Research on isoflavones
How do isoflavones work? Isoflavones activate the estrogen beta-receptor and reinforce the favourable estrogenic properties. On the other hand, isoflavones protect the estrogen alpha-receptors, lowering the proneness to estrogens-related cancers.The beta-receptors, which exercise favourable effects on health, are found in the blood cells, the lungs, the prostate, the bladder, bones and thymus. Here isoflavones stimulate their function even after the rate of estrogens has decreased.
The alpha-receptor are found in the breast tissue, the uterus, the ovaries, testicule and the liver. Here, isoflavones protect the receptor against estrogens and help reduce the proneness to tumour.
Scientific research on isoflavones
This is an overview of some of the research findings and publications regarding the possible health effects of isoflavones:- Recent clinical work found that when women were fed 45 grams of soya flour per day menopause symptoms were reduced by approximately 40 percent.(1) The reported incidence of menopause symptoms (night sweats, hot flashes) is much lower among Japanese women than among Western women: a difference in soya food consumption may be one reason for this.
- Weak estrogens such as the isoflavones may also have a role in reducing cancer risk. High blood levels of estrogen are an established risk factor for breast cancer. By competing with the more potent estrogen for binding to the estrogen receptor, weak estrogens are thought to be able to function as antiestrogens.(2,3)
- Isoflavones may help to prevent osteoporosis. The isoflavones are similar in chemical structure to a drug, ipriflavone, which has been shown to inhibit bone resorption in humans(4). Ipriflavone is maximally effective only when it is metabolised, and one of its metabolites is the soy isoflavone daidzein. Also, a recent study has found that genistein inhibits bone resorption in animals(5).
- In 1995, a review of 38 controlled studies on soya and heart disease concluded that soy is definitely effective at reducing total cholesterol, LDL ("bad") cholesterol, and triglycerides (6).
(1) Murkies AL, Lomard C, Strauss BJG, et al. Maturitas 21:189, 1995.
(2) Clark JH, Paszko A, Peck EJ. Endocrinol 100:91, 1977.
(3) Katzenellenbogen JA, Ferguson ER, Lan NC. Endocrinol 100:1252, 1977.
(4) Hollenberg, MD. TIPS, 15:108, 1994.
(5) Anderson JJ, Ambrose WW, Garner SC. J Nutr 125 ,799S (abstr), 1995.
(6) Anderson JW, Johnstone BM, Cooke-Newell ME. Meta-analysis of the effects of soy protein intake on serum lipids. N Eng J Med. 1995;333:276–281.