Vegetarian Diet and Stroke in Two Cohorts in Taiwan
abstract
This abstract is available on the publisher's site.
Access this abstract nowOBJECTIVE
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).
CONCLUSION
Taiwanese vegetarian diet is associated with a lower risk of ischemic and hemorrhagic strokes.
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Additional Info
Disclosure statements are available on the authors' profiles:
Vegetarian Diet and Incidence of Total, Ischemic, and Hemorrhagic Stroke in 2 Cohorts in Taiwan
Neurology 2020 Feb 26;[EPub Ahead of Print], THT Chiu, HR Chang, LY Wang, CC Chang, MN Lin, CL LinFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
Vegetarian diet associated with reduced stroke risk
Nutrition studies based on recall can be challenging due to confounding variables. Having cohorts that share similar principles can add to the accuracy of the study.
This study involved two cohorts, the first was a group of 6002 and the second was a group of 12,002; they were followed for 10 years. Both groups were part of a Buddhist group in Taiwan called the Tzu Chi Volunteers (also known at the Tzu Chi Health Study). They devoted their time to both charity and environmental protection. The use of tobacco and alcohol was low in both cohorts, and the vegetarian group consumed more vegetables, soy, and nuts and less meat and dairy. Egg consumption was similar in both groups.
The authors evaluated the incidence of stroke in vegetarians and non-vegetarians while also following B12 and homocysteine levels.
Compared with the PREDIMED study (42% reduction), this study added to that, showing about a 50% reduction for all forms of stroke (ischemic and hemorrhagic).
Results (Hazard ratios)
Cohort
Vegetarian
Non-vegetarian
Reduction
#1
1.16
1.99
0.51
#2
0.95
1.88
0.52
Not surprisingly, B12 levels were lower and homocysteine levels were higher in the vegetarian group, but the benefits remained. The body needs B12, B6, and folate for methylation. If there are not enough of these cofactors, homocysteine levels rise. Meat is a rich source of B12 and B6, and vegetables (foliage) provide a great source of folate. Those vegetarians who had high B12 and low homocysteine concentrations had a lower stroke risk. And those vegetarians with a low B12 and homocysteine >20 μmol/L still had lower stroke risk compared with meat eaters with normal levels.
Bottom line
If you want to avoid a stroke, eat less meat and more vegetables, nuts, and soy. And if you don’t eat meat, supplement with a B-complex vitamin. But even if you don’t take a B vitamin, your risk of stroke may still be much lower than the risk of those who eat meat, even if your B12 is low and your homocysteine is high.