People who eat vegan and vegetarian diets have a lower risk of heart disease and a higher risk of stroke, a major UK study of 48,000 people over 18-years found. They had 10 fewer cases of heart disease and three more strokes per 1,000 people compared with the meat-eaters.
The research cannot prove whether the effect is down to their diet or some other aspect of their lifestyle.
Diet experts said, whatever people's dietary choice, eating a wide range of foods was best for their health.
It analyses data from the EPIC-Oxford study, a major long-term research project looking at diet and health. Half of participants, recruited between 1993 and 2001, were meat-eaters, just over 16,000 vegetarian or vegan, with 7,500 who described themselves as pescatarian (fish-eating).
They were asked about their diets, when they joined the study and again in 2010. Medical history, smoking and physical activity were taken into account,
Altogether, there were 2,820 cases of coronary heart disease (CHD) and 1,072 cases of stroke – including 300 haemorrhagic strokes, which happen when a weakened blood vessel bursts and bleeds into the brain. The pescatarians were found to have a 13% lower risk of CHD than the meat-eaters, while the vegetarians and vegans had a 22% lower risk.
But those on plant-based diets had a 20% higher risk of stroke. The researchers suggested this could be linked to low vitamin B12 levels but said more studies were needed to investigate the connection. It is also possible that the association may have nothing to do with people's diets and may just reflect other differences in the lives of people who do not eat meat.
Objective: To examine the associations of vegetarianism with risks of ischaemic heart disease and stroke.
Design: Prospective cohort study.
Setting: The EPIC-Oxford study, a cohort in the United Kingdom with a large proportion of non-meat eaters, recruited across the country between 1993 and 2001.
Participants: 48 188 participants with no history of ischaemic heart disease, stroke, or angina (or cardiovascular disease) were classified into three distinct diet groups: meat eaters (participants who consumed meat, regardless of whether they consumed fish, dairy, or eggs; n=24 428), fish eaters (consumed fish but no meat; n=7506), and vegetarians including vegans (n=16 254), based on dietary information collected at baseline, and subsequently around 2010 (n=28 364).
Main outcome measures: Incident cases of ischaemic heart disease and stroke (including ischaemic and haemorrhagic types) identified through record linkage until 2016.
Results: Over 18.1 years of follow-up, 2820 cases of ischaemic heart disease and 1072 cases of total stroke (519 ischaemic stroke and 300 haemorrhagic stroke) were recorded. After adjusting for sociodemographic and lifestyle confounders, fish eaters and vegetarians had 13% (hazard ratio 0.87, 95% confidence interval 0.77 to 0.99) and 22% (0.78, 0.70 to 0.87) lower rates of ischaemic heart disease than meat eaters, respectively (P<0.001 for heterogeneity). This difference was equivalent to 10 fewer cases of ischaemic heart disease (95% confidence interval 6.7 to 13.1 fewer) in vegetarians than in meat eaters per 1000 population over 10 years. The associations for ischaemic heart disease were partly attenuated after adjustment for self reported high blood cholesterol, high blood pressure, diabetes, and body mass index (hazard ratio 0.90, 95% confidence interval 0.81 to 1.00 in vegetarians with all adjustments). By contrast, vegetarians had 20% higher rates of total stroke (hazard ratio 1.20, 95% confidence interval 1.02 to 1.40) than meat eaters, equivalent to three more cases of total stroke (95% confidence interval 0.8 to 5.4 more) per 1000 population over 10 years, mostly due to a higher rate of haemorrhagic stroke. The associations for stroke did not attenuate after further adjustment of disease risk factors.
Conclusions: In this prospective cohort in the UK, fish eaters and vegetarians had lower rates of ischaemic heart disease than meat eaters, although vegetarians had higher rates of haemorrhagic and total stroke.
Tammy Y N Tong, Paul N Appleby, Kathryn E Bradbury, Aurora Perez-Cornago, Ruth C Travis, Robert Clarke, Timothy J Key
[link url="https://www.bbc.com/news/health-49579820"]BBC News report[/link]
[link url="https://www.bmj.com/content/366/bmj.l4897"]BMJ abstract[/link]