ECE2006 Symposia Green over-the-counter endocrinology (4 abstracts)
Osteoporosis and the associated low- energy fractures is a major public health problem. Phytoestrogens, especially from soy foods with isoflavones, carry the potential of being a nutritional candidate for prevention of osteoporosis. Several studies have been performed to determine the role of soy intake in preventing bone loss in postmenopausal women. Studies with fracture endpoint are not yet available, but several other lines of evidence have been investigated: epidemiological and clinical studies with either markers of bone turnover or measurement of bone mineral density- and content (BMD/BMC). The presentation will focus on reviewing the clinical trials of at least 1y duration with DEXA endpoint:
Two 12 month Italian studies comparing purified genistein at 54 mg/d with estradiol (one study) and placebo (two studies) demonstrated a similar protective effect of genistein and estradiol, with gains in BMD ≈ 3% in both lumbar spine and hip for the two active groups (Morabitu 2002, Squadrito 2005).
Two of the four 2y studies completed, from Denmark and South Dakota, has demonstrated a preventive effect on lumbar spine bone loss with isoflavone-rich soy foods,15 and 40 gram protein providing 8090 mg isoflavones/d, with only minimal changes occurring in the hip in the control groups, having soy food without isoflavones (Lydeking-Olsen, 2004, Lovrien 2005). The third 2y study found less than 1% bone loss in the whole body over two years regardless of isoflavone content (5, 42 and 58 mg respectively), indicating a calcium sparing effect in the whole body bone mass. Specific- site DXA measurements were not performed in this study, making it difficult to compare with the other 2 y studies (Vitolins, 2001).
A 12 mo study did not show any difference from the placebo group (milk protein), as both groups maintained bone mass (Kreijkamp-Kaspers 2004). One 2 y study did not demonstrate any difference between soy+isoflavones, soy isoflavones and casein as all three groups lost bone (Gallagher 2005).