Effects of dietary fiber on serum cholesterol, gastrointestinal function and fecal steroid excretion
Abstract
Two crossover metabolic studies compared the effect of oat bran (OB) and wheat bran (WB) on serum cholesterol, gastrointestinal function and fecal steroid excretion in healthy, college-age men (OB 9 and WB 11 subjects). Each study consisted of feeding a constant, low fiber diet (28 days) followed by a high fiber diet (28 days) in which 14g of dietary fiber from OB or WB was added to the diet as a part of the foods consumed. Body weights were maintained and source of calories remained constant. Four, 5-day fecal collections were made during the final 20 days of each feeding period and bile acid and neutral steroids measured. Paired comparisons of the final collection period for each high fiber treatment with its low fiber treatment indicated that WB resulted in a significant decrease (8.88 versus 5.40 mg/g) and OB a significant increase (6.45 versus 8.82 mg/g) in fecal bile acid concentration. Analysis of all collection periods indicated that these changes took place by the first collection period (beginning day 8) and remained constant throughout the experiment. Daily bile acid excretion was not altered by WB (214 versus 209 mg/day) but was increased by OB (184 versus 396 mg/day) treatment. Ratio of lithocholic to deoxycholic acid, suggested as an indicator of colon cancer risk, was reduced significantly by both WB and OB treatment. Fecal weight was significantly increased and transit time and fecal pH were significantly decreased by WB and OB. Fecal moisture and stool frequency were not significantly affected by either WB or OB. A series of experiments examined the effects of bamboo shoots compared with cellulose as a dietary fiber source on serum cholesterol levels and fecal steroid excretion in rats. Bamboo shoots at levels as low as 0.25% in the diet significantly decreased serum cholesterol by 23%. Daily fecal steroid excretion was not consistently increased by bamboo shoots. Feed efficiency and weight gain were reduced by feeding bamboo shoots at levels from 15% to 2.5% in the diet, but these effects disappeared at 1% or less. These experiments suggest that bamboo shoots can reduce serum cholesterol in rats by a mechanism which does not involve changes in steroid excretion.
Degree
Ph.D.
Advisors
Story, Purdue University.
Subject Area
Nutrition
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