INCREASING AMOUNTS OF DIETARY FIBER PROVIDED BY FOODS NORMALIZES PHYSIOLOGICAL-RESPONSE OF THE LARGE-BOWEL WITHOUT ALTERING CALCIUM BALANCEOR FECAL STEROID-EXCRETION

Nine healthy, young men consumed constant diets to determine selected large-bowel, serum cholesterol and triacylglycerol, and calcium balanc e responses to 3 amounts of fiber provided by a mixture of fruit, vege tables, and grains. The diets, each consumed for 1 mo, contained 16, 3 0, and 42 g total fiber/d, of which 2.9, 4.8, and 7.7 g, respectively, was soluble. Mean daily wet and dry stool weights increased with each fiber addition. The first fiber addition increased defecation frequen cy and decreased fecal pH, bile acid concentration, and neutral steroi d concentration: the second addition had no further effect. Mean weigh t of each defecation and stool moisture did not increase and serum cho lesterol and triacylglycerol concentrations, calcium balance, and gast rointestinal transit time did not decrease as fiber intake increased. We conclude that I) fiber provided by a mixed-food diet increases stoo l weight as effectively as does wheat or oat bran; 2) even high amount s of dietary fiber do not change transit time or defecation frequency if they are already approximate to 1 and 2-3 d, respectively; 3) food patterns consistent with the food pyramid and incorporating legumes an d whole grains are necessary to achieve recommended fiber intakes of 2 0-35 g/d, even if energy intake is >12.55 MJ (3000 kcal); 4) soluble f iber provided by a mixture of whole foods has no effect on serum chole sterol concentrations or output of fetal bile acids. and 5) mixed-food fiber has little effect on calcium balance when calcium intakes are h igh (greater than or equal to 1.5 g/d).