New research findings pinpoint the specific component of rice bran responsible for its heart-healthy effects. Two small studies show that it is the oil, and not the fiber, that helps lower cholesterol.

“The findings provide evidence of the fact that plants contain compounds that are beneficial to our health,” lead study author Dr. Marlene M. Most, an associate professor at the Pennington Biomedical Research Center in Baton Rouge, Louisiana told AMN Health.

“Rice bran oil is a good example of functional food with a beneficial effect - lowering cholesterol to reduce risk for cardiovascular disease,” she added.

Previous research has also pointed to the heart-healthy effects of rice bran and rice bran oil, which is most commonly available in Japan and India, but may also be found in some specialty stores in the United States.

In one study, the researchers found that adding rice bran to the diet of men and women with moderately High cholesterol lowered cholesterol levels just as effectively as an oat bran-containing diet did. In the other study, investigators found that middle age and elderly study participants who substituted rice bran oil for their usual cooking oils experienced decreases in their cholesterol levels.

In the first study, 26 men and women were randomly assigned to a low-fiber diet, in which they consumed up to 22 grams of fiber per day, or a high-fiber diet with defatted rice bran, in which they consumed twice as much fiber as the other group. The defatted rice bran was used in muffins, cookies and breads.

At the end of the five-week study, none of the patients experienced great changes in their overall blood cholesterol levels. An unexpected finding was that subjects in the defatted rice bran group had higher levels of low-density lipoprotein (LDL) cholesterol - the artery-clogging “bad” cholesterol, the investigators reported in the American Journal of Clinical Nutrition.

In the second study, 14 participants followed two different diets for five weeks each. During the first five-week period the study participants consumed one third of their total daily dietary fat in the form of a blend of peanut oil, olive oil, corn oil, canola oil, palm oil and butter. During the second five-week period, the oil blend was replaced with rice bran oil.

The oil blend had a fatty acid composition similar to that found in rice bran oil, the researchers note. Rice bran is high in saturated fatty acids, which has been shown to have deleterious effects on cholesterol levels. Thus, a diet consisting of rice bran oil would not be expected to lower cholesterol, Most said.

At the end of the study, however, Most and her team found that the study participants’ cholesterol levels - LDL cholesterol in particular - were lowest when their diet consisted of rice bran oil.

The findings from both studies show that “it is the rice bran oil, and not the fiber, that lowers blood lipids in men and women with borderline high total cholesterol,” Most and her team write.

Despite these findings, Most believes it is too soon to recommend that Americans immediately start adding rice bran oil to their diet. “Rice bran oil…is not commonly consumed in the United States [and] it would be unreasonable to tell people to begin consuming large quantities.”

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SOURCE: American Journal of Nutrition, January 2005.