Why Cutting Back on Fat Isn’t Enough to Help the Heart

Health experts have given us a very clear message about fat in recent years — they warn us that animal fats can build up within our heart vessel walls and lead to plaques that can cause heart attacks, strokes and other heart problems.

But not all fats are equal, and there’s growing evidence that healthy fats — the ones found in plants, nuts and fish known as polyunsaturated fats — can actually protect the heart and dramatically lower risk of heart problems. In a study published in the Journal of the American Heart Association, researchers calculate exactly how much each type of fat can contribute to heart disease deaths.

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Dr. Dariush Mozaffarian, dean of the Tufts Friedman School of Nutrition and Science Policy, and his colleagues found that eating too little vegetable oils contributes to more heart-related deaths than eating saturated fats. In fact, only 3.6% of global heart deaths can be attributed to eating too much saturated fat, while just over 10% of heart deaths can be traced to eating too little plant oils — a three-fold difference. The study included detailed dietary information from studies involving 3.8 billion people in 186 countries.

“The findings suggest that in order to have the biggest impact on heart disease, we should be focusing on increasing healthful fats,” says Mozaffarian. “There is still benefit in reducing animal fats but it’s important to think about not just reducing the bad fats in the diet but increasing the good things as well in order to improve our health.”

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While numerous studies support the benefits of eating more polyunsaturated fat, Mozaffarian notes that dietary guidelines, including the most recent revision released by the U.S. government, continue to stress limiting saturated fats rather than increasing healthy fats. The latest recommendations urge Americans to eat no more than 10% of their daily calories from saturated fats, which include coconut and palm oils as well as red meats and dairy products. But history shows that when people lower the amount of saturated fat they eat, they tend to replace it with carbohydrates, which can turn into triglycerides and get stored as fat.

Mozaffarian’s study shows that for this reason, just reducing saturated fat is important, but not enough. Countries where people eat more plant and vegetable oils had fewer heart deaths due related to consuming too little polyunsaturated fat, while countries such as Russia, Germany and Egypt had the greatest burden of heart deaths traced to inadequate amounts of vegetable oils.

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Overall, the data also showed that heart-related deaths that could be blamed on saturated fats have dropped by 21% from 1990 to 2010, while deaths because people are eating too few healthy fats only declined by 9%. Deaths due to increased consumption of trans fats, found in many processed foods, however, went up by 4%. That strongly suggests that nutrition about fats needs to be more refined so people are aware of not just the dangers, but the potential benefits of different types of fats, says Mozaffarian.

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“Our findings are consistent with the recent dietary guidelines to eliminate industrial trans fats,” says Mozaffarian, “and to replace saturated fat with polyunsaturated fat. What’s missing is the crucial advice that just increasing healthy vegetable oils can substantially reduce heart disease risk even further.”