Monica Dinu and colleagues at the University of Florence published a large systematic review and meta-analysis in Critical Reviews in Food Science and Nutrition in 2017. They analyzed 86 cross-sectional studies and 10 cohort studies covering multiple health outcomes.

The review found that vegetarian diets provided a significant protective effect against ischemic heart disease, with a 25% lower rate of incidence and death. Total cancer incidence was 8% lower in vegetarians. Vegetarians also showed significantly lower body weight, lower blood lipid levels, and better blood sugar control.

Vegan diets showed an even stronger association with cancer protection, with a 15% lower risk of total cancer incidence. The authors concluded that the accumulated evidence supports significant health benefits from plant-based dietary patterns.

Michael Orlich and colleagues published this major prospective cohort study in JAMA Internal Medicine in 2013. They followed 73,308 Seventh-day Adventist men and women, recording 2,570 deaths over a mean follow-up of 5.79 years.

When all vegetarian dietary patterns were combined, participants had a 12% lower risk of dying from any cause compared to non-vegetarians. Breaking this down by diet type, pesco-vegetarians (who eat fish but no other meat) had the lowest mortality at 19% lower risk. Vegans had 15% lower risk, lacto-ovo-vegetarians had 9% lower risk, and semi-vegetarians had 8% lower risk.

The benefits were more pronounced in men than women, and were particularly strong for deaths from heart disease, kidney failure, and diabetes. The study is one of the largest ever conducted on vegetarian mortality.

Tammy Tong and colleagues at the University of Oxford published this large prospective study in the BMJ in 2019. They followed 48,188 participants from the EPIC-Oxford cohort for an average of 18.1 years, during which 2,820 cases of ischemic heart disease occurred.

Vegetarians had a 22% lower rate of ischemic heart disease compared to meat eaters. In absolute terms, this translated to about 10 fewer cases of heart disease per 1,000 people over a 10-year period. Fish eaters also showed a benefit, with a 13% lower rate.

The researchers found that about half of the difference in heart disease risk could be explained by lower body mass index, lower blood pressure, lower cholesterol, and lower rates of diabetes among vegetarians. These are all well-established risk factors for heart disease.

Frank Qian and colleagues published this systematic review and meta-analysis in JAMA Internal Medicine in 2019. They pooled data from 9 prospective studies that collectively tracked 307,099 participants, among whom 23,544 developed type 2 diabetes.

People who most closely followed a plant-based dietary pattern had a 23% lower risk of developing type 2 diabetes compared to those who least followed such patterns. When researchers looked specifically at "healthful" plant-based diets - those rich in whole grains, fruits, vegetables, nuts, and legumes - the protection was even stronger at 30% lower risk.

Importantly, "unhealthful" plant-based diets heavy in refined grains, sugary drinks, and processed foods did not show the same protection. This suggests that the quality of plant foods matters more than simply avoiding meat.

Tao Huang and colleagues published this systematic review and meta-analysis in Annals of Nutrition and Metabolism in 2012, pooling data from 7 prospective cohort studies with a total of 124,706 participants.

Vegetarians had a 29% lower risk of dying from ischemic heart disease compared to non-vegetarians. Cancer incidence was 18% lower among vegetarians. All-cause mortality was 9% lower. These are substantial risk reductions, particularly for heart disease.

The heart disease finding is the most robust and consistent result across vegetarian diet research. It aligns with the known effects of plant-based diets on cholesterol levels, blood pressure, and body weight - all major risk factors for blocked arteries and heart attacks.

The Academy of Nutrition and Dietetics, the largest organization of food and nutrition professionals in the United States with over 100,000 members, published its official position paper on vegetarian diets in the Journal of the Academy of Nutrition and Dietetics in 2016.

The position statement declared that appropriately planned vegetarian diets, including vegan diets, are healthful, nutritionally adequate, and may provide health benefits for the prevention and treatment of certain diseases. The academy stated these diets are appropriate for all stages of the life cycle, including pregnancy, infancy, childhood, adolescence, older adulthood, and for athletes.

The statement cited evidence showing vegetarians are at reduced risk of ischemic heart disease, type 2 diabetes, high blood pressure, certain types of cancer, and obesity. The qualification "appropriately planned" is important - it means including enough variety and supplementation of nutrients like vitamin B12.

This large pooled analysis published in the British Journal of Cancer in 2025 combined data from 9 prospective cohort studies spanning North America, Europe, and Asia-Pacific, covering approximately 1.8 million participants.

Vegetarians had an 8% lower risk of breast cancer compared to meat eaters, with the difference concentrated mainly in postmenopausal women. Lower risks were also observed for pancreatic cancer, prostate cancer, kidney cancer, and multiple myeloma (a blood cancer).

The enormous scale of this analysis - nearly 2 million participants - gives it statistical power that individual studies cannot achieve. By combining data across three continents with different dietary cultures and background cancer rates, the findings are less likely to be explained by confounding factors specific to one population.

Andrea Glenn and colleagues published this systematic review and meta-analysis in JAMA Network Open in 2023. Unlike most diet studies that rely on observational data, this analysis focused specifically on randomized controlled trials - the gold standard of clinical evidence - involving participants with or at high risk of cardiovascular disease.

The analysis found that vegetarian and vegan dietary patterns were associated with meaningful reductions in cardiovascular risk factors. Participants assigned to plant-based diets showed lower LDL cholesterol (the "bad" cholesterol that clogs arteries), lower blood pressure, and lower body mass index compared to those on non-vegetarian diets.

The fact that these benefits were demonstrated in controlled experiments, not just population surveys, strengthens the case that the diet itself causes the improvement rather than vegetarians simply being healthier people who also happen to exercise more or smoke less.

This meta-analysis published in Current Developments in Nutrition in 2021 pooled data from 8 observational studies involving 131,869 adult participants. The weighted mean follow-up period was 10.68 years.

Vegetarians had a 30% lower risk of dying from ischemic heart disease - the most common form of heart disease, caused by narrowed arteries that reduce blood flow to the heart. This is a large and clinically meaningful reduction.

Ischemic heart disease is the single leading cause of death globally, killing approximately 9 million people per year worldwide. A 30% reduction in mortality from this condition through dietary change alone represents one of the largest effect sizes seen in nutritional epidemiology.

Timothy Key and colleagues at the University of Oxford published a comprehensive review in the Proceedings of the Nutrition Society in 2022, summarizing findings from the EPIC-Oxford study - one of the largest studies of vegetarians ever conducted, with approximately 65,000 participants including a large proportion of vegetarians and vegans.

Across multiple health conditions tracked over decades, vegetarians consistently showed lower risk of several diseases. These included ischemic heart disease, type 2 diabetes, diverticular disease (a painful intestinal condition), kidney stones, and cataracts (clouding of the eye lens).

The breadth of conditions with lower risk in vegetarians is notable. These are not all related to cardiovascular health - they span digestive, metabolic, and eye conditions, suggesting that the benefits of a vegetarian diet extend beyond just heart protection.

An extended analysis of the Adventist Health Study 2 published in the American Journal of Clinical Nutrition in 2024 followed up on the original 2013 findings with a longer observation period. The study continued to track over 73,000 Seventh-day Adventist participants.

With the additional years of follow-up, the analysis confirmed that vegetarians had significantly lower mortality from several specific causes including kidney failure, infectious disease, diabetes, and ischemic heart disease. The protective effects were most pronounced among men and among participants who were younger at baseline.

The longer follow-up is important because dietary patterns may take years or decades to fully manifest their effects on chronic disease risk. The consistency of the findings across the original and extended analyses strengthens confidence in the vegetarian mortality advantage.