Effect of Milk and Cultured Milk Products on Type 2 Diabetes: A Global Systematic Review and Meta-analysis of Prospective Cohort Studies

Background Dairy products have been used for centuries and were generally believed to be healthy. Recently, dairy products have been implicated in the rise of non-communicable diseases especially new onset type 2 diabetes (T2D). However, the available data have been inconsistent. Objective To perform a systematic review and meta-analysis of all the available prospective studies on the effect of dairy products with incident (new onset) T2D. Methods A total of 3009 articles were retrieved from PubMed, Scopus, Medline and Science Direct from January 2000 to March 2022 from which 27 prospective cohort studies were included. We classified dairy products as ‘total dairy’ and ‘total milk’ and further stratified them based on their fat content and fermentation. A subgroup analysis was conducted in people of Asian and Western ethnicity. Results Globally, total dairy products [Relative risk (RR) − 0.14; 95% Confidence Interval (CI) − 0.23; − 0.05; I 2 = 30%], total fermented dairy [RR − 0.08; 95% CI − 0.16; − 0.00; I 2 = 41%], and plain yogurt [RR − 0.08; 95% CI − 0.15; − 0.01; I 2 = 34%] were inversely associated with incident T2D. Other dairy products including low and high fat total dairy products, low and high fat milk and cheese had a neutral effect with no significant association with T2D. Subgroup analysis by ethnicity suggested that intake of total dairy confers protective effects against incident T2D among the Asian population. The plain yogurt, in particular, showed protection against new onset T2D across both ethnicities and across age groups. Further, the subgroup analysis by age showed that the consumption of high fat dairy predisposed younger adults to new onset of T2D. Conclusion Total and fermented dairy products, particularly plain yogurt, are protective against new onset T2D while milk, cheese and other dairy products have no significant effect on incident T2D. Study Registration Number This protocol was registered on the International Prospective Register of Systematic Reviews, PROSPERO (CRD42021249202).