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

Abstract

The effects of physiological dietary phytosterol supplements on intestinal microflora activity and faecal sterols and their capacity to protect rats fed a normal or high saturated fatty-acid diet against tumour development were 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 experimental design study to diets containing 8% or 24% hydrogenated coconut oil, with or without a 24-mg/day/rat phytosterol supplement. They were instilled intrarectally with saline or methyl-nitroso-urea (MNU). Faecal sterol output was analysed for one week each month. Pathological analysis was done at the end of the 30-week experiment. Animals treated with MNU and given phytosterol supplements had tumour frequencies (8/20) similar to those not fed phytosterols (11/20). The fat-supplemented diet had no significant influence. Colonic glands were found in area of lymphoid follicles in all the groups, but were more frequent in rats on high-fat diets (P < 0.01). The coprostanol and the cholesterol excretion of the phytosterol-supplemented rats was significantly enhanced. Therefore phytosterols have an unfavourable effect on bacterial activity. These data confirm the capacity of phytosterols to decrease cholesterol absorption, but indicate that a large excess of phytosterol must be avoided until further research on its effects on carcinogenesis has been done.

Phytosterols as anticancer compounds

“…These rodent studies support a cancer protective model of dietary phytosterols with reduced colonic cell division in animals after challenge with proliferative carcinogenic stimuli. On the other hand, contrary results were obtained by the study of Quilliot et al [39] who observed a lack of effect of dietary phytosterols on carcinogen-induced colon cancer in rats. It is possible that the experimental diet formulated with hydrogenated coconut oil and low protein might have affected the latter outcomes.…”

Anticancer effects of phytosterols

“…Similarly, Choi et al (2007) determined the effect of campesterol at 10-20 mg/ml on basic fibroblast growth factorinduced angiogenesis in the chorioallantoic membrane of fertilized chicken eggs and reported reduced vascularization in the membrane in a concentration-dependent manner. Quilliot et al (2001), however, failed to observe any effect of phytosterol ingestion (24 mg per rat per day) on colon cancer in rats fed a diet with normal or high saturated fatty acids.…”

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“…In another recent study, there was no evidence that plant sterol usage at dose of 300 mg/d, decreased risk of colon and rectal cancers [156]. A similar conclusion was reached following a rat study in which rats were given the carcinogen methyl-nitroso-urea and then monitored for tumor development [157]. …”