Choline-stabilized orthosilicic acid supplementation as an adjunct to calcium/vitamin D3 stimulates markers of bone formation in osteopenic females: a randomized, placebo-controlled trial.
Mounting evidence supports a physiological role for silicon (Si) as orthosilicic acid (OSA, Si(OH)4) in bone formation. The effect of oral choline-stabilized orthosilicic acid (ch-OSA) on markers of bone turnover and bone mineral density (BMD) was investigated in a double-blind placebo-controlled trial.
Over 12-months, 136 women out of 184 randomized (T-score spine < -1.5) completed the study and received, daily, 1000 mg Ca and 20 microg cholecalciferol (Vit D3) and three different ch-OSA doses (3, 6 and 12 mg Si) or placebo. Bone formation markers in serum and urinary resorption markers were measured at baseline, and after 6 and 12 months. Femoral and lumbar BMD were measured at baseline and after 12 months by DEXA.
Overall, there was a trend for ch-OSA to confer some additional benefit to Ca and Vit D3 treatment, especially for markers of bone formation, but only the marker for type I collagen formation (PINP) was significant at 12 months for the 6 and 12 mg Si dose (vs. placebo) without a clear dose response effect. A trend for a dose-corresponding increase was observed in the bone resorption marker, collagen type I C-terminal telopeptide (CTX-I). Lumbar spine BMD did not change significantly. Post-hoc subgroup analysis (baseline T-score femur < -1) however was significant for the 6 mg dose at the femoral neck (T-test). There were no ch-OSA related adverse events observed and biochemical safety parameters remained within the normal range.
Combined therapy of ch-OSA and Ca/Vit D3 had a potential beneficial effect on bone collagen compared to Ca/Vit D3 alone which suggests that this treatment is of potential use in osteoporosis.
From the full text:
Collagen provides elasticity and structure in all connective tissues and several studies have indicated that collagen is important for bone toughness [43-45] whereas the mineral component is mainly involved in providing stiffness. Wang et al.  demonstrated that the mechanical integrity of collagen fibres deteriorates with ageing in human cortical bones and is associated with a higher fracture risk. When the collagen network becomes weaker with age, it will result in decreased toughness, possibly due to a reduction in natural cross-links or silicon content. It has previously been suggested that Si may be an integral (structural) component of connective tissues as high levels of non-dialysable Si has been reported in connective tissues and their components suggesting strong (covalent) associations .