The Truth about Fats and Oils

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Photo courtesy Scott Hollis
The lighter-flavored vegetable oils such as canola, corn and sunflower are good all- purpose cooking and baking oils. Sesame and peanut oils can be used in anything from salads to stir-fry dishes. As for storage, most vegetable oils store for several months in the pantry. Flaxseed, sesame and walnut require refrigeration.
“Butter (high in saturated fat) is bad for you; use
margarine instead.” That’s the message most of
us have been hearing for the last several decades. But now
scientists have discovered that the hydrogenation process
used to make margarine and shortening produces trans fats
that are actually twice as bad for our hearts as saturated
fats. Butter, it turns out, is a healthier choice than many
brands of margarine and shortening. Small wonder that
we’ve been so confused all this time.

It’s still true that fats and oils are high in
calories. And it’s still true that most of us eat too
much fat and more total calories than we need, causing us
to gain weight. But fats and oils are an essential part of
a healthy diet, and some are more healthful and taste
better than others. To help you make the best choices,
here’s a rundown of the health and flavor aspects of
fats and oils:

The Basics

Fats, carbohydrates and proteins are the major components
of all foods. Fats give us energy; help regulate our blood
pressure, heart rate, blood flow and nervous systems; and
carry fat-soluble vitamins (A, D, E and K) throughout our
bodies. Fats also make us feel satisfied, thus helping us
eat fewer calories. A recent study from Oxford, England,
shows that eating fat ignites certain pleasure sensors in
the brain — the same areas that light up at the
sensation of a caress, the scent of a seductive perfume or
upon winning money.

Fats are dense in calories — twice as much as
carbohydrates and proteins — which is why we need to
watch how much of them we eat.

They come in four basic types: monounsaturated,
polyunsaturated, saturated and trans fats, all of which you
can quickly learn to tell apart. The good fats are
monounsaturated and polyunsaturated fats; in addition to
olive and canola oils, other mono oils easy to find in the
grocery store are peanut and avocado. Polyunsaturated fats
that are widely available in grocery stores include
safflower, corn, sunflower, soy and cottonseed oils.

Saturated fat, primarily found in meat, chocolate and
full-fat dairy products, has both good and bad effects on
our health. Trans fats are formed when oils are partially
hydrogenated so they resemble saturated fats in texture and
consistency. Many brands of margarine and shortening
contain significant amounts of trans fats. Scientific
research now shows that many trans fats contribute more to
heart disease than the saturated fats.

Different types of fats directly impact the cholesterol
levels in our bodies. So, the trick to a heart-healthy diet
is knowing the ways cholesterol is affected by different
types of fat. Cholesterol moves back and forth from our
livers to our tissues in two basic forms: LDL (low density
lipoprotein particles or “bad” cholesterol) and
HDL (high-density lipoproteins or “good”
cholesterol). The LDL shuttles fat and cholesterol from the
liver to cells that need it, but fat can build up inside
the walls of our arteries in the process (doctors call this
“plaque build-up”). The HDL returns cholesterol
to the liver and doesn’t build up plaque at all.

Good Fats

Monounsaturated and polyunsaturated fats are found
primarily in plant, nut and seed sources, and both lower
bad LDL cholesterol while raising good HDL. Monounsaturated
fats are typically liquid at room temperature, although
they solidify somewhat if refrigerated.

An important type of polyunsaturated fat is omega-3 fatty
acid, a superstar of the nutrition world. It reduces the
risk of irregular heartbeats, lowers blood pressure and may
protect against certain types of cancer. The best omega-3
sources are flaxseeds, green leafy vegetables and walnuts
and their oils, as well as fatty fish such as salmon,
mackerel, trout and herring.

Saturated fats

Recent research shows that saturated fats are not quite the
villain they’ve been portrayed to be all these years.
It’s true that a diet high in saturated fat will
raise LDL cholesterol, but that negative effect is
counterbalanced by saturated fat’s ability to also
raise the good HDL cholesterol. Saturated fats are found in
butter, whole milk, cheese, red meat, chocolate and
coconuts. They are solid at room temperatures.

Trans Fats: Good Intentions Gone Bad?

Some trans fats naturally occur in small amounts, but the
majority are made when oils are “hydrogenated”
by heating in the presence of hydrogen and fine particles
of nickel metal. The process changes the properties of the
oil, making it more solid and easier to ship and store. But
in the process, these trans fats, which we now know are
more detrimental to our health than saturated fats, are

In the wake of growing concerns about fat in the 1950’s, the
mass marketing of these hydrogenated products took off, and
today, you’ll find them in everything from soda,
crackers and cookies to French fries, peanut butter and
many microwave popcorns (see “Tracking Down Trans
Fats,” above).

Processed food manufacturers now are under government
mandate to disclose trans fat content on nutrition labels
by 2006. “Trans fat-free” labels are already
appearing on some foods that previously depended heavily on
them, but removing this unhealthy ingredient entirely from
industrial food products is a major undertaking.

The research shows trans fats have the worst possible
effect on cholesterol metabolism — they increase LDL
(the bad) cholesterol, and they decrease HDL (the good)
cholesterol. According to Walter C. Willett, chairman of
the Department of Nutrition at Harvard University,
“This combined effect on the ratio of LDL to HDL is
double that of saturated fatty acids.” Even small
amounts of trans fats in our daily diets can do a large
amount of damage, he says. For every 2-percent increase in
the amount of calories from trans fat, the risk of heart
disease increases by 36 percent.

And incredibly, replacing that same 2 percent of calories
from trans fat with unsaturated fats conversely can reduce
the risk of heart disease by as much as 53 percent.

Separating the Good Fats from the Bad

Tracking Down Trans Fats

Because researchers have discovered that some hydrogenated
oils used to make margarine and shortening are unhealthy,
the Food and Drug Administration is requiring food
manufacturers to begin listing the amount of trans fats on
nutrition labels, but the new regulations don’t go
into effect until 2006. Click here for
more information. Here’s how you can avoid them in
the meantime:

Avoid foods that contain ingredients such as
“partially hydrogenated vegetable oil” or
“shortening,” unless they are labeled
“Trans fat-free.”

Pay attention to the order of the ingredients (they
are listed in descending order). If a partially
hydrogenated oil appears near the beginning that means the
trans fat content is high and you may want to make a
different choice. If the words appear toward the end, the
food may be acceptable.

If you want to know what percentage of trans fats a
product contains, do the math. Subtract the specific types
of fat (i.e., saturated fat) from the total fats. The
resulting number is a good estimate of the amount of trans
fat per serving.

Source: The Trans Fat Solution: Cooking and Shopping to
Eliminate the Deadliest Fat from Your Diet, by Kim Severson
(Ten Speed Press, 2003).