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Beyond oat bran: reaping the benefits without gorging on the grain.

Beyond Oat Bran

More than a dozen studies in as many years have demonstrated oat bran's cholesterol-lowering benefits for people with seriously elevated serum cholesterol levels. Over the past five years, researchers have traced these benefits to beta-glucan, a long, glucose-based molecule that resembles a kinked cellulose fiber.

But oat bran is not the only source of this key ingredient. And some of the other sources, described last month at the American Chemical Society meeting in Boston, might reduce cholesterol more efficiently than oat bran itself.

To obtain optimal amounts of beta-glucan from oat bran, a person with elevated cholesterol needs to consume roughly 100 grams -- about three bowls full -- of bran each day, notes Yrjo Malkki, director of technical research of the Food Research Center in Espoo, Finland. If that sounds unappealing, Malkki offers an alternative: Eat breads and other baked goods fortified with a beta-glucan-enriched concentrate.

Malkki makes his concentrate by grinding whole oats in a mix of water and alcohol, then washing away most of the starch and oil. The fibrous fraction that remains contains two to three times the beta-glucan concentration offered by the bran in the starting grain. However, not all the chain-like beta-glucan molecules in this concentrate -- or in oats themselves -- contain the same number of repeating links. And Malkki's data suggest that the length, or molecular weight, of a beta-glucan chain plays an important role in determining the cholesterol-lowering ability of this soluble fiber.

Molecular weight is the sum of the atomic weights for all atoms in a molecule. In rats, Malkki found that concentrates of beta-glucan molecules having a molecular weight of 1 million lowered serum cholesterol levels 10 percent; beta-glucan with a molecular weight of 2 million lowered cholesterol as much as 20 percent; and beta-glucan with a molecular weight of 3 million slashed cholesterol levels almost 30 percent. Longer or shorter chains, however, proved largely ineffective. Ironically, Malkki says, many of the purification and processing steps used by cereal manufacturers can break the relatively fragile beta-glucan chains into ineffectively small pieces.

The rat studies indicate that the concentrate with the longest effective chains offers, per gram of beta-glucan, up to 2-1/2 times the cholesterol-reducing potency of the intact bran, Malkki reports. He suspects the reason traces to the stomach and gut, where water may have a hard time getting past oils in the bran to dissolve and swell the gummy beta-glucan within.

As beta-glucan molecules soak up water, they become viscous and decrease the diffusion of bile acids -- which help digest dietary fats -- to the intestinal wall. Bile acids that reach the intestinal wall eventually get recycled. But those captured by beta-glucan are excreted, forcing the body to draw upon its cholesterol stores to replace them. The end result: less cholesterol circulating through blood vessels, where it can accumulate to form artery-clogging deposits.

Before he recognized the importance of molecular weight, Malkki had conducted a small clinical trial in which 13 men with elevated cholesterol ate two beta-glucan-enriched wheat rolls each day for eight weeks. Each pair of rolls contained a total of 7.5 to 15 grams of a beta-glucan concentrate. Malkki now attributes the small (about 5 percent) average cholesterol reduction observed in these men to the relatively short beta-glucan chains used in the concentrate, and says he expects better results from formulations with longer chains. Food-fortifying concentrates based on his patented process could reach the market in Finland later this year, he adds.

At the USDA's Northern Regional Research Center in Peoria, Ill., scientists are developing another beta-glucan concentrate. It not only offers the cholesterol-lowering benefits of oat bran, but also could substitute for animal fat in a range of foods -- from milkshades and cheese to mayonnaise, creamy gravies and cookie fillings.

Bio-organic chemist George E. Inglett mixes either oat bran or oat flour with water, then adds an enzyme that degrades the starches into starch gums. Sieving insoluble materials out of the resulting soup leaves a mix of gums, which he dries into granules or powder. Depending on the starting mix, this gelatin -- which Inglett calls "oatrim" -- contains from 1 to 25 percent beta-glucan by weight.

Inglett says tests on chicks fed a high-cholesterol diet for 10 days suggest his concentrate offers potentially significant benefits. Some 2.2 percent (by weight) of the oatrim-enriched diet consisted of beta-glucan. On average, compared with control chicks given corn- and soy-derived fiber in place of the oatrim, test chicks had 18 percent less than serum cholesterol, 15 percent less triglycerides (a form of lipids) and a whopping 49 percent lower concentration of low-density lipoprotein (LDL) cholesterol, Inglett reports. At the same time, their concentrations of high-density lipoprotein (HDL) cholesterol -- known as the "good" cholesterol -- were 18 percent higher than those of control chicks.

Oatrim containing up to 20 percent beta-glucan holds up to frying and bakes into "a perfectly good bread," Inglett says. But he thinks the biggest commercial appeal of the odorless, nearly tasteless gel will come from its ability to replace fats in low-temperature applications such as frozen desserts. He reports that 18 experienced taste-testers rated ice milk made with oatrim as "very creamy" -- approaching the taste, feel and density of premium ice cream. Unlike the comparison ice cream, which had 298 calories and 22 grams of fat per 4-ounce serving, the oatrim-enriched product contained only 135 calories and 0.5 gram of fat, he says.

Commercial demand for oat fiber has risen sharply since claims of its cholesterol-lowering ability were first widely popularized in 1987, prompting sales by the Quaker Oats Co. to skyrocket from 1 million pounds of oat bran a year 2 million pounds a month by the end of 1989, according to company spokesman Ron Bottrell in Chicago, Barley producers now hope that research findings from Montana State University will create a similar hunger for the fruits of their labors.

Most U.S. barley goes into livestock feed, which explains why Walt Newman, an animal nutritionist at Montana State in Bozeman, became interested in the grain. In 1978, he found he could lower cholesterol in rats by feeding them barley. Since barley has a hight beta-glucan content, the rat study suggested a possible explanation for the poor growth of poultry raised on it.

He and his wife, human nutritionist Rosemary Newman, reported findings in 1984 had not only confirmed a weight reduction among chickens eating barley instead of corn, but also revealed greasier feces -- evidence that the barley-fed birds excreted more fat and cholesterol. The researchers later showed that chickens fed barley also have lower blood levels of cholesterol, especially LDL cholesterol.

To establish the role of barley's beta-glucan, the Newmans went on to feed chickens barley-enriched diets, some of which contained beta-glucanase, the enzyme that breaks down beta-glucan. Only the chickens on the enzyme-free diets showed dramatic reductions in serum cholesterol, they found. However, even the enzyme-fed chickens, showed lower serum cholesterol levels than the corn-fed controls, leading the scientists to suspect that a second cholesterol-lowring agent was a work.

Studies by y Asaf A. Qureshi and his colleagues at the University of Wisconsin-Madison identified that agent as tocotrienol, an oily antioxidant related to vitamin E. Further work by Qureshi, the Newmans and others now indicates this chemical operates by inhibiting the body's synthesis of cholesterol. Says Rosemary Newman, "We have not seen any other grain that carries barley's double whammy" -- high levels of cholesterol-countering beta-glucan and tocotrienol.

Over the past decade, the Newmans have assayed barley cultivars in search of the richest beta-glucan source. They have found that something about the genetic makeup of "hull-less" barleys with "waxy-type" starch appears to optimize the soluble fiber's production. Whereas oat and barley grains typically contain about 5 percent beta-glucan, the Newmans have identified hull-less, waxy cultivars that produce 7 to 15 percent. Moreover, they say, it's possible to winnow the milled grain down to a relatively coarse fraction containing as much as 23 percent beta-glucan.

Rosemary Newman reports data from a pair of human trials -- one lasting four weeks, the other six -- confirming the ability of barley-based high-fiber diets to lower serum cholesterol as effectively as oats and up to 18 percent more effectively than wheat flour. Most volunteers started the trial with significantly elevated cholesterol levels. And to date, she says, roughly one-third of them have successfully used barley to keep their cholesterol from returning to pretrial levels.

The trick to getting people to consume effective quantities of this long-over-looked grain, she says, lies in finding interesting ways to incorporate it into the diet. Over the past two years she has been developing new recipes, in part to keep former study participants on the barley bandwagon.

One commercially available source of barley for baking and cooking is a beer-brewing byproduct known as malted barley. Though malting removes the beta-glucan, it doesn't erase barley's cholesterol-fighting potential, says food scientist Frank E. Weber of the Miller Brewing Co. in Milwaukee. That's because malting and beer brewing concentrate the oily tocotrienol, he explains. Weber reports data from a pair of month-long studies involving a total of 73 people with elevated serum cholesterol, indicating that daily consumption of as little as 3 to 5 tablespoons of malted barley can lower serum cholesterol by as much as 15 percent.

In the first study, 4 tablespoons of malted-barley bran daily lowered serum cholesterol an average of 6 percent. In the second study, participants ate a low-fat diet along with a daily dose of either 3 tablespoons of malted-barley bran or the oil derived from 4 tablespoons of the bran. Their cholesterol levels dropped an average of 10 percent, Weber says.

Moreover, the cholestrol-lowering effect of bran flour made from malted barley "is more persistent than oat bran's," he asserts. "You can stop taking [malted] barley bran and tocotrienol, and eight weeks later your cholesterol is still lower [than before the supplementation began]."

"Beta-glucan has proven cholesterol-lowering effects," says James Anderson, who pioneered oat bran's use in the dietary management of high cholesterol at the Veterans Administration Medical Center in Lexington, Ky. However, he adds, beta-glucan and tocotrienol are not panaceas. Some people with high cholesterol show little or no response to them. And among those who do respond, he points out, "we seldom see a [diet-induced] blood cholesterol reduction of greater than 20 percent. I think that's sort of the limit of its potency." Patients who need more dramatic reductions to bring their serum cholesterol ino the healthy range "probably need a more powerful drug," Anderson says.

What about people whos serum cholesterol is already in the healthy range? Dietary changes may not lower it much, if at all, these researchers observe. But beta-glucan's benefits extend to another front. The National Center Institute recommends eating at least 20 to 30 grams of fiber daily -- about twice what most U.S. adults now consume. And beta-glucan, whatever its source, could help many people fill that fiber gap.
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Title Annotation:includes related article
Author:Raloff, Janet
Publication:Science News
Date:May 26, 1990
Words:1819
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