A comprehensive review of healthy effects of vegetarian diets

Aims: A comprehensive review comparing the effect of vegetarian (V) and non-vegetarian (NV) diets on the major cardiometabolic diseases’ outcomes was performed. Data synthesis: We performed literature research (up to December 31, 2022) of the evidence separately for vascular disease (VD), obesity (OB), dyslipidemia (Dysl), hypertension (HPT), type 2 diabetes (T2D), metabolic syndrome (MetS), analyzing only cohort studies and randomized controlled studies (RCTs) and comparing the effect of V and NV diets. Cohort studies showed advantages of V diets compared to NV diets on incidence and/or mortality risk for ischemic heart disease, overweight and OB risk. Most cohort studies showed V had lower risk of HPT and lower blood pressure (BP) than NV and V diets had positive effects on T2D risk or plasma parameters. The few cohort studies on the risk of MetS reported mixed results. In RCTs, V diets, mainly low-fat-vegan ones, led to greater weight loss and improved glycemic control than NV diets and in the only one RCT a partial regression of coronary atherosclerosis. In most RCTs, V diets significantly reduced LDL-C levels (but also decreased HDL-C levels) and BP. Conclusions: In this comprehensive review of the association between V diets and cardiometabolic outcomes, we found that following this type of diet may help to prevent most of these diseases. However, the non-uniformity of the studies, due to ethnic, cultural, and methodological differences, does not allow for generalizing the present results and drawing definitive conclusions. Further, well-designed studies are warranted to confirm the consistency of our conclusions.