AbstractUsing 63 healthy subjects, we conducted an observational study to assess associations between colonic epithelial cell proliferation and dietary intake of selected nutrients. Study subjects exhibited no personal or family history of colon carcinoma, familial polyposis coli, sporadic adenomas, or chronic inflammatory bowel diseases. In this study population, a negative association between the tritiated thymidine‐labeling index and dietary intake of calcium (p<0.003) was found after the effects of age, sex, body mass index (kglm2), dietary fat, and total energy were controlled in a linear regression model. The association for calcium indicated that a daily calcium intake of 1,200 mg was associated with a predicted thymidine‐labeling index of 6%. In the same model, a positive association with the thymidine‐labeling index was found for body mass index (p<0.002) and was suggested for female gender (p<0.09). No association was found between the thymidine‐labeling index and intake of fat, protein, carbohydrate, retinol, ascorbic acid, phosphorus, or iron. Repeat measures of diet in this investigation were used to estimate a subject's daily intake of selected nutrients.