You may have read recent health studies that suggest saturated fat, or fat that comes from animal sources like dairy and meat, isn’t as harmful as we used to think. Seven meta-analyses over ten years demonstrated that the nutrient isn’t related to the development of chronic diseases like coronary heart disease and cardiovascular disease, which means that the long-standing notion that saturated fat is linked to chronic disease is now a controversial one.
Meanwhile, popular health-conscious communities like the Paleo movement have espoused a meat-heavy lifestyles, and rightfully point out that Americans got it wrong when they started seeking out low-fat, high-sugar foods.
But other experts, including nutrition researchers at the Harvard T.H. Chan School of Public Health, are pushing back on the notion that saturated fats have nothing to do with heart disease. A recent study lead by Harvard nutrition professor Frank Hu found that if people replace saturated fats with sources of polyunsaturated fat, monounsaturated fat and complex whole grains, they can lower their risk of heart disease significantly. But if people replace saturated fats with added sugars and refined carbs, as Americans tend to do, disease risk doesn't change.
"Our research does not exonerate saturated fat," Hu said in a statement. "In terms of heart disease risk, saturated fat and refined carbohydrates appear to be similarly unhealthful."
This research points out that it’s not enough to tell Americans to eat fewer sources of saturated fat. Instead, a message of healthy swaps — eating fats from fish, nuts, olive oil, avocados and seeds, instead of fatty meats — is what’s crucial.
"Dietary recommendations to reduce saturated fats should specify their replacement with unsaturated fats or with healthy carbohydrates, such as whole grains," said study co-author Yanping Li in a statement.
In other words, health experts shouldn't just tell people to stop eating a certain nutrient — they have to suggest things to replace it with.
The findings
To study the relationship between saturated fat and coronary heart disease, Hu and Li examined data from two large cohorts: 84,628 women from the Nurses’ Health Study, who were followed for 30 years, and 42,908 men from the Health Professionals Follow-Up Study, who were followed for 24 years. These participants were free of diabetes, cardiovascular disease and cancer at the beginning of the studies, and their diets were assessed with questionnaires every four years.
The researchers found that replacing just five percent of a calories from saturated fat with other kinds of fat or whole grains had a highly reduced risk of heart disease. Specifically, replacing saturated fat with polyunsaturated fat was linked to a 25 percent lower risk of heart disease. Monounsaturated fats were linked to a 15 percent lowered risk, and carbs from whole grains were linked to a 9 percent reduction in heart disease risk. These findings controlled for age, body mass index, smoking habits and exercise levels — things that are also known to influence cardiovascular disease risk.
While the research didn't examine the biological reasons that saturated fat plays a role in heart disease, it's believed that the nutrient increases levels of low-density lipoprotein cholesterol in the blood. This LDL cholesterol causes plaque to form in the arteries, which can lead to heart disease.
Changing the message
Hu’s involvement in the study is significant. He was also a part of this year’s Dietary Guidelines Advisory Committee, a panel of nutrition experts that convene every five years to advise the federal government on food policy. This year, the group continued on with their recommendation that saturated fats be no more than 10 percent of a person’s diet, but noted that the typical American eats much more than this.
Americans are still suffering the effects of the low-fat, high-carb nutrition recommendations of the 80s and 90s. Back then, experts advised people to skimp on all fats, including polyunsaturated and monounsaturated fats, in favor of starches.
This approach didn’t help people avoid cancer diagnoses, lose weight or prevent heart disease. And in fact, during the 30 or so years that low fat diets were the standard recommendation, Americans got fatter — mostly because they were filling up on refined grains like white bread and white rice instead.
Hu's study was published in the Journal of the American College of Cardiology.
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