Vegetarians have a higher risk of stroke than those who eat meat, study finds

Vegetarians have a higher risk of stroke than those who enjoy a good steak, a major study has found.

The Oxford University research, published in the BMJ, suggests that a meat-free diet may cause lower blood levels of total cholesterol, and reduce intake of vitamins which protect against such attacks.

The study, which tracked almost 50,000 Britons for 18 years, found vegetarians and vegans had a 20 per cent higher risk of stroke than those who eat meat.

Most of the increased risk was due to a higher rate of hemorrhagic stroke.  These occur when blood from an artery starts bleeding into the brain.

Vegetarians and vegans in the study had lower circulating cholesterol and lower levels of key nutrients - such as vitamin B12 and D - which could explain the link, researchers said.

However, those avoiding meat had a significantly lower chance of heart attacks, the study found.

Vegetarians were found to have a 22 per cent lower risk of heart disease, in total, while those eating fish but no meat had a 13 per cent lower risk. Experts said some of the difference might be linked to lower weight, blood pressure, and fewer cases of conditions like diabetes among those shunning meat.

Every year, around 100,000 people in the UK will suffer a heart attack.

And around 100,000 more will experience a stroke.

Most cases are ischaemic, where the blood supply is stopped, as the result of heart disease.

But 15 per cent of cases are hemorrhagic, where a weakened blood vessel supplying the brain suddenly bursts, as the result of an aneurism or raised blood pressure.

The extra stroke risk for vegetarians is equivalent to three more cases of stroke per 1000 people over 10 years.  And their reduced heart disease risk is equal to 10 fewer cases per 1000 people over the same period.

There were 2,820 cases of heart disease and 1,072 cases of stroke during the study period,  including 300 cases of hemorrhagic stroke.

Researchers said said vegetarians and vegans in the study had lower circulating levels of several nutrients, including vitamin B12, vitamin D, essential amino acids and long chain  polyunsaturated fatty acids which might contribute to the increased stroke risk.

Estimates suggest there are now around 1.7 million vegetarians and vegans in the UK.

Lead author Dr Tammy Tong, from the Nuffield Department of Population Health, Oxford University said further large studies were needed to confirm the findings, before advice was offered to the public.

Dr Stephen Burgess, Group Leader at the MRC Biostatistics Unit, University of Cambridge, said:

“In this study, after accounting for alternative risk factors, while risk of heart disease was lower in vegetarians, risk of haemorrhagic stroke was higher in vegetarians. Heart disease is more common than haemorrhagic stroke, so vegetarians did have better cardiovascular health outcomes overall despite having higher risk of haemorrhagic stroke.”

“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.”

In a linked editorial, Professor Mark Lawrence at Deakin University, Australia, suggests that the study’s stroke risk should be kept in perspective. “It is based on results from just one study and the increase is modest relative to meat eaters,” he said.