The research published in The Lancet, Diabetes & Endocrinology, provides a comprehensive analysis of the relationship between meat consumption and type 2 diabetes risk. By analyzing data from 100,000 individuals across 31 cohorts, the study found that higher consumption of unprocessed red meat and processed meat is associated with an increased risk of type 2 diabetes. However, the association with poultry consumption was less clear. The study's findings highlight the importance of reducing meat consumption, particularly processed meat, for public health. Further research is needed to fully understand the mechanisms linking meat consumption to type 2 diabetes risk and to develop sustainable dietary patterns that can effectively reduce the global burden of this disease.

Key Points

1. Meat consumption is linked to type 2 diabetes risk: Higher intake of unprocessed red meat and processed meat is associated with increased risk of type 2 diabetes.

2. Poultry consumption is less clear: The association between poultry consumption and type 2 diabetes risk is less certain.

3. Regional variations exist: The association between meat consumption and type 2 diabetes risk varies across different regions.

4. Heterogeneity is observed: The relationship between meat consumption and type 2 diabetes risk is not consistent across all individuals.

5. Mechanisms linking meat consumption to type 2 diabetes are complex: Several factors, including fatty acid composition, protein content, gut microbiota, processing additives, and advanced glycation end products, may contribute to the association between meat consumption and type 2 diabetes.

6. Reducing meat consumption can benefit public health: Lowering the consumption of unprocessed red meat and processed meat can help reduce the incidence of type 2 diabetes.

This research provides an extensive evaluation of the associations between meat consumption and type 2 diabetes risk, using data from a large number of diverse global populations. The study, part of the InterConnect project, conducted an individual-participant federated meta-analysis including over 100,000 cases of incident type 2 diabetes from 31 cohorts across 20 countries.

Study Design and Methodology:

The research involved data from 31 cohorts participating in the InterConnect project, spanning multiple global regions:

• Americas (12 cohorts)

• Eastern Mediterranean (2 cohorts)

• Europe (9 cohorts)

• South-East Asia (1 cohort)

• Western Pacific (7 cohorts)

Eligibility criteria for participants included:

• Age 18 years or older

• Available data on dietary consumption and incident type 2 diabetes

• No diagnosis of any type of diabetes at baseline

• No missing data

The study analyzed data from 1,966,444 adults, identifying 107,271 incident cases of type 2 diabetes over a median follow-up period of 10 years (IQR 7–15 years).

Analytical Approach:

• Cohort-specific hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for each meat type.

• Adjustments were made for potential confounders, including BMI.

• A random-effects meta-analysis was used to pool the results.

• Meta-regression was employed to investigate potential sources of heterogeneity.

Key Findings:

1. Meat Consumption Levels:

• Unprocessed red meat: 0–110 g/day (median across cohorts)

• Processed meat: 0–49 g/day

• Poultry: 0–72 g/day

2. Associations with Type 2 Diabetes Risk:

• Unprocessed red meat: HR 1.10 (95% CI 1.06–1.15) per 100 g/day increase (I² = 61%)

• Processed meat: HR 1.15 (95% CI 1.11–1.20) per 50 g/day increase (I² = 59%)

• Poultry: HR 1.08 (95% CI 1.02–1.14) per 100 g/day increase (I² = 68%)

3. Regional Variations:

• Positive associations were observed in North America, Europe, and the Western Pacific regions.

• Confidence intervals were wider in other regions, indicating less certainty.

4. Heterogeneity:

• No evidence was found that age, sex, or BMI explained the observed heterogeneity.

• The findings for poultry consumption were less robust under alternative modeling assumptions.

5. Substitution Analysis:

• Replacing processed meat with either unprocessed red meat or poultry was associated with a lower incidence of type 2 diabetes.

Comparison with Previous Research:

This study provides the most comprehensive evidence to date on the associations between meat consumption and type 2 diabetes risk. The findings partly align with previous evidence but show some key differences:

1. Magnitude of Associations:

• The positive associations found in this study were weaker compared to previous publication-based meta-analyses.

• This difference could reflect publication bias in earlier studies and highlights the importance of prospective pooling projects in evidence synthesis.

2. Regression Dilution:

• The smaller magnitude of associations could be due to regression dilution from using single baseline measurements of dietary habits.

3. BMI Adjustment:

• The study showed results both with and without adjustment for BMI, acknowledging BMI's potential role as both a confounder and a mediator.

4. Poultry Consumption:

• This study provides more comprehensive evidence on the association between poultry intake and incident type 2 diabetes, improving upon previous inconclusive findings.

• The association was found to be heterogeneous across populations and sensitive to modeling approaches.

5. Geographical Diversity:

• The study included previously underrepresented populations, addressing a significant gap in earlier research.

Strengths of the Study:

• Scale and Diversity: The largest meta-analysis on the topic to date, evaluating individual-level data across diverse populations.

• Harmonization: Use of a federated approach facilitated harmonization of data and standardization of analysis methods, reducing heterogeneity related to different analytical approaches.

• Comprehensive Confounding Adjustment: The study accounted for a wide range of potential confounding factors.

Mechanisms Linking Meat Consumption to Type 2 Diabetes:

The study discusses several potential mechanisms through which meat consumption could affect type 2 diabetes risk:

• Fatty Acid Composition: Red meat is rich in saturated fatty acids and low in polyunsaturated fatty acids, which could affect insulin resistance.

• Protein Content: High intake of animal proteins has been associated with increased risk of type 2 diabetes in some research.

• Gut Microbiota: Trimethylamine N-oxide, a gut microbiota-dependent metabolite generated during the digestion of choline and l-carnitine (abundant in red meat), may play a role.

• Processing Additives: Nitrate or nitrite additives and the formation of N-nitroso compounds during meat processing are associated with higher risk.

• Advanced Glycation End Products: Compounds generated when cooking meat at high temperatures may contribute to oxidative stress and insulin resistance.

• Iron Content: Long-term iron intake has been implicated in increased risk of type 2 diabetes in observational studies and Mendelian randomization analysis.

Implications and Future Directions:

• Public Health: The findings support the notion that lowering the consumption of unprocessed red meat and processed meat could benefit public health by reducing the incidence of type 2 diabetes.

• Dietary Guidelines: The results should inform dietary guidelines, emphasizing the importance of reducing meat consumption, particularly processed meat.

3. Further Research Needs:

• Investigation of the association between poultry consumption and type 2 diabetes risk, given the uncertainty in the current findings.

• Studies in under-represented regions, particularly Africa, the Middle East, South Asia, and Central and South America.

• Research on the effects of different subtypes of meat products, cooking methods, and physiological responses across populations.

• Investigation of sustainable dietary patterns to reduce meat consumption and its effect on other non-communicable diseases, multi-morbidity, and

Conclusion:

This comprehensive, global study provides strong evidence that higher meat consumption, particularly of unprocessed red meat and processed meat, is associated with a higher incidence of type 2 diabetes across diverse populations. The findings support public health initiatives to reduce meat consumption for both human health and planetary sustainability. However, uncertainty remains regarding the positive association between poultry consumption and type 2 diabetes incidence, warranting further investigation.

The study's strengths lie in its large scale, diverse population representation, and harmonized analytical approach. However, limitations such as potential residual confounding and measurement error in dietary assessment highlight the need for further research, particularly in under-represented regions and on the specific mechanisms linking meat consumption to type 2 diabetes risk.

These findings have significant implications for public health policies and dietary guidelines worldwide. They underscore the importance of considering both the type and amount of meat consumption in strategies aimed at preventing type 2 diabetes and promoting overall health. Future research should focus on addressing the remaining uncertainties, particularly regarding poultry consumption, and on developing sustainable dietary patterns that can effectively reduce the global burden of type 2 diabetes while considering broader impacts on health and the environment.

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Journal Reference

Li, C., Bishop, T. R. P., Imamura, F., Sharp, S. J., Pearce, M., Brage, S., Ong, K. K., Ahsan, H., Bes-Rastrollo, M., Beulens, J. W. J., den Braver, N., Byberg, L., Canhada, S., Chen, Z., Chung, H. F., Cortés-Valencia, A., Djousse, L., Drouin-Chartier, J. P., Du, H., Du, S., … Wareham, N. J. (2024). Meat consumption and incident type 2 diabetes: an individual-participant federated meta-analysis of 1·97 million adults with 100 000 incident cases from 31 cohorts in 20 countries. The lancet. Diabetes & endocrinology, 12(9), 619–630. https://doi.org/10.1016/S2213-8587(24)00179-7

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