An extensive analysis of nearly 50 studies indicates that plant-based diets offer numerous health advantages. Published in the journal PLOS ONE, the review examined studies from 2000 to 2023, revealing that vegetarian and vegan diets correlate with reduced risks of heart disease, cancer, and overall mortality.

The studies focused on the health impacts of vegetarian and vegan diets, which exclude all animal-derived foods, including dairy. The findings consistently showed that both dietary patterns are linked to a lower risk of cancer and ischemic heart disease, which is caused by narrowed arteries. Specifically, these diets appeared to decrease the risks of prostate cancer and gastrointestinal cancers, such as colon cancer. Additionally, vegetarian diets were associated with a lower risk of death from cardiovascular diseases.

Plant-based diets were also found to reduce risk factors for heart disease and cancer, including high body weight, inflammation, and LDL, or "bad," cholesterol.

"This research highlights that a plant-based diet can be beneficial, and even small steps towards it can make a difference," said Matthew Landry, an assistant professor of population health and disease prevention at the University of California, Irvine, and one of the review’s authors. "You don’t have to go completely vegan to see benefits. Reducing animal-based consumption by a day or two each week can still be beneficial over time."

However, Dr. Walter Willett, a professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health, emphasized that the healthiness of plant-based diets can vary. "A vegetarian diet could be predominantly refined starches and sugar, which is one of the worst dietary patterns," Willett, who was not involved in the study, noted. A healthy plant-based diet should mainly consist of whole grains, fruits, vegetables, nuts, soy, beans, and non-hydrogenated plant oils.

Why Are Plant-Based Diets So Healthy?

Researchers continue to explore the mechanisms through which plant-based diets reduce disease risk. Preventing obesity, linked to heart disease and certain cancers, is one factor, but the benefits extend beyond weight control, Landry explained. "Some benefits are independent of weight. Even when weight is stable, we see reductions in some clinical health outcomes, particularly cardiovascular disease," he said.

One possible reason is that many fruits and vegetables are rich in anti-inflammatory nutrients and antioxidants, which can reduce plaque buildup in the arteries. Plant-based diets also tend to be high in fiber, which helps lower bad cholesterol, according to Brie Turner-McGrievy, a professor of health promotion, education, and behavior at the University of South Carolina. Her 2014 study, included in the new review, found that plant-based diets can reduce risk factors for heart disease, stroke, and Type 2 diabetes. "Soluble fiber found in beans and oats is a powerful tool to lower LDL cholesterol levels," she said, noting that this benefit is best achieved through whole foods, not supplements.

Another advantage of plant-based diets may be the lower intake of saturated fat, which is harder to reduce if consuming animal-based foods. Processed meats like bacon or salami are known to raise cancer risk, and the World Health Organization considers red meat a "probable human carcinogen."

Is a Vegan or Vegetarian Diet Suitable for Everyone?

The Academy of Nutrition and Dietetics states that vegetarian and vegan diets are adequate and healthy at all life stages, including pregnancy, childhood, and older adulthood. However, the new review did not universally recommend plant-based diets.

"During pregnancy, a strict vegetarian diet is not recommended based on the current data," said Dr. Federica Guaraldi, an endocrinologist at the IRCCS Institute of Neurological Sciences of Bologna in Italy and a co-author of the review. The review found that plant-based diets did not lower the risk of gestational diabetes or hypertension in pregnant women. Additionally, vegetarian diets were linked to lower zinc levels and an increased risk of low birthweights in infants.

The review also warned that plant-based diets might lead to vitamin B12 deficiencies, which can be addressed with supplements. "A healthy plant-based diet, whether vegetarian or vegan, can meet almost all your vitamin and mineral needs," Landry said.