Are Trans Fats Bad For You?
by Philip Reeves
dietary trans fats really bad for you?
By now, most of you have heard of
trans fatty acids, or trans fats, in foods, and that they
may not be good for your cardiovascular system.
Exactly what are trans fats? Trans
fatty acids are found in nature making up from 2 percent to
5 percent of the fat in dairy products and the meat of
cattle and sheep. But most trans fat found in our food
supply come from a process called partial hydrogenation,
where hydrogen atoms are added to vegetable oils to convert
them to semisolid fats.
At the turn of the 20th century, the
original hydrogenated vegetable oil, or shortening, first
was produced and contained relatively high amounts of trans
fats. But that product soon was followed by various types of
hydrogenated vegetable oils to make margarines and other
fats used for deep-frying. Because of their stability upon
heating and ease of use these hydrogenated oils soon became
a boon to the food manufacturing industry.
Fatty acids are made up of long
chains of carbon atoms stuck together with bonds. Each
carbon has a hydrogen atom sticking out on each side of the
chain. Most of the bonds between carbons are single, but in
many cases, a single set of double bonds can be found, as in
monounsaturated acids such as olive oil. Two or more sets of
double bonds can be found in polyunsaturated fatty acids,
which are found in sunflower and soybean vegetable oils.
Both oils are liquid at room temperature.
Trans fats are made when relatively
healthy oils are hydrogenated to make the oils more solid at
room temperature - thus helping packaged foods stay on the
shelf longer without going bad. The trans fatty acids are
metabolized in the body similar to saturated fats.
What is the evidence that trans fatty
acids might be bad for you? Over the past 30 to 40 years,
numerous human studies have shown that the consumption of
trans fats in the diet, compared with other fats, will
increase serum LDL cholesterol, the bad cholesterol. They
also increase the amount of serum triglycerides and the
ratio of total serum cholesterol to HDL cholesterol, the
good cholesterol. All of these effects are associated with
an increased risk for coronary heart disease.
Other effects of consuming too many
trans fats include disturbances in the function of cells
that line the blood vessels and reductions in activities of
enzymes that process HDL-C. These effects, too, are
associated with diseases of the cardiovascular system.
What are the federal regulatory
agencies doing to protect us from these trans fats? As of
January 2006, the Food and Drug Administration ruled that
the food industry must state on food labels the amount of
trans fats found per serving. But if the food contains less
than 0.5 grams of trans fats per serving, the food can be
labelled as containing zero trans fats.
The labelling of some foods can be
tricky, depending on how much trans fat is in a serving. For
example, since dairy products such as skim milk, 2 percent
milk and whole milk (3.7 percent fat) contain natural trans
fats in small quantities, an 8-ounce serving can be labelled
as having zero trans fats.
But even though cream contains about
18 percent fat, a serving of 1 tablespoon also could be
labelled as zero trans fats. On the other hand, one serving
(½ cup) of high quality “real” ice cream with 18 percent fat
would have to be labelled as having at least 0.5 grams trans
fat. A 1-ounce serving of high-fat cheese would not contain
enough trans fat to be labelled.
Since most trans fat in foods comes
from hydrogenated vegetable oils, the margarines and fats
used for deep-frying would provide the highest intakes. For
example, one serving (1 tablespoon) of some stick margarines
contain as much as 2.5 grams of trans fat and must be
labelled as such. But one serving of the soft, tub
margarines is low enough to be labelled as having zero trans
New formulation of some hydrogenated
oils no longer contains trans fat; but some other
shortenings do. French fries made with the latter could
contain up to 6 grams of trans fat per serving.
Some of the undesirable effects of
trans fat can be seen after consuming as little as 2 grams
per day. Thus, even though a food might contain 0.499 grams
of trans fat per serving and be labelled zero trans fat, 4
servings per day of that food would contain almost 2 grams
of the unwanted fat. If we consume other foods containing
even smaller amounts of trans fat, we easily could obtain
more than 2 grams of these fats per day.
The current recommendation by some
authorities is to limit trans fat intake to less than 0.5
percent of the total energy intake. This would amount to a
little more than 1 gram per day for a 2000-calorie diet.
As a result, consumers are strongly
encouraged to read food labels and try to limit their intake
of trans fats as much as possible. Lowering the total amount
of fat consumed per day also would aide in reducing the
amount of trans fatty acids consumed.