We manufacture steroid hormones-the female hormones estrogen and progesterone, and the male hormone testosterone-from cholesterol. Adrenal corticosteroid hormones, which regulate water balance through the kidneys, and the hormone cortisone, the vital anti-inflammatory that also governs our stress response, come from cholesterol. Other jobs of cholesterol: production of vitamin D and bile acid (for the digestive process); healing and protecting skin, and antioxidant compensation when vitamin and mineral stores are low. How can mere mention of this invaluable component in our body chemistry make our blood run cold?

 

Cholesterol's reputation as a bad character actually originates in the crowd it runs with: the lipoproteins, protein molecules to which it binds in order to travel back and forth through the bloodstream to the liver, where it is manufactured. Not really a nasty round glob of fat at all, cholesterol is a crystalline substance, technically a steroid, but soluble in fats rather than water, thus classified as a lipid, as fats are. Thousands of cholesterol molecules bind with lipoproteins, spherical fat molecules that transport them through the bloodstream. Three different kinds of lipoproteins participate in this necessary process, not always with the same salutary effect. Here's how they work:

Lipoprotein(a), or Lp(a): the "really bad" cholesterol, can step in, providing the glue that actually sticks to the arterial wall. Lp(a) is an LDL particle with an extra adhesive protein wrapped around it, enabling it to attach fat globules to the walls of blood vessels. The potentially deadly results are atherosclerotic ("plaque") deposits. Simple LDL lacks adhesive power and presents little risk for cardiovascular disease. Researchers confirmed the existence of Lp(a) in the August 1996 issue of the Journal of the American Medical Association, disclosing that high levels of Lp(a) in the blood can double a man's risk of heart attack before age 55. Doctors estimate that about 20% of all Americans carry elevated levels of Lp(a).

One troubling aspect of the report, part of the ongoing 40-year-old Framingham Study, concerned the fact that the men who suffered heart attacks entered the project with no signs of heart disease and only slightly elevated cholesterol. But during the 15-year investigation, 129 men out of 2,191 developed premature heart disease.

The body also transports fats via triglycerides (TGs), the main form of body fat and the storehouse for energy. Edible oils from seeds, egg yolk and animal fats also are composed chiefly of TGs. Although not as corrosive as LDL, excess TGs intensify heart disease potential when they oxidize and damage artery linings or induce blood cells to clump. An "acceptable" level of triglycerides is thought to be 200 milligrams, although under 150 is probably healthier. And some researchers think your triglyceride reading should be below 100. High triglycerides and low HDL often occur together, increasing the risks of cardiovascular disease, high blood pressure, heart and kidney failure and other degenerative diseases.