KNOW YOUR FATS

Knowing which fats raise LDL cholesterol and which ones don't is a critical step in lowering your risk of heart disease. Saturated fat, trans fatty acids and dietary cholesterol raise blood cholesterol. Monounsaturated fats and polyunsaturated fats don’t. Some studies suggest they might even help lower LDL cholesterol slightly.

- Saturated fats -
Saturated fat is the main dietary cause of high blood cholesterol. The American Heart Association recommends that you limit your saturated fat intake to 7—10 percent of total calories (or less) each day. If you have coronary heart disease or a high LDL cholesterol level, your doctor may recommend the American Heart Association’s diet. It recommends no more than 30 percent of calories from fat, with less than 7 percent coming from saturated fat. Cholesterol is limited to 200 milligrams a day. Saturated fat is found mostly in foods from animals and some plants.

Foods from animals - These include beef, beef fat, veal, lamb, pork, lard, poultry fat, butter, cream, milk, cheeses and other dairy products made from whole milk. These foods also contain dietary cholesterol.

Foods from plants - These include coconut oil, palm oil and palm kernel oil (often called tropical oils), and cocoa butter.

- Hydrogenated fats -
During food processing, fats may undergo a chemical process called hydrogenation. This is common in margarine and shortening. Recent studies suggest that these fats may raise blood cholesterol. Use hydrogenated fats only if they contain no more than two grams of saturated fat per tablespoon. The saturated fat content of most margarines and spreads is printed on the package or Nutrition Facts label.

- Polyunsaturated and monounsaturated fats -
Polyunsaturated and monounsaturated fats are the two unsaturated fats. They're often found in liquid oils from plants.

Polyunsaturated fats - These include safflower, sesame and sunflower seeds, corn and soybeans, many nuts and seeds, and their oils.

Monounsaturated fats - These include canola, olive and peanut oils, and avocados.

Both polyunsaturated and monounsaturated fats may help lower your blood cholesterol level when you use them in place of saturated fats in your diet. But a moderate intake of all types of fat is best. Use polyunsaturated or monounsaturated oils – and margarines and spreads made from them – in limited amounts. This is better than using fats with a high saturated fat content, such as butter, lard or hydrogenated shortenings.

- Trans fatty acids -
Unsaturated fatty acids can be in one of two shapes-"cis" and "trans." These terms refer to the physical positioning of hydrogen atoms around the carbon chain. The cis form is more common than the trans form. Trans fatty acids (TFA) are found in small amounts in various animal products such as beef, pork, lamb and the butterfat present in butter and milk. TFA are also formed during the process of hydrogenation, making margarine, shortening, cooking oils and the foods made from them a major source of TFA in the American diet. Partially hydrogenated vegetable oils provide about three-fourths of the TFA in the U.S. diet.

To make foods that will stay fresh on the shelf or to get a solid fat product, such as margarine, food manufacturers hydrogenate polyunsaturated oils. Hydrogenate means to add hydrogen. When unsaturated fatty acids are hydrogenated, some of the hydrogen atoms are added on opposite sides of the molecule to the already attached hydrogen. Cis double bonds convert to trans double bonds, and the fatty acids become saturated.

How are trans fatty acids harmful?
In clinical studies, TFA or hydrogenated fats tend to raise total blood cholesterol levels but not as much as more saturated fatty acids. TFA also tend to raise LDL ("bad") cholesterol and lower HDL ("good") cholesterol when used instead of cis fatty acids or natural oils. These changes may increase the risk of heart disease.

Because there are no standard methods, it's difficult to estimate the TFA content of food items. It's also difficult to estimate intake, especially long-term intake. The four most important sources of TFA in one large group of women studied included margarine; beef, pork or lamb as the main dish; cookies (biscuits); and white bread.

Current U.S. regulations provide an incentive to manufacturers to produce foods high in TFA because food labels are not required to include the amount of TFA. Many scientists agree that the amount of TFA should be stated on food labels. Although changes in labeling are important, they are not enough. Many fast foods contain high levels of TFA. There are no labeling regulations for fast food and it can even be advertised as cholesterol-free and cooked in vegetable oil. When you take into account that eating one doughnut at breakfast (3.2 g of TFA) and a large order of french fries at lunch (6.8 g of TFA) adds 10 g of TFA to one's diet, the lack of regulations for labeling these foods can be dangerous to your health.

Is butter better than margarine?
Recent studies on the potential cholesterol-raising effects of TFA have raised public concern about the use of margarine and whether other options, including butter, might be a better choice. Some stick margarines contribute more TFA than unhydrogenated oils or other fats.

Because butter is rich in both saturated fat and cholesterol, it's potentially a highly atherogenic food (a food that causes the arteries to be blocked). Most margarine is made from vegetable fat and provides no dietary cholesterol. The more liquid the margarine, i.e., tub or liquid forms, the less hydrogenated it is and the less TFA it contains.

What can I do to regulate my intake of trans fatty acids?
The American Heart Association's Nutrition Committee strongly advises that healthy Americans over age 2 limit their intake of saturated fat to 7-10 percent of total calories and their total fat intake to no more than 30 percent of total calories. If people limit their daily intake of fats and oils to about 5-8 teaspoons, they aren't likely to get an excess of TFA.

On the basis of current data, the American Heart Association recommends that consumers follow these tips:

  • Use naturally occurring, unhydrogenated oil such as canola or olive oil when possible.
  • Look for processed foods made with unhydrogenated oil rather than hydrogenated or saturated fat.
  • Use margarine as a substitute for butter, and choose soft margarines (liquid or tub varieties) over harder, stick forms. Shop for margarine with no more than 2 grams of saturated fat per tablespoon and with liquid vegetable oil as the first ingredient.
  • French fries, doughnuts, cookies and crackers are examples of foods that are high in TFA. Avoid these foods.
  • Limit the fat in your diet. If you don't eat a lot of fat, you won't be consuming a lot of TFA.
  • Avoid commercially fried foods and commercial baked goods. Not only are these foods very high in fat, but that fat is also likely to be very hydrogenated, meaning a lot of TFA.
  • Commercial shortening and deep-frying fats will continue to be made by hydrogenation and will contain TFA. That's just one more reason to avoid fried fast food.