The Benefits of Polyunsaturated Fats in Your Diet

How hard is it to get the benefits of polyunsaturated fats in your diet?


How hard is it to get the benefits of polyunsaturated fats in your diet?

To get the benefits of polyunsaturated fats, it’s wise to eat a diet that replaces butter and margarine with oils, but it’s too early to know if that can curb inflammation.

“Inflammation plays two key roles in coronary heart disease,” explains Penny Kris-Etherton of Pennsylvania State University.

First, it helps build the plaque that narrows arteries. The process starts when the immune system mobilizes to heal an “injury” in the artery wall, often caused by oxidized LDL cholesterol. Smoking, high blood pressure, and high blood sugar can also damage the arteries and lead to plaque buildup.

“And every single step of the way, inflammatory signals produced in the plaque fuel the process,” says Kris-Etherton. After decades, the plaque—now filled with cholesterol, calcium, and cell debris—gets covered with a fibrous cap of smooth muscle cells. Then, once again, inflammation wreaks havoc.

More evidence to support the benefits of polyunsaturated fats

Dutch researchers fed 13 overweight men 3½ tablespoons of either butter or a mix of polyunsaturated-fat-rich sunflower and safflower oils (all baked into muffins).

Compared to the saturated fats in the butter, consumption of polyunsaturated fats led to lower levels of markers of inflammation such as interleukin-6, TNF-alpha, and soluble vascular cell adhesion molecules (sVCAM). All are involved in the accumulation of plaque in artery walls.

Martijn Katan, emeritus professor of nutrition at Vrije Universiteit Amsterdam sums it up by noting that the experiments that replaced saturated fat from foods like butter and high-fat dairy or meat with polyunsaturated fats from corn or soybean or sunflower oil were not perfect. But they consistently showed a fall in coronary heart disease exactly to the extent that you would expect from the fall in LDL cholesterol.

In fact, Professor Katan points to a meta-analysis of trials which found that people who replaced saturated fats with polyunsaturated fats had a 19 percent lower risk of heart disease. (That was after removing a study of trans-fat margarine from the meta-analysis that had been misclassified as a study of polyunsaturated fats.)

Studies on the Mediterranean diet 

In another study, Italian researchers assigned 180 people with the metabolic syndrome to eat either a Mediterranean diet (rich in fruits, vegetables, whole grains, beans, and olive oil and low in saturated fat) or to follow advice on “healthy food choices.”

After two years, the Mediterranean group had lower levels of several inflammatory markers, but that may be because they also lost more weight.

In a Spanish study of roughly 100 people at risk for cardiovascular disease, inflammatory markers dropped more in those assigned to eat a Mediterranean diet with extra olive oil or nuts than in those who ate the same diet without extra olive oil or nuts. But other studies have not found this.

What to do

Replace butter with oils or with a margarine that’s low in saturated fat. Replace red meat, cheese, cream, and other foods that are rich in saturated fats with fish, nuts, and soy foods.

The bottom line

Replacing foods high in saturated fats with foods that are rich in polyunsaturated fats is smart, even if it doesn’t change your inflammatory markers one iota, points out Alice Lichtenstein, director of the Cardiovascular Nutrition Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.

And what if it turns out there are limited benefits of polyunsaturated fats in your site? “Can you change inflammation with diet?” asks Lichtenstein. “The data are equivocal. You can change it by losing weight. And there are lots of other good reasons for the majority of Americans to lose weight.”

Sources: J. Nutr. doi:10.3945/jn.110.136432; N. Engl. J. Med. 352: 1685, 2005; JAMA 292: 1440, 2004; Am. J. Clin. Nutr. 89: 248, 2009; Nutr. Metab. Cardiovasc. Dis. 21 Suppl 1: S14, 2011; Br. J. Nutr. 97: 1144, 2007.

This post was originally published in 2012 and is updated regularly.