Table 1.

Studies regarding Si dietary intake and bone health in humans.

First author, year	Study design	Setting	Inclusion criteria	Exclusion criteria	Number of subjects (M-F)Mean age	Lowest quintile intake / RDA or EAR	% subject in lowest quintile intake / % subject <RDA or EAR	Highest Quintile intake	% subject in highest quintile intake	Primary outcomes	Results
Jugdaohsingh et al. 32	Cross-sectional cohort study	Free-living subjects	All participants with dietary intake data and BMD measurement were included; written informed consent.	Bone diseases, other diseases, women with premature menopause or bilateral ovariectomy, or subjects on treatments for bone diseases or other diseases.	2847 subjects (1251 men; 1596 women)30-87 years	<14 mg Si/dayMen: 7.6–18.8 mg Si/dPre-menopausal women: 7.1–16.7 mg Si/dPost-menopausal women: 5.9–16.4 mg Si/d	/	>40 mg Si/dayMen: 34.4–118.0 mg Si/dPre-menopausal women: 30.2–63.2 mg Si/dPost-menopausal women: 29.9–83.5 mg Si/d	/	Association between dietary Si intake and BMD at the left hip (total hip, trochanter, Ward’s area, and femoral neck) and at the lumbar spine (L2–L4) assessed by DXA	Marked significant differences in BMD between the highest and lowest quintiles at the hip sites for both premenopausal women (average, 9.9 ± 2.0%) and men (5.1 ± 0.8%); suggestive differences in BMD at the lumbar spine for premenopausal women and men. No significant differences for post-menopausal women.
Macdonald et al. 33	Cohort study	United Kingdom, from the APOSS study (Aberdeen Prospective Osteoporosis Screening Study)	Peri-menopause, whether or not subjected to hormone replacement therapy (HRT), with dietary intake data; written informed consent.	Other treatments for osteoporosis (e.g. bisphosphonates) at the time of this study	3199 women (mean age 48.5 ± 2.4 years)	//	//	//	//	Association between dietary Si intake and BMD at the left hip (total hip, trochanter, Ward’s area, and femoral neck) and at the lumbar spine assessed by DXA	A significant positive association between the Si intake with the diet adjusted for energy and the BMD of the hip (femoral neck) and lumbar spine. The significance of the positive association between energy-adjusted Si intake and hip BMD was confirmed only for pre-menopausal subjects and those taking HRT
Macdonald et al. 34	Cohort study	United Kingdom, from the APOSS study (Aberdeen Prospective Osteoporosis Screening Study)	Written informed consent	Other treatments for osteoporosis (e.g. bisphosphonates) at the time of the study	3198 women (n = 1170 current HRT users, n = 1010 past HRT users, n = 1018 never used HRT) 50–62 years	Lowest quartile intake: 16.5 ± 4.0 mg Si/day	25.02%	Highest quartile intake: 31.5 ± 7.3 mg Si/day	24.98%	Association between dietary energy-adjusted Si intake and markers of bone health (BMD of the left femoral neck and lumbar spine measured by DXA; urinary fPYD and fDPD; serum PINP)	Mean FN BMD was 2% lower in the lowest quartile compared to the top quartile of energy-adjusted Si intake; energy-adjusted Si intake was associated with FN BMD for oestrogen-replete women only. Quartile of dietary Si intake was negatively associated with fDPD/Cr and fPYD/Cr and positively with PINP.
Choi et al. 12	Cross-sectional study	Free-living subjects	Healthy Korean males of 19–25 years; informed consent.	History of prior medication use that may have led to alterations of bone metabolism; insufficient dietary report.	400 male subjects22.68 ± 2.00 years	Minimum Si intake 8.38 mg/day	/	Maximum Si intake 183.14 mg/day	/	Relationship between dietary Si intake and calcaneus bone density (measured by quantitative ultrasound) and the bone metabolism markers (serum total alkaline phosphatase, N-midosteocalcin and type 1 collagen C-terminal telopeptide)	Daily total Si intake had no correlation with calcaneus bone density and the bone metabolism markers, but Si intake from vegetables had a positive correlation with serum total alkaline phosphatase activity.