Abstract
BACKGRUOUND: Although some studies suggest a positive association between ultra-processed food (UPF) intake and type 2 diabetes mellitus (T2DM), little is known about the exact shape and risks associated with different units (percentage of g/day, absolute g/day, serving/day) of UPF intake and whether the association is independent of diet quality, total energy intake, and body mass index (BMI). METHODS: Prospective studies published through January 2024 were identified by searching PubMed, Embase, and Web of Science. Summary relative risks (RRs) and 95% confidence intervals (CIs) were estimated using random-effects models. A nonlinear dose-response meta-analysis was conducted using restricted cubic spline analysis. RESULTS: After screening 569 publications, a total of 12 prospective cohort studies were included. Comparing the highest vs. lowest categories of intake, summary RR for T2DM risk was 1.48 (95% CI, 1.36 to 1.61). Higher summary RRs were observed among studies from Europe and North America. Among individual UPF subgroups, processed meats (summary RR, 1.34; 95% CI, 1.16 to 1.54) were positively associated, whereas ultra-processed cereals and breads (0.98; 95% CI, 0.97 to 0.99) and packaged savory snacks (0.92; 95% CI, 0.88 to 0.95) were inversely associated. The summary RRs associated with every 10% (of g/day), 100-g/day, and 1-serving/day increase in UPF intake were 1.14 (95% CI, 1.11 to 1.17), 1.05 (95% CI, 1.03 to 1.06), and 1.04 (95% CI, 1.03 to 1.05), respectively. The dose-response curve for absolute g/d intake suggested nonlinearity, showing a steeper risk increase approximately at >300 g/day. The associations persisted after adjustment for diet quality, energy intake, or BMI. CONCLUSION: Our data suggest that UPF intake increases diabetes risk, with a potential threshold effect at 300 g/day.