Vegetarians have higher risk for stroke, lower heart disease risk

People who follow vegetarian or vegan diets may have lower odds for heart disease but higher chances of having a stroke, compared to meat eaters, a large UK study suggests.

Researchers followed 48,188 middle-aged adults without any history of heart attacks or strokes for about 18 years. During this time, 2,820 people developed coronary artery disease that can lead to heart attacks; 519 people had ischemic strokes, the most common kind, which occur when a clot blocks an artery carrying blood to the brain; and 300 people had hemorrhagic strokes, which are caused by a ruptured blood vessel in the brain.

Vegetarians - including vegans, who avoid eggs and dairy - were 22% less likely to develop coronary artery disease than meat eaters. This is the equivalent of 10 fewer cases of artery disease per 1,000 people over a decade among vegetarians compared to meat eaters, researchers calculated.

However, vegetarians and vegans were 20 percent more likely than others to have a stroke - particularly a hemorrhagic stroke. This translates over 10 years to roughly three more strokes per 1,000 people in vegetarians than in meat eaters.

“Both fish eaters and vegetarians had on average lower BMI, and lower rates of high blood pressure, high blood cholesterol and diabetes compared with meat eaters, which might explain the lower risk of heart disease in both fish eaters and vegetarians since these are all established risk factors for heart disease,” said study leader Tammy Tong, a nutritional epidemiologist at the University of Oxford in the UK.

“The reason for higher risk of stroke in vegetarians is less clear, but some recent evidence has suggested that while low cholesterol levels (are) protective against both heart disease and ischemic stroke, very low cholesterol levels might be linked to a higher risk of hemorrhagic stroke, the subtype that was found to be higher in the vegetarians,” Tong said by email.

The elevated stroke risk among vegetarians and vegans was due to 43% increased odds of a hemorrhagic stroke; there was no meaningful difference in ischemic stroke rates between this group and meat eaters.

There also was no meaningful difference in risk of heart attacks based on eating habits, researchers report in The BMJ.

Researchers assessed eating habits with questionnaires at the start of the study. Some participants completed questionnaires again an average of 14 years later.

People who ate meat - regardless of whether they also ate fish, dairy, or eggs - were classified as meat eaters. Their ranks totaled 24,428 at the start of the study and 96% remained meat eaters based on the follow-up dietary questionnaires.

Another 7,506 people ate fish, but no meat at the start of the study, and 57% of these participants who completed the second dietary questionnaires remained fish eaters.

An additional 16,254 people started out as vegetarians or vegans, eating no meat or fish, and 73% still abstained based on the follow-up dietary questionnaires.

“Dietary guidelines recommend increasing our intake of whole nutritious foods such as fruits and vegetables and reducing intake of ultra-processed foods and beverages,” said Mark Lawrence, a public health and nutrition researcher at Deakin University in Melbourne, Australia, who co-authored an editorial accompanying the study.

“Increasingly, national dietary guidelines around the world are recognizing plant-based diets for their environmental sustainability as well as health benefits,” Lawrence said by email. “Though, shifting towards plant-based dietary patterns for reasons of personal or planetary health does not necessarily mean becoming a vegetarian.”