While there are a variety of reasons for adopting a vegan diet, health reasons are attracting a lot of scientific focus. Vegans tend to be thinner, have lower cholesterol, and have lower blood pressure, and there is some evidence there are additional health benefits that can lead to longer life expectancy.
Vegans benefit from increased consumption of vegetables but can miss out on essential nutrients due to the avoidance of meat and dairy. Vegan diets are usually high in fiber, magnesium, folic acid, phytochemicals, and vitamins C and E. On the other hand, they tend to be lower in calories, saturated fat, cholesterol, omega 3 fatty acids, calcium, zinc, and vitamins B-12 and D.
Studies in the short and moderate-term have found that vegan diets can improve energy metabolism in healthy, obese, and type 2 diabetic individuals. Some believe this is due to favorable changes in the gut microbiome that are brought about due to the vegan diet, but there is currently not enough research to verify this. There is also some evidence that vegans consume more protective nutrients and phytochemicals.
Diets that are high in fruits and vegetables, nuts, vegetable oils, and whole grain are often associated with lower rates of cardiovascular disease development. These types of diets traditionally include Mediterranean and Asian diets, but recently the vegan diet has been postulated to have similar effects.
The lower risk of cardiovascular disease can be achieved by a vegetarian diet, where dairy is included. This seems to be primarily due to the increased intake of fruits and vegetables, which contain valuable nutrients, including fiber and antioxidant vitamins, and have been independently associated with a lower risk of cardiovascular disease.
While vegan diets are often seen as having lower fat content and vegans are usually thinner, the actual benefits of fat intake associated with veganism on cardiovascular diseases are disputed. In general, vegetable oils are seen as more beneficial than animal fat due to their content of monounsaturated fats, vitamin E, and α-linolenic acid.
A lot of evidence indicates that vegans and vegetarians have a lower risk of various cancers, both due directly to nutrient intake and due to secondary effects. For example, obesity is a significant factor in cancer risk, and due to the lower BMI of vegans, they also enjoy lower cancer risk.
Fruits and vegetables have been described as lowering the risk of lung, mouth, esophagus, and stomach cancers, and they tend to be consumed at higher quantities in vegans. Phytochemicals, which are abundant in vegetables and occur at a higher volume in vegan diets, have antioxidant qualities and disrupt cells to stop the progression of cancer.
While vegan diets include nutrients known to lower the risk of cancer, there can also be adverse effects of vegan diets on cancer risks. For example, low vitamin D is associated with increased cancer risk and is also generally low in vegan diets. This may explain why there are not more pronounced differences in the development of cancer between vegans and non-vegans. Vegans may have increased risks due to deficiencies but decreased risks due to increased antioxidant consumption or lower body weight.
One of the lesser-studied areas in how vegan diets can affect an individual is neurobiology and cognitive function. Studies that have focused on this have found mild or moderate improvements when patients afflicted with migraine, multiple sclerosis, fibromyalgia, and rheumatoid arthritis consumed a vegan diet. These studies are confounded by not accounting for the gluten content of the plant-based diet and by small sample sizes.
Studies looking at specific nutrients show some signs that vegan diets can be beneficial for cognition and mental health. Intake of phytochemicals, which appears to be higher in vegans, is associated with beneficial effects on mental health. In contrast, lower intake of vitamin B-12, which is common in vegans, is associated with detrimental effects on the neurologic system and cognitive health, such as stroke, Parkinson’s disease, and Alzheimer’s disease.
- Medawar, E. et al. (2019) The effect of plant-based diets on the body and the brain: a systematic review. Translational Psychiatry. https://doi.org/10.1038/s41398-019-0552-0
- Craig, W.J. (2009) Health effects of vegan diets. The American Journal of Clinical Nutrition. https://doi.org/10.3945/ajcn.2009.26736N
- Hu, F.B. (2003) Plant-based foods and prevention of cardiovascular disease: an overview. The American Journal of Clinical Nutrition. https://doi.org/10.1093/ajcn/78.3.544S