The most important studies on vegan diet

Discussions around the effects of vegan diets on our health and the environment are often marked by controversy and misconceptions. In order to dispel some of the misinformation about plant-based eating, it’s important to take a close look at vegan diet studies and the scientific findings behind them.

Research on vegan diets is essential for uncovering new insights on a variety of topics, from chronic disease prevention to sustainability. Studies and their conclusions should always be considered carefully to avoid misinterpretation. Key factors such as sample size, length of study, and participant demographics can heavily influence outcomes.

What to Look For When Reading Vegan Diet Studies

Vegan diet studies can vary greatly in their participant counts and duration. Generally, the longer a study runs and the more participants it includes, the more robust and reliable its data. While this isn’t always a hard rule, it’s often a good indicator that the findings may be more accurate or comprehensive.

A well-planned vegan diet can offer numerous benefits for many reasons, ranging from improved cardiovascular health to reduced environmental impact. Vegan diets exclude animal products such as meat, dairy, eggs, and honey, focusing instead on fruits, vegetables, legumes, nuts, seeds, and grains.

Cardiovascular Health and Type 2 Diabetes

A number of vegan diet studies suggest that this eating pattern can lower the risk of cardiovascular diseases, largely because plant-based foods tend to be higher in fiber and lower in saturated fats. These same studies also indicate that a vegan diet may reduce the likelihood of developing type 2 diabetes, as vegan meals are typically lower in calories and cholesterol.

Moreover, some research has shown a lower incidence of certain cancers (like colorectal and prostate cancer) among those who eat a plant-based diet. Other studies reveal that a vegan diet could decrease the risk of hypertension (high blood pressure).

Vegan diets often include antioxidant-rich produce, supporting general health.

Potential Health Advantages of a Vegan Diet

In 2015, the World Health Organization (WHO) classified processed meats as carcinogenic, backed by substantial studies and evidence. Red meats like beef and pork were also labeled “probably carcinogenic,” placing them in Group 2A for their potential cancer risk.^[1]

Cow’s milk has increasingly come under scrutiny for its possible connection to hormone-driven cancers, such as prostate, ovarian, and breast cancer.^[2] A 2015 study published in The American Journal of Clinical Nutrition found that regular milk consumption among women could raise their breast cancer risk by up to 30%. For men, daily milk intake could increase the likelihood of prostate cancer by approximately 9%.^[3]

Further vegan diet studies suggest that a plant-based diet may positively impact the immune system.^[4] Below is a closer look at two common health concerns: cardiovascular disease and type 2 diabetes.

Studies on Heart Disease and Type 2 Diabetes

Research finds that long-term adherence to a vegan diet can substantially reduce the likelihood of heart disease. One British project, the Oxford Vegetarian Study, reported up to a 57% decrease in cardiovascular illness among vegans compared to meat eaters.  The study concluded that frequent consumption of animal-based foods correlated with higher LDL cholesterol levels, thus heightening heart-disease risk.^[5][6]

Another 2016 study from Journal of the American College of Cardiology revealed that vegetarian diets (vegan diets included) may slash heart disease rates by as much as 25%.
Type 2 diabetes, meanwhile, is a major concern in Western nations. A large 2021 Oxford study of 474,000 participants reported that those who consume about 70g of red meat daily raise their risk of developing type 2 diabetes by roughly 30%.^[7][8]

Plant-based meals rich in vitamins and minerals may help prevent chronic illnesses.

Two Major Vegan Diet Studies Everyone Should Know

When it comes to vegan diet studies and human health, the Adventist Health Study 2 (AHS-2) and the EPIC-Oxford study are two standout investigations.

1. Adventist Health Study 2 (AHS-2)

This large-scale analysis included 96,000 participants, making it one of the biggest nutritional studies addressing vegan diets. Among the group, 4,000 were vegans, while the rest were either meat eaters, pescatarians, or vegetarians.

Results showed that vegans had a 15% reduced mortality risk over the study’s timeframe. Additionally, they tended to have the lowest LDL cholesterol levels, lower prevalence of type 2 diabetes, and lower rates of colorectal cancer. Notably, vegan participants also showed a 34% reduction in cancers like breast or cervical cancer. Another study in International Journal of Cancer indicated that vegetarian diets (including vegan diets) reduce colorectal cancer risks by roughly 22%.^[9][10]

2. EPIC-Oxford Study

Involving 65,000 volunteers—2,600 of them vegan—this project has run since 1993 and discovered that vegans have about a 30% lower risk of heart disease compared to meat eaters, plus the lowest diabetes occurrence among all diet groups. Body Mass Index (BMI) measurements were also most favorable in vegans. Additionally, the study data shows about a 19% decrease in overall cancer incidence for vegans.^[11][12]

Taken together, both major studies suggest positive health outcomes for those adopting a vegan diet—particularly fewer instances of cancer, heart disease, type 2 diabetes, high blood pressure, and obesity.

References

• [1] WHO (2015): Q&A on the carcinogenicity of the consumption of red meat and processed meat.
• [2] Genkinger, J. M., et al. (2006). Dairy products and ovarian cancer: a pooled analysis of 12 cohort studies. Cancer Epidemiol. Biomarkers Prev. 15, p. 364–372
• [3] Aune, D., et al. (2015). Dairy products, calcium, and prostate cancer risk: a systematic review and meta-analysis of cohort studies. The American Journal of Clinical Nutrition 101(1), 87–117
• [4] Weder S, Schaefer C, Keller M (2018). Die Gießener vegane Lebensmittelpyramide. Ernährungs Umschau 65 (8), 134–43.
• [5] Appleby, P. N., et al. (1999). The Oxford Vegetarian Study: an overview. The American Journal of Clinical Nutrition 70(3 Suppl), p. 525S–531S
• [6] Thorogood, M., et al. (1994). Risk of death from cancer and ischaemic heart disease in meat and non-meat eaters. BMJ 308, p. 1667–1670
• [7] Papier K, Fensom GK, Knuppel A, et al. (2021). Meat consumption and risk of 25 common conditions: outcome-wide analyses in 475,000
• [8] Yang X, et al. (2020). Meat and fish intake and type 2 diabetes: dose–response meta-analysis of prospective cohort studies. Diabetes Metab. 46(5):345-352
• [9] Orlich, M. J., et al. (2013). Vegetarian dietary patterns and mortality in Adventist Health Study 2. JAMA Intern Med. 173(13):1230-8
• [10] Orlich, M. J., et al. (2014). Vegetarian diets in the Adventist Health Study 2: a review of initial published findings. Am J Clin Nutr. 100 Suppl 1(1):353S-8S
• [11] Segovia-Siapco G, Sabaté J. (2019). Health and sustainability outcomes of vegetarian dietary patterns: a revisit of the EPIC-Oxford and the Adventist Health Study-2 cohorts. Eur J Clin Nutr. 72(Suppl 1):60-70
• [12] Travis RC, Allen NE, Appleby PN, et al. (2008). A prospective study of vegetarianism and isoflavone intake in relation to breast cancer risk in British women. Int J Cancer. 122(3):705-10