Dietary silicon interacts with oestrogen to influence bone health: evidence from the Aberdeen Prospective Osteoporosis Screening Study.

BACKGROUND

Silicon (Si), as Si(OH)(4), is derived mainly from plant-based foods. Dietary Si is associated with bone mineral density (BMD) in premenopausal but not postmenopausal women.

OBJECTIVE

To examine the association between Si intake and markers of bone health in middle-aged women and to test for interaction with oestrogen status.

METHODS

Femoral neck (FN) and lumbar spine (LS) BMD, urinary markers of bone resorption (free pyridinoline and deoxypyridinoline cross-links relative to creatinine, fPYD/Cr and fDPD/Cr) and serum markers of bone formation (N-terminal propeptide of type 1 collagen, P1NP) were measured in a cohort of 3198 women aged 50-62 years (n=1170 current HRT users, n=1018 never used HRT). Dietary Si, bioavailable Si and dietary confounders were estimated by food frequency questionnaire.

RESULTS

Mean FN BMD was 2% lower (p<0.005) in the lowest quartile (Q1) compared to the top quartile of energy-adjusted Si intake (Q4) (mean (SD) Q1, 16 (4.0) mg/d; Q4, 31.5 (7.3) mg/d). Energy-adjusted Si intake was associated with FN BMD for oestrogen-replete women only (late premenopausal women (r=+0.21, p=0.03); women on HRT [r=+0.09, p<0.001]). There was an interaction between oestrogen status and quartile of energy-adjusted Si intake on FN BMD, which was significant after adjustment for confounders (F=3.3, p=0.020), and stronger for bioavailable Si (F=5.0. p=0.002). Quartile of energy-adjusted dietary Si intake was negatively associated with fDPD/Cr and fPYD/Cr (p<0.001) and positively with P1NP (p<0.05).

CONCLUSIONS

This study suggests that oestrogen status is important for Si metabolism in bone health. Further work is required to elucidate the mechanism.