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Know Your Fats!
Knowing
which fats raise LDL cholesterol and which ones don't is the first 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 when eaten as part of a
low-saturated-fat diet.
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 710 percent of total calories (or less) each day. If
you have coronary heart disease or your LDL cholesterol level is 100 mg/dL
or greater, your doctor should recommend the Therapeutic Lifestyle
Change (TLC) Diet. It recommends 2535 percent of calories from
fat, with less than 7 percent coming from saturated fat. Cholesterol is
limited to less than 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. These fats also
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 found primarily in 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 recommended
in place of 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 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. Some scientists believe they raise
cholesterol levels more than saturated fats. 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.
Recently the FDA passed a regulation requiring trans fat to be listed
on the nutrition label by January 2006. Although changes in labeling are
important, they aren't 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. Eating one
doughnut at breakfast (3.2 g of TFA) and a large order of french fries
at lunch (6.8 g of TFA) add 10 g of TFA to one's diet, so the lack of
regulations for labeling restaurant foods can be harmful 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 710 percent of total calories. Individuals should
adjust total fat intake to meet their caloric needs. People who are
overweight or obese should limit their total fat intake to no more
than 30 percent of total calories.
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. Look for those labeled "trans-fat
free."
- French fries, doughnuts,
cookies and crackers are examples of foods that are high in TFA. Consume
them infrequently.
- Limit the saturated fat in
your diet. If you don't eat a lot of saturated fat, you won't
be consuming a lot of TFA.
- Eat commercially fried foods
and commercial baked goods infrequently. 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 eat fried fast food
infrequently.
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