Soy, a subtropical plant native to Southeastern Asia, is a member of the pea family that is rich in many nutrients such as fiber and omega-3 unsaturated fats that have been shown to provide potential benefits to heart and bone health. Bone density is a way to measure the strength of a bone and to evaluate your risk for low bone mass or the more severe bone condition of osteoporosis. Research has shown that consuming soy may be protective against low bone mass.
Soy Background Information
Soy, according to MayoClinic.com, is a food source derived from the soybean that contains rich amounts of fiber, protein, healthy unsaturated fats and isoflavones. Soy can be consumed in many forms in addition to its original soybean form, including semisolid tofu, soymilk, tempeh, miso, and tamari soy sauce, in supplement form or as an additive in various foods such as baked goods, cheese and pasta.
Soy Isoflavones
The isoflavones found in soy are a type of phytoestrogen, or compound that has been found to have estrogen-like effects in the body. Isoflavones may be protective against menopausal symptoms, cardiovascular disease and cancer, but research is limited and further confirmatory studies must be done before soy intake recommendations are established. In addition, although research on the effects of isoflavones and bone health are limited, the research that is available shows promise concerning soy isoflavones in the prevention of weak bone mass in menopausal women.
Soy and Bone Density
A 2008 study in the "European Journal of Clinical Nutrition" found that isoflavone intervention of about 90mg a day or less for about 12 weeks significantly inhibited bone resorption and stimulated bone formation in menopausal women as compared to menopausal women who did not consume isoflavones. This finding was found to be due to the decrease of urinary deoxypyridinoline, or DPD, a bone resorption marker, and the increase of serum bone-specific alkaline phosphatase, or BAP, a bone formation marker, in those individuals who consumed isoflavones. In addition, a 2010 study in the "Asia Pacific Journal of Clinical Nutrition" found that the lumbar spine bone mineral density was increased in menopausal women who consumed an average of 82mg of isoflavones over six to 12 months as compared with those individuals who did not consume isoflavones. Furthermore, a 2010 study in the journal "Bone" found that DPD was decreased significantly in those menopausal women who consumed an average of 56mg of isoflavones for 10 weeks to 12 months.
Future Research
Although promising, all studies referenced agree that there is much more research to be done to confirm any findings that have been made, such as the factors relating to the effect of isoflavones on DPD as well as to verify effects on other bone turnover markers such as BAP. Once confirmed with further research, it will be more plausible to set a recommendation for soy isoflavone intake for individuals in regards to the prevention of bone mineral density loss.
References
- National Center for Complementary and Alternative Medicine: Soy at a glance
- MayoClinic.com: Soy (Glycine max)
- National Institutes of Health Osteoporosis and Related Bone Diseases National Resource Center: Bone mass measurement: What the numbers mean
- PubMed.gov: Effect of soy isoflavone extract supplements on bone mineral density in menopausal women: meta-analysis of randomized controlled trials
- PubMed.gov: Soy isoflavone intake inhibits bone resorption and stimulates bone formation in menopausal women: meta-analysis of randomized controlled trials
- PubMed.gov: Effects of soy isoflavone supplements on bone turnover markers in menopausal women: systematic review and meta-analysis of randomized controlled trials
