Quitting smoking, engaging in aerobic exercise at least three times a week, and eating a diet high in fiber and rich in fruits and vegetables will all contribute to the maintenance of a healthy balance of good cholesterol (HDL) and bad cholesterol (LDL); if the former is 60 or above, it actually prevents heart disease, while a level below 100 for the latter is desirable for people who have a higher likelihood for developing heart disease. There are also a slew of supplements that promise to keep your lipid levels in check. Here are the pros, cons, and science behind a handful:

Garlic Several randomized tests revealed that garlic preparations had small yet significant effects on subjects' cholesterol levels after one month and three months, with average reductions ranging from 1.2 to 25.4 milligrams per deciliters. However, a 2007 study that compared raw garlic against two popular garlic supplements concluded that none of the garlic preparations showed an appreciable reduction of cholesterol.

Plant sterols Researchers at the Washington University School of Medicine in St. Louis, Missouri, showed that patients taking plant sterol supplements in conjunction with a healthy diet, regular exercisee, and a regimen of statin drugs saw a further decline in their total cholesterol. Plant sterols are effective at lessening the amount of cholesterol in the bloodstream because they compete with cholesterol for absorption by the stomach lining.

Fish oil Research published this past September at The Lancet's Web site found that fish oil may be more beneficial to patients with heart disease than certain cholesterol-reducing drugs. Though scientists are unsure as to how omega-3 promotes heart health, it is thought to improve HDL levels, which can reduce the amount of LDL in the bloodstream.

Red yeast rice A 12-week UCLA School of Medicine study found that 2.4 grams of red yeast rice a day produced a significant drop in cholesterol. A compound made by fermenting red yeast over rice, it contains lovastatin, which inhibits cholesterol-creating enzymes. But because lovastatin is often used in prescription drugs and can be toxic to the liver, the FDA banned red yeast rice supplements containing lovastatin and issued a warning in August 2007. Since then, lovastatin has been removed from commercially available red yeast rice products, which could greatly decrease its cholesterol-reducing properties.

As always, consult your physician before pursuing any route toward cholesterol reduction. If six months to a year of healthy eating and regular exercise fail to diminish your total cholesterol, your doctor may want to put you on cholesterol-reducing prescriptions such as Lipitor or Crestor. Make sure that any of the supplements you might be taking will not contrindicate any medications your doctor prescribes.