Studies that have looked at whether consuming a diet rich in monounsaturated fatty acids (MUFAs) leads to reduced risk of heart disease have shown mixed results. But according to new findings from Harvard T.H. Chan School of Public Health, it makes a difference whether the MUFAs come from plant or animal products. In the first study to separately examine types of MUFA sources in relation to heart disease, researchers found that while MUFAs from plant-based foods such as olive oil and nuts do indeed lower risk, MUFAs from animal products such as red meats and dairy do not provide benefits.

The study was published on March 16, 2018 in the American Journal of Clinical Nutrition.

“Previous studies did not differentiate the source of MUFAs. Animal products, such as red meats and high-fat dairy also contribute to MUFA intake, although these foods are also high in saturated fats. This might explain why there have been inconsistent findings regarding total MUFA intake in relation to coronary heart disease risk,” said lead author Qi Sun, assistant professor in the Department of Nutrition. “Overall, our data suggest that MUFAs from plant-based foods are beneficial and should be used in replacement of fats from animal sources.”

Using dietary information from 63,442 women participating in the Nurses’ Health Study and 29,942 men from Health Professionals Follow-Up Study, the researchers used statistical modeling to estimate the effects of substituting harmful dietary components such as saturated fats, refined carbohydrates, or trans fats with an equal number of calories from MUFAs of plant or animal sources (MUFA-Ps and MUFA-As).

The researchers found that heart disease risk was significantly lower when saturated fats, refined carbohydrates, or trans fats were replaced by MUFA-Ps, but not by MUFA-As.

Olive oil was the largest contributor of MUFA-Ps in study participants’ diets, followed by nuts, salad dressing, and oils from fried foods and baked goods. MUFA-As mainly came from red and processed meats.

Sun said that the findings suggests that MUFA intake, when primarily from animal product consumption, will not bring any health benefits because saturated fats and other nutrients in these foods largely negate them.

“We recommend focusing on diet quality rather than on specific nutrients or foods to reduce the risk of developing chronic diseases,” Sun said. “These findings underscore the importance of eating a diet that is largely plant-based.”

Supported by research grants UM1 CA186107, R01 HL034594, R01 HL35464, R01 HL60712, and UM1 CA167552 from the NIH. GZ is supported by a postdoctoral fellowship funded by Unilever R&D; FBH has received research support from the California Walnut Commission and Metagenics; QS was supported by ES021372 and ES022981 sponsored by the National Institute of Environmental Health Sciences.

Amy Roeder

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