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. (C) 2011 Elsevier Inc. All rights reserved.