DHAKA: Vegetarians have a lower risk of coronary heart disease than meat-eaters but may be at greater risk of having a stroke, researchers from Oxford University have found.
The study, however, could not prove whether the results were down to diet or some other aspect of the participants’ lifestyle.
Adopting a plant-based diet, or at least cutting out meat, has been encouraged by major scientific bodies including the World Health Organisation for its benefits to personal health and the environment.
An increase in alternative meat and dairy foods made without animals is one of the defining food trends in recent years. However, as meatless diets take off, researchers say further scrutiny is important.
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“Vegetarian and vegan diets have increased hugely in popularity over the past years … but we actually know very little about the potential health benefits or hazards of these diets,” said Dr Tammy Tong, lead author of the study.
The study, published in medical journal The BMJ, followed 48,000 people with no previous history of heart disease, angina and stroke between 1993 and 2001 before a follow-up survey in 2010, reports South China Morning Post.
Participants were asked questions on their lifestyle and medical history as well as their diet, allowing the team to classify individuals as meat-eaters, vegetarians, vegans or pescatarians (eat fish but not meat). Some of these questions were asked again in 2010 and participants were reclassified if they had switched diet. As the study involved very few vegans, these individuals were grouped with vegetarians in the analysis.
The results reveal that once factors including age, sex, smoking status and socioeconomic status were taken into account, pescatarians had a 13 per cent lower risk of coronary heart disease than meat-eaters, while vegetarians had a 22 per cent lower risk. Meanwhile, vegetarians had a 20 per cent higher risk of having a stroke than meat-eaters. There was no clear effect for pescatarians.
Overall, the findings mean that over a 10-year period there would be 10 fewer cases of coronary heart disease in vegetarians than in meat-eaters per 1,000 people, and three more cases of stroke.
While the latest study does not prove that meat-eating or vegetarianism is behind the differences in risk, Tong said the association between a vegetarian diet and coronary heart disease supports previous research.
“It was likely that the lower risk in both pescatarians and vegetarians are related to the fact that they have lower cholesterol, but also a lower BMI, lower blood pressure and also a lower rate of diabetes,” she said. No “statistically significant” conclusions could be drawn for vegans, as the group surveyed was too small.
The health of participants was followed through medical records until March 2016, during which time there were 2,820 cases of coronary heart disease and 1,072 cases of stroke.
Tong suggested one reason vegetarians might have a higher risk of stroke could be due to lower levels of cholesterol, which could increase the risk of certain types of stroke. Alternatively, the association might be down to vegetarians having lower levels of certain nutrients, such as vitamin B12.
However, others said the data suggested that was unlikely. “It may well be that people who follow alternative diets are less likely to take blood-pressure-lowering medication for hypertension and as a consequence suffer a stroke,” suggested Professor Tom Sanders from King’s College London.
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The study has limitations, including that it is based on self-reporting, and that not all participants answered questions in 2010. The study also mainly involved white people living in the UK, a culture that has traditionally been rooted in eating meat, as opposed to countries with a longer history of meat-free cuisine, such as India.
Dr Frankie Phillips, a dietitian from the British Dietetic Association, said vegetarians and vegans should not be alarmed by the results, stressing that the study does not show cause and effect.
Instead, Phillips said, everyone could benefit from eating more plants.
“That doesn’t necessarily mean becoming completely vegan or vegetarian,” she said, adding that having a diet that includes a wide range of foods ensured it provided all the necessary nutrients.
The study has touched a nerve among the global meat-free community, who have questioned the way it has been interpreted and sensationalised.
“The headline is what most people are going to see and carry to the grave … every time they meet a vegetarian or vegan in future, regardless of how healthy they are, they’ll say, ‘You’ll probably die of a stroke anyway. I’m just going to eat my meat,’” says YouTuber Mic the Vegan in a video dissecting the media coverage of the study.
BDST: 1212 HRS, SEP 13, 2019