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.
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