Blueberries may lower cholesterol

New research from the U.S. Department of Agriculture shows that blueberries may lower cholesterol as effectively as a commercial drug and have the potential for fewer adverse side effects.

In the study, Rimando reports that a compound called pterostilbene (terro-STILL-bien) possesses similar cancer chemopreventive qualities to those found in resveratrol, another compound in grapes. Pterostilbene also showed strong inhibitory activity against breast cancer cell lines. But the evidence remains preliminary and the compound has yet to be evaluated in humans, according to Rimando.

In previous research, resveratrol has been credited with helping grape plants fight off fungi and has been linked to low incidences of coronary heart disease among wine- drinking populations.

Unlike resveratrol, however, pterostilbene is already known to posses anti-diabetic properties. It was first isolated from red sandalwood (Pterocarpus santalinus). Together with resveratrol, it has also been identified in Vitis vinifera (wine grape) leaves, in Chardonnay and Gamay berries infected with fungus, and in healthy Pinot Noir and Gamay berries.

The study, prompted by pterostilbene's close structural similarity to resveratrol, was conducted with the use of a mouse mammary gland culture model that was exposed to a chemical carcinogen. The carcinogen caused precancerous cells on which the compound was tested. The mouse mammary gland test was performed by Rimando’s collaborators at the University of Illinois at Chicago.

The compound, pterostilbene, has the potential to be developed into a nutraceutical for lowering cholesterol, particularly for those who don't respond well to conventional drugs used for this purpose, the researcher says. Findings were described today at the 228th national meeting of the American Chemical Society, the world's largest scientific society.

"We are excited to learn that blueberries, which are already known to be rich in healthy compounds, may also be a potent weapon in the battle against obesity and heart disease, which are leading killers in the U.S.," says study leader Agnes M. Rimando, Ph.D., a research chemist with the USDA's Agricultural Research Service (ARS). She works at the ARS' Natural Products Utilization Research Unit in Oxford, Miss.

Researchers have suspected for some time, based on anecdotal studies, that blueberries may play a role in lowering cholesterol, says Rimando.

In this new laboratory study using rat liver cells, Rimando and her collaborators, Rangaswami Nagmani and Dennis Feller, of the University of Mississippi's School of Pharmacy, exposed the cells to four other compounds found in blueberries. Of the four compounds, pterostilbene showed the highest potency for activating the cells' PPAR-alpha receptor, which in turn plays a role in reducing cholesterol and other lipids.

Pterostilbene was similar in activity to ciprofibrate, a commercial drug that lowers LDL (bad) cholesterol and triglycerides. But ciprofibrate, whose mechanism of action on cells is less specific, can have side effects such as muscle pain and nausea. Pterostilbene, which targets a specific receptor, is likely to have fewer side effects, Rimando says, adding that the compound did not show any signs of cell toxicity in preliminary studies.

Until studies are conducted in humans, no one knows how many blueberries a person needs to eat to have a positive effect at lowering cholesterol, Rimando cautions. Her study adds to a growing list of health benefits attributed to the little antioxidant-rich fruit, including protection against aging, heart disease and cancer, as well as acting as a memory booster.

The American Chemical Society is a nonprofit organization, chartered by the U.S. Congress, with a multidisciplinary membership of more than 159,000 chemists and chemical engineers. It publishes numerous scientific journals and databases, convenes major research conferences and provides educational, science policy and career programs in chemistry. Its main offices are in Washington, D.C., and Columbus, Ohio.