Vegetarian diet, Seventh Day Adventists and risk of cardiovascular mortality: a systematic review and meta-analysis.

BACKGROUND

Dietary interventions are an important component of cardiovascular risk factor management although their impact on cardiovascular risk and mortality remains uncertain. We have studied influence of a vegetarian diet on cardiovascular risk and mortality.

METHODS

We searched MEDLINE and EMBASE for comparative studies that evaluated clinical outcomes associated with vegetarian diet as compared to non-vegetarian controls or the general population. Relevant studies were pooled using random effects meta-analysis for risk of death, ischaemic heart disease (IHD) and cerebrovascular disease. We conducted subgroup analysis according to specific type of cohort (e.g. Seventh Day Adventist [SDA]) and gender.

RESULTS

Eight studies met the inclusion criteria with 183,321 participants (n=183,321). There was significant heterogeneity in all the meta-analyses, particularly evident with the studies of SDA. In all instances, we found that SDA studies showed greater effect size as compared to non-SDA studies: death (RR 0.68 95% CI 0.45-1.02 vs RR 1.04 95% CI 0.98-1.10), ischaemic heart disease (IHD) (RR 0.60 95% CI 0.43-0.80 vs RR 0.84 95% CI 0.74-0.96) and cerebrovascular disease (RR 0.71 95% CI 0.41-1.20 vs RR 1.05 95% CI 0.89-1.24). Sex specific analyses showed that IHD was significantly reduced in both genders but risk of death and cerebrovascular disease was only significantly reduced in men.

CONCLUSIONS

Data from observational studies indicates that there is modest cardiovascular benefit, but no clear reduction in overall mortality associated with a vegetarian diet. This evidence of benefit is driven mainly by studies in SDA, whereas the effect of vegetarian diet in other cohorts remains unproven.