Objective: To determine how a vegetarian diet affects stroke incidence in 2 prospective cohorts and to explore whether the association is modified by dietary vitamin B₁₂ intake.

Methods: Participants without stroke in the Tzu Chi Health Study (cohort 1, n = 5,050, recruited in 2007-2009) and the Tzu Chi Vegetarian Study (cohort 2, n = 8,302, recruited in 2005) were followed until the end of 2014. Diet was assessed through food frequency questionnaires in both cohorts at baseline. Stroke events and baseline comorbidities were identified through the National Health Insurance Research Database. A subgroup of 1,528 participants in cohort 1 were assessed for serum homocysteine, vitamin B₁₂, and folate. Associations between vegetarian diet and stroke incidences were estimated by Cox regression with age as time scale, adjusted for sex, education, smoking, alcohol, physical activities, body mass index (only in cohort 1), hypertension, diabetes, dyslipidemia, and ischemic heart diseases.

Results: Vegetarians had lower serum vitamin B₁₂ and higher folate and homocysteine than nonvegetarians. In cohort 1, 54 events occurred in 30,797 person-years follow-up. Vegetarians (vs nonvegetarians) experienced lower risk of ischemic stroke (hazard ratio [HR], 0.26; 95% confidence interval [CI], 0.08-0.88). In cohort 2, 121 events occurred in 76,797 person-years follow-up. Vegetarians (vs nonvegetarians) experienced lower risk of overall stroke (HR, 0.52; 95% CI, 0.33-0.82), ischemic stroke (HR, 0.41; 95% CI, 0.19-0.88), and hemorrhagic stroke (HR, 034; 95% CI, 0.12-1.00). Our explorative analysis showed that vitamin B₁₂ intake may modify the association between vegetarian diet and overall stroke (p interaction = 0.046).[ Full article]

Conclusion: Taiwanese vegetarian diet is associated with a lower risk of ischemic and hemorrhagic strokes.