Role of Soya in improving our Bone Health Certain components (isoflavones), which occur naturally in soya, may be beneficial in the case of bone health. Isoflavones have a chemical structure similar to that of oestradiol (endogenous estrogen), are thought to be of benefit for bone health. Based on evidence from 17 in vitro studies of cultured bone cells, 24 in vivo studies of animal models for postmenopausal osteoporosis, 15 human observational/epidemiologic studies, and 17 dietary intervention studies, Setchell and Lydeking-Olsen concluded in 2003 that diets containing phyto-estrogens have bone-sparing effects in the long term (1). An intervention study in 66 postmenopausal women consuming 40 g/d of soy protein that provided 90 mg/d of aglycone isoflavones for 6 months, reported significant net savings in lumbar spine bone mineral content and bone mineral density of 3.5% and 2.8%, respectively (2). In another study, similar anti-osteoporotic effect of soy isoflavones was reported in 69 perimenopausal women receiving 80 mg/d of aglycone soy isoflavones for 6 months (3). In a study reported by Chen et al in 2004, 203 women were randomly assigned to three treatment groups (placebo, N=67; 40 mg aglycone isoflavones, N=68; and 80 mg aglycone isoflavones, N=68) (4). Favorable effect of isoflavone supplementation on rates of change in bone mineral content at the total hip and trochanter was reported among later postmenopausal women (> 4 y), in women with lower body weight (< 55.5 kg), or among women with lower level of calcium intake (< 1,095 mg/d) after one year of treatment. However, no beneficial effect was reported for bone mineral density. Lydeking-Olsen et al also carried out a 2-y randomized, placebo-controlled trial in 2004 to determine the potential benefit of soymilk to prevent bone loss in postmenopausal Caucasian women with established osteoporosis or at least three risk factors for osteoporosis (5). In the study, 23 women received soymilk that delivered 76 mg/d of aglycone isoflavones, 22 women received transdermal progesterone, 22 women received the soymilk with isoflavones together with the transdermal progesterone, and 22 women received soymilk with low isoflavone content (1 mg/d) or progesterone-free-cream. At the end of two years, bone mineral content and bone mineral density of the lumbar spine were protected among the women receiving the soymilk with isoflavones or the transdermal progesterone. Significantly losses in bone mineral content and bone mineral density of the lumbar spine were observed among the placebo group and among the women receiving the combination treatment. In a large prospective cohort study of soyfood consumption and risk of bone fracture among 24,403 postmenopausal women in the Shanghai Women’s Health Study, Zhang et al reported the incidence of bone fracture over 4.5 year was found to be inversely related to quintiles of soy protein intake (p < 0.01 for trend) suggesting the potential long-term benefit of soy intake against osteoporosis (6). Conclusion In 2008, two meta-analysis reviewing the effect of soy isoflavones on bone health were published (7,8). The first meta-analysis combining the results of nine studies with a total of 432 subjects found that isoflavone intervention significantly inhibits bone resorption and stimulates bone formation (7). These favorable effects occur even if
Posted on: Fri, 13 Sep 2013 09:42:02 +0000