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Fast facts on fats: What to eat, what to avoid

  • Story Highlights
  • You should eat as little trans fat as possible, experts say
  • Monounsaturated fat helps lower blood cholesterol levels
  • Roughly two-thirds of the fat you eat should be unsaturated
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By Maureen Callahan
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Cooking Light

From curbside snack carts to four-star restaurants, New York City chefs have until next summer to rid their kitchens of trans fat. It's a bold move, but a necessary one, according to city health officials.

Not all fats are bad for you, but experts say you should eat as little trans fat as possible.

"When you look at the evidence, there's no question artificial trans fat increases the risk for coronary heart disease," says Sonia Angell, M.D., director of cardiovascular disease prevention and control at New York City's Department of Health.

"The most conservative estimates show that the replacement of these fats with heart-healthy alternatives can decrease coronary artery disease risk by 6 percent, and it is likely even higher."

In fact, a recent Harvard University study showed that women with low blood levels of trans fat are three times less likely to develop heart disease. .

The Big Apple's impending trans fat ban is making other cities, food companies, and scientific experts pay closer attention to the increasingly complex relationships between dietary fat and health. Here's the latest on fats, including where each is found, what it does, and how much or how little to eat. Putting the right types and amounts of fat into your diet

Trans fat

There are two types of trans fat: the kind that occurs naturally in small amounts in animal products, and the artificial kind produced by adding hydrogen to liquid oils so they remain solid at room temperature, which helps extend a food's shelf life. So far no studies have examined how natural trans fat impacts health, but the artificial kind raises levels of LDL ("bad") cholesterol and lowers HDL ("good") cholesterol, raising the risk of heart disease.

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• Where it's found: Most commercially produced fried foods, baked goods, and stick margarines are made with artificial trans fat. Natural trans fat can be found in red meat, milk, butter, and cheese.

How much to eat: As little as possible. The American Heart Association (AHA) suggests limiting trans fat to less than one percent of your daily calories, about two grams if you follow a 2,000-calorie-per-day plan. That figure includes artificial trans fat as well as natural, since natural trans fat sources are often high in another type of fat linked to heart-disease risk factors-saturated fat.
"If you're mindful that you want to decrease both trans fat and saturated fat, you're in a good position. I think some people are so focused on trans fat that they forget about saturated fat," says Alice Lichtenstein, D.Sc., director of the Cardiovascular Nutrition Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging in Boston, Massachusetts.

Recent news: The food world is working at warp speed to find replacements for artificial trans fat. In addition to New York, eight other large American cities --including Los Angeles, California; Philadelphia, Pennsylvania; and Boston -- have legislation pending to limit or ban artificial trans fat.

"It's just a matter of time before these fats virtually disappear from the American landscape," says William Connor, M.D., a researcher at Oregon State Health Sciences University.

• Trans fat fine print: A product must contain less than 0.5 grams of trans fat per serving in order to bear a "no trans fat" label, according to the Food and Drug Administration. However, such products may still contain up to 0.49 grams of trans fat.

To keep your intake low, stick to recommended serving sizes and read ingredients lists; they're arranged in order, so the presence of partially hydrogenated oil can provide a clue as to the presence of artificial trans fat in a "trans fat-free" product.

Saturated fat

This type of fat raises LDL cholesterol and sets the stage for heart disease by encouraging the formation of plaque in arteries.

• Where it's found: Animal products like whole milk, cream, butter, lard, and fatty cuts of meat. Also a component of cocoa butter and tropical oils (palm, palm kernel, and coconut).

How much to eat: Less than 10 percent of your total calories per day (20 grams if you eat 2,000 calories) is a good starting point. For optimal heart health, the AHA recommends seven percent (16 grams).

Recent news: Just one meal high in saturated fat may damage blood vessels and hinder the ability of HDL cholesterol to protect arteries. Normally, HDL guards blood vessels from inflammation that contributes to artery-clogging plaque, says Stephen Nicholls, M.D., a cardiologist at the Cleveland Clinic Foundation.

Not so after a meal high in saturated fat. When Nicholls and colleagues fed 14 healthy volunteers two meals of carrot cake and a milk shake-one made with highly saturated coconut oil and one with polyunsaturated safflower oil-two things happened: The ability of blood vessels to expand and contract (a sign of healthy arteries) and the anti-inflammatory action of HDL were impaired for as much as six hours after the high saturated fat meal. In contrast, when the cake and milk shake were made with polyunsaturated fat, arterial and HDL functions improved. Just how much saturated fat was in that test meal?

"We likened it to people eating a double cheeseburger, fries, and a shake, which, unfortunately, is not that uncommon a meal," Nicholls says. Remodel your meals

Polyunsaturated fat

This type of fat helps reduce blood cholesterol levels when substituted for saturated fats. One variety, omega-3 fatty acids, also helps lower blood pressure, control inflammation, and protect against irregular heartbeats.

• Where it's found: Vegetable oils like safflower, sunflower, sesame, corn, and soy, and nuts and seeds. Omega-3s are found in fatty fish, such as salmon and mackerel, flaxseed, and walnuts.

How much to eat: Authorities say 40 to 78 grams in a 2,000-calorie diet should come from fat, with polyunsaturated and monounsaturated fats comprising the bulk. However, there is no specific recommended amount for either.

The AHA puts omega-3s in a separate category and suggests two to three meals of fatty fish a week. Two components of omega-3 fatty acid molecules have different benefits: EPA (eicosapentaenoic acid) helps alleviate arterial inflammation and prevent blood platelets from clumping together, while DHA (docosahexaenoic acid) is valuable to the retina and brain.

Plant sources of omega-3s confer heart-health benefits similar to those of other foods rich in polyunsaturated fats, but because the chemical structure of the omega-3 fatty acid they contain (alpha-linolenic acid, or ALA) is different, the body does not convert it as readily to EPA or DHA, Connor says.

Recent news: Two studies from the University of Pittsburgh suggest omega-3s found in fish may help improve mood and increase gray matter in the brain. In the first, researchers demonstrated that people with high blood levels of omega-3s tended to be more agreeable and less likely to report mild symptoms of depression than those with low levels. In the second study, researchers uncovered a possible mechanism behind the mood differences: People with high blood levels of omega-3s have more gray matter in the areas of the brain linked to mood. Although preliminary, the findings provide increasing support for including omega-3s in a healthful diet. Eight great recipes rich in omega-3 fatty acids

Monounsaturated fat

Monounsaturated fat helps lower blood cholesterol levels when substituted for saturated fat in the diet.

• Where it's found: Olives, avocados, and olive, canola, and peanut oils.

How much to eat: Again, roughly two-thirds of the fat you eat should be unsaturated, either monounsaturated or polyunsaturated fat. Get the most out of nutrition labels

Recent news: Monounsaturated fat may help protect against heart disease and diabetes, particularly among people with a cluster of conditions-insulin resistance, high blood pressure, high cholesterol levels, and big waistlines-referred to as metabolic syndrome.

A recent Italian study put 180 men and women with metabolic syndrome on either a low-calorie Mediterranean-style diet rich in monounsaturated fats, fruits, vegetables, and whole grains or a diet of 30 percent of calories from any type of fat. At the study's end two years later, half of the subjects who followed the Mediterranean-style diet were no longer diagnosed with metabolic syndrome.

"Compared to their baseline values the Mediterranean group had a significant increase in HDL and a decrease in both triglycerides [a type of blood fat similar to cholesterol] and blood sugar, all good changes," says Kathy McManus, M.S., R.D., of Harvard's Brigham and Women's Hospital in Boston. Avocado recipes that pack a punch of healthful fat

How to keep track of your daily intake

The best tools for keeping track of your intake of fats are the Food and Drug Administration Daily Values, the percentages listed on all nutrition labels. For example, the Daily Value (DV) for total fat, based on a 2,000-calorie diet, is 65 grams (g) or 30 percent of calories from fat. A food containing 13g of total fat per serving would state on the label that its DV for fat is 20 percent. That means one serving of this food contains 20 percent of total fat you should eat in a given day.

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