title: Dietary silicon interacts with oestrogen to influence bone health: evidence from the Aberdeen Prospective Osteoporosis Screening Study.
abstract: 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.
authors.affiliation: Musculoskeletal Research Programme, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK. h.macdonald@abdn.ac.uk
authors.forename: Helen M
authors.initials: HM
authors.lastname: Macdonald
authors.forename: Antonia C
authors.initials: AC
authors.lastname: Hardcastle
authors.forename: Ravin
authors.initials: R
authors.lastname: Jugdaohsingh
authors.forename: William D
authors.initials: WD
authors.lastname: Fraser
authors.forename: David M
authors.initials: DM
authors.lastname: Reid
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Powell
mesh_terms: D015519:Bone Density / Q000502:physiology*; D004032:Diet; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D005272:Femur Neck / Q000502:physiology; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology; D008875:Middle Aged; D010024:Osteoporosis / Q000175:diagnosis*; D012825:Silicon / Q000378:metabolism*; D011795:Surveys and Questionnaires
chemical_list: D004967:Estrogens; D012825:Silicon