Background Meat consumption may elevate type 2 diabetes (T2D) risk. However, evidence is based largely on European and North American populations, with heterogeneous analysis strategies and a greater focus on red meat than poultry. We aimed to investigate the associations of unprocessed red meat, processed meat and poultry with T2D from worldwide cohorts with harmonised analytic approaches.

Methods We conducted individual-participant federated meta-analysis of 1,966,444 adults in 31 cohorts from the Americas (12), Eastern Mediterranean (2), Europe (9), South Asia (1), and Western Pacific (7) participating in the InterConnect project. Cohort-specific hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for each meat type, adjusted for potential confounders including body mass index (BMI), and pooled using a random-effects meta-analysis, with meta-regression to investigate potential sources of heterogeneity.

Findings In total, 107,271 incident T2D cases were identified during a median follow-up of 10 years. Median consumption across cohorts ranged from 0-110 g/day for unprocessed red meat, 0-49 g/day for processed meat, and 0-72 g/day for poultry. Greater consumption of each of the three types of meat was associated with increased incidence of T2D, with HRs (95% CI) of 1·10 (1·06-1·15) per 100 g/day of unprocessed red meat (I2 61%), 1·15 (1·11-1·20) per 50 g/day of processed meat (I2 59%), and 1·08 (1·02-1·14) per 100 g/day of poultry (I2 68%). Positive associations were observed in North America, Europe, and Western Pacific; confidence intervals were wide in other regions. There was no evidence that age, sex or BMI explained the heterogeneity. The findings for poultry were weaker under alternative modelling assumptions. Replacing processed meat with unprocessed red meat or poultry was associated with a lower T2D incidence.

Interpretation: Meat consumption, particularly of unprocessed red meat and processed meat, is a risk factor for developing T2D across populations. These findings highlight the public health importance of reducing the consumption of meat for human health and should inform dietary guidelines.