Silica is useful as a vitamin D co-factor in building bones, hair, teeth.
No consensus on bioavailability of the different forms of silica
No consensus on how much silica is needed
Some useful papers are attached to the bottom of this web page.
Update; Silicon, Vitamin D and Bone Health - multiple studies
See web (March 2018)
- Silicon: A Review of Its Potential Role in the Prevention and Treatment of Postmenopausal Osteoporosis May 2016
 Download the PDF from VitaminDWiki
"Average daily dietary intake of silicon is 20–50 mg for European and North American populations 14. Daily intake of silicon is higher in China and India (140–200 mg/day) where grains, fruits, and vegetables form a larger part of the diet 52, 53. China and India also have the lowest prevalence of hip fractures compared to all other regions of the world"
"Diets containing more than 40 mg/day of silicon have been positively associated with increased femoral bone mineral density compared to dietary intake of less than 14 mg/day" - Silicon: An Overlooked Trace Mineral LEF 2003
"In addition to connective tissue and bone health, several other promising health benefits of silicon, such as protection against aluminum toxicity and protection of arterial tissue have been reported." - Terry Talks Nutrition - Silica Date: Sometime before 2018
 Download the TTN PDF from VitaminDWiki
Silica increases Calcium into bone by 50%
Silica increases Callogen formation by 50%
Recommensd 20 mg daily, but 40-80 mg if had recent bone fracture, ostoporosis - Silica: The Mineral Your Bones Need That Your Doctor Probably Won’t Tell You About SaveOurBones
"Silica is found not only in the earth’s crust, but also in the human body. It’s present in nearly all body tissue, including bone"
"Too little silica can bring about calcification of connective and soft tissue, causing stiffness and loss of elasticity. Considered symptoms of aging, these issues may well be symptoms of silica deficiency. Hair, skin, and fingernail health is enhanced by silica as well."
..."you should aim to get at least 10 mg per day. To give you an example, a medium-sized banana contains about 6 mg of silica, and a carrot contains about 1.5 mg." - SILICA: THE COMMON LINK BETWEEN BONE AND CONCRETE Evolution Health