M ore 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 betaglucan 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 at 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-glucanenriched 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 cholesterollowering 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; betaglucan 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 Mailkki 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 21/2 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 betaglucan 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 betaglucan chains used in the concentrate, and says he expects better results from formulations with longer chains. Foodfortifying concentrates based on his patented process could reach the market in Finland later this year, he adds.