Plant-rich diets are among the best-studied for health.
The evidence on well-planned, whole-food plant diets is strong and consistent: major dietetic associations describe them as healthful and nutritionally adequate, with benefits for heart health, weight and type-2 diabetes.
Photo: Bill Ebbesen / Wikimedia Commons (CC BY)
−32%
Heart disease
vs. omnivore controls
−50%
Type-2 diabetes
Qian et al., 2019 meta-analysis
−14%
All cancers
Adventist Health-2
−34%
Hypertension
Evidence varies by diet
Legumes
Whole grains
Vegetables
Fruit
Nuts & seeds
"Appropriately planned vegetarian, including vegan, diets are healthful, nutritionally adequate, and may provide health benefits for the prevention and treatment of certain diseases. These diets are appropriate for all stages of the life cycle."
01
Heart disease
In small controlled trials, intensive lifestyle programmes built around whole-food plant diets reduced coronary artery narrowing. Plant-based diets lower LDL cholesterol and blood pressure.
02
Type-2 diabetes
In the Adventist Health Study-2, vegans had the lowest rates of type-2 diabetes of any diet group. Plant-rich eating improves insulin sensitivity and blood-sugar control.
03
Cancer risk
Processed meat is a Group 1 carcinogen (WHO). Red meat is Group 2A. High-fibre, whole-food plant diets are associated with lower colorectal cancer risk; evidence for other cancers is weaker.
04
Longevity
In the 'Blue Zones' — communities reported to have exceptional longevity — traditional diets are described as mostly plant-based, built on beans, whole grains and vegetables.
05
Antimicrobial resistance
About 73% of antimicrobials sold worldwide are used in farmed animals. Routine use breeds resistant bacteria that can move into the human population.
06
Pandemic risk
About three in four emerging infectious diseases come from animals: new avian and swine flu strains have emerged from farmed animals, MERS from camels and SARS via the wildlife trade. Industrial farming crowds billions of genetically similar animals together.
The strongest evidence
Where the research is clearest.
Plant-based eating has been studied for several health conditions. Evidence varies by outcome and by the foods included; these are some of the better-studied areas.
Heart disease
Small trials of intensive lifestyle programmes, combining a low-fat vegetarian diet with exercise, stress management and smoking cessation, found some regression of coronary narrowing. Plant-rich diets can support heart health alongside medical care.
Type 2 diabetes
Vegetarian and vegan diets can improve blood sugar control in adults with type 2 diabetes. Trials support benefits for HbA1c and body weight; medication changes should be supervised by a clinician.
High blood pressure
Some plant-rich eating patterns lower blood pressure in clinical trials, though results vary and evidence for vegan diets alone is less certain. Limiting sodium and eating potassium-rich foods can help; treatment needs remain individual.
Certain cancers
The World Health Organization classifies processed meat as a Group 1 carcinogen (the same evidence category as tobacco, not the same size of risk). Wholegrains and dietary fibre have strong evidence for reducing colorectal cancer risk.
By the numbers
Disease risk on plant-based diets
Large cohort studies link vegetarian and plant-based diets with lower risk of heart disease, type 2 diabetes and some cancers. EPIC-Oxford also found a higher stroke risk among vegetarians. These are associations, not proof of cause.
Risk difference in large studies (%)
Ischaemic heart disease (vegetarians)−22%
Total stroke (vegetarians)+20%
Type 2 diabetes (highest vs lowest plant-based diet score)−23%
All cancers (vegans)−16%
Tong et al., BMJ 2019 (EPIC-Oxford) · Qian et al., JAMA Intern. Med. 2019 · Tantamango-Bartley et al., 2013 (AHS-2)
Watch
Forks Over Knives
The 2011 documentary follows Dr. T. Colin Campbell and Dr. Caldwell Esselstyn and explores their advocacy of whole-food, plant-based eating for chronic disease prevention and management.
A well-planned plant-based diet can be nutritionally adequate. These five nutrients deserve attention, along with iodine, selenium and zinc. Use fortified foods and appropriate supplements where needed.
Vitamin B12
Use a reliable B12 supplement or sufficient fortified foods. B12 is made by microorganisms and occurs naturally in animal foods. Follow an appropriate dose schedule; weekly tablets need a different dose from daily ones.
Omega-3 (ALA → EPA/DHA)
Ground flax, chia and hemp provide ALA; the amount matters. Conversion to EPA and DHA is limited. An algae-based EPA/DHA supplement supplies these directly, without fish.
Iron
Lentils, beans, tofu, pumpkin seeds, dark greens and fortified grains all carry iron. Pair them with something containing vitamin C (citrus, peppers, tomatoes) and absorption jumps significantly.
Calcium
Fortified plant milks, tofu set with calcium, tahini, kale, bok choy, dried figs. Easy to hit daily targets once you know which foods carry it.
Vitamin D
Same advice as for everyone: if you don't get regular sunlight, supplement. This is a population-wide issue, not a vegan one.
Who actually says this
Professional guidance, in their own words.
These professional bodies provide guidance on planning vegetarian and vegan diets. Their statements differ in scope, including the ages and life stages covered.
"It is the position of the Academy of Nutrition and Dietetics that, in adults, appropriately planned vegetarian and vegan dietary patterns can be nutritionally adequate and can offer long-term health benefits such as improving several health outcomes associated with cardiometabolic diseases."
"Plant-based diets can support healthy living at every age and life stage. But as with any diet, you should plan your plant-based eating to meet your nutritional needs."
"With good planning, a vegetarian diet can be a healthy choice that meets your growing child’s nutritional needs."
Athletes on plants
Performance, endurance, and recovery on a plant-based diet.
The idea that serious athletic performance requires animal protein is one of the more persistent myths in nutrition. The evidence from elite sport does not support it. The following examples are illustrative — not a claim that all athletes do or should eat plants, but that the 'you can't perform without animal products' assumption is false.
Scott Jurek
Ultramarathon running
One of the greatest ultramarathon runners of his generation, Jurek won the Western States 100 seven consecutive times and set a course record on the Appalachian Trail while eating fully plant-based. His case is notable not because he is an outlier but because he trained and competed at the highest level for decades on plants.
Venus Williams
Tennis
Williams adopted a vegan/raw-food diet after her 2011 diagnosis of Sjogren's syndrome, an autoimmune condition, to help manage symptoms. She has described her approach as flexible rather than strictly vegan. She later returned to the top 10 and finished 2017 ranked No. 5; her experience is a personal account, not clinical evidence.
Novak Djokovic
Tennis
Djokovic adopted a largely plant-based diet following a food intolerance diagnosis in 2010. He describes the change as a turning point in his career, associated with improved recovery times, better sleep, and fewer injuries. He holds the record for most Grand Slam singles titles.
Patrik Baboumian
Strongman
Multiple-record-holding strongman and Germany's strongest man 2011, Baboumian set a world record in yoke walking — carrying 555 kg — on a fully plant-based diet. He is frequently cited in discussions of plant-based strength sports because his discipline has historically been seen as the most protein-demanding.
Skin, inflammation, hormones
The less-discussed effects of what you eat.
The research connecting diet to skin health is earlier-stage than the cardiac or metabolic evidence, but it is consistent in direction. High-glycaemic diets and diets rich in dairy appear to be associated with higher rates of acne in multiple observational studies, plausibly through hormonal pathways — dairy contains naturally occurring growth hormones, and the glycaemic spike from processed foods raises IGF-1. A 2007 randomised controlled trial published in the American Journal of Clinical Nutrition found significant acne reduction in participants following a low-glycaemic diet.
More broadly, plant-based diets are associated with lower systemic inflammation, measured by C-reactive protein and other inflammatory markers. Chronic low-grade inflammation is implicated in a wide range of conditions — arthritis, cardiovascular disease, depression, and several cancers — meaning the anti-inflammatory effect of plant foods is one of the most plausible mechanisms behind the broader health benefits. Omega-3 fatty acids (from flaxseed, walnuts, and algae-derived supplements), polyphenols (from berries, dark greens, and legumes), and fibre all contribute to this effect.
Children and pregnancy
The question people worry most about, answered directly.
Plant-based eating during pregnancy and childhood requires careful planning, appropriate supplements, and attention to growth and nutrient intake. Professional guidance differs, and evidence on strictly vegan diets in children remains limited. A registered dietitian or qualified clinician can help families meet the needs of each life stage.
During pregnancy and childhood, vegan diets need reliable vitamin B12 supplementation and careful attention to vitamin D, iodine, calcium, iron, zinc, protein, energy, and omega-3 fats. Algae-derived supplements can provide DHA. Fortified foods and supplements should be chosen for the person's age and needs; iodised salt alone may not provide enough iodine. Seek professional advice for pregnancy and infant feeding.
Evidence on vegan children's long-term growth and development remains limited. Some studies report lower body fat or cholesterol, while others identify concerns about height, bone mineral content, or nutrient status. A 2025 ESPGHAN review found the evidence on normal growth inconclusive and recommended regular monitoring and nutritional counselling.
A note on the "we evolved to eat meat" argument.
Our ancestors ate what was available, and diets varied widely — some hunter-gatherer groups ate a lot of meat, others very little. Since farming began, most people in most places have lived mainly on plant staples — grains, legumes, roots and greens — with animal foods as occasional additions.
The modern question is not "what could our bodies tolerate". It is "what helps them live the longest, healthiest lives". Large studies keep pointing towards diets built mainly on plants.
A carefully planned vegan diet can meet needs, but children and pregnancy require particular care. Seek qualified dietary advice and plan calories, protein, iron, calcium, B12, vitamin D, iodine and omega-3.
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