Vegetarian and pescatarian diets are linked to lower risk of ischaemic heart disease, study findsBMJ 2019; 366 doi: https://doi.org/10.1136/bmj.l5397 (Published 05 September 2019) Cite this as: BMJ 2019;366:l5397
Following a vegetarian (including vegan) or pescatarian diet is linked to a lower risk of developing ischaemic heart disease than eating a diet that includes meat, research has found.
But the prospective cohort study,1 carried out by University of Oxford researchers, also found that vegetarians and vegans had a higher risk of haemorrhagic and total stroke than meat eaters, which could be due to low blood levels of total cholesterol or a low intake of certain vitamins.
The researchers used data from the EPIC-Oxford study to explore the risks of ischaemic heart disease and stroke in meat eaters (participants who consumed meat, regardless of whether they also consumed fish, dairy, or eggs; n=24 428), pescatarians (who consumed fish but no meat; n=7506), and vegetarians including vegans (n=16 254) over an 18 year period to 2010.
Over the follow-up period they found 2820 cases of ischaemic heart disease and 1072 cases of total stroke (519 ischaemic stroke and 300 haemorrhagic stroke).
The study, published in The BMJ,1 showed that the risk of ischaemic heart disease in pescatarians was 13% lower (hazard ratio 0.87 (95% confidence interval 0.77 to 0.99)) and in vegetarians was 22% lower (0.78 (0.70 to 0.87)) than in meat eaters. This took into account potentially influential factors such as medical history, smoking, use of dietary supplements, and physical activity.
Generalising the results
The lower rate of ischaemic heart disease is equal to 10 fewer cases (95% confidence interval 6.7 to 13.1 fewer) in vegetarians than in meat eaters in every 1000 people consuming these diets over 10 years. The difference may be at least partly due to the lower body mass index and lower incidence of high blood pressure, high blood cholesterol, and diabetes linked to these diets, the authors said.
In contrast, vegetarians and vegans had a 20% higher risk of stroke (hazard ratio 1.20 (1.02 to 1.40)) than meat eaters, equivalent to three more cases of stroke (0.8 to 5.4 more) per 1000 people over 10 years, mainly owing to a higher rate of haemorrhagic stroke. Vegetarians and vegans in the study had lower circulating cholesterol and lower levels of several nutrients (such as vitamin B12) than the meat eaters, which could explain these findings, the authors suggested.
The study paper said, “Future work should include further measurements of circulating levels of cholesterol subfractions, vitamin B12, amino acids, and fatty acids in the cohort to identify which factors might mediate the observed associations.
“Additional studies in other large scale cohorts with a high proportion of non-meat eaters are needed to confirm the generalisability of these results and assess their relevance for clinical practice and public health.”
Stephen Burgess, of the MRC Biostatistics Unit at the University of Cambridge, commented on the study for the Science Media Centre in London. He said, “While the differences observed were small in magnitude, this study suggests that taking up a vegetarian diet may not be universally beneficial for all health outcomes.
“When considering cardiovascular health, switching to a vegetarian diet should not be seen as an end in itself but should be considered alongside additional dietary and lifestyle changes. In isolation, the benefit of switching to a meat-free diet is not likely to be substantial.”
The study, funded by the UK Medical Research Council and the Wellcome Trust’s Our Planet Our Health team, had a number of limitations, including that diet groups were self reported and the study was limited mainly to white European participants.