EFFECTS OF MILK AND MILK-PRODUCTS ON RECTAL MUCOSAL CELL-PROLIFERATION IN HUMANS

Intake of dairy products and major dairy constituents (e.g., calcium) has been proposed to reduce the risk of colorectal cancer, although ep idemiological studies have yielded inconclusive results. We conducted a randomized cross-over trial to test the effects of high- and low-dai ry consumption diets on rectal mucosal proliferation, a possible inter mediary marker for large bowel cancer. From a gastroenterology clinic at an academic medical center, we recruited 40 patients, ages 25-79 ye ars, who had either a history of a large bowel adenoma or a first-degr ee relative with large bowel cancer. Participants completed a baseline questionnaire covering demographic characteristics, health history, a nd habits and a food frequency questionnaire. They were randomized to a 12-week diet of either high dairy intake (six dairy servings/day) or low dairy intake (<0.5 serving of dairy products/day), with an interv ening 12-week washout period in which they were asked to resume their usual diet before crossing over to the alternate study diet for the la st 12-week period of the study. Adherence to the study diets was monit ored by a daily dairy intake checklist and periodic, unscheduled 24-h dietary recalls. Biopsies of the rectal mucosa were obtained at the be ginning and end of each intervention phase. Two assays of rectal mucos al cell proliferation were performed: immunohistochemical determinatio n of proliferating cell nuclear antigen and whole crypt mitotic count. We found no statistically significant changes in either of these prol iferation measures as a result of high or low dairy intake. There was no correlation between the labeling index for proliferating cell nucle ar antigen and whole crypt mitotic count; however, measures of the loc ation and intensity of cell proliferation within the rectal crypt were highly correlated between the two assays. Thus, our study indicates t hat greater consumption of dairy products over a 12-week: period does not change rectal mucosal cell proliferation.