The American Journal of Clinical Nutrition 34: OCTOBER © 1981 American Society for Clinical Nutrition 1981, pp. 2111-2116. Printed in U.S.A. Limits of predicting gastrointestinal transit time from other measures of bowel function1’2 J. L. Slavin, M.S., C. T Sempos, M.S., P. M. Brauer, M.S., and J. A. Marlett,3 Ph.D. ABSTRACT The two aims of these experiments were first, to examine the relationships between mean daily stool weight, mean weight per stool, frequency of defecation, dye transit time, dietary fiber intake, and transit time of small radiopaque pellets, and second, to determine the ability of these measures of bowel function, singly or in combination, to predict gastrointestinal transit time ofthe pellets. Variables were observed simultaneously in 13 healthy women consuming controlled low and high cellulose diets. All except one of the correlation coefficients between the measures of bowel function were significant. Stepwise regression analysis retained log stool weight, fiber and dye transit to predict log of the mean transit time of all pellets (R2 = 71.3); the same three variables were selected to predict log of the transit time of 80% of the pellets (R2 = 59.4). Mean daily stool weight explained about 50% of the variation for both measures of transit, while dye transit and dietary fiber explained the rest. Log transformation of either stool weight or pellet transit time or both variables improved the prediction by about 10%. These results suggest that prediction of pellet gastrointestinal transit time from other measures of bowel function may be limited and is influenced significantly by the fiber level of the diet. Am. J. Clin. Nuir. 34: 2111- 2116, 1981. KEY WORDS Gastrointestinal transit time, stool weight, dietary fiber, correlation of bowel functions Introduction Gastrointestinal transit time is mainly a colonic event ( 1) and has been suggested as a measure of overall colonic function (2). The availability ofa method to estimate gut transit that could be conveniently and easily used in a field study of a large number of individuals would be useful in the study of the role of dietary fiber in bowel function. Correlations between transit time and other measures of bowel function, that are simpler to determine, suggest it may be possible to predict transit time from one or more of these measures. The transit time of small radiopaque pellets has been correlated with mean daily stool weight (2-7), dye (8), and frequency of defe- cation, although the correlation with defeca- tion frequency was significant in only one (9) of three (9-11) studies. However, rate of pas- sage of dye has been criticized because it cannot be conveniently quantitated in feces (12) and may not always be visible (13). Further, dietary fiber appears to influence the correlations of pellet transit time with stool weight (7), defecation frequency (9), or dye (8). Stool collection and access to x-ray facili- ties are necessary to conveniently quantitate the pellets, whereas mean daily stool weight would require only stool collection. Deter- mination of defecation frequency and transit time of dye would not require stool collection from competent, adequately instructed adults. The aims of this study, therefore, were to examine the correlations between these various measures of bowel function assessed in subjects consuming constant diets and to determine whether stool weight, defecation frequency, and dye transit time, singly or in From the Department of Nutritional Sciences, Uni- versity of Wisconsin-Madison, 1300 Linden Drive, Mad- ison, WI 53706. 2 Supported in part by University of Wisconsin Amer- ican Cancer Society Institutional Grant IN-35Q-6, Na- tional Institutes of Health Grant AM2l7l2, and The College of Agricultural and Life Sciences, University of Wisconsin-Madison. Author to whom requests for reprints should be addressed. 2111 by guest on April 16, 2012 www.ajcn.org Downloaded from