Eating animal fat increases stroke risk — while vegetable fat may decrease it

Eating high amounts of red meat and animal fat can be bad for your heart, but vegetable fat may not be as bad. According to a new study, vegetable fat may actually decrease the risk of stroke. However, the findings are still preliminary, and the study has one big caveat: almost all participants were white.

It’s the first study to comprehensively analyze the impact on stroke risk from different types of fat, the study authors say, and the findings are intriguing.

“Our findings indicate the type of fat and different food sources of fat are more important than the total amount of dietary fat in the prevention of cardiovascular disease including stroke,” said Fenglei Wang, Ph.D., lead author of the study and a postdoctoral fellow in the department of nutrition at Harvard’s T.H. Chan School of Public Health in Boston.

Researchers investigated data gathered over 27 years from over 117,000 participants in the Nurses’ Health Study (1984-2016) and Health Professionals Follow-up Study. At the beginning of the study (and every 4 years) participants were asked to complete food frequency questionnaires that included that amount and type of fat in their diets over the previous year. They split the participants into 5 groups (or quintiles) based on how much animal and vegetarian fat they consumed. Although self-reporting is not entirely reliable, it’s one of the best options researchers have for tracing the eating habits of a large number of participants.

“Among those who consumed the most non-dairy animal fat (in the highest quintile of non-dairy animal fat), the non-dairy animal fat intake is ~17% of total energy and vegetable fat intake is ~ 13%; among those who consumed the most vegetable fat (in the highest quintile of vegetable fat), the non-dairy animal fat intake is 10% and vegetable fat intake is ~ 20%,” Wang told ZME Science.

Out of all these participants, 6,189 had a stroke. Those in the highest quintile of non-dairy animal fat were 16% more likely to experience a stroke than those in the lowest quintile. Dairy products (such as cheese, butter, or milk) did not appear to influence the risk of stroke. Meanwhile, participants in the quintile that ate the most vegetable fat were 12% less likely to experience a stroke compared to those who ate the least.

“Our interpretation is that higher intake of non-dairy animal fat is associated with higher stroke risk, whereas higher vegetable fat intake is associated with lower stroke risk,” Wang explained for ZME Science.

However, the participants may not be representative of the entire population. Of them, 63% were women, all were free of heart diseases and cancer at enrolment, and most notably, 97% of them were white.

“Our findings might not be generalizable to other populations. Further studies are needed to investigate these associations in other demographics,” Wang explains.

There’s also a problem of not knowing what types of animal or vegetable fat participants consume. Researchers didn’t have access to this detailed information, which would be useful in evaluating this association, says Wang.

“For example, we did not observe associations between saturated fat and stroke risk. But the associations might differ for saturated fat from vegetable, dairy, or non-dairy animal foods. For future steps, finer categories will help us better understand how types and sources of fat are associated with the disease risk.”

Although these are still preliminary findings, the researchers do offer a suggestion: that we eat less animal fat, especially fat associated with red meat.

“We would recommend the general public to reduce consumption of red and processed meat, minimize fatty parts of unprocessed meat if consumed, and replace lard or tallow (beef fat) with non-tropical vegetable oils such as olive oil, corn or soybean oils in cooking to lower their stroke risk,” Wang concludes.

“Many processed meats are high in salt and saturated fat, and low in vegetable fat. Research shows that replacing processed meat with other protein sources, particularly plant sources, is associated with lower death rates,” said Alice H. Lichtenstein, D.Sc., FAHA, the Stanley N. Gershoff professor of nutrition science and policy at Tufts University in Boston, and lead author of the American Heart Association’s 2021 scientific statement, Dietary Guidance to Improve Cardiovascular Health, where the new study will be presented.

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