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

A diet-wide Mendelian randomization analysis: causal effects of dietary habits on type 2 diabetes

Background

Traditional clinical studies have indicated a link between certain food intakes and type 2 diabetes (T2D), but the causal relationships between different dietary habits and T2D remain unknown. Using Mendelian randomization (MR) approaches, we investigated the potential causal association between dietary habits and T2D risk.

Methods

We collected publicly available genome-wide association studies' summary statistics for 18 dietary habits from the UK Biobank and T2D data from the DIAbetes Genetics Replication And Meta-analysis (DIAGRAM) consortium. We applied the inverse variance weighted (IVW) method, supplemented with the MR-Egger method, weighted median method (WMM), simple method, weighted mode, MR-Egger regression, and the MR pleiotropy residual sum and outlier test to determine whether a particular diet was causal for T2D.

Results

Reliable and robust MR estimates demonstrated that poultry intake has a causal effect on a higher risk of T2D (IVW: OR 6.30, 95% CI 3.573-11.11, p = 2.02e - 10; WMM: OR 5.479, 95% CI 0.2758-10.88, p = 1.19e - 06). Conversely, dried fruit intake (IVW: OR 0.380, 95% CI 0.237-0.608, p = 5.57e - 05; WMM: OR 0.450, 95% CI 0.321-0.630, p = 3.33e - 06) and cereal intake (IVW: OR 0.455, 95% CI 0.317-0.653, p = 1.924e - 05; WMM: OR 0.513, 95% CI 0.379-0.694, p = 1.514e - 05) were causally associated with T2D as protective factors. Sensitivity analyses confirmed the reliability and robustness of these findings.

Discussion

Our study established the causal effects of poultry intake, dried fruit intake, and cereal intake on T2D, identifying poultry intake as a risk factor and the other two as protective factors. Further research into potential mechanisms is required to validate these novel findings.

The protective association of dairy intake and the adverse impact of iron on gestational diabetes risk

Background: Gestational diabetes (GDM) is a pregnancy-related glucose intolerance with significant implications for maternal and fetal health. Calcium is essential for insulin secretion and metabolism, while iron intake may also impact GDM. This case-control study was conducted to investigate the relationship between calcium and iron intake with the risk of GDM. Methods: GDM was defined as Fasting Blood Sugar>92mg/dL or 75g Oral-Glucose-Tolerance-Test 120-minutes>153mg/dL. A 168-Item food-frequency-questionnaire was used to collect dietary calcium and iron intake from 24-40 weeks of gestation. The impact of total iron, red, processed/unprocessed meat consumption, calcium, and dairy intake on GDM were investigated. Results: A total of 229 GDM and 205 non-GDM women (18-45 years) participated. GDM group had higher pre-pregnancy weight, weight gain, and pre-pregnancy BMI. Across all models, GDM risk significantly increased in the third and fourth quartiles of iron intake. The fourth quartile had an Odds Ratio (OR) of 2.68 (CI 95%, 4.89-1.56; P<0.001) compared to the reference. Heme-iron consumption in the fourth quartiles increased GDM risk. In the second calcium intake model, ORs for the second, third, and fourth quartiles were 0.51 (CI 95%, 0.91-0.25), 0.43 (CI 95%, 0.77-0.24), and 0.35 (CI 95%, 0.63-0.19), respectively (P<0.001 all), reducing GDM risk by 50-65% compared to the first quartile. Dairy consumption in all quartiles of the first and second models was associated with lower GDM risk. Conclusions: Consumption of heme-iron through red and processed meat associated with an increased chance of developing GDM. Dairy intake reduces the chances of developing GDM in pregnant women.

Meat and meat products - a scoping review for Nordic Nutrition Recommendations 2023

Meat is not only a source of several nutrients but also a proposed risk factor for several non-communicable diseases. Here, we describe the totality of evidence for the role of meat intake for chronic disease outcomes, discuss potential mechanistic pathways, knowledge gaps, and limitations of the literature. Use of the scoping review is based on a de novo systematic review (SR) and meta-analysis on the association between poultry intake and cardiovascular disease (CVD) and type 2 diabetes (T2D), qualified SRs (as defined in the Nordic Nutrition Recommendations 2023 project) on meat intake and cancer by the World Cancer Research Fund (WCRF), the International Agency for Research on Cancer (IARC), and a systematic literature search of SRs and meta-analyses. The quality of the SRs was evaluated using a modified AMSTAR 2 tool, and the strength of evidence was evaluated based on a predefined criteria developed by the WCRF. The quality of the SRs was on average critically low. Our findings indicate that the evidence is too limited for conclusions for most of the chronic disease outcomes. However, findings from qualified SRs indicate strong evidence that processed meat increases the risk of colorectal cancer and probable evidence that red meat (unprocessed, processed, or both) increases the risk. The evidence suggests that both unprocessed red meat and processed meat (also including processed poultry meat) are probable risk factors for CVD mortality and stroke, and that total red meat and processed meat are risk factors for CHD. We found no sufficient evidence suggesting that unprocessed red meat, processed red meat, total red meat, or processed meat (including red and white meat) would be protective of any chronic disease. There was also no sufficient evidence to conclude on protective effect of poultry on any chronic diseases; effects on the risk of CVD, stroke, and T2D, to any direction, were regarded as unlikely.

The association between consumption of red and processed meats with metabolic syndrome and its components in obese and overweight women: a cross-sectional study

OBJECTIVES

Previous studies have shown a relation between the consumption of different types of meats and chronic disorders. This study aims to investigate the association between red and processed meat intake with metabolic syndrome (MetS) and its components in healthy obese and overweight women.

METHODS

This cross-sectional study was conducted on Iranian women. The dietary assessment and body composition were measured by a validated food frequency questionnaire (FFQ) and bioelectrical impedance analysis, respectively. Blood samples were collected by standard protocols.

RESULTS

A total of 231 women (mean age 36.47 ± 8.44 years) were included in the current study. After controlling for potential confounders, there was a marginally significant associations between higher intake of processed meat with the MetS (OR:1.01, 95% CI: 0.94,2.94, P:0.06) and high serum triglycerides (TG) (OR:1.27, 95% CI: 0.94,2.98, P:0.07). There was a significant associations between high intake of red meats with lower odds of higher waist circumference (WC) (OR:0.31, 95% CI: 0.10,0.97, P:0.04). Also, there was a significant associations were found between high intake of processed meats with greater odds of having lower high-density lipoprotein cholesterol (HDL-c) (OR:0.64, 95% CI: 0.30,0.95, P:0.03).

CONCLUSIONS

The current study suggests that higher intakes of processed meat may be associated with the MetS in Iranian women with excess body weight, while this was not the case for red meat. More studies however are necessary in different communities to draw definitive conclusions.

White meat consumption and risk of cardiovascular disease and type 2 diabetes: a systematic review and meta-analysis

Objectives

The aim was to systematically review the associations among white meat consumption, cardiovascular diseases (CVD), and type 2 diabetes (T2D).

Methods

Databases MEDLINE, Embase, and Cochrane Central Register of Controlled Trials and Scopus were searched (15th October 2021) for randomized intervention trials (RCTs, ≥ 4 weeks of duration) and prospective cohort studies (≥12 month of follow-up) assessing the consumption of white meat as the intervention/exposure. Eligible outcomes for RCTs were cardiometabolic risk factors and for cohorts, fatal and non-fatal CVD and incident T2D. Risk of bias was estimated using the Cochrane's RoB2 and Risk of Bias for Nutrition Observational Studies. Meta-analysis was conducted in case of ≥3 relevant intervention studies or ≥5 cohort studies using random-effects models. The strength of evidence was evaluated using the World Cancer Research Fund's criteria.

Results

The literature search yielded 5,795 scientific articles, and after screening 43 full-text articles, 23 cohort studies and three intervention studies were included. All included intervention studies matched fat content of intervention and control diets, and none of them showed any significant effects on the selected outcomes of white meat when compared to red meat. Findings from the cohort studies generally did not support any associations between white meat intake and outcomes. Meta-analyses were conducted for CVD mortality (RR: 0.95, 95% CI: 0.87-1.02, P = 0.23, I2 = 25%) and T2D incidence (RR: 0.98, 95% CI: 0.87-1.11, P = 0.81, I2 = 82%).

Conclusion

The currently available evidence does not indicate a role, beneficial or detrimental, of white meat consumption for CVD and T2D. Future studies investigating potentially different health effects of processed versus unprocessed white meat and substitution of red meat with white meat are warranted.Registration: Prospero registration CRD42022295915.

Reinstating acute-phase insulin release among sedentary adults at high risk for type 2 diabetes with Yoga and Walking based lifestyle modification

BACKGROUND

We compared the impact of 2 lifestyle modifying physical activities, yoga (YBLM) or walking (WBLM) on impaired beta cell function (IBF) or insulin resistance (IR) in restoring acute phase insulin release (APIR) among prediabetes at high risk for type 2 diabetes (HRDM).

METHOD

Male and female adults (N = 42, 38.1 ± 4.8 years) with abdominal obesity (Male:103 ± 8.1 cm) Female: 92 ± 11.1 cm), randomized into YBLM (n = 20) and WBLM (n = 22), were monitored for the practice of the intervention, 45 min a day/5 days a week for 12 weeks. Blood sample was collected at 0th minute to estimate the level of Fasting Blood Glucose (FBG), Sr. Insulin and lipid profile and at 10th minute (APIR). IBF, IR and sensitivity (IS) reading were checked in HOMA-2 calculator.

RESULT

Wilcoxon sign rank t-test denoted an improved APIR among the subjects with IBF (p = 0.008) and not among the subjects with IR (p = 0.332). However, regression analysis yielded an improved APIR among subjects with IBF (F(1,10) = 7.816, p = 0.002) with the management of body weight and lipid profile and IR (F(1,13) = 17.003, p = 0.001) being found influenced with selected lipid components. In all, during the post assessment period, an impressive boost in APIR was manifested among people shifted to Normoglycemia (n = 14, 35.9%).

CONCLUSION

Intriguingly, we postulate the potential role of YBLM over WBLM in the management of lipid profile and body weight on accelerating APIR either through improved Beta cell compensation or by sensitizing skeletal muscles regulating IR, helping improve glucose tolerance resulting in either remission or management of prediabetes.

Poultry Consumption and Human Cardiometabolic Health-Related Outcomes: A Narrative Review

Poultry meats, in particular chicken, have high rates of consumption globally. Poultry is the most consumed type of meat in the United States (US), with chicken being the most common type of poultry consumed. The amounts of chicken and total poultry consumed in the US have more than tripled over the last six decades. This narrative review describes nutritional profiles of commonly consumed chicken/poultry products, consumption trends, and dietary recommendations in the US. Overviews of the scientific literature pertaining to associations between, and effects of consuming chicken/poultry on, body weight and body composition, cardiovascular disease (CVD), and type II diabetes mellitus (T2DM) are provided. Limited evidence from randomized controlled trials indicates the consumption of lean unprocessed chicken as a primary dietary protein source has either beneficial or neutral effects on body weight and body composition and risk factors for CVD and T2DM. Apparently, zero randomized controlled feeding trials have specifically assessed the effects of consuming processed chicken/poultry on these health outcomes. Evidence from observational studies is less consistent, likely due to confounding factors such as a lack of a description of and distinctions among types of chicken/poultry products, amounts consumed, and cooking and preservation methods. New experimental and observational research on the impacts of consuming chicken/poultry, especially processed versions, on cardiometabolic health is sorely needed.

Red meat consumption, cardiovascular diseases, and diabetes: a systematic review and meta-analysis

AIMS

Observational studies show inconsistent associations of red meat consumption with cardiovascular disease (CVD) and diabetes. Moreover, red meat consumption varies by sex and setting, however, whether the associations vary by sex and setting remains unclear.

METHODS AND RESULTS

This systematic review and meta-analysis was conducted to summarize the evidence concerning the associations of unprocessed and processed red meat consumption with CVD and its subtypes [coronary heart disease (CHD), stroke, and heart failure], type two diabetes mellitus (T2DM), and gestational diabetes mellitus (GDM) and to assess differences by sex and setting (western vs. eastern, categorized based on dietary pattern and geographic region). Two researchers independently screened studies from PubMed, Web of Science, Embase, and the Cochrane Library for observational studies and randomized controlled trials (RCTs) published by 30 June 2022. Forty-three observational studies (N = 4 462 810, 61.7% women) for CVD and 27 observational studies (N = 1 760 774, 64.4% women) for diabetes were included. Red meat consumption was positively associated with CVD [hazard ratio (HR) 1.11, 95% confidence interval (CI) 1.05 to 1.16 for unprocessed red meat (per 100 g/day increment); 1.26, 95% CI 1.18 to 1.35 for processed red meat (per 50 g/day increment)], CVD subtypes, T2DM, and GDM. The associations with stroke and T2DM were higher in western settings, with no difference by sex.

CONCLUSION

Unprocessed and processed red meat consumption are both associated with higher risk of CVD, CVD subtypes, and diabetes, with a stronger association in western settings but no sex difference. Better understanding of the mechanisms is needed to facilitate improving cardiometabolic and planetary health.

Red meat consumption is associated with prediabetes and diabetes in rural Vietnam: a cross-sectional study

OBJECTIVE

To examine the association between red/processed meat consumption and glycaemic conditions (i.e. prediabetes (preDM) and diabetes mellitus (DM)) among middle-aged residents in rural Khánh Hòa, Vietnam.

DESIGN

In this cross-sectional study, a multinomial logistic regression model was used to examine the association between daily consumption of red/processed meat (0-99 g, 100-199 g or ≥ 200 g) and preDM/DM with adjustments for socio-demographic, lifestyle-related and health-related variables.

SETTING

Khánh Hòa Province, Vietnam.

PARTICIPANTS

The study used data collected through a baseline survey conducted during a prospective cohort study on CVD among 3000 residents, aged 40-60 years, living in rural communes in Khánh Hòa Province.

RESULTS

The multinomial regression model revealed that the relative-risk ratios for DM were 1·00 (reference), 1·11 (95 % CI = 0·75, 1·62) and 1·80 (95 % CI = 1·40, 2·32) from the lowest to the highest red/processed meat consumption categories (Ptrend = 0·006). The corresponding values for preDM were 1·00 (reference), 1·25 (95 % CI = 1·01, 1·54) and 1·67 (95 % CI = 1·20, 2·33) (Ptrend = 0·004). We did not find any evidence of statistical significance in relation to poultry consumption.

CONCLUSION

Increased red/processed meat consumption, but not poultry consumption, was positively associated with the prevalence of preDM/DM in rural communes in Khánh Hòa Province, Vietnam. Dietary recommendations involving a reduction in red/processed meat consumption should be considered in low- and middle-income countries.

Protein Intake from Various Foods Sources Is Negatively Associated with Cardiometabolic Risk Markers in Italian Older Adults

OBJECTIVES

To examine the relationships between protein intake from various food sources and cardiometabolic risk markers in Italian older adults.

DESIGN

Cross-sectional study.

SETTING

Unconventional settings across Italy (e.g., exhibitions, health promotion campaigns).

PARTICIPANTS

People 65+ years who provided a written informed consent.

MEASUREMENTS

Blood pressure (BP), blood glucose, total blood cholesterol, and anthropometric indices were assessed. Daily protein intake was estimated for 12 food items listed in a food frequency questionnaire.

RESULTS

Three-thousand four-hundred twenty-four older adults (mean age: 72.7 ± 5.7 years; 55% women) were included in the study. Results of linear regression analysis indicated that protein intake from several food sources was negatively associated with BP, waist and hip circumferences, and waist-to-hip ratio in both sexes. Blood glucose levels were inversely associated with many protein sources in women. Positive associations were observed between some protein sources and total blood cholesterol in both men and women.

CONCLUSION

Our findings suggest that dietary protein is differentially associated with cardiometabolic risk factors depending on sex and food sources.

Health effects associated with consumption of unprocessed red meat: a Burden of Proof study

Characterizing the potential health effects of exposure to risk factors such as red meat consumption is essential to inform health policy and practice. Previous meta-analyses evaluating the effects of red meat intake have generated mixed findings and do not formally assess evidence strength. Here, we conducted a systematic review and implemented a meta-regression-relaxing conventional log-linearity assumptions and incorporating between-study heterogeneity-to evaluate the relationships between unprocessed red meat consumption and six potential health outcomes. We found weak evidence of association between unprocessed red meat consumption and colorectal cancer, breast cancer, type 2 diabetes and ischemic heart disease. Moreover, we found no evidence of an association between unprocessed red meat and ischemic stroke or hemorrhagic stroke. We also found that while risk for the six outcomes in our analysis combined was minimized at 0 g unprocessed red meat intake per day, the 95% uncertainty interval that incorporated between-study heterogeneity was very wide: from 0-200 g d-1. While there is some evidence that eating unprocessed red meat is associated with increased risk of disease incidence and mortality, it is weak and insufficient to make stronger or more conclusive recommendations. More rigorous, well-powered research is needed to better understand and quantify the relationship between consumption of unprocessed red meat and chronic disease.

A study to correlate effect of dietary modification on biochemical and cardiovascular parameters among prediabetics

Objectives:

Dietary factors are important in the prevention and treatment of prediabetes and diabetes mellitus (DM). This study was designed to evaluate the prevalence, associated risk factors, dietary modification, and calories consumption calculated by the food frequency questionnaire and correlate them with the metabolic parameters, namely blood glucose, HbA1c, lipid profile, and cardiovascular parameters as heart rate variability and carotid intima media thickness (CIMT) among the prediabetics.

Methods:

An experimental interventional study was carried out in the Department of Physiology and Medicine at the RUHS College of Medical Sciences and Associated Group of Hospitals. The assessments were done at baseline and after 6 months of post-dietary modification. The total duration of the study was 6 months. A total of 250 prediabetic subjects were enrolled. Study Group A (n = 125) was engaged in dietary modification, whereas Group B (n = 125) was considered as control. The dietary assessment was done by a food frequency questionnaire.

Result:

After dietary modification, a decrease in the body mass index (1.3%), systolic blood pressure (3.1%), diastolic blood pressure (3.1%), blood glucose (2.8%), triglyceride (2.8%), high density lipoprotein (0.9%), HbA1c (2%), cholesterol (1.4%), and low-frequency/high-frequency ratios (1%), carotid intima media thickness (1.6%), as compared to control, was noticed after 6 months of dietary modification.

Conclusion:

This study suggested that prediabetics required health education including nutritional education as diet modification can play an important role to encourage diabetes-onset prevention and its related complications. The health-care providers and workers should increase the awareness about the importance of diet and encourage the prediabetics toward a healthy lifestyle, which may help in the quality of life and appropriate self-care, primary prevention of diabetes and its complications.

CTRI Registration:

CTRI/2017/06/008825.

Ultra-processed food and risk of type 2 diabetes: a systematic review and meta-analysis of longitudinal studies

BACKGROUND

The consumption of some food groups is associated with the risk of diabetes. However, there is no evidence from meta-analysis which evaluates the consumption of ultra-processed products in the risk of diabetes. This study aimed to review the literature assessing longitudinally the association between consumption of ultra-processed food and the risk of type 2 diabetes and to quantify this risk through a meta-analysis.

METHODS

We conducted a systematic review and meta-analysis with records from PubMed, Latin American and Caribbean Literature in Health Sciences (LILACS), Scielo, Scopus, Embase, and Web of Science. We included longitudinal studies assessing ultra-processed foods and the risk of type 2 diabetes. The review process was conducted independently by two reviewers. The Newcastle Ottawa scale assessed the quality of the studies. A meta-analysis was conducted to assess the effect of moderate and high consumption of ultra-processed food on the risk of diabetes.

RESULTS

In total 2272 records were screened, of which 18 studies, including almost 1.1 million individuals, were included in this review and 72% showed a positive association between ultra-processed foods and the risk of diabetes. According to the studies included in the meta-analysis, compared with non-consumption, moderate intake of ultra-processed food increased the risk of diabetes by 12% [relative risk (RR): 1.12; 95% confidence interval (CI): 1.06-1.17, I2 = 24%], whereas high intake increased risk by 31% (RR: 1.31; 95% CI: 1.21-1.42, I2 = 60%).

CONCLUSIONS

The consumption of ultra-processed foods increased the risk for type 2 diabetes as dose-response effect, with moderate to high credibility of evidence.

Quantity and variety of food groups consumption and the risk of diabetes in adults: A prospective cohort study

BACKGROUND

Evidence remains inconsistent regarding the association between quantity of food groups and diabetes, and remains scarce regarding the relation of dietary diversity with diabetes.

OBJECTIVE

We aimed to evaluate the prospective relation of variety and quantity of 12 major food groups with new-onset diabetes.

METHODS

A total of 16,117 participants who were free of diabetes at baseline from China Health and Nutrition Survey were included. Dietary intake and variety score were measured by three consecutive 24-h dietary recalls combined with a household food inventory in each survey round. The study outcome was new-onset diabetes, defined as self-reported physician-diagnosed diabetes during the follow-up period. Cox proportional hazards models and restricted cubic spline analysis were used to estimate hazard ratios (HR) and dose-response relation, respectively.

RESULTS

During a median follow-up duration of 9.0 years, a total of 1088 (6.7%) participants developed new-onset diabetes. Overall, there was a significant inverse association between dietary variety score and the risk of new-onset diabetes (per one point increment; HR, 0.85; 95% CI, 0.80-0.90). In addition, there were U-shaped associations of refined grains, whole grains, nuts, red meat, poultry, processed meat, dairy products, and aquatic products intake with diabetes, and L-shaped associations of legumes, vegetables, fruits, and eggs intake with diabetes (all P values for nonlinearity <0.001).

CONCLUSION

Our results suggested that greater variety of food groups consumption was associated with significantly lower risk of new-onset diabetes. Furthermore, when the quantity of food groups intakes was relatively low, there was a negative correlation between the quantity of each different food group consumption and diabetes risk; however, when intake exceeded certain thresholds, the risks of new-onset diabetes increased or reached a plateau.

Processed and Unprocessed Red Meat Consumption and Risk for Type 2 Diabetes Mellitus: An Updated Meta-Analysis of Cohort Studies

Type II diabetes mellitus (T2DM) is a metabolic disorder that occurs in the body because of decreased insulin activity and/or insulin secretion. The incidence of T2DM has rapidly increased over recent decades. The relation between consumption of different types of red meats and risk of T2DM remains uncertain. This meta-analysis was conducted to quantitatively assess the associations of processed red meat (PRM) and unprocessed red meat (URM) consumption with T2DM. We searched PubMed, Embase, Web of Science and The Cochrane Library for English-language cohort studies published before January 2021. Summary relative risks (RR) with 95% confidence interval (CI) were estimated using fixed effects and random effects. Additionally, dose-response relationships were explored using meta-regression. Fifteen studies (n = 682,963 participants, cases = 50,675) were identified. Compared with the lowest intake group, high consumption of PRM and URM increased T2DM risk by 27% (95% CI 1.15-1.40) and 15% (95% CI 1.08-1.23), respectively. These relationships were consistently strongest for U.S-based studies, though the effects of sex are inconclusive. In conclusion, PRM and URM are both positively associated with T2DM incidence, and these relationships are strongest in the U.S. reduction of red meat consumption should be explored as a target for T2DM prevention initiatives.

Meat and fish intake and type 2 diabetes: Dose-response meta-analysis of prospective cohort studies

AIMS

This meta-analysis aimed to quantitatively examine the possible associations between total meat, red meat, processed meat, poultry and fish intakes and type 2 diabetes (T2D).

METHODS

Relevant articles were identified in PubMed, Embase and Web of Science databases using a search time up to January 2019. Generalized least-squares trend estimations and restricted cubic spline regression models were used for analysis.

RESULTS

Twenty-eight articles were included in the analysis. When comparing the highest with the lowest category of meat intake, the summary relative risk of T2D was 1.33 (95% CI: 1.16-1.52) for total meat, 1.22 (95% CI: 1.16-1.28) for red meat, 1.25 (95% CI: 1.13-1.37) for processed meat, 1.00 (95% CI: 0.93-1.07) for poultry and 1.01 (95% CI: 0.93-1.10) for fish. In the dose-response analysis, each additional 100g/day of total and red meat, and 50g/day of processed meat, were found to be associated with a 36% (95% CI: 1.23-1.49), 31% (95% CI: 1.19-1.45) and 46% (95% CI: 1.26-1.69) increased risk of T2D, respectively. In addition, there was evidence of a non-linear dose-response association between processed meat and T2D (P=0.004), with the risk increasing by 30% with increasing intakes up to 30g/day.

CONCLUSION

Our meta-analysis has shown a linear dose-response relationship between total meat, red meat and processed meat intakes and T2D risk. In addition, a non-linear relationship of intake of processed meat with risk of T2D was detected.

Red meat, poultry and fish consumption and risk of diabetes: a 9 year prospective cohort study of the China Kadoorie Biobank

AIMS/HYPOTHESIS

Previous evidence linking red meat consumption with diabetes risk mainly came from western countries, with little evidence from China, where patterns of meat consumption are different. Moreover, global evidence remains inconclusive about the associations of poultry and fish consumption with diabetes. Therefore we investigated the associations of red meat, poultry and fish intake with incidence of diabetes in a Chinese population.

METHODS

The prospective China Kadoorie Biobank recruited ~512,000 adults (59% women, mean age 51 years) from ten rural and urban areas across China in 2004-2008. At the baseline survey, a validated interviewer-administered laptop-based questionnaire was used to collect information on the consumption frequency of major food groups including red meat, poultry, fish, fresh fruit and several others. During ~9 years of follow-up, 14,931 incidences of new-onset diabetes were recorded among 461,036 participants who had no prior diabetes, cardiovascular diseases or cancer at baseline. Cox regression analyses were performed to calculate adjusted HRs for incident diabetes associated with red meat, poultry and fish intake.

RESULTS

At baseline, 47.0%, 1.3% and 8.9% of participants reported a regular consumption (i.e. ≥4 days/week) of red meat, poultry and fish, respectively. After adjusting for adiposity and other potential confounders, each 50 g/day increase in red meat and fish intake was associated with 11% (HR 1.11 [95% CI 1.04, 1.20]) and 6% (HR 1.06 [95% CI 1.00, 1.13]) higher risk of incident diabetes, respectively. For both, the associations were more pronounced among men and women from urban areas, with an HR (95% CI) of 1.42 (1.15, 1.74) and 1.18 (1.03, 1.36), respectively, per 50 g/day red meat intake and 1.15 (1.02, 1.30) and 1.11 (1.01, 1.23), respectively, per 50 g/day fish intake. There was no significant association between diabetes and poultry intake, either overall (HR 0.96 [95% CI 0.83, 1.12] per 50 g/day intake) or in specific population subgroups.

CONCLUSIONS/INTERPRETATION

In Chinese adults, both red meat and fish, but not poultry, intake were positively associated with diabetes risk, particularly among urban participants. Our findings add new evidence linking red meat and fish intake with cardiometabolic diseases.

DATA AVAILABILITY

Details of how to access the China Kadoorie Biobank data and rules of China Kadoorie Biobank data release are available from www.ckbiobank.org/site/Data+Access.

Dietary Protein Consumption and the Risk of Type 2 Diabetes: ADose-Response Meta-Analysis of Prospective Studies

The relationship between dietary protein consumption and the risk of type 2 diabetes (T2D) has been inconsistent. The aim of this meta-analysis was to explore the relations between dietary protein consumption and the risk of T2D. We conducted systematic retrieval of prospective studies in PubMed, Embase, and Web of Science. Summary relative risks were compiled with a fixed effects model or a random effects model, and a restricted cubic spline regression model and generalized least squares analysis were used to evaluate the diet–T2D incidence relationship. T2D risk increased with increasing consumption of total protein and animal protein, red meat, processed meat, milk, and eggs, respectively, while plant protein and yogurt had an inverse relationship. A non-linear association with the risk for T2D was found for the consumption of plant protein, processed meat, milk, yogurt, and soy. This meta-analysis suggests that substitution of plant protein and yogurt for animal protein, especially red meat and processed meat, can reduce the risk for T2D.

Vegetarian Epidemiology: Review and Discussion of Findings from Geographically Diverse Cohorts

Epidemiologic cohort studies enrolling a large percentage of vegetarians have been highly informative regarding the nutritional adequacy and possible health effects of vegetarian diets. The 2 largest such cohorts are the European Prospective Investigation into Cancer and Nutrition-Oxford (EPIC-Oxford) and the Adventist Health Study-2 (AHS-2). These cohorts are described and their findings discussed, including a discussion of where findings appear to diverge. Although such studies from North America and the United Kingdom have been important, the large majority of the world's vegetarians live in other regions, particularly in Asia. Findings from recent cohort studies of vegetarians in East and South Asia are reviewed, particularly the Tzu Chi Health Study and Indian Migration Study. Important considerations for the study of the health of vegetarians in Asia are discussed. Vegetarian diets vary substantially, as may associated health outcomes. Cohort studies remain an important tool to better characterize the health of vegetarian populations around the globe.

Effect of diet composition on insulin sensitivity in humans

Diet composition has a marked impact on the risk of developing type 2 diabetes and cardiovascular disease. Prospective studies show that dietary patterns with elevated amount of animal products and low quantity of vegetable food items raise the risk of these diseases. In healthy subjects, animal protein intake intensifies insulin resistance whereas plant-based foods enhance insulin sensitivity. Similar effects have been documented in patients with diabetes. Accordingly, pre-pregnancy intake of meat (processed and unprocessed) has been strongly associated with a higher risk of gestational diabetes whereas greater pre-pregnancy vegetable protein consumption is associated with a lower risk of gestational diabetes. Population groups that modify their traditional dietary habit increasing the amount of animal products while reducing plant-based foods experience a remarkable rise in the frequency of type 2 diabetes. The association of animal protein intake with insulin resistance is independent of body mass index. In obese individuals that consume high animal protein diets, insulin sensitivity does not improve following weight loss. Diets aimed to lose weight that encourage restriction of carbohydrates and elevated consumption of animal protein intensify insulin resistance increasing the risk of developing type 2 diabetes and cardiovascular disease. The effect of dietary components on insulin sensitivity may contribute to explain the striking impact of eating habits on the risk of type 2 diabetes and cardiovascular disease. Insulin resistance predisposes to type 2 diabetes in healthy subjects and deteriorates metabolic control in patients with diabetes. In nondiabetic and diabetic individuals, insulin resistance is a major cardiovascular risk factor.

Modifying effect of metabotype on diet-diabetes associations

Purpose

Inter-individual metabolic differences may be a reason for previously inconsistent results in diet–diabetes associations. We aimed to investigate associations between dietary intake and diabetes for metabolically homogeneous subgroups (‘metabotypes’) in a large cross-sectional study.

Methods

We used data of 1517 adults aged 38–87 years from the German population-based KORA FF4 study (2013/2014). Dietary intake was estimated based on the combination of a food frequency questionnaire and multiple 24-h food lists. Glucose tolerance status was classified based on an oral glucose tolerance test in participants without a previous diabetes diagnosis using American Diabetes Association criteria. Logistic regression was applied to examine the associations between dietary intake and diabetes for two distinct metabotypes, which were identified based on 16 biochemical and anthropometric parameters.

Results

A low intake of fruits and a high intake of total meat, processed meat and sugar-sweetened beverages (SSB) were significantly associated with diabetes in the total study population. Stratified by metabotype, associations with diabetes remained significant for intake of total meat (OR 1.67, 95% CI 1.04–2.67) and processed meat (OR 2.23, 95% CI 1.24–4.04) in the metabotypes with rather favorable metabolic characteristics, and for intake of fruits (OR 0.83, 95% CI 0.68–0.99) and SSB (OR:1.21, 95% CI 1.09–1.35) in the more unfavorable metabotype. However, only the association between SSB intake and diabetes differed significantly by metabotype (p value for interaction = 0.01).

Conclusions

Our findings suggest an influence of metabolic characteristics on diet–diabetes associations, which may help to explain inconsistent previous results. The causality of the observed associations needs to be confirmed in prospective and intervention studies.

Electronic supplementary material

The online version of this article (10.1007/s00394-019-01988-5) contains supplementary material, which is available to authorized users.

Impact of Diet on the Incidence of Cataract Surgery among Diabetic Patients: Findings from the 45 and Up Study

OBJECTIVE

To examine the impact of diet on the incidence of cataract surgery among the working-aged diabetic population in Australia.

METHODS

This cohort study was conducted among 8,752 participants with diabetes aged 45-65 years who were recruited to the 45 and Up Study from 2006 to 2016. The data was linked to the Medicare Benefits Schedule to obtain data on cataract surgery. Diabetes was defined as self-reported on questionnaire or diabetes medication history based on Pharmaceutical Benefits Scheme. Diet was assessed at baseline, using a self-administered questionnaire and healthy diet scores were calculated based on Australian Dietary Guidelines. Cox regression was used to evaluate the association between diet and the incidence of cataract surgery during the follow-up.

RESULTS

During a mean follow-up of 8.4 years (73,431 person-years), 914 diabetic participants underwent cataract surgery with a corresponding rate of 12.4 cases per 1,000 person-years. After adjusting for age and gender, the hazard ratios (HR) of cataract surgery for the highest compared to the lowest intake quintile of red meat and poultry were 1.24 (95% CI, 1.00-1.55) and 1.24 (95% CI, 1.02-1.51), respectively. Further adjustment for demographic, lifestyle and dietary factors resulted in no significant difference between cataract surgery risk and healthy diet scores or specific diet groups. In gender-stratified analyses, increasing consumption of red meat (HR for highest versus lowest quintile, 1.39; 95% CI, 1.00-1.93; P for trend = 0.01) and poultry (HR for highest versus lowest quintile, 1.40; 95% CI, 1.05-1.87; P for trend = 0.01) were associated with a higher risk of cataract surgery in women after adjustment of age, gender, income, education level, body mass index, hypertension, cardiovascular disease, family history of diabetes, diabetes duration, insulin use, lifestyle, and other dietary factors.

CONCLUSION

Higher consumption of red meat and poultry is related to an elevated risk of cataract surgery in the working-aged female population with diabetes.

Substitution of red meat with poultry or fish and risk of type 2 diabetes: a Danish cohort study

PURPOSE

We examined associations between substitution of red meat (total, processed and unprocessed, low fat and high fat) with poultry or fish and substitution of processed red meat with unprocessed red meat and the risk of type 2 diabetes.

METHODS

A cohort of 53,163 participants from the Danish Diet, Cancer and Health study were followed for incident type 2 diabetes (6879 cases; median follow-up time 15.4 years). Diet was assessed by a validated 192-item food frequency questionnaire at baseline. Adjusted Cox proportional hazard models were used to calculate hazard ratios (HR) and 95% confidence intervals (CI) for type 2 diabetes associated with specified food substitutions of 150 g/week.

RESULTS

Replacing total red meat with fish was associated with a lower risk of type 2 diabetes [HR 0.96 (95% CI 0.94, 0.99)] as was replacement of processed red meat with poultry or fish [HR poultry 0.96 (95% CI 0.93, 0.99)]; HR fish 0.94 [(95% CI 0.91, 0.97)]. Replacing low fat red meat or high fat red meat with fish was associated with a lower risk of type 2 diabetes whereas similar substitutions, with poultry, were not. Replacing processed red meat with unprocessed red meat was also associated with a lower risk of type 2 diabetes [HR 0.96 (95% CI 0.93, 0.99)].

CONCLUSIONS

Replacing processed red meat with poultry, replacing total or processed red meat with fish, and replacing processed red meat with unprocessed red meat were all associated with a lower risk of type 2 diabetes.

Effects of processed red meat consumption on the risk of type 2 diabetes and cardiovascular diseases among Korean adults: the Korean Genome and Epidemiology Study

PURPOSE

Few studies have evaluated the effects of processed red meat (PRM) consumption on chronic disease risk, especially among low average PRM consumption populations. This study examined association between PRM intake and type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD) incidences in Korea.

METHODS

Participants (n = 10,030; aged 40-69 years) were recruited from the Ansan-Ansung cohort study, a subset of Korean Genome Epidemiology Study. Validated 103-item semi-quantitative food frequency questionnaire was used to assess dietary information, at baseline (2001-2002) and at second follow-up (2005-2006). T2DM and CVD incidences were identified using biennial questionnaire-based interview during a 10-year follow-up period. Cox proportional hazards regression analysis was used to calculate multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Over the 10-year follow-up period, 668 and 493 incident cases of T2DM (62,130 person-years) and CVD (63,150 person-years), respectively, were documented. In crude models, comparing the highest and lowest levels of PRM intake, no significant association occurred with incident T2DM [HR, 95% CI (0.94, 0.76-1.17)], while significant association occurred with incident CVD (0.67, 0.51-0.88). However, in adjusted models, this association was no longer significant, showing HRs (95% CI) of PRM intake for T2DM and CVD of 1.07 (0.85-1.35) and 1.14 (0.85-1.55), respectively.

CONCLUSIONS

PRM intake did not affect T2DM and CVD incidences among Korean middle-aged adults, although extremely low average consumption of PRM may explain the finding. Therefore, limiting PRM intake may not be a top priority for the prevention of chronic diseases in Korean population.

Vegetarian diet, change in dietary patterns, and diabetes risk: a prospective study

Background/objectives

Vegetarian diets are inversely associated with diabetes in Westerners but their impact on Asians—whose pathophysiology differ from Westerners—is unknown. We aim to investigate the association between a vegetarian diet, change in dietary patterns and diabetes risk in a Taiwanese Buddhist population.

Methods

We prospectively followed 2918 non-smoking, non-alcohol drinking Buddhists free of diabetes, cancer, and cardiovascular diseases at baseline, for a median of 5 years, with 183 incident diabetes cases confirmed. Diet was assessed through a validated food frequency questionnaire at baseline and a simple questionnaire during follow-ups. Incident cases of diabetes were ascertained through follow-up questionnaires, fasting glucose and HbA1C. Stratified Cox Proportional Hazards Regression was used to assess the effect of diets on risk of diabetes.

Results

Consistent vegetarian diet was associated with 35% lower hazards (HR: 0.65, 95% CI: 0.46, 0.92), while converting from a nonvegetarian to a vegetarian pattern was associated with 53% lower hazards (HR: 0.47, 95% CI: 0.30, 0.71) for diabetes, comparing with nonvegetarians while adjusting for age, gender, education, physical activity, family history of diabetes, follow-up methods, use of lipid-lowering medications, and baseline BMI.

Conclusion

Vegetarian diet and converting to vegetarian diet may protect against diabetes independent of BMI among Taiwanese.

Meat, Dietary Heme Iron, and Risk of Type 2 Diabetes Mellitus: The Singapore Chinese Health Study

We evaluated the relationships of red meat, poultry, fish, and shellfish intakes, as well as heme iron intake, with the risk of type 2 diabetes mellitus (T2D).The Singapore Chinese Health Study is a population-based cohort study that recruited 63,257 Chinese adults aged 45-74 years from 1993 to 1998. Usual diet was evaluated using a validated 165-item semiquantitative food frequency questionnaire at recruitment. Physician-diagnosed T2D was self-reported during 2 follow-up interviews in 1999-2004 and 2006-2010. During a mean follow-up of 10.9 years, 5,207 incident cases of T2D were reported. When comparing persons in the highest intake quartiles with those in the lowest, the multivariate-adjusted hazard ratio for T2D was 1.23 (95% confidence interval (CI): 1.14, 1.33) for red meat intake (P for trend < 0.001), 1.15 (95% CI: 1.06, 1.24) for poultry intake (P for trend = 0.004), and 1.07 (95% CI: 0.99, 1.16) for fish/shellfish intake (P for trend = 0.12). After additional adjustment for heme iron, only red meat intake remained significantly associated with T2D risk (multivariate-adjusted hazard ratio = 1.13, 95% CI: 1.01, 1.25; P for trend = 0.02). Heme iron was associated with a higher risk of T2D even after additional adjustment for red meat intake (multivariate-adjusted hazard ratio = 1.14, 95% CI: 1.02, 1.28; P for trend = 0.03). In conclusion, red meat and poultry intakes were associated with a higher risk of T2D. These associations were mediated completely for poultry and partially for red meat by heme iron intake.

Dietary Protein Consumption and the Risk of Type 2 Diabetes: A Systematic Review and Meta-Analysis of Cohort Studies

Recently, some studies have focused on the relationship between dietary protein intake and the risk of type 2 diabetes mellitus (T2DM), but the conclusions have been inconsistent. Therefore, in this paper, a systematic review and meta-analysis of cohort studies regarding protein consumption and T2DM risk are conducted in order to present the association between them. We searched the PubMed and Embase databases for cohort studies on dietary protein, high-protein food consumption and risk of T2DM, up to July 2017. A summary of relative risks was compiled by the fixed-effect model or random-effect model. Eleven cohort studies regarded protein intake and T2DM (52,637 cases among 483,174 participants). The summary RR and 95% CI (Confidence Interval) of T2DM was 1.12 (1.08–1.17) in all subjects, 1.13 (1.04–1.24) in men, and 1.09 (1.04–1.15) in women for total protein; 1.14 (1.09–1.19) in all subjects, 1.23 (1.09–1.38) in men, and 1.11 (1.03–1.19) in women for animal protein; 0.96 (0.88–1.06) in all subjects, 0.98 (0.72–1.34) in men, and 0.92 (0.86–0.98) in women for plant protein. We also compared the association between different food sources of protein and the risk of T2DM. The summary RR (Relative Risk) and 95% CI of T2DM was 1.22 (1.09–1.36) for red meat, 1.39 (1.29–1.49) for processed meat, 1.03 (0.89–1.17) for fish, 1.03 (0.64–1.67) for egg, 0.89 (0.84–0.94) for total dairy products, 0.87 (0.78–0.96) for whole milk, 0.83 (0.70–0.98) for yogurt, 0.74 (0.59–0.93) in women for soy. This meta-analysis shows that total protein and animal protein could increase the risk of T2DM in both males and females, and plant protein decreases the risk of T2DM in females. The association between high-protein food types and T2DM are also different. Red meat and processed meat are risk factors of T2DM, and soy, dairy and dairy products are the protective factors of T2DM. Egg and fish intake are not associated with a decreased risk of T2DM. This research indicates the type of dietary protein and food sources of protein that should be considered for the prevention of diabetes.

Food groups and risk of type 2 diabetes mellitus: a systematic review and meta-analysis of prospective studies

The aim of this systematic review and meta-analysis was to synthesize the knowledge about the relation between intake of 12 major food groups and risk of type 2 diabetes (T2D). We conducted a systematic search in PubMed, Embase, Medline (Ovid), Cochrane Central, and Google Scholar for prospective studies investigating the association between whole grains, refined grains, vegetables, fruits, nuts, legumes, eggs, dairy, fish, red meat, processed meat, and sugar-sweetened beverages (SSB) on risk of T2D. Summary relative risks were estimated using a random effects model by contrasting categories, and for linear and non-linear dose–response relationships. Six out of the 12 food-groups showed a significant relation with risk of T2D, three of them a decrease of risk with increasing consumption (whole grains, fruits, and dairy), and three an increase of risk with increasing consumption (red meat, processed meat, and SSB) in the linear dose–response meta-analysis. There was evidence of a non-linear relationship between fruits, vegetables, processed meat, whole grains, and SSB and T2D risk. Optimal consumption of risk-decreasing foods resulted in a 42% reduction, and consumption of risk-increasing foods was associated with a threefold T2D risk, compared to non-consumption. The meta-evidence was graded “low” for legumes and nuts; “moderate” for refined grains, vegetables, fruit, eggs, dairy, and fish; and “high” for processed meat, red meat, whole grains, and SSB. Among the investigated food groups, selecting specific optimal intakes can lead to a considerable change in risk of T2D.

Using both principal component analysis and reduced rank regression to study dietary patterns and diabetes in Chinese adults

OBJECTIVE

We examined the association between dietary patterns and diabetes using the strengths of two methods: principal component analysis (PCA) to identify the eating patterns of the population and reduced rank regression (RRR) to derive a pattern that explains the variation in glycated Hb (HbA1c), homeostasis model assessment of insulin resistance (HOMA-IR) and fasting glucose.

DESIGN

We measured diet over a 3 d period with 24 h recalls and a household food inventory in 2006 and used it to derive PCA and RRR dietary patterns. The outcomes were measured in 2009.

SETTING

Adults (n 4316) from the China Health and Nutrition Survey.

RESULTS

The adjusted odds ratio for diabetes prevalence (HbA1c≥6·5 %), comparing the highest dietary pattern score quartile with the lowest, was 1·26 (95 % CI 0·76, 2·08) for a modern high-wheat pattern (PCA; wheat products, fruits, eggs, milk, instant noodles and frozen dumplings), 0·76 (95 % CI 0·49, 1·17) for a traditional southern pattern (PCA; rice, meat, poultry and fish) and 2·37 (95 % CI 1·56, 3·60) for the pattern derived with RRR. By comparing the dietary pattern structures of RRR and PCA, we found that the RRR pattern was also behaviourally meaningful. It combined the deleterious effects of the modern high-wheat pattern (high intakes of wheat buns and breads, deep-fried wheat and soya milk) with the deleterious effects of consuming the opposite of the traditional southern pattern (low intakes of rice, poultry and game, fish and seafood).

CONCLUSIONS

Our findings suggest that using both PCA and RRR provided useful insights when studying the association of dietary patterns with diabetes.

Meat Consumption and Risk of Developing Type 2 Diabetes in the SUN Project: A Highly Educated Middle-Class Population

BACKGROUND

Meat consumption has been consistently associated with the risk of diabetes in different populations. The aim of our study was to investigate the incidence of type 2 diabetes according to baseline total meat consumption in a longitudinal assessment of a middle-aged Mediterranean population.

METHODS

We followed 18,527 participants (mean age: 38 years, 61% women) in the SUN Project, an open-enrolment cohort of a highly educated population of middle-class Spanish graduate students. All participants were initially free of diabetes. Diet was assessed at baseline using a semi-quantitative food frequency questionnaire of 136-items previously validated. Incident diabetes was defined according to the American Diabetes Association's criteria.

RESULTS

We identified 146 incident cases of diabetes after a maximum of 14 years of follow-up period (mean: 8.7 years). In the fully adjusted model, the consumption of ≥3 servings/day of all types of meat was significantly associated with a higher risk of diabetes (HR: 1.85; 95% CI: 1.03-3.31; p for trend = 0.031) in comparison with the reference category (<2 servings/day). When we separated processed from non-processed meat, we observed a non-significant higher risk associated with greater consumption of processed meat and a non-significant lower risk associated with non-processed meat consumption (p for trend = 0.123 and 0.487, respectively). No significant difference was found between the two types of meat (p = 0.594).

CONCLUSIONS

Our results suggest that meat consumption, especially processed meat, was associated with a higher risk of developing diabetes in our young Mediterranean cohort.

Diabetes mellitus associated with processed and unprocessed red meat: an overview

According to American Diabetes Association "as many as 1 in 3 American adults will have diabetes by 2050" imposing a serious burden on healthcare services and highlighting a substantial need to reduce "new-cases" incidence. Diabetes is inextricably linked to diet, in the prevention-spectrum. Red-meat-intake has been positively associated with reduced glycemic control. However, divergence exists among meat subtypes (i.e. fresh and processed) and the magnitude of their impact on diabetes development. The present overview attempted to summarize the latest data regarding red-meat subtypes on the examined association. Four meta-analysis and 10 prospective studies, focusing on the role of fresh and processed red meat in diabetes prevention, were selected. All of studies highlighted the aggravating role of processed meat-products in diabetes incidence, while fresh meat reached significance in only half of them. Therefore, the contribution of fresh red meat on diabetes remains inconclusive. Valid conclusions seem more robust concerning processed-meat-consumption.

Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity: A Comprehensive Review

Suboptimal nutrition is a leading cause of poor health. Nutrition and policy science have advanced rapidly, creating confusion yet also providing powerful opportunities to reduce the adverse health and economic impacts of poor diets. This review considers the history, new evidence, controversies, and corresponding lessons for modern dietary and policy priorities for cardiovascular diseases, obesity, and diabetes mellitus. Major identified themes include the importance of evaluating the full diversity of diet-related risk pathways, not only blood lipids or obesity; focusing on foods and overall diet patterns, rather than single isolated nutrients; recognizing the complex influences of different foods on long-term weight regulation, rather than simply counting calories; and characterizing and implementing evidence-based strategies, including policy approaches, for lifestyle change. Evidence-informed dietary priorities include increased fruits, nonstarchy vegetables, nuts, legumes, fish, vegetable oils, yogurt, and minimally processed whole grains; and fewer red meats, processed (eg, sodium-preserved) meats, and foods rich in refined grains, starch, added sugars, salt, and trans fat. More investigation is needed on the cardiometabolic effects of phenolics, dairy fat, probiotics, fermentation, coffee, tea, cocoa, eggs, specific vegetable and tropical oils, vitamin D, individual fatty acids, and diet-microbiome interactions. Little evidence to date supports the cardiometabolic relevance of other popular priorities: eg, local, organic, grass-fed, farmed/wild, or non-genetically modified. Evidence-based personalized nutrition appears to depend more on nongenetic characteristics (eg, physical activity, abdominal adiposity, gender, socioeconomic status, culture) than genetic factors. Food choices must be strongly supported by clinical behavior change efforts, health systems reforms, novel technologies, and robust policy strategies targeting economic incentives, schools and workplaces, neighborhood environments, and the food system. Scientific advances provide crucial new insights on optimal targets and best practices to reduce the burdens of diet-related cardiometabolic diseases.

Do Behavioral Risk Factors for Prediabetes and Insulin Resistance Differ across the Socioeconomic Gradient? Results from a Community-Based Epidemiologic Survey

To examine whether behavioral risk factors associated with diabetes (diet, BMI, waist circumference, physical activity, and sleep duration) are also related to both prediabetes and insulin resistance (IR), we used data from Boston Area Community Health (BACH) Survey (2010-2012, n = 3155). Logistic and linear regression models were used to test the association of lifestyle factors with prediabetes status, insulin resistance, and prediabetes or insulin resistance. All regression models were stratified by education and income levels (to examine whether risk factors had differential effects across socioeconomic factors) and adjusted for age, gender, race/ethnicity, family history of diabetes, and smoking status. We found that large waist circumference was consistently associated with higher levels of insulin resistance (IR) and increased odds of prediabetes. While the association between large waist circumference and IR was consistent across all levels of SES (P < 0.001), the association between large waist circumference and prediabetes was only statistically significant in the highest socioeconomic strata with odds ratios of 1.68 (95% CI 1.07-2.62) and 1.88 (95% CI 1.22-2.92) for postgraduate degree and income strata, respectively. There was no association between diet, physical activity, sleep duration, and the presence of multiple risk factors and prediabetes or IR within SES strata.

Secular trends in meat and seafood consumption patterns among Chinese adults, 1991-2011

BACKGROUND/OBJECTIVES

Several studies have suggested differential health effects in relation to different meat composition in Western population. The purpose of the study was to examine secular trends in meat and seafood consumption patterns among Chinese adults between 1991 and 2011.

SUBJECTS/METHODS

Our longitudinal data are from 21,144 adults aged 18-75 in the China Health and Nutrition Survey, prospective cohort study. We assessed the intakes of meat and subtypes with three 24-h dietary recalls. We conducted multilevel mixed-effect logistic and linear regression models to examine meat consumption dynamics.

RESULTS

The proportions of Chinese adults who consumed red meat, poultry and seafood increased from 65.7% in 1991 to 86.1% in 2011, from 7.5 to 20.9% and from 27.4 to 37.8%, respectively. With rapid decrease in meat intakes since 2009, the intakes of total meat, red meat, poultry and seafood among their consumers were 86.7 g/day, 86.4 g/day, 71.0 g/day and 70.3 g/day in 2011, respectively, which were just slightly higher compared with those in 1991. Fatty fresh pork has been predominantly component of total meat overtime, which consituted 54.0% of total meat intake, 80.0% of fresh red meat intake and 98.7% of fatty fresh red meat intake in 2011.

CONCLUSION

Over the past two decades, meat consumption patterns of Chinese adults have been characterized by having a predominant intake of fatty fresh pork, suboptimal intakes of seafood and increased proportion of adults having excessive intakes of red meat and poultry overtime.

Type of vegetarian diet, obesity and diabetes in adult Indian population

BACKGROUND

To investigate the prevalence of obesity and diabetes among adult men and women in India consuming different types of vegetarian diets compared with those consuming non-vegetarian diets.

METHODS

We used cross-sectional data of 156,317 adults aged 20-49 years who participated in India's third National Family Health Survey (2005-06). Association between types of vegetarian diet (vegan, lacto-vegetarian, lacto-ovo vegetarian, pesco-vegetarian, semi-vegetarian and non-vegetarian) and self-reported diabetes status and measured body mass index (BMI) were estimated using multivariable logistic regression adjusting for age, gender, education, household wealth, rural/urban residence, religion, caste, smoking, alcohol use, and television watching.

RESULTS

Mean BMI was lowest in pesco-vegetarians (20.3 kg/m2) and vegans (20.5 kg/m2) and highest in lacto-ovo vegetarian (21.0 kg/m2) and lacto-vegetarian (21.2 kg/m2) diets. Prevalence of diabetes varied from 0.9% (95% CI: 0.8-1.1) in person consuming lacto-vegetarian, lacto-ovo vegetarian (95% CI:0.6-1.3) and semi-vegetarian (95% CI:0.7-1.1) diets and was highest in those persons consuming a pesco-vegetarian diet (1.4%; 95% CI:1.0-2.0). Consumption of a lacto- (OR:0.67;95% CI:0.58-0.76;p < 0.01), lacto-ovo (OR:0.70; 95% CI:0.51-0.96;p = 0.03) and semi-vegetarian (OR:0.77; 95% CI:0.60-0.98; p = 0.03) diet was associated with a lower likelihood of diabetes than a non-vegetarian diet in the adjusted analyses.

CONCLUSIONS

In this large, nationally representative sample of Indian adults, lacto-, lacto-ovo and semi-vegetarian diets were associated with a lower likelihood of diabetes. These findings may assist in the development of interventions to address the growing burden of overweight/obesity and diabetes in Indian population. However, prospective studies with better measures of dietary intake and clinical measures of diabetes are needed to clarify this relationship.

High cholesterol intake is associated with elevated risk of type 2 diabetes mellitus - a meta-analysis

BACKGROUND & AIMS

Some foods rich in cholesterol are associated with high risk of type 2 diabetes (T2D). To confirm the association between dietary cholesterol intake and T2D risk, we performed a meta-analysis of observational studies.

METHODS

We searched for longitudinal studies that provided data on the relative risk (RR) for T2D in relation to the cholesterol intake level using MEDLINE (from 1950 for July 10, 2013) and EMBASE (from 1974 to July 10, 2013). The RR for the highest vs. lowest cholesterol intake category or for an increment of 100 mg/day in cholesterol consumption was pooled with an inverse-variance method.

RESULTS

Five studies met the inclusion criteria. Compared with the lowest category, the highest category had a significantly higher association with T2D risk (RR [95% confidence interval (CI)], 1.25 [1.16-1.36]). The pooled RR for a 100-mg/day increment was also significant (RR [95% CI], 1.11 [1.06-1.15]).

CONCLUSION

Current meta-analysis suggested that high intake of cholesterol was positively associated with future T2D risk.

Taiwanese vegetarians and omnivores: dietary composition, prevalence of diabetes and IFG

Introduction

Vegetarian diets have been shown to improve glucose metabolism and reduce risk for diabetes in Westerners but whether Chinese vegetarian diets have the same benefits is unknown.

Methods

We evaluated the association between diet and diabetes/impaired fasting glucose (IFG) among 4384 Taiwanese Buddhist volunteers and identified diabetes/IFG cases from a comprehensive review of medical history and fasting plasma glucose.

Results

Vegetarians had higher intakes of carbohydrates, fiber, calcium, magnesium, total and non-heme iron, folate, vitamin A, and lower intakes of saturated fat, cholesterol, and vitamin B12. Besides avoiding meat and fish, vegetarians had higher intakes of soy products, vegetables, whole grains, but similar intakes of dairy and fruits, compared with omnivores. The crude prevalence of diabetes in vegetarians versus omnivores is 0.6% versus 2.3% in pre-menopausal women, 2.8% versus 10% in menopausal women, and 4.3% versus 8.1% in men. Polytomous logistic regression adjusting for age, body mass index, family history of diabetes, education, leisure time physical activity, smoking and alcohol, showed that this vegetarian diet was negatively associated with diabetes and IFG in men (OR for diabetes: 0.49, 95% CI: 0.28–0.89; OR for IFG: 0.66, 95% CI: 0.46–0.95); in pre-menopausal women (OR for diabetes: 0.26, 95% CI: 0.06–1.21; OR for IFG: 0.60, 95% CI: 0.35–1.04); and in menopausal women (OR for diabetes: 0.25, 95% CI: 0.15–0.42; OR for IFG: 0.73, 95% CI: 0.56–0.95).

Conclusion

We found a strong protective association between Taiwanese vegetarian diet and diabetes/IFG, after controlling for various potential confounders and risk factors.

Associations between red meat intake and biomarkers of inflammation and glucose metabolism in women

BACKGROUND

Greater red meat intake is associated with an increased type 2 diabetes and cardiovascular disease risk. However, the relation of red meat intake to biomarkers of inflammation and glucose metabolism has not been investigated thoroughly.

OBJECTIVE

We hypothesized that greater red meat intake would be associated with biomarkers of inflammation and glucose metabolism, which would be partly explained by body mass index (BMI).

DESIGN

We analyzed cross-sectional data from diabetes-free female participants in the Nurses' Health Study (n = 3690). Multiple linear regression was conducted to assess the associations of total, unprocessed, and processed red meat intakes (quartile categories) with plasma C-reactive protein (CRP), ferritin, adiponectin, fasting insulin, and hemoglobin A1c (Hb A1c).

RESULTS

Greater total, unprocessed, and processed red meat intakes were associated with higher plasma CRP, ferritin, fasting insulin, and Hb A1c and lower adiponectin after adjustment for demographic information (P-trend ≤ 0.03 for all). Adiponectin was not associated with any type of red meat intake when further adjusted for medical and lifestyle factors. After adjustment for BMI, most of these associations with inflammatory and glucose metabolic biomarkers were substantially attenuated and no longer significant. BMI accounted for a statistically significant proportion of associations with CRP, Hb A1c, and fasting insulin (P-contribution ≤ 0.02 for all) but not with ferritin. Substituting a serving of total red meat intake with alternative protein food in a combination of poultry, fish, legumes, and nuts was associated with significantly lower CRP (β ± SE: -0.106 ± 0.043), ferritin (-0.212 ± 0.075), Hb A1c (-0.052 ± 0.015), and fasting insulin (-0.119 ± 0.036) (all P ≤ 0.02 for comparison of extreme quartiles for all).

CONCLUSIONS

Greater red meat intake is associated with unfavorable plasma concentrations of inflammatory and glucose metabolic biomarkers in diabetes-free women. BMI accounts for a significant proportion of the associations with these biomarkers, except for ferritin. Substituting red meat with another protein food is associated with a healthier biomarker profile of inflammatory and glucose metabolism.

Red meat, dietary heme iron, and risk of type 2 diabetes: the involvement of advanced lipoxidation endproducts

There is growing evidence of disordered iron homeostasis in the diabetic condition, with links proposed between dietary iron intakes and both the risk of disease and the risk of complications of advanced disease. In the United States, Britain, and Canada, the largest dietary contributors of iron are cereals and cereal products and meat and meat products. This review discusses the findings of cohort studies and meta-analyses of heme iron and red meat intakes and the risk of type 2 diabetes. These suggest that processed red meat is associated with increased risk, with high intakes of red meat possibly also associated with a small increased risk. Historically, humans have relied on large quantities of heme iron and red meat in their diets, and therefore it is paradoxical that iron from meat sources should be associated with the risk of type 2 diabetes. A reason for this association may be drawn from studies of dietary advanced glycation and lipoxidation endproducts present in processed food and the mechanisms by which insulin output by pancreatic islet cells might be influenced by the protein modifications present in processed red meat.

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.

Red meat consumption is associated with the risk of type 2 diabetes in men but not in women: a Japan Public Health Center-based Prospective Study

The relationship between different types of meat intake and the risk of type 2 diabetes remains unclear. We prospectively examined the association between total meat, total red meat, unprocessed red meat, processed meat and poultry intake and the incidence of type 2 diabetes. Subjects were 27 425 men and 36 424 women aged 45–75 years who participated in the second survey of the Japan Public Health Center-based Prospective Study, and had no history of type 2 diabetes, cancer, stroke, IHD, chronic liver disease or kidney disease. Meat intake was estimated using a validated 147-item FFQ. OR of self-reported, physician-diagnosed type 2 diabetes over 5 years were estimated using a multiple logistic regression. A total of 1178 newly diagnosed cases of type 2 diabetes were self-reported. Intakes of total meat and total red meat were associated with the increased risk of type 2 diabetes in men but not in women. The multivariate-adjusted OR for the highest quartile compared with the lowest quartile of total meat and total red meat intake were 1·36 (95% CI 1·07, 1·73; P for trend=0·006) and 1·48 (95% CI 1·15, 1·90; P for trend=0·003) for men, respectively, and 0·82 (95% CI 0·62, 1·09; P for trend=0·14) and 0·77 (95% CI 0·57, 1·02; P for trend=0·08) for women, respectively. Intakes of processed red meat and poultry were not associated with the increased risk of diabetes in either men or women. In conclusion, elevated intake of red meat is associated with the increased risk of type 2 diabetes in Japanese men but not in women.

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.

Association between dietary meat consumption and incident type 2 diabetes: the EPIC-InterAct study

AIMS/HYPOTHESIS

A diet rich in meat has been reported to contribute to the risk of type 2 diabetes. The present study aims to investigate the association between meat consumption and incident type 2 diabetes in the EPIC-InterAct study, a large prospective case-cohort study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) study.

METHODS

During 11.7 years of follow-up, 12,403 incident cases of type 2 diabetes were identified among 340,234 adults from eight European countries. A centre-stratified random subsample of 16,835 individuals was selected in order to perform a case-cohort design. Prentice-weighted Cox regression analyses were used to estimate HR and 95% CI for incident diabetes according to meat consumption.

RESULTS

Overall, multivariate analyses showed significant positive associations with incident type 2 diabetes for increasing consumption of total meat (50 g increments: HR 1.08; 95% CI 1.05, 1.12), red meat (HR 1.08; 95% CI 1.03, 1.13) and processed meat (HR 1.12; 95% CI 1.05, 1.19), and a borderline positive association with meat iron intake. Effect modifications by sex and class of BMI were observed. In men, the results of the overall analyses were confirmed. In women, the association with total and red meat persisted, although attenuated, while an association with poultry consumption also emerged (HR 1.20; 95% CI 1.07, 1.34). These associations were not evident among obese participants.

CONCLUSIONS/INTERPRETATION

This prospective study confirms a positive association between high consumption of total and red meat and incident type 2 diabetes in a large cohort of European adults.

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.

Leucine signaling in the pathogenesis of type 2 diabetes and obesity

Epidemiological evidence points to increased dairy and meat consumption, staples of the Western diet, as major risk factors for the development of type 2 diabetes (T2D). This paper presents a new concept and comprehensive review of leucine-mediated cell signaling explaining the pathogenesis of T2D and obesity by leucine-induced over-stimulation of mammalian target of rapamycin complex 1 (mTORC1). mTORC1, a pivotal nutrient-sensitive kinase, promotes growth and cell proliferation in response to glucose, energy, growth factors and amino acids. Dairy proteins and meat stimulate insulin/insulin-like growth factor 1 signaling and provide high amounts of leucine, a primary and independent stimulator for mTORC1 activation. The downstream target of mTORC1, the kinase S6K1, induces insulin resistance by phosphorylation of insulin receptor substrate-1, thereby increasing the metabolic burden of β-cells. Moreover, leucine-mediated mTORC1-S6K1-signaling plays an important role in adipogenesis, thus increasing the risk of obesity-mediated insulin resistance. High consumption of leucine-rich proteins explains exaggerated mTORC1-dependent insulin secretion, increased β-cell growth and β-cell proliferation promoting an early onset of replicative β-cell senescence with subsequent β-cell apoptosis. Disturbances of β-cell mass regulation with increased β-cell proliferation and apoptosis as well as insulin resistance are hallmarks of T2D, which are all associated with hyperactivation of mTORC1. In contrast, the anti-diabetic drug metformin antagonizes leucine-mediated mTORC1 signaling. Plant-derived polyphenols and flavonoids are identified as natural inhibitors of mTORC1 and exert anti-diabetic and anti-obesity effects. Furthermore, bariatric surgery in obesity reduces increased plasma levels of leucine and other branched-chain amino acids. Attenuation of leucine-mediated mTORC1 signaling by defining appropriate upper limits of the daily intake of leucine-rich animal and dairy proteins may offer a great chance for the prevention of T2D and obesity, as well as other epidemic diseases of civilization with increased mTORC1 signaling, especially cancer and neurodegenerative diseases, which are frequently associated with T2D.

Red meat consumption and risk of type 2 diabetes: 3 cohorts of US adults and an updated meta-analysis

BACKGROUND

The relation between consumption of different types of red meats and risk of type 2 diabetes (T2D) remains uncertain.

OBJECTIVE

We evaluated the association between unprocessed and processed red meat consumption and incident T2D in US adults.

DESIGN

We followed 37,083 men in the Health Professionals Follow-Up Study (1986-2006), 79,570 women in the Nurses' Health Study I (1980-2008), and 87,504 women in the Nurses' Health Study II (1991-2005). Diet was assessed by validated food-frequency questionnaires, and data were updated every 4 y. Incident T2D was confirmed by a validated supplementary questionnaire.

RESULTS

During 4,033,322 person-years of follow-up, we documented 13,759 incident T2D cases. After adjustment for age, BMI, and other lifestyle and dietary risk factors, both unprocessed and processed red meat intakes were positively associated with T2D risk in each cohort (all P-trend <0.001). The pooled HRs (95% CIs) for a one serving/d increase in unprocessed, processed, and total red meat consumption were 1.12 (1.08, 1.16), 1.32 (1.25, 1.40), and 1.14 (1.10, 1.18), respectively. The results were confirmed by a meta-analysis (442,101 participants and 28,228 diabetes cases): the RRs (95% CIs) were 1.19 (1.04, 1.37) and 1.51 (1.25, 1.83) for 100 g unprocessed red meat/d and for 50 g processed red meat/d, respectively. We estimated that substitutions of one serving of nuts, low-fat dairy, and whole grains per day for one serving of red meat per day were associated with a 16-35% lower risk of T2D.

CONCLUSION

Our results suggest that red meat consumption, particularly processed red meat, is associated with an increased risk of T2D.