How do soy phytoestrogens help maintain bone mass?

Research presented at the North American Menopause Society Meeting 2000, has confirmed that soy foods have beneficial effects on the activity of bone cells. Post-menopausal women who consumed soy drink or soy nuts each day for a period of three months, experienced a drop in NTx - a chemical marker showing that bone-dissolving cells were less active when consuming the soy diet. The level of a protein called osteocalcin also increased indicating that the bone-making cells were more active ¹⁴ .

Soy protein ¹⁵ and the isoflavone genistein ¹⁶ has been shown to help maintain bone mass and prevent osteoporosis in rats, according to studies which simulated the post-menopausal period in women. In fact genistein was almost as effective as Premarin, the commonly prescribed form of Hormone Replacement Therapy. The same protection was not found in studies using purified isoflavone extracts from red clover. These contain two other isoflavones and only a small amount (9%) of genistein ¹⁷ .

Short-term studies in post-menopausal women have found an improvement in bone mineral density (BMD) and/or bone mineral content (BMC) with the consumption of soy. Postmenopausal women who consumed 40 grams of soy protein with naturally occurring isoflavones daily for six months, significantly increased the BMD and BMC of their spines, in a study at the Department of Food Science and Human Nutrition, University of Illinois ¹⁸ . In peri-menopausal women, supplementing the diet with soy protein with naturally occurring isoflavones for six months suppressed bone loss from their spine ¹⁹ . Incorporating 45 grams of soy grits into the daily diets of Australian women resulted in a 5% increase in BMC, according to a short term study from the Royal Women's Hospital, Melbourne. ²⁰