 7 %) in China are sparse.

PARTICIPANTS

A total of 1739 participants aged 45-59 years from Hangzhou were included in the final analysis.

RESULTS

Three dietary patterns were ascertained and labelled as traditional southern Chinese, Western and grains-vegetables patterns. After controlling of the possible confounders, participants in the highest quartile of Western pattern scores had greater OR for HbA1c ≥ 7·0 (OR = 1·05; (95 % CI 1·000, 1·095); P = 0·048) than did those in the lowest quartile. Compared with those in the lowest quartile of grains-vegetables pattern, participants in the highest quartile had lower OR for HbA1c ≥ 7·0 (OR = 0·82; (95 % CI 0·720, 0·949); P = 0·038). Besides, no significant relationship between the traditional southern Chinese pattern and HbA1c ≥ 7·0 was observed (P > 0·05).

CONCLUSIONS

This study indicated that the Western pattern was associated with a higher risk, and the grains-vegetables pattern was associated with a lower risk for HbA1c ≥ 7·0. Future prospective studies are needed to confirm our findings.

Dietary iron intake and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of prospective cohort studies

PURPOSE

We aimed to assess the long-term association of total, heme, non-heme, and supplemental iron intake and risk of type 2 diabetes (T2D).

METHODS

PubMed, Scopus, and Web of Science were searched to October 2021. Two researchers extracted data in duplicate and rated the certainty in the estimates using the GRADE approach. Random-effects models were applied to estimate the relative risks (RRs) and 95% CIs. Dose-response associations were modeled by a one-stage weighted mixed-effects meta-analysis.

RESULTS

Eleven prospective cohort studies 323,788 participants and 28,837 incident cases of T2D were included. High versus low category meta-analysis indicated that higher heme iron intake was associated with a 20% higher risk of T2D (95% CI 1.07, 1.35; I² = 77%, n = 11; GRADE = moderate). Dose-response analysis indicated a positive monotonic association, wherein each 1 mg/day increment in heme iron intake was related to a 16% higher risk (95% CI 1.03, 1.30). No significant relationship was detected between dietary intakes of total, non-heme, and supplemental iron and risk of T2D (GRADE = very low).

CONCLUSIONS

In summary, higher heme iron intake was associated with a higher risk of T2D. Our results are in line with existing evidence indicating that adopting a Western-style dietary pattern, rich in dietary sources of heme iron, was associated with a higher risk of T2D.

REGISTRY AND REGISTRY NUMBER

The protocol of this systematic review was registered at PROSPERO (registration number: CRD42021226835).

Dietary iron intake and the risk of type 2 diabetes mellitus in middle-aged and older adults in urban China: a prospective cohort study

The association between dietary Fe intake and diabetes risk remains inconsistent. We aimed to explore the association between dietary Fe intake and type 2 diabetes mellitus (T2DM) risk in middle-aged and older adults in urban China. This study used data from the Guangzhou Nutrition and Health Study, an on-going community-based prospective cohort study. Participants were recruited from 2008 to 2013 in Guangzhou community. A total of 2696 participants aged 40-75 years without T2DM at baseline were included in data analyses, with a median of 5·6 (interquartile range 4·1-5·9) years of follow-up. T2DM was identified by self-reported diagnosis, fasting glucose ≥ 7·0 mmol/l or glycosylated Hb ≥ 6·5 %. Cox proportional hazard models were used to estimate hazard ratios (HR) and 95 % CI. We ascertained 205 incident T2DM cases during 13 476 person-years. The adjusted HR for T2DM risk in the fourth quartile of haem Fe intake was 1·92 (95 % CI 1·07, 3·46; Ptrend = 0·010), compared with the first quartile intake. These significant associations were found in haem Fe intake from total meat (HR 2·74; 95 % CI 1·22, 6·15; Ptrend = 0·011) and haem Fe intake from red meat (HR 1·86; 95 % CI 1·01, 3·44; Ptrend = 0·034), but not haem Fe intake from processed meat, poultry or fish/shellfish. The association between dietary intake of total Fe or non-haem Fe with T2DM risk had no significance. Our findings suggested that higher dietary intake of haem Fe (especially from red meat), but not total Fe or non-haem Fe, was associated with greater T2DM risk in middle-aged and older adults.

Relationship between Energy Balance and Circulating Levels of Hepcidin and Ferritin in the Fasted and Postprandial States

Markers of iron metabolism are altered in new-onset diabetes, but their relationship with metabolic signals involved in the maintenance of energy balance is poorly understood. The primary aim was to explore the associations between markers of iron metabolism (hepcidin and ferritin) and markers of energy balance (leptin, ghrelin, and the leptin/ghrelin ratio) in both the fasted and postprandial states. These associations were also studied in the sub-groups stratified by diabetes status. This was a cross-sectional study of individuals without disorders of iron metabolism who were investigated after an overnight fast and, in addition, some of these individuals underwent a mixed meal test to determine postprandial responses of metabolic signals. The associations between hepcidin, ferritin, and leptin, ghrelin, leptin/ghrelin ratio were studied using several multiple linear regression models. A total of 76 individuals in the fasted state and 34 individuals in the postprandial state were included. In the overall cohort, hepcidin was significantly inversely associated with leptin (in the most adjusted model, the β coefficient ± SE was -883.45 ± 400.94; p = 0.031) and the leptin/ghrelin ratio (in the most adjusted model, the β coefficient ± SE was -148.26 ± 61.20; p = 0.018) in the fasted state. The same associations were not statistically significant in the postprandial state. In individuals with new-onset prediabetes or diabetes (but not in those with normoglycaemia or longstanding prediabetes or diabetes), hepcidin was significantly inversely associated with leptin (in the most adjusted model, the β coefficient ± SE was -806.09 ± 395.44; p = 0.050) and the leptin/ghrelin ratio (in the most adjusted model, the β coefficient ± SE was -129.40 ± 59.14; p = 0.037). Leptin appears to be a mediator in the link between iron metabolism and new-onset diabetes mellitus. These findings add to the growing understanding of mechanisms underlying the derangements of glucose metabolism.

Vitamin D decreases pancreatic iron overload in type 2 diabetes through the NF-κB-DMT1 pathway

Emerging evidence has deemed vitamin D as a potential candidate for the intervention of type 2 diabetes (T2D). Herein, we explored the underlying mechanisms of T2D prevention by vitamin D, concentrating on pancreatic iron deposition reported recently. Zucker diabetic fatty (ZDF) rats were treated by vitamin D, with age-matched Zucker lean rats as control. As expected, vitamin D treatment for ZDF rats normalized islet morphology and β-cell function. Moreover, vitamin D alleviated iron accumulation and apoptosis in pancreatic cells of ZDF rats, accompanied by lowered divalent metal transporter 1 (DMT1) expression. Consistently, similar results were observed in high glucose-stimulated INS-1 cells treated with or without vitamin D. Nuclear factor-κB (NF-κB), a transcription factor involving DMT1 regulation, was activated in pancreases of ZDF rats and INS-1 cells exposed to high glucose, but inactivated by vitamin D or BAY 11-7082, a NF-κB inhibitor. Futhermore, IL-1β functioning as NF-κB activator abolished the suppression of NF-κB activation, DMT1 induction and the attenuation of apoptosis as a consequence of vitamin D incubation. Our study showed that iron overload in pancreas may contribute to T2D pathogenesis and uncovered a potentially protective role for vitamin D on iron deposition of diabetic pancreas through NF-κB- DMT1 signaling.

Unintended Consequences: Nutritional Impact and Potential Pitfalls of Switching from Animal- to Plant-Based Foods

Consumers are shifting towards plant-based diets, driven by both environmental and health reasons. This has led to the development of new plant-based meat alternatives (PBMAs) that are marketed as being sustainable and good for health. However, it remains unclear whether these novel PBMAs to replace animal foods carry the same established nutritional benefits as traditional plant-based diets based on pulses, legumes and vegetables. We modelled a reference omnivore diet using NHANES 2017–2018 data and compared it to diets that substituted animal products in the reference diet with either traditional or novel plant-based foods to create flexitarian, vegetarian and vegan diets matched for calories and macronutrients. With the exception of the traditional vegan diet, all diets with traditional plant-based substitutes met daily requirements for calcium, potassium, magnesium, phosphorus, zinc, iron and Vitamin B12 and were lower in saturated fat, sodium and sugar than the reference diet. Diets based on novel plant-based substitutes were below daily requirements for calcium, potassium, magnesium, zinc and Vitamin B12 and exceeded the reference diet for saturated fat, sodium and sugar. Much of the recent focus has been on protein quality and quantity, but our case study highlights the risk of unintentionally increasing undesirable nutrients while reducing the overall nutrient density of the diet when less healthy plant-based substitutes are selected. Opportunities exist for PBMA producers to enhance the nutrient profile and diversify the format of future plant-based foods that are marketed as healthy, sustainable alternatives to animal-based products.

The association between dietary patterns with type 2 diabetes mellitus and pre-diabetes in the Henan rural cohort study

OBJECTIVE

We aimed to investigate whether dietary patterns were associated with the risk of type 2 diabetes mellitus (T2DM) or pre-diabetes in adults of rural area in Henan.

DESIGN

Cross-sectional study. Principal component analysis was used to identify dietary patterns, while multivariate logistic regression analysis and restricted cubic spline regression models were used to analyse the association between dietary patterns and both pre-diabetes and T2DM.

SETTING

Rural area of Henan province, China.

PARTICIPANTS

A total of 38 779 adults aged 18-79 years were recruited from the Henan rural cohort study as the subjects.

RESULTS

The prevalence of pre-diabetes and T2DM in rural Henan was 6·8 % and 9·4 %, respectively. A total of three dietary patterns were assessed in the present study. Dietary pattern I with a high intake of red meat and white meat; dietary pattern II with a high intake of grains, nuts, milk and eggs and dietary pattern III with a high intake of vegetables, staple food and fruits. The highest quintile (Q5) of pattern III could reduce 32·7 % risk of pre-diabetes. The Q5 of pattern II showed a 15·5 % decreased risk of T2DM, in a U-shaped dose-response manner; meanwhile, the Q5 of pattern III was significantly associated with reduced risks of T2DM (OR: 0·582, 95 % CI (0·497, 0·682)).

CONCLUSIONS

Pattern III is beneficial for reducing risk of pre-diabetes or T2DM. Though a higher consumption of 'grains-nuts-egg' may associate with a reduced risk of T2DM, excessive intakes should be avoided. This study may provide a reference for the prevention of diabetes on dietary precautions.

Association between Habitual Dietary Iron Intake and Glucose Metabolism in Individuals after Acute Pancreatitis

Dietary intake of iron is known to be associated with impaired glucose metabolism. However, its involvement in derangements of glucose metabolism after acute pancreatitis (AP) is not completely understood. The aim was to investigate the association between dietary iron intake and markers of glucose metabolism in individuals after an attack of AP. Fasting blood samples were collected to analyse markers of glucose metabolism (fasting plasma glucose (FPG) and haemoglobin A1c (HbA1c)). The EPIC-Norfolk food frequency questionnaire was used to determine the habitual intake of dietary iron (total, haem, and non-haem). Multivariable linear regression analyses were conducted and six statistical models were built to adjust for covariates. A total of 109 individuals after AP were studied in a cross-sectional fashion. Total iron (β (95% confidence interval) = -0.19 (-0.35, -0.05); p = 0.01 in the most adjusted model) and non-haem iron (β (95% confidence interval) = -0.19 (-0.33, -0.04); p = 0.03 in the most adjusted model) were significantly associated with FPG, consistently in all adjusted model. Total iron and non-haem iron did not have consistent significant associations with HbA1c. Dietary haem iron intake was not associated with either FPG or HbA1c. Habitual intake of dietary iron is inversely associated with FPG in individuals after an attack of AP and may be involved in the pathogenesis of new-onset diabetes after pancreatitis. Prospective longitudinal studies are now warranted to unveil the specific mechanism underlying the involvement of dietary iron.

Dietary Nonheme, Heme, and Total Iron Intake and the Risk of Diabetes in Adults: Results From the China Health and Nutrition Survey

OBJECTIVE

Excessive iron intake has been linked to diabetes risk. However, the evidence is inconsistent. This study examined the association between dietary heme and nonheme iron intake and diabetes risk in the Chinese population.

RESEARCH DESIGN AND METHODS

We included 17,026 adults (8,346 men and 8,680 women) who were part of the China Health and Nutrition Survey (1991-2015) prospective cohort. Dietary intake was measured by three consecutive 24-h dietary recalls combined with a household food inventory. Diabetes cases were identified through a questionnaire. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% CIs.

RESULTS

A total of 547 men and 577 women developed diabetes during 202,138 person-years of follow-up. For men, the adjusted HRs (95% CIs) for quintiles of nonheme iron intake were 1.00, 0.77 (0.58-1.02), 0.72 (0.54-0.97), 0.63 (0.46-0.85), and 0.87 (0.64-1.19) (P-nonlinearity = 0.0015). The corresponding HRs (95% CIs) for women were 1.00, 0.63 (0.48-0.84), 0.57 (0.43-0.76), 0.58 (0.43-0.77), and 0.67 (0.49-0.91) (P-nonlinearity < 0.0001). The dose-response curves for the association between nonheme iron and total iron intake and diabetes followed a reverse J shape in men and an L shape in women. No significant associations were observed between heme iron intake and diabetes risk.

CONCLUSIONS

Total iron and nonheme iron intake was associated with diabetes risk, following a reverse J-shaped curve in men and an L-shaped curve in women. Sufficient intake of nonheme or total iron might be protective against diabetes, while excessive iron intake might increase the risk of diabetes among men.

Animal based low carbohydrate diet is associated with increased risk of type 2 diabetes in Tehranian adults

BACKGROUND

To investigate the association of low carbohydrate diet (LCD) score with the risk of type 2 diabetes among adults.

METHODS

This cohort study was conducted on 4356 healthy participants aged ≥ 19 years old, who were followed-up for a mean duration of 3 years within the framework of the Tehran Lipid and Glucose Study. LCD score was calculated using a food frequency questionnaire according to intake of carbohydrate, protein, and fat at baseline. Diabetes was defined according to the criteria of the American Diabetes Association. Multivariable logistic regression models, adjusted for potential confounders, were used to estimate risk of diabetes across quartiles of LCD score.

RESULTS

Mean ± SD age of the study participants (44.4% men) was 40.5 ± 13.0 years. The median (25-75 interquartile range) of LCD score was 17.0 (12.0-21.0) and after a 3 year follow-up period, 123 (2.8%) incident cases of diabetes were ascertained. After adjustment for confounding variables, including age, sex, smoking status, physical activity, total calorie intake, saturated fatty acid, waist circumference, educational level, and family history of diabetes, the multivariable-adjusted ORs (95% CIs) of type 2 diabetes, comparing the highest with the lowest quartiles, were 2.16 (1.16-4.04) for total LCD score (P-value = 0.015), 1.81 (1.06-3.11) for animal-based LCD score (P-value = 0.029), and 1.47 (0.85-2.52) for plant-based LCD score (P-value = 0.160).

CONCLUSION

Our findings suggest that a higher adherence to LCD, mostly with higher intakes of protein and fat from animal-source foods, can increase the incidence of diabetes; however, a plant-based low-carbohydrate dietary pattern is not significantly associated with risk of type 2 diabetes.

Influence of ferritin levels and inflammatory markers on HbA1c in the Type 2 Diabetes mellitus patients

Objective:

Diabetes Mellitus (DM) is a significant public health issue worldwide due to the associated comorbidities. Recent studies have demonstrated a strong relationship between blood glucose levels and serum ferritin levels in patients with type 2 DM. The aim of the study was to investigate the association between Ferritin Levels and Inflammatory Markers on HbA1c in the Type 2 Diabetes Mellitus Patients.

Methods:

This single-center, cross-sectional, controlled study included patients who were admitted to the Endocrine and Metabolic Disorders outpatient clinics of the Private Kütahya Hospital in the province of Kutahya in the Western Turkey. The study included a total of 172 patients, 84 of whom had type 2 DM and 88 without diabetes and constituted the control group. A total of 190 patients with DM were admitted to the Adult Endocrine and Metabolic Diseases Outpatient Clinics of the hospital between July 1, 2018 and September 1, 2018, and among these, the study was conducted on 172 volunteer patients who met the study inclusion criteria and who did not have any missing data. The HbA1c levels, serum ferritin, hemoglobin (Hb), insulin, Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), C-Reactive Protein (CRP), lipid profiles, and uric acid levels were compared between the groups.

Results:

The serum ferritin levels of the patients with type 2 DM significantly increased with increasing HbA1c levels (p<0.01). A strong positive correlation was found between serum ferritin levels and HbA1c and fasting blood glucose (FBG) levels (p<0.01).

Conclusions:

Our study results show a significant relationship between HbA1c levels and serum ferritin and CRP levels, suggesting that serum ferritin and CRP levels can be used as a routine screening tool for the early diagnosis of DM. However, further large-scale, prospective studies are needed to confirm these findings.

Independent and combined effects of dietary iron composition and selected risk factors on the risk of NAFLD in a Chinese population

Iron is an essential mineral required for most forms of life. However, very little is known in relation to the different forms of dietary iron on the development of NAFLD. The aims of this study were to investigate the effects of iron intake from different food types on risk of NAFLD and whether this effect may be modified by other factors. We conducted a hospital-based case–control study including 1,273 NAFLD cases and 1,273 gender and age-matched controls. We conducted in-person interviews while participants completed a questionnaire on food habits. We assessed animal- and plant-derived intake of iron and fat. We observed that animal-derived iron intake (>4.16 mg/day) was positively associated with augmented NAFLD risk in a Chinese population (OR_adjusted = 1.66 in the highest quartile compared with the lowest, 95% confidence interval [CI] = 1.01–2.73). In contrast, a high consumption of iron (>16.87 mg/day) from plant-based foods was associated with a decreased NAFLD risk (ORadjusted = 0.61 in the highest quartile compared with the lowest; 95% CI = 0.40–0.935). In addition, high intake of fat or being overweight may exacerbate this effect. Reduced consumption of iron and fat from animal sources could reduce NAFLD risk, as would weight loss.

The role of systemic inflammation in the pathogenesis of insulin resistance and metabolic syndrome in patients with chronic hepatitis C

The systemic inflammatory response plays a key role in the development of atherosclerosis, insulin resistance (IR) and diabetes mellitus 2-type (diabetes mellitus). IR in patients with chronic hepatitis C (CHC) is considered as a possible factor in the progression of fibrosis, a predictor of the development of DM T2 and a component of the metabolic syndrome. The use of biomarkers of non-specific inflammation can be a valuable tool for assessing the risks of IR and cardiovascular diseases in patients with chronic hepatitis C. Aim of the study. To determine the role of nonspecific inflammation in the formation of IR and metabolic syndrome in patients with chronic hepatitis C. Materials and methods. The study included 205 patients with CHC aged 18 to 69 years. Patients with CHC are randomized into two groups depending on the presence of IR: group 1 - patients with a HOMA index ≥2.77, which corresponded to IR (n=110); group 2 (n=95). The levels of serum iron, C-reactive protein (CRP), serum ferritin and adipose tissue hormones [leptin, resistin, adiponectin and tumor necrosis factor-α (TNF-α)] were additionally investigated. Results. At all stages of development of IR, nonspecific inflammation was detected (according to ferritin, CRP and serum iron), increasing with increasing HOMA index [Homeostasis Model of Assessment - Insulin Resistance (HOMA-IR)] (Matthews D., 1985), metabolic syndrome and its components. In the analysis of indicators in patients with chronic hepatitis C with a body mass index

Dietary patterns are associated with type 2 diabetes mellitus among middle-aged adults in Zhejiang Province, China

Background

Although some studies have shown the associations between dietary patterns and the risk T2DM in a general population, the associations in middle-aged Chinese have been rarely studied to date. In this study, we aimed to characterize dietary patterns in Chinese adults aged 45-59y (n = 1918) and to evaluate the relationship between dietary patterns and the risk of T2DM.

Methods

The study population was a part of the population-based the Nutrition and Health Study conducted in the city of Hangzhou, Zhejiang Province, China. Dietary intake was assessed by using a validated food frequency questionnaire (FFQ). Multivariate logistic regression analyses were used to estimate the associations between dietary patterns and the risk of T2DM, adjusting for potential confounders.

Results

Three major dietary patterns were identified using factor analysis, including the traditional southern Chinese, the Western, and the grains-vegetables patterns. After adjusting for the potential confounders, subjects in the highest quartile of the Western dietary pattern scores had greater odds ratio(OR) for T2DM(OR = 1.28; 95% confidence interval (CI): 1.103–1.697; P = 0.02) than did those in the lowest quartile. Compared with those in the lowest quartile, subjects in the highest quartile of the grains-vegetables dietary pattern scores had a lower OR for T2DM (OR = 0.72; 95% CI:0.596–0.952; P = 0.04). Moreover, no significant association was found between the traditional southern Chinese dietary pattern and risk of developing T2DM.

Conclusions

Our findings indicated that the Western dietary pattern was associated with an elevated risk, whereas the grains-vegetables dietary pattern was associated with a reduced risk of T2DM. Further researches are needed to confirm these findings.

Nutritional management in women with polycystic ovary syndrome: A review study

Polycystic ovary syndrome (PCOS) is endocrine disorder in women of reproductive age, which leads to reproductive, hormonal and metabolic abnormalities. Due to the presence of insulin resistance, PCOS increases the risk of chronic diseases like type 2 diabetes, hypertension, lipid disorders, cardiovascular diseases and malignancies such as breast and endometrial cancer. The actual cause of this syndrome is unknown but environmental factors such as dietary habits play an important role in prevention and treatment and lifestyle modifications are the most important therapeutic strategies in these patients. The approach of the diet therapy in these patients must be to reach specific goals such as improving insulin resistance, metabolic and reproductive functions that will be possible through the design of low-calorie diet to achieve weight loss or maintaining a healthy weight, limit the intake of simple sugars and refined carbohydrates and intake foods with a low glycemic index, reduction of saturated and trans fatty acids and attention to possible deficiencies such as vitamin D, chromium and omega-3. Given the prevalence of overweight and obesity and insulin resistance, a relatively low reduction in weight, about 5%, can improve problems such as insulin resistance, high levels of androgens, reproductive system dysfunctions and fertility in these women.

Branched-chain amino acid, meat intake and risk of type 2 diabetes in the Women's Health Initiative

Knowledge regarding association of dietary branched-chain amino acid (BCAA) and type 2 diabetes (T2D), and the contribution of BCAA from meat to the risk of T2D are scarce. We evaluated associations between dietary BCAA intake, meat intake, interaction between BCAA and meat intake and risk of T2D. Data analyses were performed for 74 155 participants aged 50-79 years at baseline from the Women's Health Initiative for up to 15 years of follow-up. We excluded from analysis participants with treated T2D, and factors potentially associated with T2D or missing covariate data. The BCAA and total meat intake was estimated from FFQ. Using Cox proportional hazards models, we assessed the relationship between BCAA intake, meat intake, and T2D, adjusting for confounders. A 20 % increment in total BCAA intake (g/d and %energy) was associated with a 7 % higher risk for T2D (hazard ratio (HR) 1·07; 95 % CI 1·05, 1·09). For total meat intake, a 20 % increment was associated with a 4 % higher risk of T2D (HR 1·04; 95 % CI 1·03, 1·05). The associations between BCAA intake and T2D were attenuated but remained significant after adjustment for total meat intake. These relations did not materially differ with or without adjustment for BMI. Our results suggest that dietary BCAA and meat intake are positively associated with T2D among postmenopausal women. The association of BCAA and diabetes risk was attenuated but remained positive after adjustment for meat intake suggesting that BCAA intake in part but not in full is contributing to the association of meat with T2D risk.

Overview of iron metabolism in health and disease

Iron is an essential element for numerous fundamental biologic processes, but excess iron is toxic. Abnormalities in systemic iron balance are common in patients with chronic kidney disease and iron administration is a mainstay of anemia management in many patients. This review provides an overview of the essential role of iron in biology, the regulation of systemic and cellular iron homeostasis, how imbalances in iron homeostasis contribute to disease, and the implications for chronic kidney disease patients.

Associations between dietary intakes of iron, copper and zinc with risk of type 2 diabetes mellitus: A large population-based prospective cohort study

BACKGROUND & AIMS

Abnormal homeostasis of iron, copper and zinc has been included in the pathogenesis of type 2 diabetes mellitus (T2DM). However, the evidence of associations between dietary intakes of these elements and T2DM is limited. We thought to examine the association between dietary intakes of iron, copper and zinc with risk of T2DM in Japanese population.

METHODS

A prospective study encompassing 16,160 healthy Japanese men and women aged 40-65 years in whom the associations between dietary intakes of iron, copper and zinc, determined by a validated self-administered food frequency questionnaire, with risk of 5-year cumulative incidence of validated physician-diagnosed T2DM, were evaluated by logistic regression model.

RESULTS

We ascertained 396 self-reported new cases of diabetes within 5-year period. Dietary intakes of iron (total and nonheme but not heme iron) and copper were positively associated with risk of T2DM; the multivariable OR in the highest versus lowest quartiles of intakes were 1.32 (1.04, 1.70; P-trend = 0.03) and 1.55 (1.13, 2.02; P-trend = 0.003), respectively. These associations were more evident in the high risk group; older, overweight, smokers and those with family history of diabetes. The dietary intake of zinc was inversely associated with risk of T2DM; the multivariable OR was 0.64 (0.54, 1.00; P-trend = 0.003), and such association was evident among younger subjects (age 40-55 years) only.

CONCLUSIONS

Dietary intakes of iron and copper were associated with a higher risk, while dietary intake of zinc was associated with a reduced risk of T2DM in Japanese population.

Diabetes in HFE Hemochromatosis

Diabetes in whites of European descent with hemochromatosis was first attributed to pancreatic siderosis. Later observations revealed that the pathogenesis of diabetes in HFE hemochromatosis is multifactorial and its clinical manifestations are heterogeneous. Increased type 2 diabetes risk in HFE hemochromatosis is associated with one or more factors, including abnormal iron homeostasis and iron overload, decreased insulin secretion, cirrhosis, diabetes in first-degree relatives, increased body mass index, insulin resistance, and metabolic syndrome. In p.C282Y homozygotes, serum ferritin, usually elevated at hemochromatosis diagnosis, largely reflects body iron stores but not diabetes risk. In persons with diabetes type 2 without hemochromatosis diagnoses, serum ferritin levels are higher than those of persons without diabetes, but most values are within the reference range. Phlebotomy therapy to achieve iron depletion does not improve diabetes control in all persons with HFE hemochromatosis. The prevalence of type 2 diabetes diagnosed today in whites of European descent with and without HFE hemochromatosis is similar. Routine iron phenotyping or HFE genotyping of patients with type 2 diabetes is not recommended. Herein, we review diabetes in HFE hemochromatosis and the role of iron in diabetes pathogenesis in whites of European descent with and without HFE hemochromatosis.

Metabolomic profiling identifies potential pathways involved in the interaction of iron homeostasis with glucose metabolism

Objective

Elevated serum ferritin has been linked to type 2 diabetes (T2D) and adverse health outcomes in subjects with the Metabolic Syndrome (MetS). As the mechanisms underlying the negative impact of excess iron have so far remained elusive, we aimed to identify potential links between iron homeostasis and metabolic pathways.

Methods

In a cross-sectional study, data were obtained from 163 patients, allocated to one of three groups: (1) lean, healthy controls (n = 53), (2) MetS without hyperferritinemia (n = 54) and (3) MetS with hyperferritinemia (n = 56). An additional phlebotomy study included 29 patients with biopsy-proven iron overload before and after iron removal. A detailed clinical and biochemical characterization was obtained and metabolomic profiling was performed via a targeted metabolomics approach.

Results

Subjects with MetS and elevated ferritin had higher fasting glucose (p < 0.001), HbA1c (p = 0.035) and 1 h glucose in oral glucose tolerance test (p = 0.002) compared to MetS subjects without iron overload, whereas other clinical and biochemical features of the MetS were not different. The metabolomic study revealed significant differences between MetS with high and low ferritin in the serum concentrations of sarcosine, citrulline and particularly long-chain phosphatidylcholines. Methionine, glutamate, and long-chain phosphatidylcholines were significantly different before and after phlebotomy (p < 0.05 for all metabolites).

Conclusions

Our data suggest that high serum ferritin concentrations are linked to impaired glucose homeostasis in subjects with the MetS. Iron excess is associated to distinct changes in the serum concentrations of phosphatidylcholine subsets. A pathway involving sarcosine and citrulline also may be involved in iron-induced impairment of glucose metabolism.

•

This metabolomic study focuses on pathways linking iron status to insulin resistance.

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Metabolomic differences in Metabolic Syndrome with/without iron overload are shown.

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Phlebotomy changes methionine, glutamate and long-chain phosphatidylcholines levels.

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Phosphatidylcholines are involved in the interaction of iron and glucose homeostasis.

Iron in red meat-friend or foe

In developed countries, due to high content and bioavailability, red and processed meats are the main sources of iron in the diet. Adequate intake of this nutrient is essential for the proper development and functioning of the human body, and its deficiencies are associated mainly with the occurrence of anemia, which is one of the most widespread nutritional problems in the world. However, excessive intake of iron can be detrimental to health. Studies have shown that high consumption of red meat and its products, and thereby iron, particularly in the form of heme, increases the risk of non-communicable diseases, including cancers, type II diabetes and cardiovascular disease. Due to the high nutritional value, the presence of red meat in the diet is preferable, but according to World Cancer Research Fund International its consumption should not exceed 500g per week. Furthermore, there are several potential ways to suppress the toxic effects of heme iron in the diet.

Long-term risk of type 2 diabetes in relation to habitual iron intake in women with a history of gestational diabetes: a prospective cohort study

BACKGROUND

An iron overload may induce pancreatic islet damage and increase risk of diabetes. Women with a history of gestational diabetes mellitus (GDM) are at high risk of developing type 2 diabetes mellitus (T2DM) after pregnancy.

OBJECTIVE

We aimed to examine the association of habitual iron intake with long-term risk of T2DM in this high-risk population.

DESIGN

We included 3976 women with a history of GDM from the Nurses' Health Study II cohort as part of the ongoing Diabetes & Women's Health Study. The women were followed up through 2009. Iron intake was assessed with the use of a validated food-frequency questionnaire in 1991 and every 4 y thereafter. We used Cox proportional hazards models to estimate HRs and 95% CIs.

RESULTS

We documented 641 incident T2DM cases during 57,683 person-years of observation. Adjusted HRs for T2DM for the highest quartile compared with the lowest quartile were 1.64 (95% CI: 1.20, 2.25; P-trend = 0.02) for total iron intake and 1.80 (95% CI: 1.18, 2.74; P-trend = 0.005) for dietary heme iron intake. In addition, women who consumed ≥30.0 mg supplemental Fe/d, compared with nonusers, had an adjusted HR of 1.83 (95% CI: 1.25, 2.70; P-trend = 0.002).

CONCLUSION

In women with a history of GDM, greater intakes of total iron, dietary heme iron, and supplemental iron were associated with higher risk of T2DM.

Elevated Total Iron-Binding Capacity Is Associated with an Increased Risk of Celiac Disease

BACKGROUND

Several lines of evidence suggest that abnormal iron homeostasis may itself play an important role in the development of celiac disease.

AIM

We sought to determine whether abnormalities in iron status could be detected prior to the diagnosis of celiac disease, and to understand the relationship between altered iron indices and the natural history of celiac disease.

METHODS

We conducted a case-control study at two major tertiary referral hospitals. Cases were comprised of patients with celiac disease in whom iron status was assessed prior to the diagnosis. Each case was matched to five controls without known gastrointestinal disease according to age and sex. Information on potential covariates and laboratory values within 1, 1-3, and 3-5 years prior to diagnosis was collected. We used conditional logistic regression to evaluate the effect of iron indices on risk of celiac disease.

RESULTS

We identified 157 celiac cases and 695 matched controls. Compared to participants with normal TIBC, the age-adjusted risk of celiac disease was significantly elevated among patients with elevated TIBC. For each 10 μg/dL increase in TIBC, the risk of celiac disease increased by 4.6, 3.8, and 7.9% within 1, 1-3, and 3-5 years prior to diagnosis, respectively. Patients with elevated pre-diagnosis TIBC were more likely to have abnormal liver enzymes and osteoporosis.

CONCLUSIONS

Elevated TIBC is associated with an increased risk of celiac disease. Further investigation into the potential role of altered iron homeostasis may uncover important environmental factors that contribute to the development of celiac disease.

High protein and cholesterol intakes associated with emergence of glucose intolerance in a low-risk Canadian Inuit population

Objective

The rate of type 2 diabetes mellitus among Inuit is 12·2 % in individuals over 50 years of age, similar to the Canadian prevalence. Given marked dietary transitions in the Arctic, we evaluated the dietary and other correlates of not previously diagnosed glucose intolerance, defined as type 2 diabetes mellitus, impaired fasting glucose or impaired glucose tolerance.

Design

Cross-sectional analyses were limited to adults with a completed 2 h oral glucose tolerance test and without pre-existing diabetes. Anthropometric assessments, health and medication usage questionnaires and a 24 h dietary recall were administered.

Setting

Canadian International Polar Year Inuit Health Survey (2007–2008).

Subjects

Inuit adults (n 777).

Results

Glucose intolerance was associated with older age and adiposity. Percentage of energy from protein above the Acceptable Macronutrient Distribution Range of 35 %, compared with intake within the range, was associated with increased odds of glucose intolerance (OR=1·98; 95 % CI 1·09, 3·61) in multivariable analyses. Further, cholesterol intake in the highest three quartiles combined (median exposures of 207, 416 and 778 mg/d, respectively) compared with the lowest quartile (median intake of 81 mg/d) was associated with glucose intolerance (OR=2·15; 95 % CI 1·23, 3·78) in multivariable analyses. Past-day traditional food consumption was borderline protective of glucose intolerance (P=0·054) and high fibre intake was not significantly protective (P=0·08).

Conclusions

The results contribute to the existing literature on high protein and cholesterol intakes as they may relate to diabetes risk.

Ferritin as a Risk Factor for Glucose Intolerance amongst Men and Women Originating from the Indian Subcontinent

Background. Serum ferritin predicts the onset of diabetes; however, this relationship is not clear amongst South Asians, a population susceptible to glucose intolerance and anaemia. Objective. This study tests whether ferritin levels reflect glucose tolerance in South Asians, independent of lifestyle exposures associated with Indian or British residence. Methods. We randomly sampled 227 Gujaratis in Britain (49.8 (14.4) years, 50% men) and 277 contemporaries living in Gujarati villages (47.6 (11.8) years, 41% men). Both groups underwent a 75 g oral-glucose-tolerance test. We evaluated lifestyle parameters with standardised questionnaires and conducted comprehensive clinical and lab measurements. Results. Across sites, the age-adjusted prevalence of diabetes was 9.8%. Serum ferritin was higher amongst diabetics (P = 0.005), irrespective of site, gender, and central obesity (P ≤ 0.02), and was associated with fasting and postchallenge glucose, anthropometry, blood pressure, triglycerides, and nonesterified fatty acids (P < 0.001). Diabetes was less in those with low ferritin (<20 mg/mL), P < 0.008, and risk estimate = 0.35 (95% CI 0.15-0.81), as were blood pressure and metabolic risk factors. On multivariate analysis, diabetes was independently associated with ferritin (P = 0.001) and age (P < 0.001). Conclusion. Ferritin levels are positively associated with glucose intolerance in our test groups, independent of gender and Indian or UK lifestyle factors.

Distribution of serum transferrin, and its associations with metabolic disorders among Chinese: A nation-wide, health and nutrition survey

SCOPE

This study examined the associations of serum transferrin and metabolic disorders among Chinese population.

METHODS AND RESULTS

This study is based on nation-wide, population-based China Health and Nutrition survey including 8564 men and women aged 18 years or older. Anthropometric and fasting blood glucose, insulin, lipids, and transferrin data were collected. Elevated transferrin concentrations associated with higher body mass index, waist circumference, lipids, insulin, glucose (all p < 0.0001). Serum transferrin concentrations increased gradually with increasing numbers of metabolic syndrome (MetS) components among men and women (p = 0.0003). Elevated concentrations of transferrin were significantly related with higher risk of MetS (p = 0.0006), obesity (p = 0.0089), overweight (p < 0.0001). No associations between transferrin concentrations and risk of diabetes and high blood pressure were observed in both men and women.

CONCLUSION

Elevated transferrin concentrations were positively associated with risk of MetS and obesity, but not with risk of diabetes among Chinese.

A review of potential metabolic etiologies of the observed association between red meat consumption and development of type 2 diabetes mellitus

Epidemiological studies suggest that red and processed meat consumption is related to an increased risk of type 2 diabetes. However, it is not clearly understood which components of red and processed meat contribute to this increased risk. This review examines potential mechanisms addressing the role of saturated fatty acid, sodium, advanced glycation end products (AGEs), nitrates/nitrites, heme iron, trimethylamine N-oxide (TMAO), branched amino acids (BCAAs) and endocrine disruptor chemicals (EDCs) in the development of type 2 diabetes based on data from published clinical trials and animal models. TMAO which is derived from dietary carnitine and choline by the action of bacterial enzymes followed by oxidation in the liver may be a strong candidate molecule mediating the risk of type 2 diabetes. BCAAs may induce insulin resistance via the mammalian target of rapamycin complex 1 (mTORC1) and ribosomal protein S6 kinase β 1 (S6k1)-associated pathways. The increased risk associated with processed meat compared with red meat suggests that there are interactions between the saturated fat, salt, and nitrates in processed meat and iron, AGEs and TMAO. Intervention studies are required to clarify potential mechanisms and explore interactions among components, in order to make firm recommendations on red and processed meat consumption.

Iron metabolism is prospectively associated with insulin resistance and glucose intolerance over a 7-year follow-up period: the CODAM study

OBJECTIVES

Several markers of iron metabolism have been associated with insulin resistance (IR) and type 2 diabetes mellitus in cross-sectional studies. However, prospective data on these associations are scarce, and it is currently unclear in which tissues iron metabolism may contribute to IR. Therefore, we investigated whether markers of iron metabolism were associated with IR in muscle, liver, and adipocytes, and with glucose intolerance over a 7-year follow-up period.

DESIGN AND METHODS

Serum ferritin, transferrin, total iron, non-transferrin-bound iron, and transferrin saturation were determined at baseline of a prospective cohort study in 509 individuals (60 % men, age 59 ± 6.9 years, body mass index 28.5 ± 4.3). Both at baseline and after a 7-year follow-up (n = 386), measures of glucose, insulin (during glucose tolerance tests), and non-esterified fatty acids were obtained. Using generalized estimating equations, we investigated associations between baseline iron markers and indices of muscle, liver, and adipocyte insulin resistance (adipocyte IR), as well as glucose intolerance, over the 7-year period.

RESULTS

Over a 7-year period, baseline serum ferritin (per 10 μg/L increase) was positively associated with homeostasis model assessment insulin resistance (HOMA2-IR) [β = 0.77 % (95 % CI 0.50-1.03)], hepatic insulin resistance (hepatic IR) [β = 0.39 % (0.23-0.55)], adipocyte IR [β = 1.00 % (0.65-1.35)], and AUCglucose [β = 0.32 % (0.18-0.46)] after adjustment for several covariates, including inflammatory markers (all p < 0.001). Similarly, serum transferrin (per 0.1 g/L) was associated with HOMA2-IR [β = 2.66 % (1.55-3.78)], hepatic IR [β = 1.16 % (0.47-1.85)], adipocyte IR [β = 3.75 % (2.27-5.25)], and AUCglucose [β = 1.35 % (0.74-1.96)] over 7 years.

CONCLUSIONS

Iron metabolism and related factors may contribute to IR in muscle, liver, and adipocytes, eventually leading to impaired glucose metabolism and hyperglycaemia.

Diet, lifestyle, and genetic risk factors for type 2 diabetes: a review from the Nurses' Health Study, Nurses' Health Study 2, and Health Professionals' Follow-up Study

The epidemiological evidence collected from three large US cohorts (Nurses' Health Study, Nurses' Health Study 2, and Health Professionals' Follow-up Study) has yielded important information regarding the roles of overall diet, individual foods and nutrients, physical activity and other lifestyle factors in the development of type 2 diabetes. Excess adiposity is a major risk factor for diabetes, and thus, maintaining a healthy body weight and avoidance of weight gain during adulthood is the cornerstone of diabetes prevention. Independent of body weight, the quality or type of dietary fat and carbohydrate is more crucial than the quantity in determining diabetes risk. Higher consumption of coffee, whole grains, fruits, and nuts is associated with lower risk of diabetes, whereas regular consumption of refined grains, red and processed meats, and sugar-sweetened beverages including fruits juices is associated with increased risk. Dietary patterns rich in fruits and vegetables, whole grains, and nuts and legumes but lower in red and processed meats, refined grains, and sugar-sweetened beverages are consistently associated with diabetes risk, even after adjustment for body mass index. The genome-wide association studies conducted in these cohorts have contributed substantially to the discoveries of novel genetic loci for type 2 diabetes and other metabolic traits, although the identified common variants explain only a small proportion of overall diabetes predisposition. Taken together, these ongoing large cohort studies have provided convincing epidemiologic evidence that a healthy diet, together with regular physical activity, maintenance of a healthy weight, moderate alcohol consumption, and avoidance of sedentary behaviors and smoking would prevent the majority of type 2 diabetes cases.

Predisposing factors associated with uncomplicated type 2 diabetes among adults in a diabetic clinic, Enugu State, Nigeria

BACKGROUND

The role of micronutrients and other predisposing factors associated with the aetiology of type 2 diabetes in Nigeria is not well established. The objectives of this study were to investigate predisposing factors associated with uncomplicated type 2 diabetes among a Nigerian adult population.

METHODS

Predisposing factors associated with uncomplicated type 2 diabetes were investigated in 60 Igbo (a major tribe in Eastern Nigeria) adults aged 30-90 years. This study was carried out at the Diabetic Clinic, University of Nigeria Teaching Hospital (UNTH) Ituku-Ozalla, Enugu. Packed cell volume (PCV), serum ferrtin and some anthropometric parameters were measured alongside fasting blood sugar (FBS).

RESULTS

PCV recorded a statistically significant lower (p<0.001) mean value at 32.94±0.61% in the patients when compared with the control group with a mean value of 39.06±1.02%. Serum ferritin revealed a statistically significant higher (p<0.01; 110.20±15.17 ng/ml) mean value in the patients when compared with the control group (20.4±5.64 ng/ml). However, PCV (32.00±0.88%) and body mass index (BMI) (31.99±1.12 Kg/m(2)) recorded a statistically significant lower (p<0.05) mean value in female patients when compared with their corresponding males. There was no significant correlation (p>0.05) between serum iron ferritin, FBS and all other anthropometric predictors of incidence of type 2 diabetes.

CONCLUSION

Type 2 diabetes is not associated with elevated levels of serum iron ferritin. Hence, serum ferritin may not be a better predictor of type 2 diabetes, especially in uncomplicated cases.

Gender differences in associations of serum ferritin and diabetes, metabolic syndrome, and obesity in the China Health and Nutrition Survey

SCOPE

This study examines gender differences in associations of serum ferritin and diabetes, metabolic syndrome (MetS), and obesity in Chinese.

METHODS AND RESULTS

Based on a nationwide, population-based China Health and Nutrition survey this study included 8564 men and women aged 18 years or older. Anthropometric and fasting blood glucose, insulin, lipids, ferritin, and transferrin data were collected. Ferritin concentrations were higher in men than women (201.55 ± 3.6 versus 80.46 ± 1.64 ng/mL, p < 0.0001). The prevalences of MetS, diabetes, obesity, and overweight were 8.05, 8.97, 4.67, 25.88% among men and 14.23, 6.58, 5.81, 26.82% among women, respectively. Elevated ferritin concentrations were associated with higher body mass index, waist circumference, lipids, insulin, glucose (all p < 0.0001). Serum ferritin concentrations increased gradually with aging among women. The inverted U-shaped association between serum ferritin and age was observed among men. Elevated concentration of ferritins were significantly related with higher risk of MetS (p < 0.0001), obesity (p = 0.010), overweight (p < 0.0001), and diabetes (p < 0.0001) among men, but not among women.

CONCLUSION

There was a gender difference in associations between ferritin and MetS, obesity, and diabetes in Chinese adults. Further evaluations of the variation in gender on these associations are warranted to understand the mechanisms behind gender differences.