Carnitine is an amino acid -- a building block for protein -- that studies have shown may be valuable for repairing AZT-induced muscle damage and wasting. Overall, the nutrient is necessary for the mitochondria, each cell's energy-producing factory, to use fatty acids. So carnitine is key in translating dietary fat into energy. Yet ironically, it is one of several amino acids which nutritionists deem "nonessential" because they are produced by the body itself.

Deficiencies in two other amino acids -- methionine and lysine -- as well as in vitamins B6 and C and niacin, can result in lowered carnitine levels. Some studies report reduced levels of methionine and lysine in people with AIDS-related wasting; others have shown deficiencies in vitamins B6 and C in people with HIV. Larry Lyle, a San Diego osteopathic doctor with a mostly HIV practice, says, "I've treated some of my patients with carnitine and they've shown increased energy."

There are two types of carnitine: L-carnitine and D-carnitine. L-carnitine is sold as tablets or powder. DAAIR, a New York City nonprofit buyers club, reports that its research supports a dose of three grams (or three level teaspoonfuls) daily of pure L-carnitine taken with food. DAAIR suggests continuing at least 30 days for noticeable results. Avoid D-carnitine because it can induce diarrhea and nausea.

A word to the wise: Whether in tablets or powder, carnitine is très expensive. If you have insurance, ask your physician to prescribe the pharmaceutical form, Carnitor. The bulk powdered form is cheaper and may be more readily absorbed than pills.