Originally published June 14 2005
Relationship between soy isoflavones and bone health unclear, researchers say
by Mike Adams, the Health Ranger, NaturalNews Editor
Researchers at the 2004 Experimental Biology Symposium in Washington, DC, say that the relationship between soy isoflavones and bone health is inconsistent and inconclusive. The inconsistencies could be because of the life stages of the human and animal subjects studied, estrogen status, study participants' relationship with their environment and genetics. Researchers say more studies are needed to see if soy isoflavones can benefit bone health or not.
Evidence of the effect of purified soy isoflavones and soy protein isolates containing isoflavones on bone health in rats and in humans is inconsistent.
Differences may be because of synergies or antagonisms among the isoflavones, threshold or biphasic dose effects, life stage of animals or human subjects, estrogen status, and environment-genetic interactions, including the ability to produce metabolites upon ingestion of isoflavones.
The number of women who had a substantial and a clinically important decline in the Modified Mini-Mental State Examination was greater in the estrogen plus progestin group than in the placebo group (3).
Subsequently, the estrogen-alone arm was stopped after an average of a 7-y follow-up, because it increased the risk of stroke and was not effective in reducing heart disease, although it reduced hip fractures.
Consequently, many postmenopausal women are turning to botanical dietary supplements containing isoflavones as an alternative to HT, but evidence of protection against postmenopausal bone loss is limited.
A large multisite trial found a synthetic isoflavone, ipriflavone, was not effective in reducing bone loss in postmenopausal women (20), whereas, studies using purified genistein (21) and red clover isoflavone (22) found these supplements effective on bone.
Equol [7-hydroxy-3-(4'-hydroxyphenyl)-chroman] is the end product of intestinal bacterial metabolism of daidzein (31).
Equol producers are characterized by higher consumption of energy as carbohydrates and fiber (32).
Setchell et al. (31) put forward a hypothesis that equol production is the key to clinical effectiveness of isoflavones in various tissues, including heart and bone.
Use of semipurified diets provides constant dietary components, but some of these studies have used calcium-deficient diets.
This supplement is the responsibility of the Guest Editors to whom the Editor of The Journal of Nutrition has delegated supervision of both technical conformity to the published regulations of The Journal of Nutrition and general oversight of the scientific merit of each article.
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