Soy and Osteoporosis

The objective in the Exposure to Soy-Based Formula in Infancy and Endocrinological and Reproductive Outcomes in Young Adulthood was to examine the “association between infant exposure to soy formula and health in young adulthood. (Strom, 2001, p. 1). Naturally, infants who were fed soy formula received relatively high doses (per unit of body weight) of phytoestrogen  at a time in their development where “permanent changes are theoretically possible.” (Strom, 2001, p. 2). The study focused on 952 young adults who as infants had been participants in a University of Iowa study during the years from 1965-1978.  These young adults were later contacted by telephone, and follow up studies done. The conclusions relative to soy and osteoporosis were that the differences in bone density between those who had consumed soy formula as opposed to those who had consumed cow’s milk formula were small and few reached statistical significance. (Strom, 2001, p. 9).

The study done by The North American Menopause Society studied the relationship between soy and osteoporosis in the realm of menopausal symptoms and overall health. As related to this, “although some data suggest that isoflavones may favorable affect bone health, few human studies have been conducted and all involved small numbers of subjects in trials of short duration.” (Greenwood, 2000, p. 4).  It was concluded that further clinical studies are necessary to demonstrate that soy plays a definitive role in limiting the extent of osteoporosis.

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The Journal of American Medical Association conducted a randomized controlled trial regarding the effect of soy protein on bone mineral density (one of many things relative to soy consumption).  The study was a double-blind, randomized, placebo-controlled trial of postmenopausal women aged 60-70 years.  Bone mineral density of the hip and lumbar was assessed “using dual-energy x-ray absorptiometry scanning.  Lipid assessment included total cholesterol, low-density lipoprotein, high-density lipoprotein, and triglycerides.” (Kreijkamp-Kaspers, 2004, p. 1).  At the conclusion of the study, there were no major differences between the placebo group and the group who had received soy supplements. Both groups showed similar dietary patterns, therefore the study is considered conclusive. (Kreijkamp-Kaspers, 2004, p. 6).

As reported in the Archives of Internal Medicine, while there were many benefits associated with the use of soy products, such as reduction in certain cancers and cardiovascular diseases, there were few benefits in the realm of osteoporosis reported. Asians show a much lower rate of colon, prostate and breast cancers as well as cardiovascular disease, and it is notable that Asians consume a much higher percentage of soy in their daily diets. (Glazier, 2001, p. 4).

Contrary to the above findings, the American Medical Association conducted a study of Postmenopausal women, soy consumption and bone fractures, and found that “soy food consumption was associated with a significantly lower risk of fracture, particularly among women in the early years following menopause.” (Zhang, 2000, p. 1).  24,403 postmenopausal women were studied.  These women were part of the Shanghai Women’s Health Study, of approximately 75,000 Chinese Women from 40 to 70 years of age. Those in the highest soy protein intake group had a “37 percent reduced relative risk for fracture compared to the lowest intake group.” (Zhang, 2000, p.2).

In the Journal of Clinical and Experimental Obstetrics and Gynocology, the phyto selective estrogen receptor modulator was studied in the ingestion of Femarelle which is a “potent, non-estrogen phytoSERM that has been shown through numerous published studies to safely increase bone density in post menopausal women as opposed to soy proteins containing isoflavones which are not considered to improve bone density in post-menopausal women. (Yoles, 2004, p. 1).

Ipriflavone is a synthetic isoflavone and is metabolized in the body to seven metabolites, including daidzein, a major isoflavone in soy. (Ipriflavone, 2005, pg. 1).  The major biological effects of ipriflavone are in the area of bone physiology.  “Bone is a complex tissue that is in constant flux, known as remodeling. In a number of laboratory studies, IP has been shown to both stimulate bone growth and inhibit resorption of bone mineral….which would be of importance in reversing the effects of osteoporosis.” (Ipriflavone, 2005, p. 3).

In an article written by John Robbins who writes for “The Food Revolution: How Your Diet Can Help Save Your Life and The World,” the initial question he throws out for discussion is whether soyfoods are a blessing or a curse. He notes in particular that while the alternative health hype has told us that ingesting soy foods will lower our risk of some cancers as well as cardiovascular diseases, and lengthen our lives to boot, soybeans actually “contain large quantities of natural toxins or anti-nutrients including potent enzyme inhibitors that block the action of trypsin and other enzymes needed for protein digestion….they can produce serious distress, reduced protein digestion and chronic deficiencies in amino acid uptake.” (Robbins, 2004, pg. 2).   Robbins himself found no correlation between consuming soy products and lowering one’s risk for osteoporosis, and related our high rates of bone fractures to a sedentary lifestyle combined with consumption of highly processed, high salt, high animal protein diet. (2004, p. 6).