"Overall, the present study has shown that United Kingdom adults who were fish eaters or vegetarians had lower risks of ischaemic heart disease than meat eaters, but that vegetarians had higher risks of stroke", the researchers said.
The participants - who were grouped by meat-eaters (24,428), pescetarians (7,506), and vegetarians, including vegans (16,254) - had no history of CHD or stroke.
"It does seem that the lower risk of coronary heart diseases does exceed the higher risk of stroke, if we look at the absolute numbers", said lead researcher Tammy Tong, a nutritional epidemiologist at the Nuffield Department of Population Health at the University of Oxford.
For heart disease, those who ate fish had a 13% less chance of developing heart disease compared with meat-eaters while vegetarians and vegans had 22% lower risk.
And the absolute reduction in the risk for heart disease and increased risk for stroke is modest, she said.
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.
"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".More news: Nicki Minaj retires from music, gives reason
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It's unclear why the research found the higher risk of stroke in vegetarians, but those who conducted the study suggest it's due to "very low cholesterol levels or very low levels of some nutrients", like vitamin B12. More concerning is getting enough Vitamin D, the so-called "sunshine vitamin", which is important for our bones, teeth, and immune system, and can be hard to include in your diet if you are vegetarian, and very hard if you are vegan. Pescatarian diets are often similar to vegetarian diets, but with the inclusion of seafood like fish and shrimp. The report was published September 4 in the BMJ journal.
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.
They added: "Vegetarian and vegan diets have become increasingly popular in recent years, partly due to perceived health benefits, as well as concerns about the environment and animal welfare".
To reach that finding, Tong and her colleagues collected dietary, health and demographic data from about 48,000 United Kingdom adults without a history of heart problems, about 24,400 of whom ate meat and 7,500 of whom ate fish but not meat. They were ten teamed into meat-eaters, pescetarians, and vegetarians including vegans.
The study followed more than 48,000 participants in the United Kingdom for almost 18 years.
In addition to diet, participants also were asked about lifestyle, medical history, socioeconomic status, physical activities, alcohol consumption and smoking, Body mass index also was calculated.
Not getting enough of these nutrients may increase the risk of certain health problems, she said. "For those who do eat meat, cutting back to less than 90g of red or processed meat a day is advised".