Plant-based diets reduce cancer and heart disease risks, study shows

By Dr. Chinta SidharthanReviewed by Susha Cheriyedath, M.Sc.May 16 2024

In a recent study published in the journal PLOS ONE, researchers conducted an umbrella review to assess whether diets free of animal-based food products and rich in plants or plant-based foods lowered the risks associated with cancer and cardiometabolic diseases and decreased the mortality risk.

Cardiovascular health and cancer risk associated with plant based diets: An umbrella review. Image Credit: Wild As Light / Shutterstock

Background

The two leading causes of disability and mortality worldwide are cancer and cardiovascular disease, and various studies have identified diet as one of the most important modifiable risk factors for these diseases. Research has also found that unhealthy diets characterized by an increased intake of salt, sugars, refined grains, and processed red meats and insufficient intake of whole grains, vegetables, fruits, and legumes also increase the mortality rate and result in higher disability-adjusted life years.

A vegan or vegetarian diet has been recommended by various health professions as a treatment for a wide range of metabolic diseases such as type 2 diabetes, obesity, hypertension, and atherosclerosis. The popularity of plant-based diets has also increased significantly in the face of growing concerns about the ethical treatment of animals, the state of the environment, and socio-economic inequalities.

However, given the substantial heterogeneity in study design, exposures, outcomes, and various other factors associated with assessing the efficacy of plant-based diets, opportunities to comprehensively assess their benefits in health and disease have been limited.

About the study

This umbrella review examined numerous systematic reviews, meta-analyses, and other reviews investigating the impact of diets free of animal products on the risk factors for cardiometabolic diseases and cancer and on lowering the mortality risk associated with these diseases among an all-inclusive study population.

This review considered plant-based diets, including veganism, ovo-vegetarians, lacto-vegetarians, and lacto-ovo-vegetarians. Gender, age, ethnicity, socio-economic status of the participants, or geographical origin of the study or participants were not considered grounds for excluding a study from the review. However, vegetarian diet regimens that limited but did not altogether avoid the consumption of poultry or fish were excluded to reduce heterogeneity among the studies.

Data obtained from the studies included the target population, type of diet, review type, and a wide range of clinical measurements such as levels of triglycerides, total cholesterol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterols, C-reactive protein, and apolipoprotein B. Measurements such as body weight, body mass index (BMI), glycosylated hemoglobin (HbA1c), fasting blood glucose, and systolic and diastolic blood pressures were also extracted from the studies.

Additionally, information on the risk and types of cardiac events, gestational diabetes, cardiovascular diseases, cancer, and gestational hypertension, as well as mortality due to cardiovascular disease or cancer, was obtained from included studies. The estimated risk was reported as a hazard ratio, odds ratio, or relative risk in all the included studies.

Results

The review found that vegan and vegetarian diets were linked to significant improvements in glycemic control, lipid profiles, and BMI, as well as lowering inflammation and the risks of cancer and ischemic heart disease. The risk of cardiovascular disease-associated mortality was also found to be lower with vegetarian diets. However, among pregnant women, the risk of gestational hypertension or diabetes was not found to change in association with a vegetarian diet.

The findings suggested that vegan or vegetarian diets were linked to significantly lower LDL and total cholesterol levels, HbA1C, and fasting blood glucose levels compared to omnivorous diets. Furthermore, inflammation, based on serum levels of C-reactive protein, as well as body weight and BMI, was found to be lower in association with a plant-based diet than an omnivorous diet. However, the impact of vegan or vegetarian diets on triglycerides, HDL cholesterol, and blood pressure remains unclear.

The researchers stated, however, that it can be assumed that many of the individuals following a plant-based diet also make other healthy lifestyle choices, such as avoiding or reducing tobacco, alcohol, or sugar-sweetened beverages and foods and exercising regularly, which could contribute to lowering the risk of ischemic heart disease and other cardiovascular diseases.

The risk of cancer was also found to be lower in association with vegetarian diets than with omnivorous diets. While the results were inconsistent when the analysis was stratified according to various types of cancer, the review found that the risk of gastrointestinal tract-related cancers was higher in association with diets rich in processed red meats. Furthermore, the lowering of hyperinsulinemia due to the increased consumption of whole grains and other plant-based foods could also potentially modify the risk of colorectal cancer.

Conclusions

Overall, the review reported that plant-based diets provided various benefits that lowered the risk of cancer, cardiometabolic disorders, and cardiovascular disease. However, given the high heterogeneity in study characteristics and findings on the benefits of plant-based diets, the researchers believe that these restrictive diet regimens must be recommended with caution.