Face the fats: Some types of
dietary fat are better than others
February 9, 2005
You're ready to saute fresh vegetables for dinner,
but you hesitate with uncertainty. Do you cook the vegetables
in butter or margarine? Or would canola oil or olive
oil be better? Maybe you should avoid fat altogether
and use a nonfat cooking spray instead.
First, know that not all fats are created equal. Most
foods contain several different kinds of fat —
including saturated, polyunsaturated, monounsaturated
and trans fat — and some types are better for
your health than others are. It's not necessary that
you completely eliminate all fats from your meals. Rather,
be sure to choose the best types of fat and enjoy them
in moderation.
Fat: A necessary nutrient
Your body needs fat to function properly. Besides being
an energy source, fat is a nutrient used in the production
of cell membranes, as well as in several hormone-like
compounds called eicosanoids. These compounds help regulate
blood pressure, heart rate, blood vessel constriction,
blood clotting and the nervous system. In addition,
dietary fat carries fat-soluble vitamins — vitamins
A, D, E and K — from your food into your body.
Fat also helps maintain healthy hair and skin, protects
vital organs, keeps your body insulated, and provides
a sense of fullness after meals (satiety).
But too much fat can negatively impact your health.
Eating large amounts of high-fat foods adds excess calories,
which can lead to weight gain and obesity. Obesity is
a risk factor for several diseases, including diabetes,
heart disease, cancer, gallstones, sleep apnea and osteoarthritis.
And too much of certain types of fat — such as
saturated fat or trans fat — can increase your
blood cholesterol levels and your risk of coronary artery
disease.
Healthy fats
When choosing fats, your best options are monounsaturated
and polyunsaturated fats. These fats, if used in place
of others, can lower your risk of heart disease by reducing
the total and low-density lipoprotein (LDL) cholesterol
levels in your blood. Cholesterol, which your body produces
for building cells, is the main substance in fatty deposits
(plaques) that can develop in your arteries. Plaques
that build up can reduce blood flow through your vessels,
increasing your risk of heart disease and stroke.
One type of polyunsaturated fat, omega-3 fatty acids,
may be especially beneficial to your heart. Omega-3s
appear to decrease the risk of coronary artery disease.
They may also protect against irregular heartbeats and
help lower blood pressure levels.
Here are the differences among these healthy fats as
well as the best food sources for each type:
- Monounsaturated fat remains liquid
at room temperature but may start to solidify in the
refrigerator. Foods high in monounsaturated fat include
olive, peanut and canola oils. Avocados and most nuts
also have high amounts of monounsaturated fat.
- Polyunsaturated fat is usually
liquid at room temperature and in the refrigerator.
Foods high in polyunsaturated fats include vegetable
oils, such as safflower, corn, sunflower, soy and
cottonseed oils.
- Omega-3 fatty acids are polyunsaturated
fats found mostly in seafood. Good sources of omega
3s include fatty, cold-water fish, such as salmon,
mackerel and herring. Flaxseeds, flax oil and walnuts
also contain omega-3 fatty acids, and small amounts
are found in soybean and canola oils.
Harmful fats
Saturated and trans fats are less healthy kinds of
fats. They can increase your risk of heart disease by
increasing your total and LDL ("bad") cholesterol.
Dietary cholesterol isn't technically a fat, but it's
found in food derived from animal sources. Intake of
dietary cholesterol increases blood cholesterol levels,
but not as much as saturated and trans fats, and not
to the same degree in all people.
Here are how these fats differ and what their common
food sources are:
- Saturated fat. Usually solid or
waxy at room temperature, saturated fat is most often
found in animal products — such as red meat,
poultry, butter and whole milk. Other foods high in
saturated fat include coconut, palm and other tropical
oils.
- Trans fat. Also referred to as
trans-fatty acids, trans fat comes from adding hydrogen
to vegetable oil through a process called hydrogenation.
This makes the fat more solid and less likely to turn
rancid. Hydrogenated fat is a common ingredient in
commercial baked goods — such as crackers, cookies
and cakes — and in fried foods such as doughnuts
and french fries. Shortenings and some margarines
also are high in trans fat. Look for the words partially
hydrogenated in the list of ingredients to see if
the product has trans fat. Some food labels state
if the product has no trans-fatty acids. By January
1 of 2006, food manufacturers will have to list trans
fat content on nutrition labels.
- Dietary cholesterol. Your body
naturally manufactures all of the cholesterol it needs,
but you also get cholesterol from animal products,
such as meat, poultry, seafood, eggs, dairy products,
lard and butter.
A daily limit for fat intake
The U.S. Department of Agriculture (USDA) and the Department
of Health and Human Services (HHS) recommend that fat
make up no more than 35 percent of your daily calories.
This means that if you consume 1,800 calories a day,
consume no more than 70 grams of fat a day. (To figure:
Multiply 1,800 by 0.35 to get 630 calories, and divide
that number by 9, the number of calories per gram of
fat, to get 70 grams of total fat.) Keep in mind, however,
that this is an upper limit and that most of these fat
calories should come from monounsaturated and polyunsaturated
sources.
In addition, the USDA and HHS recommend these upper
limits for saturated fat and dietary cholesterol for
healthy adults:
Type of fat
Saturated fat
Dietary cholesterol
Recommendation
Less than 10 percent of your total daily calories
Less than 300 milligrams a day
Though the USDA and HHS haven't yet established an
upper limit for trans fat, they do suggest that you
keep your trans fat intake as low as possible.
Be aware that many foods contain different kinds of
fat and varying levels of each type. For example, butter
contains unsaturated fats, but a large percentage of
the total fat is saturated fat. And canola oil has a
high percentage of monounsaturated fat, but also contains
smaller amounts of polyunsaturated fat and saturated
fat.
Tips for choosing the best types of fat
Limit fat in your diet, but don't try to cut it out
completely. Focus on reducing foods high in saturated
fat, trans fat and cholesterol, and select more foods
made with unsaturated fats. Consider these tips when
making your choices:
- Saute with olive oil instead of butter.
- Use olive oil instead of vegetable oil in salad
dressings and marinades.
- Use canola oil when baking.
- Sprinkle slivered nuts or sunflower seeds on salads
instead of bacon bits.
- Snack on a small handful of nuts rather than potato
chips or processed crackers. Or try peanut butter
or other nut-butter spreads — nonhydrogenated
— on celery, bananas, or rice or popcorn cakes.
- Add slices of avocado, rather than cheese, to your
sandwich.
- Prepare fish such as salmon and mackerel, which
contain monounsaturated and omega-3 fats, instead
of meat one or two times a week.
Monounsaturated and polyunsaturated fats have few adverse
effects on blood cholesterol levels, but you still need
to consume all fats in moderation. Eating large amounts
of any fat adds excess calories. Fat contains 9 calories
per gram, compared with 4 calories per gram for protein
and carbohydrates. Also make sure that fatty foods don't
replace more nutritious options, such as fruits, vegetables,
legumes or whole grains.
Source:www.mayoclinic.com
|
