Oat Bran Has a Slight Effect, Study Finds : Health: Analysis indicates that cholesterol is lowered 7% at most.
Oat bran, whose role as a cholesterol-fighting food has been disputed, appears to have a specific, but small, cholesterol-lowering effect after all, according to a new analysis that scientists are calling the most definitive word yet on the purported benefits of the product.
The analysis, combining the results of 12 previous studies, found that eating a large bowl of ready-to-eat oat bran cereal or three packets of instant oatmeal a day can, on the average, reduce the total cholesterol in the blood by 2% or 3%. For people with high cholesterol levels, the reduction can be as great as 6% or 7%.
“We have pretty much answered the confusion about the role of oats in lowering cholesterol,” said Cynthia M. Ripsin, a researcher at the University of Minnesota in Minneapolis and the principal author of the study. It is being published today in the Journal of the American Medical Assn.
Ripsin added: Oat bran is “not a magic bullet. It is probably not going to make a big difference,” particularly for people whose cholesterol level is so high that a modest reduction would not be significant. For such people, Ripsin said, oat bran should be viewed as an adjunct to other recommended activities, such as following a diet low in cholesterol and saturated fats, weight loss, exercise and stopping smoking.
The study was funded in part by the Quaker Oats Co., a leading cereal manufacturer. Ripsin said the statistical analysis, which began as her master’s thesis, was conducted independently of the company and with “complete control” by the researchers. The medical journal report has a total of 16 authors from many universities.
It is uncertain exactly how oat bran might lower one’s cholesterol level. The leading theories suggest that the soluble fiber component of the bran forms a gel in the intestine, according to David Kritchevsky of the Wistar Institute in Philadelphia, who has been a paid consultant to Quaker Oats Co.
As the theory goes, this gel can trap cholesterol and other substances, interfering with their absorption into the circulation from food or helping to remove cholesterol made in the body, Kritchevsky said.
Some oat bran studies had suggested that cholesterol reductions may simply have been a result of substituting carbohydrate-containing foods, such as oat bran, for fatty foods. The new report suggests that while food substitution does play a role, oat bran consumption has an additional effect on cholesterol level, independent of the rest of the diet.
But the analysis leaves unresolved the question of whether cereal manufacturers should be allowed to make a cholesterol-lowering health claim about oat bran on food labels. The Food and Drug Administration is drafting regulations on this subject. Sales of oat bran food have slumped in recent years, as skepticism has increased about health claims related to the products.
When asked what the FDA should do, Ripsin declined to offer an opinion. “I am comfortable with the results of the study, but I haven’t thought about what somebody else is going to do with this,” she said.
For adults, the recommended cholesterol level is 200 milligrams per deciliter or less. A moderate level is between 200 and 239. A high level is considered 240 or greater.
The researchers used a statistical technique known as “meta-analysis” to combine the results of previous trials that met their criteria for scientific rigor. After reviewing data from 20 published and unpublished trials as of March, 1991, they selected the results of 12 for detailed analysis. In these trials, the mean cholesterol value was 229.
The overall conclusion was that people who consume about three grams per day of soluble fiber, the amount of fiber in a bowl of ready-to-eat oat bran cereal or three packets of instant oatmeal, can lower the total cholesterol level between five and six milligrams per deciliter. According to Ripsin, the data also suggested that people who consumed larger amounts of soluble fiber each day and those with blood cholesterol levels of 240 or greater would have greater reductions.
Dr. Frank Sacks of Harvard Medical School, whose widely publicized 1990 study of oat bran cast doubt on its cholesterol-cutting role, said that while the new analysis was “very good” from a scientific standpoint, the effect of oat bran was “totally trivial.”
“The very small effect was too small to be detected in any single study,” Sacks said in a telephone interview. “In my opinion, it is so small that it is not clinically relevant.”
Sacks said that in contrast to oat bran, cholesterol-lowering drugs are capable of lowering cholesterol levels as much as 20% to 25%. Major dietary changes are also able to reduce the cholesterol by similar amounts in some individuals.
Small reductions in cholesterol may have little impact on the risk of heart disease for one individual, but they may be important for large populations of people. The medical journal report cites the 1984 Lipid Research Clinics Program study, which concluded that a 1% reduction in cholesterol levels could decrease overall heart disease mortality in the United States by 2%.
This means that a lowering of cholesterol by 1% may prevent a fatal heart attack in only 2 of 100 people, but in a population of 1 million, that could mean 20,000 lives saved.
The new analysis concluded that “if even the segment of the population at increased risk for cardiovascular disease were able to reduce its total cholesterol level 2% to 3%, this would have a very beneficial impact on rates of heart disease.”
