A grapefruit a day may keep the cardiologist away. An international study found that eating one grapefruit daily can significantly reduce cholesterol levels, a major risk factor for heart disease.

Researchers in Israel, Poland and Singapore divided 57 men and women with high cholesterol into three groups. The test subjects had all had recent coronary bypass surgery and were not taking cholesterol-lowering statin drugs during the study period.

One-third were given fresh red grapefruit along with regular balanced meals, another third white (or blond) grapefruit with their meals and the remainder, just the meals.

The patients who received either red or white grapefruit showed significant drops in blood cholesterol levels, while those not eating grapefruit showed no changes. Red grapefruit was more effective than white at lowering abnormal lipid levels, particularly, triglycerides.

The researchers suggested that the effect may be linked to the high level of antioxidants contained in grapefruit. Red grapefruits are generally higher in antioxidants than white varieties. But they left open the possibility that other compounds in grapefruit may be responsible for the effect. Grapefruit juice appears to have the same effect as whole fruit.

However, the researchers also warned that grapefruit is known to interact with certain medications. In the 1990s, researchers using grapefruit juice to mask the taste of medications in research studies found that grapefruit juice can increase the absorption of certain medications and interfere with the absorption of other drugs.

The University of Florida has launched the Web site, www.druginteractioncenter .org, to help consumers identify whether grapefruit may impact the effectiveness of their medications. Most prescription drugs and all over-the-counter drugs are not affected, the center says. Individuals taking medications should consult with their doctor before adding grapefruit to their diet.