Vegan and vegetarian diets are linked to a lower risk of heart disease, but may increase the risk of stroke, a new study suggests.
People who follow plant-based diets have a 22% lower risk of heart disease than meat eaters, researchers from the University of Oxford found, while pescatarians have 13% reduced risk of heart disease.
However, the study suggests vegetarians and vegans are a fifth more likely to suffer a stroke than meat eaters.
The authors of the study, who looked at 48,188 people with no history of heart disease or stroke, suggested this heightened risk may be partly due to a lack of vitamins such as B12 or vitamin D, in the plant-based diet.
The study, which was published in the British Medical Journal (BMJ), looked at three groups of people: meat eaters (24,428 people), pescatarians (7,506 people), and vegetarians and vegans (16,254 people).
They were followed over a period of 18 years and their health was checked. During this time, there were 2,820 cases of ischaemic heart disease recorded – which is when your coronary arteries become narrowed by a build-up of fatty material within their walls – and 1,072 cases of stroke among the overall group.
After adjusting for factors that might influence the results, researchers found fish eaters had a 13% reduced risk of heart disease than meat eaters, while vegetarians and vegans had a 22% lower risk. This was equivalent to 10 fewer cases of ischaemic heart disease in vegetarians and vegans than in meat eaters per 1,000 people over 10 years.
The authors partly attributed this to lower body mass index and lower rates of high blood pressure, high blood cholesterol, and diabetes with these diets.
“Vegetarians and vegans in the study have lower circulating levels of several nutrients.”
But the researchers also found vegetarians and vegans had a 20% higher rate of stroke compared to meat eaters, which is equivalent to three more cases of stroke per 1,000 people over 10 years. This was mostly due to a higher rate of haemorrhagic stroke – the type caused by bleeding in or around the brain.
The team said the increased risk of stroke could be down to lower levels of vitamins among the vegetarians and vegans in the study, but cautioned that further investigation was needed.
“Vegetarians and vegans (in the study) have lower circulating levels of several nutrients (eg, vitamin B12, vitamin D, essential amino acids, and long chain n-3 polyunsaturated fatty acids), and differences in some of these nutritional factors could contribute to the observed associations,” the researchers said.
They also suggested that the low blood levels of total cholesterol among vegetarians and vegans may play a role.
Commenting on the study, Tracy Parker, senior dietitian at the British Heart Foundation, said: “Whilst this is an interesting finding, this study is observational and doesn’t provide us with enough evidence, so more research in this area would be needed.
“Whether you’re a committed carnivore, a veggie, or a vegan, one way to reduce your risk of heart and circulatory diseases is to ensure you’re eating a balanced diet, packed with plenty of fruit and vegetables, wholegrains, beans, lentils, nuts and seeds. For those who do eat meat, cutting back to less than 90g of red or processed meat a day is advised.”