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

BackgroundDairy 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.ObjectiveTo perform a systematic review and meta-analysis of all the available prospective studies on the effect of dairy products with incident (new onset) T2D.MethodsA 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.ResultsGlobally, 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 similar findings with total dairy products and milk having protective effects on T2D among the Asian population while fermented dairy products were protective against T2D in western populations. Among the fermented dairy products, plain yogurt, in particular, showed protection against T2D across both ethnicities. Further, subgroup analysis by age showed that the consumption of high fat dairy predisposed younger adults to T2D.ConclusionTotal and fermented dairy products, particularly plain yogurt, are protective against new onset T2D while milk, cheese and other dairy products have a neutral effect with no effect on incident T2D.Study Registration NumberThis protocol was registered on the International Prospective Register of Systematic Reviews, PROSPERO (CRD42021249202).