TIME

Uh Oh, Unsaturated Fats May Not Be As ‘Good’ As We Thought

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Recent analyses don't support the current logic that foods rich in omega-3 fatty acids are far better for us than those with saturated fats, but that doesn't mean hamburgers are instantly healthier than lean cuts of salmon

Not all fats are created equal, especially when it comes to their effects on the heart. The good ones—like omega-3 fatty acids, which are found in salmon and other fish, and plant oils—tend not to gum up our heart vessels and cause plaques like the fats found in beef and pork and in dairy products do.

At least that’s what heart experts and nutritionist have been telling us, based on studies that linked the unhealthy saturated fats to higher rates of atherosclerosis (hardening of the arteries) and more vessel-clogging cholesterol in the blood. Studies also showed that people who ate more healthy unsaturated fats tended to have lower rates of heart disease than those who consumed diets higher in animal, or saturated, fats.

MORE: Fish: The Fountain of Youth?

But those analyses relied on self reports of what people ate, and such recollections can be unreliable. To address the problem of potential bias in self-reported diets, Dr. Rajiv Chowdhury at the University of Cambridge and his colleagues reviewed 32 studies that involved self-reports, but also analyzed 17 in which scientists measured omega-3 fatty acid levels in the participants’ blood, and 27 trials in which volunteers were randomly assigned to take omega-3 supplements. Overall, their review included data from 660,000 participants.

They found, as reported in the Annals of Internal Medicine, that higher omega-3 consumption had very little effect on heart disease rates. In fact, rates for people eating more of the omega-3 fatty acids, or taking omega-3 supplements, were similar to those who consumed lower amounts.

MORE: Omega-3 Supplements Don’t Lower Heart Disease Risk After All

More surprising, while people eating higher amounts of saturated fats did indeed have slightly elevated rates of heart problems, this increase wasn’t statistically significant, meaning that it could have been due to chance.

In another study, published in JAMA Internal Medicine, researchers studying a group of elderly patients with macular degeneration found that taking supplements of omega-3 fatty acids did not lower their risk of having heart events such as a heart attack or stroke, or dying from heart disease.

The idea that supplements may not be as helpful in preventing disease has been gaining momentum in recent years, as more in-depth analyses show that popping vitamin or nutrient pills has little effect on everything from lowering cancer rates to heart problems. In its latest analysis, in fact, the U.S. Preventive Services Task Force, a government-commissioned group that conducts period reviews of health data and recommendations, could not find strong evidence that supplements lower risk of heart disease or cancer, and advised consumers to swap out their pills for foods containing essential nutrients instead.

So is that burger now as healthy as a slab of salmon? Not quite. The results from Chowdhury’s team may reflect a bias as well, since the studies that are published tend to be those with extreme results. Since the studies did not compare the same people over time, but instead analyzed those with different levels of omega-3 consumption, it’s also possible that other factors affecting heart disease also played a role in the rates that each group showed.

Dr. Linda Van Horn, professor of preventive medicine at Northwestern University and a member of the nutrition committee of the American Heart Association, admits that the findings, particularly about saturated fat, raise some potentially valid questions that the committee will address at its next meeting. “This data will clearly be on the agenda of the nutrition committee, and I’m sure as we go forward in formulating the transitional nature of dietary recommendations, many of these points will be taken into consideration,” she says.

For now, however, she says that the results shouldn’t be interpreted as suggesting that current advice about reducing or avoiding saturated fat is completely wrong. It may just take the right kinds of studies to confirm that higher amounts of the fats can boost heart disease, while higher amounts of omega-3 fatty acids and lower heart events.

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