Large cohort studies suggest vegans have a modest edge in overall mortality risk compared to regular meat-eaters, but the advantage is smaller and less certain than many people assume. The best-known study on the topic, following more than 73,000 people in the Adventist Health Study 2, found that vegans had roughly a 15% lower risk of dying from any cause during the study period, though this result did not quite reach conventional statistical significance. That ambiguity captures the state of the science well: vegan diets consistently show benefits in specific disease categories while introducing risks in others, and the net effect on lifespan depends heavily on how well the diet is managed.
What the Largest Studies Actually Found
The Adventist Health Study 2 (AHS-2) is the go-to dataset for this question because it tracked a large population that included a substantial number of vegans over several years. Compared to nonvegetarians, vegans showed a hazard ratio of 0.85 for all-cause mortality, meaning about a 15% lower death rate. But the confidence interval crossed 1.0, which means the result was not statistically conclusive. Pesco-vegetarians in the same study fared slightly better, with a hazard ratio of 0.81 that did reach significance.1PubMed Central. Vegetarian Dietary Patterns and Mortality in Adventist Health Study 2
The EPIC-Oxford study, one of the largest European cohorts tracking vegetarians and vegans, paints a mixed picture. Vegans in that study had lower risks of diabetes, diverticular disease, and cataracts compared to meat-eaters. But the researchers noted a higher risk of bone fractures in vegans, and there was not enough data on vegans specifically to draw firm conclusions about many other conditions, including overall mortality.2PubMed Central. Plant-based diets and long-term health: findings from the EPIC-Oxford study
A striking counterpoint comes from a study of Chinese adults aged 80 and older, which found that vegetarians and vegans were actually less likely to reach age 100 than omnivores. Vegans had about 29% lower odds of becoming centenarians. The authors noted that in elderly populations with already limited caloric intake, removing animal foods may create nutritional shortfalls that matter more than in younger groups.3The American Journal of Clinical Nutrition. Vegetarian diet and likelihood of becoming centenarians in Chinese adults aged 80 y or older: a nested case-control study
Heart Disease and Stroke
Heart disease is the leading cause of death worldwide, so any diet’s effect on cardiovascular health matters enormously for longevity. Vegan diets reliably lower LDL cholesterol and blood pressure, both major risk factors. A meta-analysis of randomized trials found that vegetarian and vegan diets reduced LDL cholesterol by about 10% on average.4European Heart Journal. Vegetarian or vegan diets and blood lipids: a meta-analysis of randomized trials In randomized controlled trials, vegan interventions specifically were associated with LDL cholesterol drops of roughly 15% to 25%.5The American Journal of Cardiology. Plant-Based Diets and Plasma Lipids One trial showed significant reductions in several atherogenic markers, including lipoprotein(a) and small dense LDL particles, within just four weeks on a defined plant-based diet.6PubMed Central. Consumption of a defined, plant-based diet reduces lipoprotein(a), inflammation, and other atherogenic lipoproteins and particles within 4 weeks
Yet these favorable biomarkers have not translated into a clear reduction in actual cardiovascular events for vegans. A systematic review examining at least 73,000 individuals found that none of the included studies reported a significantly increased or decreased risk of any cardiovascular outcome in vegans compared to non-vegans. One study in the review did suggest vegans might face greater risk of ischemic stroke, though this finding also fell short of statistical significance.7The Journal of Nutrition. A Systematic Review of the Association Between Vegan Diets and Risk of Cardiovascular Disease A separate meta-analysis found a borderline reduction in ischemic heart disease risk for vegans versus non-vegetarians, with a summary risk ratio of 0.82.8PubMed Central. Vegetarian and vegan diets and the risk of cardiovascular disease, ischemic heart disease and stroke: a systematic review and meta-analysis of prospective cohort studies
The disconnect between improved blood lipids and ambiguous cardiovascular outcomes is one of the more puzzling findings in this literature. One possible explanation involves vitamin B12 deficiency and elevated homocysteine, which are common in vegans and can independently raise cardiovascular risk. This is addressed further below.
Cancer Risk Is Not Uniformly Lower
A meta-analysis of prospective studies found that vegans had a roughly 23% lower risk of total cancer compared to non-vegetarians.9PubMed Central. Vegetarian and vegan diets and cancer incidence: a systematic review and meta-analysis of prospective studies That sounds impressive, but the picture gets complicated when you look at specific cancer types. Breast cancer risk in vegans showed a borderline reduction, and prostate cancer results were inconclusive.
Colorectal cancer is where the findings get genuinely surprising. A large pooled analysis of 1.8 million people across nine prospective studies found that vegans had a 40% higher risk of colorectal cancer compared to meat-eaters. Rectal cancer risk was even more elevated, at 78% higher. Pescatarians, by contrast, had a 15% lower colorectal cancer risk.10British Journal of Cancer. Vegetarian diets and cancer risk: pooled analysis of 1.8 million women and men in nine prospective studies on three continents Researchers are still working to explain this result. Possible factors include lower intake of certain protective nutrients found in fish, differences in gut microbiota, or residual confounding. Whatever the explanation, it complicates the simple narrative that avoiding meat automatically lowers cancer risk across the board.
Diabetes Prevention
If there is one disease category where vegan diets show consistently strong results, it is type 2 diabetes. In the AHS-2 cohort, vegans had a 62% lower risk of developing diabetes even after controlling for BMI and lifestyle factors. The protective effect was particularly strong among Black participants, who saw a 70% reduction in risk.11PubMed Central. Perspective: Plant-Based Eating Pattern for Type 2 Diabetes Prevention and Treatment: Efficacy, Mechanisms, and Practical Considerations A meta-analysis of randomized controlled trials found that plant-based diets improved insulin resistance and fasting insulin levels in people with overweight or obesity.12PubMed Central. Effects of Plant-Based Diets on Markers of Insulin Sensitivity: A Systematic Review and Meta-Analysis of Randomised Controlled Trials Given that diabetes is a major contributor to cardiovascular disease, kidney failure, and premature death, these findings carry real weight for the longevity question.
The Fracture Problem
Bone health is where vegan diets face their starkest challenge. Vegans consistently show lower bone mineral density than omnivores, and this translates into a meaningfully higher fracture risk. A recent meta-analysis found that vegans had a 75% higher risk of hip fracture compared to meat-eaters.13PubMed. Vegetarian and Vegan Diets and the Risk of Hip Fracture in Adults: A Systematic Review and Meta-analysis Data from the UK Women’s Cohort Study found a similar pattern, with vegetarians showing a 33% higher hip fracture risk than regular meat-eaters, though pescatarians showed no elevated risk.14PubMed Central. Risk of hip fracture in meat-eaters, pescatarians, and vegetarians: results from the UK Women’s Cohort Study
The likely culprits are lower calcium intake, insufficient vitamin D, and lower overall protein consumption. Researchers have noted that the fracture risk in vegans may be substantially reducible with adequate supplementation and dietary planning, but the default vegan diet without supplementation leaves bones vulnerable.15PubMed. Fracture Risk in Vegetarians and Vegans: the Role of Diet and Metabolic Factors Hip fractures in older adults carry serious mortality implications on their own, so this is not a minor footnote.
Vitamin B12 and the Homocysteine Problem
Vitamin B12 is found almost exclusively in animal products, and without supplementation, vegans inevitably develop deficiency. This is not a fringe concern. In the German Vegan Study, nearly half of participants had B12 levels below the normal threshold, and their homocysteine levels were elevated as a consequence.16Annals of Nutrition and Metabolism. German Vegan Study: Diet, Life-Style Factors, and Cardiovascular Risk Profile Elevated homocysteine is associated with increased cardiovascular risk, with each 5 micromol/L increase above the baseline linked to about a 20% higher risk of circulatory problems.17PubMed. Is vitamin B12 deficiency a risk factor for cardiovascular disease in vegetarians?
This creates an ironic situation: a diet that lowers cholesterol and blood pressure may simultaneously raise cardiovascular risk through a different pathway. Researchers have suggested that B12 deficiency could negate some of the cardiovascular benefits of plant-based diets.18The American Journal of Clinical Nutrition. Vitamin B-12 status among vegetarians The fix is straightforward — take a B12 supplement — but many vegans do not, or do not take enough.
Omega-3 Gaps and What the Body Can Do About Them
Vegans get virtually no preformed EPA or DHA, the long-chain omega-3 fatty acids found in fish and seafood that are linked to cardiovascular and brain health. The body can convert the plant-based omega-3, ALA, into EPA and DHA, but the conversion rate is low, leaving vegans with substantially reduced tissue concentrations of these fats.19The American Journal of Clinical Nutrition. Achieving optimal n–3 fatty acid status: the vegetarian’s challenge… or not
There is some encouraging news, though. A controlled trial found that ALA supplementation significantly boosted EPA, DPA, and DHA levels across all dietary patterns, including vegans. People who started with the lowest EPA levels saw the largest gains, with EPA rising by about 63% and DHA by about 27%.20Frontiers in Nutrition. Impact of α-linolenic acid supplementation on long-chain n-3 fatty acid profiles in Western, flexitarian, vegetarian, and vegan diets Algae-based DHA supplements are another option. Whether low omega-3 status in vegans actually shortens life is still debated, but it remains a plausible contributor to the stroke risk signal seen in some studies.
Iron Absorption Adapts, but Not All Nutrients Do
A common concern is that plant-based iron is harder to absorb than the heme iron found in meat. Compounds like phytic acid in legumes and whole grains can bind iron and zinc, reducing their uptake.21The American Journal of Clinical Nutrition. Bioavailability of iron, zinc, and other trace minerals from vegetarian diets But the body appears to adjust. A controlled trial measuring actual iron absorption found that vegans absorbed significantly more non-heme iron from a test meal than omnivores did, likely because their bodies had adapted by lowering hepcidin, a hormone that regulates iron uptake.22PubMed Central. Dietary Adaptation of Non-Heme Iron Absorption in Vegans: A Controlled Trial Vegans do tend to have lower iron stores, but in countries with abundant and varied food supplies, this has not been clearly linked to adverse health outcomes. Some researchers have even speculated that moderately lower iron stores might reduce the risk of certain chronic diseases.
Not All Plant-Based Diets Are Equal
A vegan diet that relies heavily on refined grains, sweetened beverages, and ultra-processed plant-based products looks very different from one built around whole grains, vegetables, legumes, and nuts. The health implications differ just as sharply. A study in The Lancet Regional Health found that increasing the share of plant-sourced whole foods in the diet was associated with lower cardiovascular disease risk and mortality. But increasing the share of plant-sourced ultra-processed foods was associated with higher risk. A 10% increase in ultra-processed plant foods was linked to a 5% increase in cardiovascular disease incidence, while a 10% increase in non-ultra-processed plant foods was linked to a 7% decrease.23The Lancet Regional Health – Europe. Ultra-processed foods with plant-based diets and cardiovascular disease risk
Another analysis found that the combination of a healthful plant-based diet with lower ultra-processed food consumption was associated with a 22% lower mortality risk, while simply eating more plant foods regardless of processing showed weaker effects.24PubMed Central. The role of ultra-processed foods in plant-based diets: associations with human health and environmental sustainability The takeaway: “vegan” tells you what someone avoids, not what they eat. The quality of the foods filling that space matters enormously.
The Healthy User Problem
A persistent challenge in interpreting all of this research is that people who choose a vegan diet tend to differ from the general population in ways that have nothing to do with what they eat. They are more likely to exercise, less likely to smoke, more likely to maintain a healthy weight, and more likely to engage with the healthcare system. These behaviors independently affect longevity, and no amount of statistical adjustment can fully disentangle them from the effects of diet itself.25PubMed Central. Healthy user and related biases in observational studies of preventive interventions: a primer for physicians This is part of why the Adventist Health Study 2 is so valued: Seventh-day Adventists as a group already tend to be health-conscious and non-smoking, which makes the comparison between vegans and non-vegetarians within that community more meaningful than comparing vegans to the general population.
Epigenetic Aging Clocks
A newer area of research uses molecular markers on DNA to estimate biological age, which can differ from chronological age depending on lifestyle and environment. A study of a Dutch population found that veganism was significantly associated with slower epigenetic aging on two established clocks, even after adjusting for exercise, BMI, smoking, and other confounders.26PubMed Central. Nutritional associations with decelerated epigenetic aging: vegan diet in a Dutch population A twin study that randomized identical twins to vegan versus omnivorous diets found that the vegan group showed decreases in overall epigenetic age acceleration over just eight weeks.27PubMed Central. Unveiling the epigenetic impact of vegan vs. omnivorous diets on aging: insights from the Twins Nutrition Study (TwiNS)
These are intriguing findings, but they measure a surrogate marker, not actual lifespan. Epigenetic clocks predict mortality risk at the population level, yet we do not know whether the changes observed over weeks or months of dietary intervention persist over decades or truly translate into extra years. The research is early-stage and worth watching, though it is too soon to hang longevity claims on it.
Muscle Mass and Aging on a Vegan Diet
Maintaining muscle mass becomes critical for health and survival as people age. Sarcopenia, the progressive loss of muscle, increases the risk of falls, fractures, disability, and death. A randomized controlled trial in older adults found that those who switched to a self-selected vegan diet experienced significant losses in thigh muscle volume and appendicular lean mass over the study period, while an omnivorous control group maintained theirs.28The American Journal of Clinical Nutrition. A self-selected vegan diet reduces skeletal muscle mass in healthy older adults: a randomized controlled trial The vegan group that also performed resistance exercise lost less muscle than unsupervised vegans, but still lost more than the omnivore group.
That said, this may be a protein quantity and quality issue rather than a fundamental limitation of plant-based eating. Another trial showed that when older adults consumed a high-protein vegan diet using mycoprotein as a primary source, their daily muscle protein synthesis rates matched those of omnivores on a comparable protein intake.29British Journal of Nutrition. A mycoprotein-based high-protein vegan diet supports equivalent daily myofibrillar protein synthesis rates compared with an isonitrogenous omnivorous diet in older adults: a randomised controlled trial Researchers have suggested that less restrictive plant-based diets, or those carefully planned to meet protein targets, may protect against sarcopenia in older adults.30PubMed Central. Association between a plant-based diet and the risk of sarcopenia among older adults: a case-control study The implication is that older vegans need to be particularly deliberate about protein intake, combining complementary plant proteins and potentially using protein-rich foods like soy, legumes, or mycoprotein at each meal.
Gut Microbiome and the Fiber Connection
Vegan diets tend to be far higher in dietary fiber than typical Western diets, and fiber is the primary fuel for beneficial gut bacteria. These microbes produce short-chain fatty acids, which help reduce inflammation and are thought to protect against cardiovascular disease, diabetes, and neurodegenerative conditions.31PubMed. Gut Microbiota and Dietary Strategies for Age-Related Diseases The gut microbiome is increasingly recognized as a mediator between diet and chronic disease, and high-fiber plant-based diets appear to push it in a favorable direction. How much of the longevity signal from vegan diets flows through the microbiome versus through more direct metabolic pathways remains an open question, but it is a plausible piece of the puzzle.
Amino Acid Restriction and Aging Biology
One of the more speculative but scientifically interesting angles involves specific amino acids. Animal protein, especially red meat, is rich in methionine and branched-chain amino acids. Research in animal models has linked restriction of these amino acids to longer lifespan and improved metabolic health, operating through pathways related to cellular growth signaling and oxidative stress. Epidemiological studies have found associations between high animal protein intake and the promotion of age-related diseases.32ScienceDirect. The impact of dietary protein intake on longevity and metabolic health This suggests that a vegan diet may confer some benefit simply by reducing exposure to these specific amino acids, independent of its other nutritional properties. The evidence for this in humans is still largely observational and mechanistic, not from direct trials measuring lifespan. But it represents one of the more biologically plausible reasons a vegan diet might slow aging processes.