Vegetarian and vegan diets: benefits and drawbacks

TLDR

Plant‑based diets are increasingly popular for their health and environmental benefits, with prospective studies and RCTs linking vegetarian eating to lower risks of cardiovascular disease, diabetes, hypertension, dementia, and cancer, though evidence for cardiovascular events and cancer is limited and unhealthy plant‑based diets lacking key nutrients or high in processed foods can raise morbidity and mortality. Further mechanistic studies are needed to determine whether the benefits of healthy, minimally processed vegetarian diets are all‑or‑nothing and to assess the effects of plant‑based diets with small amounts of animal products, such as pescetarian or Mediterranean patterns, on cardiometabolic health and to elucidate the biological mechanisms linking dietary factors to CVD and metabolic diseases.

Abstract

Plant-based diets have become increasingly popular thanks to their purported health benefits and more recently for their positive environmental impact. Prospective studies suggest that consuming vegetarian diets is associated with a reduced risk of developing cardiovascular disease (CVD), diabetes, hypertension, dementia, and cancer. Data from randomized clinical trials have confirmed a protective effect of vegetarian diets for the prevention of diabetes and reductions in weight, blood pressure, glycosylated haemoglobin and low-density lipoprotein cholesterol, but to date, no data are available for cardiovascular event rates and cognitive impairment, and there are very limited data for cancer. Moreover, not all plant-based foods are equally healthy. Unhealthy vegetarian diets poor in specific nutrients (vitamin B12, iron, zinc, and calcium) and/or rich in highly processed and refined foods increase morbidity and mortality. Further mechanistic studies are desirable to understand whether the advantages of healthy, minimally processed vegetarian diets represent an all-or-nothing phenomenon and whether consuming primarily plant-based diets containing small quantities of animal products (e.g. pesco-vegetarian or Mediterranean diets) has beneficial, detrimental, or neutral effects on cardiometabolic health outcomes. Further, mechanistic studies are warranted to enhance our understanding about healthy plant-based food patterns and the biological mechanisms linking dietary factors, CVD, and other metabolic diseases.