The Joy of Oats
It pains me to read studies in human nutrition. Most of the news seems bad. Worse, I develop a yen for anything put on the dietetic hit list. Eggs were dull sustenance until someone got serious about studying cholesterol; now I collect omelet recipes.
It's different with things we're supposed to add. When research showed that some members of the cabbage family seem to stave off a few types of cancer, I happily added broccoli to salads and stir-fries. For me, maybe the best of the foods now bearing the Eat Me for Health label is oats.
Oat bran--the outer portion of the oat grain--has received most of the publicity. Soluble fiber, such as that in beans and especially in oat bran, apparently lowers blood cholesterol in people who eat fair quantities of it. Other kinds of things our mothers urged us to eat for bulk or roughage, like wheat bran, don't have that result. The fiber they contain is considered insoluble. It's useful and healthy enough, but doesn't seem to have much effect on cholesterol.
This is one of those cart-before-horse discoveries. The effect of oat bran on blood cholesterol levels was documented before the reasons for that effect were understood. In fact, they're still unclear.
Recently, British researchers have charted part of the bran's effect on the digestive system, an important first step in understanding how it works on body chemistry. According to New Scientist magazine, E. Lund and his colleagues at the Institute of Food Research in Norwich, England, fed male rats a diet rich in oat gum or finely ground rolled oats--real oatmeal. In oat-fed rats, they found that the small intestine contents were wetter and more viscous than in rats fed normal fare. The oat-fed rats also had a kind of boundary layer at the mucosal surface of their small intestines.
The research team determined that the source of these effects was glucan, a substance concentrated in the oat bran. Somehow, the glucan-produced intestinal reactions blocked the absorption of dietary cholesterol. The higher the proportion of oats in its diet, the less cholesterol in a rat's bloodstream.
Exactly how this works isn't clear, the mechanism is still the subject of speculation. One of the more fascinating possibilities is that the viscous effect slows the rate at which the body recovers bile salts. These are substances secreted by the liver to aid digestion, but they are rich in cholesterol. (That's one of the toughest problems in trying to reduce cholesterol---the liver manufactures the stuff. A cholesterol-free diet doesn't guarantee a cholesterol-free bloodstream, in rats or in humans.) A related possibility is that intestinal bacteria ferment the oat fiber, producing compounds that then inhibit the production of cholesterol by the liver.
Whatever the reason, oats really do work. The British researchers think they are the only common food in Western diets producing important changes in the consistency of intestinal contents, and--so far--the only one with an established record of lowering blood cholesterol.
The mounting evidence that oats are a remarkably healthy food may even be healthy for Alaska's economy. Oats do well here; in 1987, Alaska farmers planted 5700 acres in that grain. Much of it was used for animal feed right on the farms where it was grown, but what was sold brought in $96,000 for the farmers--and that was before all the news about oats and cholesterol.
I'm willing to help support those farmers. With visions of steaming bowls of oatmeal porridge for breakfast and crusty slices of oat bread at dinner, I think I can live with an oat-rich diet.
