Mechanisms of the intestinal effects of dietary fats and milk products on colon carcinogenesis

Dietary fat may promote colon cancer by increasing fatty acids (FA) and secondary bile acids (BA) in the colonic lumen. These cytotoxic surfactants can damage colonic epithelial cells and thus induce a compensatory hyperproliferation of crypt Cells. Our studies show that the hyperproliferative effect of type and amount of dietary fat is not simply due to changes in colonic FA and BA. This indicates that an additional, at present unknown, cytotoxic factor is involved. The hyperproliferative effect of dietary fat is inversely related to the amount of calcium in the diet. In rat and man, dietary calcium precipitates colonic cytotoxic surfactants and thus inhibits luminal cytotoxicity. These inhibitory effects on metabolic risk factors suggest a preventive effect of dietary calcium on colon carcinogenesis. (C) 1997 Elsevier Science Ireland Ltd

Calcium in milk products precipitates intestinal fatty acids and secondary bile acids and thus inhibits colonic cytotoxicity in humans

Dietary calcium may reduce the risk of colon cancer, probably by precipitating cytotoxic surfactants, such as secondary bile acids, in the colonic lumen. We previously showed that milk mineral, an important source of calcium, decreases metabolic risk factors and colonic proliferation in rats, We non report the effects of the habitual intake of milk calcium on metabolic risk factors in healthy subjects. A double-blind, cross-over metabolic study was performed in 13 healthy males, Placebo milk products (calcium, 3 mM) were compared with regular milk products (calcium, 30 mM), In each 1-week period, the habitual diet was recorded, and urine and feces were collected for 1 and 3 days, respectively. Milk calcium significantly increased fecal pH and fecal excretion of phosphate (132%), total fat (139%), free fatty acids (195%), and bile acids (141%), indicating intestinal complexation. In fecal water, the concentrations of long-chain fatty acids, secondary bile acids (deoxycholic and lithocholic acid), neutral sterols, and phospholipids were about halved (P <0.05), Consistent with these changes in soluble hydrophobic surfactants, calcium decreased the cytotoxicity of fecal crater from 68 +/- 9 to 28 +/- 12% (P <0.005), Calcium in milk products precipitates luminal cytotoxic surfactants and thus inhibits colonic cytotoxicity. Therefore, habitual dietary calcium may contribute to a nutritional modulation of colon cancer risk

Interlaboratory Evaluation of 3 Culture Media for Postimplantation Rodent Embryos

The first aim of the study was to compare the ability of rat serum, human serum, and a mixture of human and rat serum (4:1) to support in vitro development of rodent postimplantation embryos. The comparison was made in three laboratories using rat embryos and in one laboratory using mouse embryos. Batches of sera, initial developmental stage, duration of culture, and endpoints were identical in the laboratories. The second aim of the study was to evaluate if other variables that could not be standardized would significantly influence the results of the laboratories. No reproducible difference was observed among the culture media or among the laboratories except that growth and differentiation were slower in the laboratory using mouse embryos. Further experiments are needed to exclude small differences in performance of the media