Efficacy of dietary fiber in lowering serum cholesterol

Abstract

I n the last few years, increasing attention has been given to lowering serum cholesterol levels to reduce high rates of coronary artery disease in the U.S. population.Q Using the new classification, it is estimated that approximately 32% of adult men and 27% of adult women in the United States require intervention for either borderline-high or high serum cholesterol levels.3 Considering the magnitude of the problem, in order to minimize health care costs, more emphasis is being given to dietary therapy and physical activity.2 Although the benefits of reducing consumption of cholesterol-raising saturated fats and cholesterol are well recognized and form the basis of Step-One and Step-Two Diets,1)2 an increase in dietary fiber has not been included as an essential component of dietary therapy. In this issue of the Journal, Hunninghake et al4 report the results of a nearly year-long multicenter trial of the efficacy of dietary fiber in the treatment of hypercholesterolemia. Using 20 g per day of a mixed dietary fiber supplement consisting mainly of watersoluble fibers (guar gum and pectin), and some water-insoluble fibers (pea, soy, and corn bran), the investigators observed, on average, a 5% lowering of total cholesterol and 9% lowering of low-density lipoprotein (LDL) cholesterol levels in 59 of the 93 hypercholesterolemic patients who complied with the therapy and Step-One Diet. Although the reductions in serum cholesterol values ranged from 1.6% to 6.6%, and in LDL cholesterol levels from 4.3% to 10.9%, the persistence of the hypocholesterolemic effect of dietary fiber over the long term was noteworthy. The study, however, has some limitations, which include exclusion of 34 subjects due to various reasons and lack of an intent-to-treat analysis. In addition, information on the nature and severity of gastrointestinal side effects that led 7 patients to withdraw from the study was not provided. The study, nevertheless, contributes importantly to our knowledge of long-term persistence of lipid-lowering action of dietary fiber over and above that of a Step-One Diet. Still, some questions remain unanswered. Is there a place for dietary fiber or its supplements in the management of hypereholesterolemia?