Silica is a major (naturally occurring) trace element in the human body derived predominantly from the diet. The intake and metabolism of which has only recently been determined. It provides strength and flexibility to connective tissue — cartilage, tendons, skin, bone, teeth, hair, and blood vessels, and it is essential in the formation of collagen. Silica aids in the repair and maintenance of vital lung tissues while defending them from pollution and aids in skin regeneration.
The main route of entry of silicon in to the body is from the gastrointestinal tract. However, the gastrointestinal absorption, metabolism and excretion of silicon is still poorly understood.
There are many forms of silica and a lot of them are not water soluble. Orthosilicic acid is the form of silica predominantly absorbed by humans and is found in numerous tissues including bone, tendons, aorta, liver and kidney. Since silica has been shown to transfer calcium and other essential micronutrients necessary for proper bone formation, and bones need it to calcify, silica may play a role in stopping osteoporosis.
Interestingly, although science knows silica plays an integral role in collagen and bone formation, it is not clear how it all fits together with cell biology. It's definitely not as clear as the processes for calcium, potassium or magnesium. Silica is one of the minerals that has levels decrease as we age. Luckily only a very small amount is needed to stay healthy. Overall it appears to be a bit of a cellular mystery.