How nice, brown rice: Study shows rice bran lowers blood pressure in rats

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Public release date: 2-Mar-2006

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American Chemical Society

How nice, brown rice: Study shows rice bran lowers blood pressure in

rats

Thousands of years ago, humans began scrubbing off and discarding the

outer layer of long-grain rice, preferring the polished white kernel

beneath. Now, for the first time, scientists in Japan have shown that

this waste product of rice processing, called rice bran,

significantly lowers blood pressure in rats whose hypertension

resembles that of humans.

The team reports their findings in the March 8 issue of the Journal

of Agricultural and Food Chemistry, published by the American

Chemical Society, the world’s largest scientific society.

A commonly prescribed class of drugs called ACE inhibitors dilates

the arteries of hypertensive patients and thus decreases their risk

of stroke, heart attack and kidney disease. But the drugs can also

carry side effects: chronic cough, allergic reactions, dizziness,

even kidney problems.

What if some component of our diet could work in similar fashion,

with few or no side effects? Researchers at Tohoku University and

Japan’s National Research Institute of Brewing demonstrated that

adding rice bran to the diets of hypertensive, stroke-prone rats

lowered the animals’ systolic blood pressure by about 20 percent and,

via the same mechanism, inhibited angiotensin-1 converting enzyme, or

ACE.

“There’s much work being done on various bran fractions to nail down

any health benefits,” says the journal’s editor, Seiber, Ph.D.,

who is also director of the U.S. Department of Agriculture’s Western

Regional Research Center in , Calif. “This particular paper

caught my attention for two reasons: the potential of bringing a

waste product like rice bran into beneficial use, and the way the

group went about their study with good controlled experiments using

an appropriate model.”

It’s still not clear whether simply eating more brown rice, which

retains some of its bran, would reduce the risk of heart disease.

However, previous research in humans, as well as animals with high

cholesterol, does suggest that certain fractions of rice bran can

lower levels of unhealthy LDL cholesterol.

The Tohoku study adds antihypertensive activity to the picture, along

with a host of other biochemical markers that track blood glucose

(implicated in diabetes), lipid profile, kidney function and the

harmful effects of free radicals.

For example, high levels of a marker called 8-OHdG indicate

biological stress and genetic damage due to oxygen-based free

radicals. The researchers found that rice bran, which contains

various forms of the antioxidant Vitamin E, markedly lowered the

rats’ levels of the peptide 8-OHdG.

“Oxidative stress plays an important role in the initiation and

progression of cardiovascular diseases,” explained lead author

Ardiansyah [editor note: name is correct as written, there is no

first name], a Ph.D. candidate at the university’s School of

Agricultural Science.

He added one more element to the research that is new: using enzymes

to clip components of rice bran from its cell walls, rather than

extracting a fraction with ethanol. “I think enzymatic treatment will

be more suitable for applications if we’d like to use [rice bran as]

functional food,” he said.

The researchers’ next step is to elucidate the mechanisms by which

specific components of rice bran inhibit ACE and lower cholesterol.

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http://www.eurekalert.org/pub_releases/2006-03/acs-hnb030206.php