Effects of high- and low-fiber diets on human feces

Increased- and low-fiber diets composed of common hospital foods were tested for their ability to alter stool weight, frequency of defecation, transit time, and absorption efficiency. The diets were calculated to be isocaloric and similar in protein, fat, and carbohydrate. They were dissimilar in ash and fiber. No stimulants, secretagogues, food concentrates, or extracts were used on either diet. Six normal, healthy, male subjects consumed each constant diet for five to eight days. Diets and stool composites were analyzed for protein, fat, fiber, moisture, and ash. Carbohydrate and calories were calculated. Stool weight during ingestion of the low-fiber diet averaged 51 gm. per day; subjects had an average of one bowel movement every 33 hr.; and the mean transit rate was 48 hr. When subjects consumed the increased-fiber diet, values were 157 gm., 19h., and 12 hr., respectively. Measurements of fecal protein, fat, carbohydrate, and calories from the low-fiber diet were less than half those observed when the increased-fiber diet was consumed. By altering specific components of a normal diet, e.g., fiber, significant differences can be made in bowel habit and absorption efficiency.