Twenty Years of Studies Confirm the Power of Eating Plants

A comprehensive review of meta-analyses that were published between 2000 and 2023 was released in May 2024.  It evaluated the impact of vegan and vegetarian diets on the risk factors associated with the development of cardiometabolic diseases and cancer in adults, children and pregnant women.  (1)

This review was a joint undertaking between researchers from the University of Bologna in Italy and the Stanford University School of Medicine in the US who pooled together data from 48 previously-published meta-analyses.  Total participants numbered in the hundreds of thousands and there were no restrictions placed on age, gender, ethnicity, geographical origin, or socio-economic status. Three rating tools were employed to independently assess the quality of the reviews and meta-analyses used for this study. (1)

This paper is particularly compelling because it is an umbrella review.  Observational studies and randomized trials gather essential data and are used in meta-analyses to identify meaningful associations.  Umbrella reviews go one step further by comparing and contrasting the meta-analyses for a comprehensive summary of available evidence.  (2)

For this meta-analysis, study results focusing on both vegetarian and vegan diets were analyzed and reported separately if the authors communicated the results according to the type of diet; if data from vegan and vegetarian subjects were mixed, they were all reported as vegetarian.


To start, here are a few definitions:

Omnivore – A person who eats both plant-sourced foods and animal-sourced foods.

Vegetarian – A person who eats plant-sourced foods and excludes meats and may or may not exclude eggs and dairy products.

Vegan – A person who eats only plant-sourced foods.


Results of the Umbrella Meta-Analysis (1)

Compared to omnivores, vegetarian and vegan eaters are significantly less likely to develop cardiovascular disease and cancer.

A vegetarian diet is associated with decreased mortality from cardiovascular diseases.

Compared to omnivores, vegetarians and vegans have lower total and LDL cholesterol, reduced blood pressures, decreases in fasting blood glucose and HbA1c, lower body weight and BMI, diminished levels of inflammation and lower risks of coronary heart disease.

The overall risk of cancer and the risk for colorectal cancer in particular is lower in vegetarians and vegans compared to omnivores.

Eating red processed meats is significantly linked to increased cancers of the gastrointestinal tract.  This association encompasses both the greater risk of cancer caused by eating red processed meat and the protective factors that come from eating more fruits and vegetables.

Vegetarians and vegans are generally lower in body weight and carry less body fat than omnivores, a factor that is linked to decreased risks for pancreatic and colorectal cancer.

Pregnancy risks were similar in omnivores, vegans and vegetarians with no differences in the development of gestational diabetes or hypertension during pregnancy or in the birth weight of the baby.


Discussion About the Umbrella Meta-Analysis (1)

The researchers note that there are many reasons for this lower risk of cardiovascular diseases, metabolic diseases and cancer in people who eat a vegetarian or vegan diet.

A diet made up mostly of plant-sourced foods is much higher in the many health-protective nutrients that are present only in plants.  These include bioactive compounds like fiber and polyphenols that are produced only by plants.  In addition, eating a wide variety of plants is an excellent way to source the vitamins and minerals necessary for good health.

Although it is not always true, vegans and vegetarians are more likely to engage in healthy lifestyles that include less smoking and alcohol and regular exercise.  They also, by definition, eat no meat and are more likely to eat less sugar and sugar-sweetened beverages, refined grains, sweets, salt and snack foods than omnivores


Conclusions of the Umbrella Meta-Analysis  (1)

The findings of this meta-analysis suggest that vegetarian and vegan diets are associated with significant health benefits although the researchers caution that this study is limited by the many differences amongst the past studies used for this meta-analysis.  Participant demographics, geographic origins, sample sizes and dietary patterns all varied significantly.

The authors sum up their findings as follows, “Our study evaluates the different impacts of animal-free diets for cardiovascular health and cancer risk showing how a vegetarian diet can be beneficial to human health and be one of the effective preventive strategies for the two most impactful chronic diseases on human health in the 21st century.”



1  Capodici, A., Mocciaro, G., Gori, D., Landry, M.J., Masini, A., Sanmarchi, F., et al.  Cardiovascular health and cancer risk associated with plant based diets: An umbrella review.  2024. PLoS ONE 19(5): e0300711.

2  Aromataris, E., Fernandez, R., Godfrey, C.M., Holly, C., Khalil, H., Tungpunkom, P.   Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach. Int J Evid Based Healthc. 2015 Sep;13(3):132-140. Doi:10.1097/XEB.0000000000000055. PMID: 26360830.


Promoting a healthy adventurous lifestyle powered by plants and the strength of scientific evidence.

My name is Debra Harley (BScPhm) and I welcome you to my retirement project, this website. Over the course of a life many lessons are learned, altering deeply-rooted ideas and creating new passions.

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