There are many plant sterols but the best known are beta-sitosterol, stigmasterol and campesterol. Plant sterols have many claimed health benefits. Studies show that plant sterols have a weak estrogenic effect and that they act as weak agonist for estrogen receptors. Plant sterols have a structure similar to that of cholesterol. Plant sterols can modulate the immune system and can replace cholesterol in the intestinal micelles, thereby reducing cholesterol absorption. Epidemiological studies also show that consumption of plant sterols reduces the risk of cancer of colon, prostate, ovary, stomach and breast.
The aim of this study was to investigate the estrogenic effects of the plant sterols beta-sitosterol, beta-sitosterol glucoside and Moducare (mixture of beta-sitosterol, beta-sitosterol glucoside). The test was carried out on estrogen dependent (this means that estrogen stimulates cancer growth) human breast cancer cells in vitro and in vivo.
First the effect of the plant sterols was determined in vitro on cancer cells. Only beta-sitosterol and Moducare increased cell growth. In the second test, the cancer cells were implanted in ovariectomized athymic mice and the estrogenic and anti-estrogenic effects of the plant sterols were determined. Dietary beta-sitosterol, beta-sitosterol glucoside and Moducare did not influence tumor growth, but they markedly reduced estradiol induced tumor growth and also reduced serum estradiol levels. The expression of the antiapoptotic marker B-cell lymphoma/leukaemia in tumours was downregulated.
The researchers concluded that beta-sitosterol and Moducare stimulated cancer cells in vitro and that dietary beta-sitosterol and Moducare protected against estrogen stimulated tumor growth. These findings suggest that beta-sitosterol could have potential benefits for women with a risk for estrogen-dependent breast cancer. However more studies are required to investigate the short and long term effects of plant sterols, their interactions with other drugs and their possible use as dietary supplements.
Source: Young H. Ju, Laura M. Clausen, Kimberly F. Allred, Anthony L. Almada and William G. Helferich
. Beta-Sitosterol, Beta-Sitosterol Glucoside, and a Mixture of Beta-Sitosterol and Beta-Sitosterol Glucoside Modulate the Growth of Estrogen-Responsive Breast Cancer Cells In Vitro and in Ovariectomized Athymic Mice . Journal of Nutrition, 2004, 134:1145-1151