Cholesterol — The Facts and the Myths
By now, most people know that high levels of blood cholesterol can lead to
blocked arteries. If an artery that supplies blood to your heart becomes
blocked, a heart attack may occur. If an artery that supplies blood to your
brain becomes blocked, a stroke could occur. Still, confusion abounds over
the role of diet in affecting cholesterol.
Although often portrayed as a dietary evil, cholesterol is essential to
life. The body needs it to make sex hormones, bile, vitamin D, cell
membranes, and nerve sheaths. These and other functions fall to serum
cholesterol, a waxy, fatlike compound, termed a "lipid," that circulates in
the blood stream. The liver manufactures about a gram each day, which is all
the body requires.
Dietary cholesterol is found only animal products. The body does not need
this cholesterol, but anyone other than a strict vegetarian who excludes all
animal products will consume varying amounts of it. Many factors – exercise,
genetics, gender, and other components of the diet – influence how the human
body processes dietary cholesterol; some people can consume large amounts
but have normal blood levels, while others eat very little but have high
blood cholesterol. Diet appears to account for about 20 percent of the
cholesterol in the body, with the remaining 80 percent produced by the
Good versus bad cholesterol
To travel through the
bloodstream, cholesterol molecules attack themselves to lipid-carrying
proteins, or lipoproteins. Two types of lipoproteins are the major
transporters of cholesterol: low-density lipoproteins (LDLs) carry
two-thirds of it; most of the remainder is attacked to high-density
lipoproteins (HDLs). LDLs tend to deposit cholesterol in the artery walls,
leading to atherosclerosis and an increased risk of heart disease. In
contrast, HDLs collect cholesterol from the artery walls and other tissues
and take it to the liver to be metabolized and eliminated form the body.
this is why LDLs are often called the "bad" cholesterol and HDLs the "good."
A third type, very-low-density lipoprroteins (VLDLs), carries a small amount
of cholesterol and triglycerides.
A blood cholesterol test measures the amount of cholesterol in the blood.
This can be expressed in two ways, in terms of milligrams (mg) of
cholesterol per deciliter, or millimoles (mmol) of cholesterol per liter.
The multiplication factor 0.026 converts the milligram system to the
millimole system. A value below 200 mg/dl (5.2 mmol/l) is considered
desirable. If the total is more than 200 mg/dl, LDL and HDL levels should be
measured individually. LDL levels should be below 130 mg/dl (3.5 mmol/l);
130 to 159 (3.5-3.9) is classified as borderline high, over 160 (4.0) is
considered high risk for coronary artery disease and a heart attack. HDL
levels should be at least 45 mg/dl (1.2 mmol/l), and the higher the better.
In assessing cardiovascular risk, doctors calculate the LDL/HDL ratio by
dividing the total cholesterol by the HDL figure. A desirable ratio is less
How diet can help
Experts agree that dietary
modification is appropriate if the total cholesterol count is greater than
200 mg/dl (5.2 mmol/l) or if the LDL level exceeds 130 mg/dl (3.5 mmol/l).
Reducing intake of saturated fats has the greatest effect on lowering blood
cholesterol levels. A diet that limits fat intake to 20 percent or less of
total calories and restricts saturated fats to 7 percent or less can lower
total blood cholesterol an average of 14 percent. Most people can
significantly lower intake of saturated fats by cutting down on, or
eliminating fatty meats, whole milk, and other full-fat dairy products, as
well as tropical oils (coconut, palm, and palm kernel). It is also important
to lower intake of trans fatty acids found in partially hydrogenated oils
and foods containing them such as cookies, crackers, other commercial baked
goods, many snack foods, and some margarines and spreads.
Tobacco should be avoided.
Firsthand and secondhand smoke both cause a drop in health-promoting
antioxidants such as vitamin C. Tobacco smoke also encourages the immune
system to increase LDLs.
Stricter diets yield even better results
Try a vegetarian diet. The vegetarian low-fat (less than 10 percent
of calories) program developed by Dr. Dean Ornish can lower LDL cholesterol
substantially. His program also calls for exercise and meditation.
sure to include foods that actually lower cholesterol. It isn't just
what you don't eat that matters consuming foods that have a
cholesterol-lowering effect also helps. Flavonoid-rich foods, including
citrus fruits and onions, are known to promote healthy cholesterol levels.
Soluble fiber is flaxseed. The pectin in apples and other fruits lowers
cholesterol, as does the soy protein found in tofu, tempeh, and soy milk. It
has also been established that regular daily consumption of carrots can lead
to a reduction of LD cholesterol levels.
Eat fish rich in omega-3s.
Two or three servings a week of salmon, sardines, and other cold-water fish
are linked with a thought that the omega-3 fatty acids in fish reduced
cardiovascular risk by lowering blood cholesterol levels; however, recent
studies suggest that their benefit comes from interfering with blood
clotting and from possible changes in the way the liver metabolizes other
Eat lots of soy products. A large body of evidence has
shown that adding soy protein to a low-fat diet helps to lower cholesterol
levels. Soy protein is found in soybeans and products made from these beans,
including tofu and soy beverages.
Look for margarine with plant sterols.
Plant sterols have been shown to help lower cholesterol levels when consumed
as part of a heart-healthy diet. They are found in plant-sterol enriched
margarines, vegetable oils, nuts, sesame and sunflower seeds, soy and other
At one time, increasing the intake of polyunsaturated fats –
corn, cottonseed, safflower, soy, and sunflower oils – was advocated to
lower cholesterol, but studies have found that these oils reduce the levels
of the protective HDLs at the same time as they lower the harmful LDLs. In
contrast, monounsaturated fats found in canola and olive oils, some nuts and
avocados have the opposite effect, cutting LDLs without altering HDL levels.
The role of dietary cholesterol is still unclear; recent studies indicate it
is not as potent in raising blood cholesterol as saturated fats are. Still,
some experts recommend limiting dietary cholesterol intake to 300 mg a day –
the mount in one an done-half egg yolks, 4 oz (115 g) of beef liver, or 2
cups of whole milk, a 6-oz (170 g) steak, and 1 cup of ice cream.
exercise, weight loss, and stress reduction can all lower cholesterol or
improve the LDL/HDL ratio. Women are protected from developing coronary
artery disease during their reproductive years by the estrogen their body
produces; but according to the most recent research, estrogen supplements
taken after menopause do not offer similar protection.
intake lowers the risk of heart attack. This may be due to alcohol's ability
to raise HDL, its tendency to reduce the stickiness of platelets, or the
presence of antioxidants, such as resveratrol, in red wine. If dietary and
other lifestyle changes fail to reduce blood cholesterol, drugs may be