This off-white rice may be heart healthy

A natural constituent quiets the signal of a hormone active in cardiovascular disease.

ANAHEIM American diners, like their Japanese counterparts, prefer white rice over brown. But a semi-polished Japanese rice that falls sort of midway between the two grains in both color and flavor may offer a compromise for people who want to salvage some of brown rice’s health benefits in a starch with a more refined flavor.

Indeed, the outer coating of this beige rice – a layer which manufacturers ordinarily polish off of brown rice in the process of making it white – offers cardiovascular benefits. At least that’s what researchers at Temple University School of Medicine in Philadelphia and at Wakayama Medical University in Japan conclude from their collaborative test-tube studies. They described their findings April 26 at the American Physiological Society annual meeting.

Rice grains are seeds. And the Kinme-mai type that these researchers are focusing on retains both the seed’s embryo and a thin skin known as the subaleurone layer.

Satoru Eguchi at Temple has spent years investigating the role of a hormone – angiotensin-II – and ways to limit its action in people with cardiovascular disease and diabetes. There are medicines to block angiotensin-II, which not only plays a role in hypertension but also the excessive growth of smooth muscle cells on the inside of blood vessels (a risk factor in stroke and cardiovascular disease). But Eguchi has been scouting for foods that might do the same thing, without a drug’s side effects. And the physiologist now thinks Kinme-mai rice shows promise.

In the lab, treating vascular smooth-muscle cells with angiotensin-II triggers them to proliferate – much as they would in the vessels of people with coronary artery disease. But the researchers prepared an extract of constituents in the subaleurone layer of Kinme-mai. And after incubation in this extract, Eguchi says, those cells largely ignored angiotensin-II. The rice extract “had a strong inhibitory effect on its growth-promoting signal,” he says. A survey of genes showed that many respond to the rice extract, pointing to how and why it’s active.

This extract could serve as the basis for a new line of drugs. But even better, Eguchi says, would be to encourage people to eat rice that hasn’t been stripped of its subaleurone layer.

“In Japan, we usually eat three cups of rice each day,” notes Hirotoshi Utsunomiya of Wakayama Medical University. That is only about half of the consumption rate there a half-century ago. But these researchers believe that at even Japan’s current levels of consumption, rice retaining the subaleurone layer might offer demonstrable heart benefits. To find out, they’re planning tests of this rice extract in animal models of human heart disease – and measurements of any cardiovascular impacts from Kinme-mai consumption in human diners.

For people who want to do their own experimentation, Eguchi notes that this rice has been marketed for decades in Japan and in recent years has become available in many U.S. groceries.

The APS meeting is taking place under the aegis of Experimental Biology 2010. (This umbrella conference, sponsored by APS and five other biomedical research societies, is also hosting the annual meetings of another 17 guest research societies this year.)

Janet Raloff

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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