Essentiality and Function of Silicon

Summary

Silicon, considered heretofore an environmental contaminant, is one of the most recent trace elements to be established as “Essential” for higher animals. A series of experiments contributed to the establishing of silicon as an essential element beginning with in vitro studies on young bone, suggesting a physiological role for silicon in bone calcification processes. This was followed by in vivo studies showing an effect of silicon on the rate of bone mineralization. The conclusive evidence showing that silicon is essential for animals was reported in 1972 with the establishment of a deficiency state in chicks incompatible with normal growth, and the contrasting normal growth on a diet containing a silicon supplement. The effect on growth was marked, suggesting that silicon must play an important role in the body’s metabolic processes. Later work demonstrates the importance of silicon in connective tissue metabolism. An in vivo requirement for silicon is established in articular cartilage and connective tissue formation involving glycosaminoglycans. Furthermore silicon is shown to be a component of glycosaminoglycan-protein complexes and collagen. More recently silicon has been shown to be a cellular component of connective tissue, its presence being demonstrated in osteogenic cells where it is found to be a major anion. And most recently, skull and other bone abnormalities associated with reduced collagen content have been produced in silicon deficient chicks under conditions promoting near optimal growth using a semi-synthetic diet. The findings demonstrate that silicon has a significant effect on the bone matrix, independent of vitamin D and are strong confirmatory evidence of silicon’s essentiality for bone formation and for a physiological role for silicon in chicks growing at a near maximal rate. A relationship established between silicon and aging is probably related to glycosaminoglycan changes.