The Effects of Soy Isoflavones on Bone Mineral Density in Pre- and Postmenopausal Women:Decreasing the Risk of Osteoporosis Jennifer Wyckoff FN315 Advanced Nutrition
Introduction Osteoporosis is a disease in which bones become fragile and more likely to break. If not prevented or if left untreated, osteoporosis can progress painlessly until a bone breaks. These broken bones, also known as fractures, occur typically in the hip, spine, and wrist. Of the 10 million Americans estimated to have osteoporosis, eight million are women and two million are men. 1 Certain people are more likely to develop osteoporosis than others. Factors that increase the likelihood of developing osteoporosis and broken bones are called "risk factors." Many of these risk factors include: Being female Older age Menopause Low estrogen levels
Estrogen and Bone Health The primary estrogen hormone in humans, estradiol, helps in maintaining bone density by stopping the activation of the enzyme caspase-3.1 Caspase-3 initiates the process of apoptosis, which prevents osteoblasts from forming and developingnew bone. When estrogen levels severely reduce after menopause, the risk for osteoporosis and other disease increase. Osteoclast production increases and more bone is lost than produced. Hormone replacement therapy (HRT) has been initiated to compensate for the estrogen lost during menopause. With HRT the risk of osteoporosis is reduced along with menopausal symptoms, but is unfavorable because it may increase the risk for certain types of cancers after long-term use.
Soy Isoflavones What are Soy Isoflavones? Organic compounds that act as phytoestrogens Antioxidants Two major types of isoflavones: Genistein and Daidzein Most commonly found in soybean products: soy nuts and tempeh Diets rich in soy isoflavones are the newest alternative to HRT because theyreduce the risk of osteoporosis by acting as estrogens and helping to create new bone. Does not share the same side effects as traditional HRT (cancer). Genistein Daidzein
Efficacy of a soy rich diet in preventing postmenopausal osteoporosis: the Menfis randomized trial2 The objective of this study was to compare the effects of a soy rich diet to hormone replacement therapy (HRT) in regards to bone mineral density (BMD) and bone turnover at postmenopausal age. Methods: 187 postmenopausal women aged 39-60 at the University of Bari, in Southern Italy. Subjects were split into 3 groups. A soy-rich diet group, a hormone replacement therapy group, and a control group. The women in the diet intervention group continued their usual diets but added a soy food serving every day. They were also asked to replace two meals twice a week with two phytoestrogens rich foods from a menu. Biomarkers of bone turnover and bone mineral density were measured at the beginning of the study and at the end of the study 6 months later. Results: Although diet was not as effective as HRT, soy isoflavone products still showed improved results compared to that of the control group in increasing BMD and bone turnover. Conclusion: The diet intervention group had a large increase of osteocalcin compared to the other two groups, which would help to promote the building of new bone.
Soy isoflavone intake increases bone mineral density in the spine of menopausal women: Meta-analysis of randomized controlled trials3 The objective of this study was to determine how effective soy isoflavones are in optimizing bone health. Many research studies conclude isoflavones have no significant benefits, to slight increase in bone mineral density. Therefore, this study used a statistical method to combine the previous research and determine whether isoflavones are useful or not. Methods: Previous research studies were measured to determine the consistency of the research done in proving the effects of soy isoflavone. The studies chosen were limited to female participants, subjects must have ingested soy isoflavones for at least 3 months, a control group was used for the study, and spine bone mineral density (SBMD) or spine bone mineral content (SBMC) were used as an index of bone mass. Results: Spine bone mineral density (SBMD)increased significantly by subjects who consumed a soy-rich diet. Conclusion: The effects were best when 90mg/day of isoflavones were consumed.
Effects of soy protein isolate and moderate exercise on bone turnover and bone mineral density in postmenopausal women4 It has been shown in earlier research that physical activity helps to increase BMD in older women. Because of this, researchers wanted to determine if a moderately-intense physical activity regimen combined with a soy rich diet could maximize bone turnover and BMD. Methods: Participants in this study were women that were 2 years post-menopause and between the ages of 50-65. Subjects of this study were split into 4 groups. One group had a diet that consisted of soy protein isolate, the second group had a diet of milk protein isolate, the third group was soy protein isolate with moderate exercise, and the fourth group was milk protein isolate with moderate exercise. Results: The results of this study showed that soy consumption improved bone turnover, but showed no significant effects on BMD. Moderate-intensity exercise showed no effects on bone turnover or BMD. This was believed to be due to the short timeframe of the study and the small number of subjects that lasted through the study.
Soybean and soy isoflavone intake indicate a positive change in bone mineral density for 2 years in young Korean women5 Measuring the effects of soy beans and soy isoflavones on BMD in young Korean women over a period of 2 years. Younger Korean women were chosen for this particular study because of the fact that skeletal bone mass accumulation occurs during adolescence. Typically, postmenopausal women are chosen for these subjects because of their high risk for osteoporosis and low BMD. These researchers believe it is best to determine bone markers at this critical period in order to plan properly for future bone health. Methods: 34 young and healthy Korean women aged 20-26. Dietary intake of soy was taken every 4 months. Because of the soy-rich diets in Asia, the researchers did not dictate how much or how little soy needed to be consumed throughout the study. Results: The results of this study showed that BMD slightly increased each year and was significantly higher at the end of the study compared to the initial measurements at the start of the research. The average daily intake of soy isoflavones from the subjects was 39g daily. The soybean consumption rate was also around 0.46, which means that the participants consumed soy products approximately every other day. Conclusion: Soy bean and isoflavone have a positive effect on the changes of BMD. Though this diet is not as efficient as HRT, it is still a good alternative.
References National Osteoporosis Foundation. www.NOF.org ChiechiLM, Secreto G, D’Amore M, Fanelli M, Venturelli E, Cantatore F, Valerio T, Laselva G, Loizzi P. Efficacy of a soy-rich diet in preventing postmenopausal osteoporosis: the Menfis randomized trial. Maturitas: The European Menopause Journal. 2002;42:295-300. Ma DF, Qin L, Wang P, Katoh R. Soy isoflavone intake increases bone mineral density in the spine of menopausal women: Meta-analysis of randomized controlled trials. Clinical Nutrition. 2008;27:57-64. Evans E, Racette S, Pelt R, Peterson L, Villareal D. Effects of soy protein isolate and moderate exercise on bone turnover and bone mineral density in postmenopausal women. Menopause. 2007;14:481-488. Song Y, Paik HY, Juong H. Soybean and soy isoflavone intake indicate a positive change in bone mineral density for 2 years in young Korean women. Nutrition Research. 2008;28:25-30.