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Fat facts and fat fiction

New research can help you make the best choices for your health

Consumer Reports on Health: February 2013

If you’re confused about fats these days, you’re in good company. With research coming in at breakneck speed 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 we review what the strongest evidence says about healthy choices to make at the grocery store and in your kitchen.

Are saturated fats still bad?

Yes, no lucky break here: saturated fat, found mainly in such food as meat, butter, and full-fat cheese or ice cream, is still worse for you than the unsaturated fat found in vegetable oils, nuts, and avocados. Replacing saturated fat with unsaturated fat lowered the risk of heart attacks, strokes, and other cardiovascualr events, according to a 2012 review by the independent Cochrane Collaboration. It concluded that for every 1,000 people in the studies, there were 77 such events for people on a regular diet compared with 66 for those on a reduced saturated-fat diet.

But there’s an important caveat: Make sure you replace saturated fat with with healthful alternatives, not refined carbohydrates (which are found in such items as white bread and many snack foods). Otherwise, you probably won’t reduce your risk of heart disease and may well increase it, according to a recent report from the United Nations. As Penny Kris-Etherton, Ph.D., distinguished professor of nutrition at Penn State University, puts it: "It’s not that saturated fats aren’t bad anymore. It’s that saturated fats and refined carbohydrates are equally bad."

Are monounsatured fats better than polyunsaturated ones?

There are two main kinds of unsaturated fats: monounsaturated and polyunsaturated. And not all experts agree that they are created equal. On the 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 monounsaturated fat. But when researchers directly compare the two kinds of fats, they generally find that polyunsaturated fat, found abundantly in safflower, soybean, and sunflower oils, seems to protect the heart more than monounsaturated fat does.

The American Heart Association recommends minimum dietary intake levels for certain polyunsaturated fats that the body has trouble synthesizing on its own. For example, it suggests getting at least 5 percent to 10 percent of fat calories from omega-6 polyunsaturated fats and eating at least two servings a week of fish rich in omega-3 polyunsaturated fats (see next question for more on omega-6 and omega-3 fats). But it makes no specific minimum recommendation for monounsaturated fat.

Choosing a variety of plant-based oils, plus low-mercury fish such as salmon twice a week, will help you meet the recommended intake levels and get plenty of all the "good" fats.

Should I consider the omega-6 to omega-3 ratio?

Omega-6 and omega-3 are two types of polyunsaturated fat—a "good" fat. Some experts think that it's important to get the right mix of the two fats to maximize their benefits and limit their potential risks.

Many studies suggest that diets rich in omega-3 fats—especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), found in high levels in fish—are linked to lower rates of cardiovascular disease. But some experts worry that getting too much omega-6 fat, found mainly in such oils as corn and soybean, might  promote inflammation, which can lead to cardiovascular and other problems and block the beneficial effects of omega-3s. So they recommend limiting omega-6 fats and getting more omega-3 fats from traditional sources such as fish.

However, the most recent evidence suggests that omega-6 fats may not in fact increase inflammation. And the American Heart Association’s current position is that omega-3 and omega-6 fats are beneficial. It says that it is more important to meet the minimum recommended intakes for both fats than to try to achieve any specific consumption ratio. Still, there are important gaps and limitations in the research, and conclusions may change as more evidence surfaces.  

Can you get enough omega-3 without consuming fish or taking supplements?

Probably not. Only a small amount of the alpha-linoleic acid (ALA) found in such oils as canola, flaxseed, and soybean is converted in the body to the more-beneficial omega-3s—EPA and DHA.

But most people can get enough omega-3s by eating fatty fish—such as salmon and sardines, which are also low in mercury—at least twice a week. People who have coronary heart disease should consider taking a fish-oil pill, since they need about a gram a day of those fatty acids. Check with a doctor before taking omega-3 pills because they can interact with some medications. See Is Fish Oil Right For You? and our guide to the benefits and risks of eating fish for details.

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.

Philip Calder, Ph.D., professor of nutritional immunology at the University of Southampton in England and editor-in-chief of the British Journal of Nutrition, notes that while more research is needed, for now, "There’s not that much evidence that coconut oil offers an advantage over other types of oil, and it’s likely to raise your cholesterol."

What to do? Your best bet for now is to limit consumption of those oils but keep an open mind until more research comes in.

How does processing affect the benefits and risks of oil?

Oils may be processed using mechanical pressing or heat and chemicals, a method that 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, mechanically pressed oils also contain more antioxidants.

Processed or refined oils do have some pluses, though. They are less expensive, last longer, and can hold up to high-heat uses such 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. A form of hexane is classified as an air pollutant by the Environmental Protection Agency and as a neurotoxin by the Centers for Disease Control and Prevention, and environmental groups have raised concerns about residues that might be left behind in the oil.

Testing by an organic advocacy group found trace amounts of hexane residue (less than 10 parts per million) in a sample of soybean oil. But almost all of the research on hexane toxicity has involved factory workers breathing in high concentrations of airborne hexanes. At very low exposure levels through food, there is no reason to think it should be a health problem, says the toxicologist John L. O’Donoghue, Ph.D., of the University of Rochester School of Medicine and Dentistry.

If you’re concerned about hexane in oil, look for labels that say it was ìexpeller pressed. Oils that carry the "USDA Organic" label are also produced without hexane. And see our reviews and Ratings of olive oil.

Can fats affect your cancer risk?

It’s your 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 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. For advice on what weight-loss strategy migh work for you, see our diet Ratings.

Shopper's guide to fats and oils

Oils with the lowest amount of saturated fat are listed first in each category. Solid fats, such as stick margarine and shortening, are likely to contain trans fats, which should be avoided. Unrefined oils will have a stronger, more distinctive taste than refined oils.

Shopper’s guide to fats and oils
Type of fat/oil Fatty acids %[1] Taste Cost [2] Best uses
Mono Poly Sat
Everyday oils
Safflower 14 75 6 Neutral $$ Good all-purpose oils for salads and cooking, including pan-frying and deep-frying. Suitable for some baked items (brownies, muffins).  
Canola

63

 

28 7 Neutral $

Sunflower

20 66 10 Neutral $$
Grapeseed 16 70 10 Neutral $$
Corn 28 55 13 Neutral $
Olive 73 11 14 Distinctive fruitiness in better virgin oils $$ to $$$ Extra-virgin is good for salads and light sautéeing. Use lower-grade oils for higher-heat cooking.
Soybean 23 58 16 Neutral $ Good all-purpose oil; sometimes labeled
“vegetable oil.”

Peanut

46 32 17

Neutral to mild nutty flavor

$$ Good for all-around use. Unrefined oil adds flavor to Asian dishes.
Tub margarine (vegetable-oil base) 32 46 21 Mild $ Good substitute for butter for most uses.
Specialty oils (use occasionally)
Almond 70 17 8 Distinctive $$$ Unrefined oils are good for dipping, in salads, or drizzled on food. Toasted oils pack extra flavor.
Flaxseed 18 68 9 Distinctive $$$
Walnut 23 63 9 Distinctive $$$
Sesame 40 42 14 Distinctive $$$
Solid fats (use sparingly)

Stick margarine

39 24 15 Mild $ Solid fats are best for some baked goods (flaky piecrusts, pastries) or when used judiciously to impart richness (in buttery sauces, for example). Shortening and stick margarine can contain trans fats, which should be avoided.
Shortening 45 26 25 Neutral to mild $
Lard (pork fat) 45 11 39 Mild, savory $
Palm 37 9 49 Mild $$
Butter 21 3 51 Mild $
Coconut 6 2 87 Mild $$ to $$$

[1] Percentages calculated per 100 grams. Percentages do not add up to 100 because we did not include some minor constituents. “High-oleic” versions of some oils have higher monounsaturated and lower polyunsaturated fat content.

[2] Cost calculations based on an informal shopper survey.

Editor's Note: This article first appeared in the monthly newsletter Consumer Reports on Health. 
   

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