• People on a plant-based diet, like vegetarians and vegans, have a lower risk of heart disease, but higher risk of stroke.
  • This may be partly because non-meat-eaters have lower cholesterol, but also lower levels of nutrients like vitamin B12 and vitamin D, according to researchers. It's unclear exactly how it works. 
  • People in the study who ate fish instead of meat, however, had lower risks of heart disease without the increase in stroke. 
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As meatless diets are becoming increasingly popular, researchers are studying whether they may have unexpected health risks. Case in point: Vegetarians and vegans, while they have lower rates of heart disease, may face a greater risk of stroke, according to a new study published Wednesday in The BMJ. 
For the study, researchers from Oxford University looked at the dietary habits and health of 48,188 adult men and women in the UK over the course of 18 years. 
They found that participants with a plant-based diet, including both vegetarians and vegans, had lower rates of heart disease but higher rates of stroke than meat eaters.
Non-meat-eaters were at a significantly higher risk for a particular kind of stroke — a hemorrhagic stroke, which occurs when a blood vessel ruptures and begins bleeding into the brain. 
People who avoided meat but ate fish, however, had a lower risk of heart disease without increasing their risk for stroke. More research is needed to understand just what kind of diet is best for protecting your health.
Read more: Healthy plant-based diet tied to lowered heart risk

Low cholesterol from eating less meat may mean better overall heart health

The results of this study are consistent with previous research that found a significantly lower risk of heart disease among vegetarians — as much as 24% lower death rates from heart disease, according to one study. 
Researchers suspect this is partly caused by lower levels of cholesterol in the blood, which typically come from a meat-free diet. However, that doesn't entirely explain the difference, and data suggests eating more fruits, vegetables, legumes, and fiber also provide health benefits. 
Researchers also found that vegetarians and vegans were less likely to smoke and more likely to exercise regularly. They also reported lower rates of high blood pressure, cholesterol problems, diabetes, and long-term illnesses. 
But even after adjusting for lifestyle factors like smoking, exercise, and body mass index, vegetarians and vegans still had lower rates of heart disease. 

Cholesterol and other nutrients in animal protein may protect against brain hemorrhage

This new research supports earlier findings that low cholesterol levels, though typically thought of as a healthy thing, may somehow cause a higher risk of hemorrhagic stroke. 
In addition to low cholesterol levels, vegetarians and vegans also had lower levels of vitamin B12, vitamin D, and amino acids than meat eaters, which may be related to their higher stroke risk. 
Researchers concluded that more studies are needed to test how those nutrients might play a role in preventing strokes.