Posted on 10/02/2009 at 06:01:13 PM by Student BloggerBy: Jovana K.
Osteoporosis, characterized by a low bone mineral density, is a silent disease that ultimately results in fragility fractures. Fragility fractures lead to significant morbidity and mortality among North Americans. With the rapidly aging population, it is estimated that 1 in 2 adults will be at risk for osteoporosis related fractures by the year 2020. Thus, there exists an urgent need to decrease this risk and the use of prevention, rather than treatment strategies may prove to be more effective.
It has been hypothesized that attainment of peak bone mass, the maximum amount of bone mass achieved during the life cycle, protects against osteoporosis in later life. Thus, exposure to bioactive food components with the potential to modulate bone cell activity, may augment peak bone mass and thereby confer protection against osteoporosis. Recent scientific evidence suggests that exposure to soy isoflavones, abundant in soy foods including soy protein formula, during a sensitive stage of development may favorably modulate bone metabolism through estrogen-like activity. The United Nations Standing Committee on Nutrition identifies the sensitive stage of development to be from pre-pregnancy to 24 months of child's life so introducing soy isoflavones during this developmental window may improve bone development.
Animal studies using the CD-1 mouse model have shown that neonatal exposure to soy isoflavones, at levels similar to that of infants consuming soy protein formula, improves bone mineral density, bone structure and bone strength of the femur and lumbar spine in adult females. In contrast, males treated with soy isoflavone did not exhibit significant benefits or adverse effects at the femur or lumbar spine, suggesting that early exposure to soy isoflavones may be sex specific. Piglets fed soy based formula from postnatal day 2 to 35 had greater tibial bone mineral density and trabecular bone volume than sow-fed piglets. The observed effects in piglets were associated with an up-regulation of bone formation and a down-regulation of bone resorption, which suggests that soy isoflavones may have positive effects on bone modeling and remodeling.
The relationship between soy isoflavones and bone development has been investigated in numerous human feeding intervention trials. However, the longest studies followed infants to one year of life. Findings from these studies suggest that consumption of soy protein formula does not have a significant effect on infant length, head circumference, body weight, bone mineral content or biochemical markers of bone formation. Prospective studies should be conducted in humans to determine whether exposure to soy protein formula can improve adult bone health and provide protection against osteoporosis. Moreover, because estrogenic compounds can disrupt reproductive health studies should investigating whether exposure to dietary estrogens (i.e. soy isoflavones) altered fertility and reproductive function.