Calcium supplements interact significantly with long-term diet while suppressing rectal epithelial proliferation of adenoma patients

BACKGROUND. Calcium supplements to the western-style diet may reduce the ri sk for colorectal neoplasia. Using rectal epithelial proliferation (REP) me asurements as a biomarker of response to intervention, the authors evaluate d the effects of 1-year calcium supplementation in adenoma patients and its possible interactions with the patients' dietary and lifestyle habits. METHODS. Consenting adenoma patients, without a family history of colorecta l neoplasia, were randomly selected to receive 3.75 g calcium carbonate (1. 5 g Ca2+) daily or to receive no treatment. All had their long-term dietary and lifestyle habits assessed and their REP labeling index (LI) evaluated before and at end of follow-up. The change in LI was compared between group s, and statistical associations were examined between mean nutrient consump tion and treatment effect and between lifestyle and treatment effect. RESULTS. Fifty-two adenoma patients (33 treated and 19 untreated) completed intervention and follow-up. There were no significant differences between study groups in age, weight, cigarette smoking, or medication use. The LI d ecreased in 58% of calcium-intervened patients and in only 26% of noninterv ened patients (P = 0.04); the mean LI x 100 (+/- standard deviation ) of th e former fell from 5.04 +/- 1.93 to 4.54 +/- 1.58, and rose from 4.32 +/- 1 .58 to 4.93 +/- 1.58 in the latter (P = 0.04). A lower fat, a higher carboh ydrate, fiber, or fluid intake each interacted with the calcium supplementa tion to decrease the LI (P = 0.02, 0.001, 0.02, and 0.08, respectively). CONCLUSIONS. Long-term calcium supplements significantly suppressed REP in adenoma patients, and long-term dietary habits contributed to this effect. Patient diet should be assessed when researchers use REP as a biomarker in calcium chemoprevention studies. Study results indicated that relevant diet ary counseling may be useful in addition to calcium supplements in persons at increased risk for colorectal neoplasia. (C) 2001 American Cancer Societ y.