Plant-based diets and long-term health: findings from the EPIC-Oxford study.

Observational prospective cohorts in the UK: EPIC-Oxford (approximately 65,000 adults, men and women; vegetarian, vegan, and meat-eater groups) along with the Oxford Vegetarian Study and UK Biobank; dietary exposure assessed by questionnaires; follow-up up to about two decades; nonrandomized design.

Plant-based diets are associated with generally good long-term health and several advantages, including lower BMI, lower LDL cholesterol, and lower blood pressure, which help explain reduced ischemic heart disease risk. Vegetarians and vegans show lower risks for ischemic heart disease and diabetes, and lower overall cancer risk, but higher risks for bone fractures (especially hip fractures) and potential nutrient deficiencies (notably vitamin B12, vitamin D, and calcium) if not fortified or supplemented. In EPIC-Oxford, vegetarians had a 23% lower risk of ischemic heart disease after approximately 18 years; vegans 18% lower (not statistically significant due to small numbers); combined 22% lower (17% after BMI adjustment). Stroke risk was higher in vegetarians by 17%, particularly haemorrhagic stroke (approximately 48% higher; vegan figures less certain). Diabetes risk was 35% lower in vegetarians and 47% lower in vegans; after BMI adjustment, 11% and 1% lower, respectively (vegan result not statistically significant due to small numbers). All cancers combined were 10% lower in vegetarians and 18% lower in vegans; cervical cancer was higher in vegetarians by about 90%; stomach cancer and haematological cancers lower in vegetarians; colorectal cancer not different. Fracture risk was higher in vegetarians (all sites 11% higher; hip 34% higher) and higher in vegans (all fractures 50% higher; hip fractures 164% higher), with stronger effects at low BMI. All-cause mortality did not differ meaningfully (vegetarians HR 1.00; vegans HR 1.14). Vitamin B12 deficiency is common among vegans (about 52% below 118 pmol/L); vegetarian deficiency about 7%; meat-eaters less than 1%. Overall interpretation: plant-based diets are generally healthful but carry specific risks; benefits may be driven by lower BMI and LDL-cholesterol, while nutrient deficiencies and fracture risk require attention via fortification and/or supplementation; more research is needed, especially in larger vegan cohorts.

Observational design with potential residual confounding (smoking, alcohol, socio-economic factors); diet assessment relies on self-report and is subject to error; relatively small number of vegans (about 2,500) limiting precision; possible reverse causation; imperfect diet classification; results may not generalize beyond UK-based populations.