Experts disagree on which fats should be consumed and in what exact proportions

April 29, 2013

If you’re confused about fats these days, you’re in good company. With much research being published in recent years, even experts have a hard time agreeing about which fats we should consume, and in what exact proportions, to improve our health and prevent chronic disease. ¶ Here’s what the strongest evidence says about healthful choices.

Are saturated fats still “bad”? Yes, the best available evidence suggests that saturated fat found in such food as meat, full-fat cheese and cake is still worse for you than the unsaturated fat in vegetable oils, nuts and avocados. According to a recent report from the United Nations, there is convincing evidence that replacing saturated fat with polyunsaturated fat reduces the risk of heart disease. And a 2012 review of studies by the independent Cochrane Collaboration found that replacing saturated fat with unsaturated fat lowered the risk of cardiovascular events, such as heart attacks and strokes.

There’s an important caveat: When cutting saturated fats, substitute with healthful alternatives, not refined carbohydrates (which are found in such items as white bread, pizza and snack foods). Otherwise, you probably won’t reduce your risk of heart disease and may well increase it, according to the U.N. report.

Which are better: mono- or polyunsaturated oils? Nutritionists can’t agree about this one, though they do agree that unsaturated fats are better than saturated ones.

On one hand, there is plenty of evidence to support the health benefits of the Mediterranean diet, which calls for generous amounts of olive oil, a mostly mono-unsaturated fat. But when researchers make direct comparisons of mono- and polyunsaturated fats, they generally find stronger evidence of a cardio-protective effect for polyunsaturated fat, found abundantly in safflower, soybean and sunflower oils.

Should I consider the omega-6 to omega-3 ratio? Omega-6 and omega-3 are two types of polyunsaturated fat — a “good” fat. Many studies suggest that diets rich in two omega-3 fats — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both found in high levels in fish — are linked to lower rates of cardiovascular disease.

To maximize those heart benefits, some experts recommend limiting omega-6 fat found in sources such as corn oil and soybean oil, which have become common in the human diet only in the past 100 years or so, and getting more omega-3s from traditional sources such as fish.

According to some experts, getting too much omega-6 fat might be harmful because it might promote inflammation, which can lead to cardiovascular and other problems, and block the beneficial anti-inflammatory effects of omega-3s. While the jury is still out, recent evidence suggests that omega-6 fats may not in fact increase inflammation.

Can fats affect cancer risk? It’s body fat, not the fat in your food, that you should worry about most when it comes to cancer risk. According to a comprehensive 2007 review of studies by the World Cancer Research Fund and the American Institute for Cancer Research, there is no strong, convincing evidence that eating more or less total fat, or any individual type of fat, has any significant effect on cancer.

Since obesity is one of the few diet-related factors that is strongly and consistently linked to a risk of cancer, the best diet for cancer prevention may be one that can help you maintain a healthy weight.

Are coconut and palm oil good for you or not? The consensus is that those oils are loaded with cholesterol-raising saturated fat. But dissenters say there is emerging evidence that tropical oils, especially coconut oil, behave differently in the body than animal-derived saturated fats and might have underappreciated health benefits.

What to do? Your best bet for the time being is to limit consumption of those oils but keep an open mind.

How does processing affect the benefits and risks of oil? Oils may be processed using mechanical pressing or heat and chemicals, which can affect its flavor and potentially its health benefits.

Olive oil, for example, is prized for the complex flavors that are strongest when the oil is fresh from the fruit. That’s why higher grades (extra virgin and virgin) are given only to mechanically pressed oil that hasn’t been treated with heat or chemicals. Those premium oils contain higher quantities of antioxidants, which are eliminated or reduced from lesser oils during processing.

Processed or refined oils do have some pluses, though. They are less expensive, last longer and can hold up to such high-heat uses as frying without smoking and breaking down into potentially toxic compounds. On the minus side, refined oils may have been extracted with hexane, an industrial solvent. But at very low exposure levels through food, there is no reason to think that this should be a health problem, says toxicologist John L. O’Donoghue of the University of Rochester School of Medicine and Dentistry.

Copyright 2013. Consumers Union of United States Inc.

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