Gabe Mirkin, M.D.
Fat is classified into saturated fats, polyunsaturated fats,
and monounsaturated fats. Saturated fats appear to increase
your risk for heart attacks when you take in more calories than
you burn.
Monounsaturated fats are considered healthful because
they form LDL cholesterol that is resistant to oxidation; plaques
are formed by oxidized LDL. Good sources include olive oil and
avocados.
We used to think that all polyunsaturated fats help to
prevent heart attacks when they replace saturated fats, but now
we have different information. Polyunsaturated fats are classified by their structures into
omega-3s and omega-6s, and you need both types; these are
called the essential fatty acids because you cannot make them in
your body and must get them from your food.
For most of the time humans have been on earth we
have eaten foods that contain omega-6's and omega-3's in a
ratio of about 2:1. However, over the last 50 years in North
America, the ratio has changed; it now ranges from 10:1 to 20:1.
Today our diet includes huge amounts of oils that are extracted
from plants and used for cooking or in prepared foods. These
oils (such as corn oil, safflower oil, cottonseed oil, peanut oil,
soybean oil) are primarily omega-6s. We have decreased our
intake of omega-3's, found primarily in whole grains, beans and
other seeds, and seafood. Eating too much omega-6 and too
little omega-3 causes clots and constricts arteries to increase risk
for heart attacks, increases swelling to worsen arthritis, and
aggravates a skin disease called psoriasis. It may block a
person’s ability to respond to insulin, causing high insulin and
blood sugar levels and obesity. It increases hormone levels of
insulin like growth factor-1 that causes certain cancers. To get
your ratio on omega-6s to omega-3s back to a more healthful
2:1, eat seafood, whole grains, beans and other seeds, and
reduce your intake of foods made with or cooked in vegetable
oils.
The most unhealthful fats are the polyunsaturated oils
that have been processed to form trans fats (partially
hydrogenated vegetable oils); see reports #N198 and #N185.
Checked 12/8/07