Summary A protective effect of calcium against colorectal cancer has been described in Anglo-Saxon but not in Latin communities, and no such effect has been observed regarding adenomas. We investigated the relationship between calcium, dairy products and the adenoma-carcinoma sequence in a French region by comparing small adenoma (< 10 mm, n = 154), large adenoma (n = 208) and polyp-free (n = 426) subjects, and cancer cases (n = 171) with population controls (n = 309). There was no protective effect of calcium against colorectal tumours except for low fat calcium and large adenomas in men (OR for highest quintile= 0.3, P for trend = 0.06). There was even a trend towards an increased risk of cancer with dairy calcium in men and nondairy calcium in women. Vitamin D was inversely related to the risk of small adenomas in women (OR for highest quintile = 0.4, P for trend = 0.04). Regarding dairy products, only consumption of yoghurt displayed an inverse relationship with risk of large adenomas, in both men and women. These data failed to demonstrate a protective effect of calcium against colorectal carcinogenesis. They suggest that the type of dairy product might be the important factor with regard to prevention of colorectal tumours. (Benito et al., 1991;Tuyns et al., 1988; Negri et al., 1990). Dairy products have also been studied not only because they are the main source of dietary calcium, but also because other components may be of interest, such as the lactose content or the bacteria in fermented dairy products. To date, no significant association has been described between calcium intake and colorectal adenomas (Kampman et al., 1994a). This finding is all the more important since certain of the current intervention studies with calcium supplements use adenoma recurrence as an end point.France has a tradition of high calcium intake, mainly in the form of cheese. In order to define further the effect of calcium, phosphate, vitamin D and dairy product intake on the adenoma-carcinoma sequence, we carried out a casecontrol study in a French community of the relationship between these nutrients, as well as calcium-containing foods and the different macroscopic steps of colorectal carcinogenesis, namely small adenoma, large adenoma and cancer.
Materials and methodsCases and controls A case-control study was set up between 1985 and 1990 to investigate risk factors for the different macroscopic steps of the adenoma-carcinoma sequence. Its general design has already been described Sample size calculations were based on fat intake, one of the suspected major risk factors for colorectal cancer. Considering the proportion of the population exposed to a high-fat diet, with a power of 80% to demonstrate a relative risk of 2.0 at the 5% level of significance, it was calculated that at least 140 cases and 280 controls were needed in each group.Two groups of patients with adenomas and polyp-free controls were selected from the endoscopy lists of all gastroenterologists in the area, whether in private or public practice. Adeno...
