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Fat Facts: Good Fats vs. Bad Fats

The right fats are actually good for you.

From the WebMD Archives

After so many years of being told otherwise, the idea that fat is good for you is hard to swallow, but true. Are you eating the right type of fat? There are good fats and bad fats to look for in your diet.

Fat Facts: What's Good About Fat

Fat is the target of much scorn, yet it serves up health benefits you can't live without.

Fat supplies essential fatty acids (EFAs). "Your body is incapable of producing the EFAs, known as linoleic acid and alpha-linolenic acid, so it must derive them from food," explains Wahida Karmally DrPH, RD, professor of nutrition at Columbia Universityand director of nutrition at The Irving Institute for Clinical and Translational Research.

In addition, fat ferries vitamins A, D, E, and K -- known as the fat-soluble vitamins -- into and around the body.

"Fat is also necessary for maintaining healthy skin, and it plays a central role in promoting proper eyesight and brain development in babies and children," Karmally tells WebMD.

For all the good it does, fat is often fingered as the culprit in the battle of the bulge. It's easy to understand why. At 9 calories per gram, any type of fat -- good or bad -- packs more than twice the calories of carbohydrate and protein.

Yet, it's a mistake to equate dietary fat with body fat. You can get fat eating carbs and protein, even if you eat little dietary fat.

"Excess calories from any source is what's responsible for weight gain, not fat per se," says Alice H. Lichtenstein, DSc, professor of nutrition at Tufts University and director of the Cardiovascular Nutrition Laboratory. "In the scheme of things, total calorie intake matters the most."

Fat Facts: What's Bad About Fat

There is a well-established link between fat intake and heart disease and stroke risk.

Diets rich in saturated fat and trans fat (both "bad" fats) raise blood cholesterol concentrations, contributing to clogged arteries that block the flow of oxygen-rich blood to the heart and brain.

But there's a caveat: Very low-fat diets -- 15% or 34 grams of fat in a 2,000-calorie diet -- may not reduce artery-clogging compounds in the bloodstream in everyone. Nor can most people maintain a very low-fat diet in the long run. The American Heart Association (AHA) recommends that we get 20% to 35% of our calories from fat. Most Americans get 34% or more.

When it comes to dietary fat, quantity and quality count.

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Dietary Fat: What's Right for You?

When examining food labels for fat content, it pays to know your daily fat allowance to understand how a serving of that food fits into your diet.

"People tend to buy the same foods over and over, so it's worth it to read labels and find foods you like that are low in saturated and trans fat," Lichtenstein says.

Suggested daily fat intake is tied to calorie needs. The two fats to limit are:

  • Saturated fat found in meats, butter, cream, or ice cream, and other foods with animal fat.
  • Trans fat, a man-made fat found in some margarines or packaged baked.

Here are some examples of healthy daily fat allowances.

1,800 Calories a Day

  • 40 to 70 grams of total fat
  • 14 grams or less of saturated fat
  • 2 grams or less of trans fat

2,200 Calories a Day

  • 49 to 86 grams of total fat
  • 17 grams or less of saturated fat
  • 3 grams or less of trans fat

2,500 Calories a Day

  • 56 to 97 grams of total fat
  • 20 grams or less of saturated fat
  • 3 grams or less of trans fat.

MyPyramid.gov helps you determine a daily calorie level right for you. If you want to lose weight, eat less than what MyPyramid suggests for your age, gender, and physical activity level, but don't eat less than 1,600 calories a day.

The Facts on Unsaturated Fats

Dietary fat is categorized as saturated or unsaturated. Unsaturated fats -- monounsaturated and polyunsaturated -- should be the dominant type of fat in a balanced diet, because they reduce the risk of clogged arteries.

While foods tend to contain a mixture of fats, monounsaturated fat is the primary fat found in:

  • olive, canola, and sesame oils
  • avocado
  • nuts, such as almonds, cashews, and pistachios; peanuts and peanut butter

Polyunsaturated fat is prevalent in:

  • corn, cottonseed, and safflower oils
  • sunflower seeds and sunflower oil
  • flaxseed and flaxseed oil
  • soybeans and soybean oil
  • tub margarine
  • seafood

The Facts on Omega-3 Fats

When it comes to good-for-you fat, seafood stands out. Seafood harbors omega-3 fats called DHA (docosahexanoic acid) and EPA (eicosapentanoic acid), unsaturated fats considered central to a child's brain development and eyesight, and for heart health.

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Omega-3 fats are linked to lower levels of blood triglycerides (fats), reduced risk of clots that block the flow of blood to the heart and brain, and a normal heart beat, among other benefits.

Seafood contains preformed omega-3 fats, the type the body prefers. Adults and children can make DHA and EPA from the essential fat alpha-linolenic acid, found in foods such as walnuts and flax, but experts say less than 10% is actually converted. Fatty, cold-water fish, such as salmon, sardines, and tuna are rich in preformed omega-3s.

The Facts on Unhealthy Saturated Fat

When eaten to excess, saturated fat contributes to clogged arteries that block blood flow, increasing the risk of heart attack and stroke. Saturated fat is worse than dietary cholesterol when it comes to raising blood cholesterol levels, a risk factor for heart disease and stroke.

Saturated fat is concentrated in fatty meats, and full-fat dairy foods including cheese, ice cream, and whole milk. Animal foods supply most saturated fat in our diet. But highly saturated vegetable fats such as coconut oil, palm, palm kernel oil, and cocoa butter are also unhealthy. They're widely used in packaged foods including milk chocolate, cookies, crackers, and snack chips.

There's no dietary requirement for saturated fat because your body produces all that it needs. Yet, there's no need to completely avoid foods with saturated fat in the name of good health. Foods such as meat, cheese, and milk pack a multitude of nutrients such as protein, vitamins, and minerals. Just try to keep saturated fat to less than 7% of all the fat you eat.

The Facts on Trans Fat: A Bad Fat in a League of Its Own

Like saturated fat, trans fat contributes to clogged arteries. Even worse, it's been linked to certain cancers, including breast and colorectal, in population studies.

Researchers from Harvard School of Public Health have estimated that eliminating trans fats from the American diet could prevent about a quarter of a million heart attacks and related deaths every year.

Trace amounts of naturally-occurring trans fat are present in fatty meats and full-fat dairy foods. But, by far, most of the trans fat we eat is the end product of hydrogenation. Hydrogenation (the addition of hydrogen) converts oil into a firmer, tastier product with a longer shelf life. In the process, some of the unsaturated fat in the oil becomes saturated.

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Partially hydrogenated fat -- trans fat -- is gradually being removed from most packaged foods. But it's still found in some stick margarine, shortening, fast food, cookies, crackers, granola bars, and microwave popcorn.

There is no dietary requirement for trans fat, although it's nearly impossible to completely avoid. It helps to read nutrition food labels, but there's a hitch.

"Even when the food label lists the trans fat content of a processed food as zero, a serving may contain up to nearly half a gram of trans fat by law," says Karmally.

Small amounts of some "trans-fat-free" foods can really add up. For example, a box of cookies labeled "0 trans fats" could actually have half a gram per serving. Thus four cookies could contain close to 2 grams of trans fat -- the upper limit suggested for many adults.

3 Easy Ways to Avoid Bad Fats

Here are three simple ways to avoid bad fats, including trans fat:

1. Avoid packaged foods when possible. Instead, choose whole foods, or foods you make at home. For example, you can make your own macaroni and cheese from scratch, or your own flavored rice mixes.

2. Eat lean sources of protein, low-fat dairy foods, whole grains, legumes -- such as garbanzo beans and black beans -- and fruits and vegetables.

3. Use healthy oils such as olive, canola, and sunflower oil, and small amounts of tub margarine for cooking and flavoring foods.

"It takes more than counting fat grams to protect your health," Lichtenstein says.

WebMD Feature Reviewed by Kathleen M. Zelman, MPH, RD, LD on October 30, 2008

Sources

SOURCES:

Wahida Karmally, DrPH, RD, CDE, CLS, The Irving Institute for Clinical and Translational Research, Columbia University, New York City.

Alice H. Lichtenstein, D.Sc, Gershoff Professor of Nutrition Science and Policy, Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy, Tufts University.

MyPyramid.gov web site.

American Heart Association Nutrition Committee, Circulation, 2006; vol 114: pp 82-96.

Cheajes, V. American Journal of Epidemiology, 2008; vol 167: pp 1312-1320.

Vinikoor, L. American Journal of Epidemiology, 2008; vol 168: pp 289-297.

Mozaffarian D. New EnglandJournal of Medicine, April 13, 2006; vol 354: pp 1601-1613.

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