Paul Appleby and colleagues at the University of Oxford published this pooled analysis in the American Journal of Clinical Nutrition in 2016, combining data from two large UK prospective cohorts: the Oxford Vegetarian Study and EPIC-Oxford. The study included 60,310 participants, of whom 20,324 were vegetarians (including 2,228 vegans), and recorded 5,294 deaths before age 90.

The central finding was striking: vegetarians had a hazard ratio of 1.02 compared to regular meat eaters - meaning their mortality rate was essentially identical. Fish eaters had a ratio of 0.96 and low meat eaters had 0.93, but none of these differences reached statistical significance.

This is critical because the UK cohorts represent health-conscious populations where both vegetarians and meat eaters are relatively well-educated and health-aware. When you compare vegetarians to similarly health-conscious omnivores rather than the general population, the mortality advantage disappears.

The same 2019 BMJ study by Tammy Tong that found lower heart disease risk in vegetarians also revealed an uncomfortable trade-off. Among the 48,188 EPIC-Oxford participants tracked for 18 years, there were 1,072 stroke cases, including 519 ischemic strokes (caused by blocked blood vessels) and 300 hemorrhagic strokes (caused by bleeding).

Vegetarians had a 20% higher rate of total stroke compared to meat eaters. In absolute terms, this meant about 3 extra cases of stroke per 1,000 people over 10 years. The increased risk was driven primarily by hemorrhagic stroke - the bleeding type, which is often more severe and deadly than the clotting type.

The researchers noted that lower cholesterol levels in vegetarians, while protective against heart disease, may paradoxically increase hemorrhagic stroke risk. Very low cholesterol can weaken blood vessel walls in the brain, making them more prone to rupture.

Tammy Tong and colleagues published this analysis from EPIC-Oxford in BMC Medicine in 2020. They tracked 54,898 participants for an average of 17.6 years, during which 3,941 total fractures occurred, including hip, wrist, arm, ankle, leg, and other fractures.

Vegetarians had a 25% higher risk of hip fracture compared to meat eaters. Vegans had dramatically higher risk - 131% higher, more than double the rate of meat eaters. In absolute numbers, vegans experienced about 14.9 extra hip fractures per 1,000 people over 10 years.

The risks remained elevated even after accounting for differences in body weight. Lower intake of calcium and protein, both critical for bone strength, is the likely explanation. Hip fractures are particularly serious in older adults - about 20-30% of people over 65 who break a hip die within a year.

Neufingerl and Eilander published this comprehensive systematic review in the journal Nutrients in 2022, analyzing 141 studies that compared nutrient intake and status between people eating plant-based diets and meat eaters.

The results revealed widespread nutritional gaps. Among vegans, 44% were deficient in vitamin B12 - a nutrient found almost exclusively in animal products and essential for nerve function and blood cell formation. Among vegetarians, 32% were B12 deficient. Vegetarians and vegans also had lower levels of vitamin D, iron, zinc, iodine, calcium, and the omega-3 fatty acids EPA and DHA.

These deficiencies are not just theoretical concerns. B12 deficiency can cause irreversible nerve damage and cognitive decline. Low iron causes anemia and fatigue. Low calcium and vitamin D weaken bones. Low omega-3 fatty acids may explain the higher stroke risk seen in vegetarians. While supplements can address these gaps, most vegetarians do not supplement adequately.

Sebastian Ocklenburg and Jutta Borawski published this meta-analysis in the Journal of Affective Disorders in 2021. They pooled data from 13 studies comparing depression scores between 8,057 vegetarians and 41,832 non-vegetarian controls.

Vegetarians scored significantly higher on depression measures, with a standardized mean difference of 0.21. While this is considered a small effect size statistically, it was consistent across studies and statistically significant. In practical terms, it means vegetarians as a group reported more depressive symptoms.

The authors acknowledged that the direction of the relationship is unclear - it is possible that people who are already depressed are more likely to adopt vegetarian diets, rather than the diet causing depression. However, nutritional deficiencies common in vegetarians (particularly B12, iron, zinc, and omega-3 fatty acids) are all known to affect brain chemistry and mood regulation.

Iguacel and colleagues published a systematic review and meta-analysis in Nutrition Reviews in 2019 examining bone mineral density and fracture risk in people following plant-based diets compared to omnivores.

Vegetarians and vegans had significantly lower bone mineral density at both the femoral neck (the top of the thigh bone near the hip) and the lumbar spine compared to omnivores. These are the two sites where fractures are most dangerous and debilitating, particularly in older adults.

A subsequent 2025 update in Nutrition Reviews confirmed that vegetarians had about 25% higher hip fracture risk while vegans had approximately 75% higher hip fracture risk compared to meat eaters. The lower bone density is likely driven by lower calcium intake, lower protein intake, lower vitamin D levels, and lower body weight - all factors that contribute to bone strength.

Timothy Key and colleagues at the University of Oxford published this comprehensive summary of EPIC-Oxford findings in the Proceedings of the Nutrition Society in 2022. After following approximately 65,000 participants for decades, the overall picture was more nuanced than simple "vegetarian is healthier" messaging suggests.

While vegetarians did have lower risk of ischemic heart disease, type 2 diabetes, and several other conditions, they also had higher risk of stroke (particularly hemorrhagic stroke) and bone fractures. When all causes of death were combined, there were no differences in overall life expectancy between vegetarians and meat eaters.

This finding is crucial because it shows that the benefits and risks of a vegetarian diet roughly cancel each other out in terms of total survival. The lower heart disease deaths are offset by higher stroke and fracture-related deaths. A diet that trades one set of health risks for another is not straightforwardly "healthier."

The extended analysis of the Adventist Health Study 2, published in the American Journal of Clinical Nutrition in 2024, revealed a concerning finding that complicated the otherwise positive results for vegetarians. While younger vegetarians showed clear mortality benefits, the picture reversed for older participants.

At estimated age 85, vegetarians had higher cause-specific mortality from neurological conditions including stroke, dementia, and Parkinson''s disease. These are all conditions in which adequate nutrition - particularly vitamin B12, omega-3 fatty acids, and certain amino acids found primarily in animal products - plays an important protective role.

This age-dependent reversal suggests that long-term vegetarian diets may carry cumulative nutritional risks that manifest later in life. B12 deficiency in particular can take years to develop because the body stores several years'' worth, but once stores are depleted, irreversible neurological damage can occur.

Tak and colleagues published this systematic review and meta-analysis in the journal Nutrients in 2021, examining stroke risk specifically in vegetarian populations. They identified 7 prospective cohort studies that compared stroke incidence between vegetarians (29,705 participants with 408 stroke cases) and non-vegetarians (627,728 participants with 13,026 stroke cases).

While the overall pooled result for total stroke did not reach statistical significance, the subgroup analyses revealed important patterns. Hemorrhagic stroke risk was elevated in vegetarians across multiple studies. The EPIC-Oxford cohort, which is the largest and best-designed study of Western vegetarians, showed the clearest signal with a 20% higher total stroke rate.

The biological explanation centers on very low cholesterol levels. While low LDL cholesterol protects against heart attacks, extremely low cholesterol may weaken the walls of small blood vessels in the brain. Additionally, lower intake of B12 and omega-3 fats may impair blood vessel health and increase inflammation in ways that raise stroke risk.