Phytosterols have an unfavourable effect on bacterial activity and no evident protective effect on colon carcinogenesis

The effects of physiological dietary phytosterol supplements on intestinal microflora activity and faecal sterols and their capacity to protect rats f ed a normal or high saturated fatty-acid diet against tumour development we re studied. A group of 80 female Wistar rats were fed an 8% lipid diet for 4 weeks (adaptation period) and then randomly assigned in a factorial exper imental design study to diets containing 8% or 24% hydrogenated coconut oil , with or without a 24-mg/day/rat phytosterol supplement. They were instill ed intrarectally with saline or methyl-nitroso-urea (MNU), Faecal sterol ou tput was analysed for one week each month, Pathological analysis was done a t the end of the 30-week experiment. Animals treated with MNU and given phy tosterol supplements had tumour frequencies (8/20) similar to those not fed phytosterols (11/20). The fat-supplemented diet had no significant influen ce. Colonic glands were found in area of lymphoid follicles in all the grou ps, but were more frequent in rats on high-fat diets (P < 0.01), The copros tanol and the cholesterol excretion of the phytosterol-supplemented rats wa s significantly enhanced, Therefore phytosterols have an unfavourable effec t on bacterial activity. These data confirm the capacity of phytosterols to decrease cholesterol absorption, but indicate that a large excess of phyto sterol must be avoided until further research on its effects on carcinogene sis has been done. (C) 2001 Lippincott Williams & Wilkins.