On the mechanisms underlying the essentiality of silicon interactions with aluminium and copper

Silicon was confirmed as an essential element in experiments (1972) in which rats and chicks fed on a silicon-depleted diet showed reduced weight gains and pathological changes in the formation and structures of collagenous connective tissue and bone. The biochemical mechanisms underlying the effects of silicon deficiency have until recently been obscure, with no evidence for any organic binding of silicon. Recent studies have shown that silicic acid, Si(OH)(4), the form in which silicon exists in physiology, interacts with aqueous aluminium species to form hydroxyaluminosilicates that can have low bio-availability and toxicity. It is now established that the gastro-intestinal absorption of aluminium is greatly reduced in the presence of silicic acid. More recent studies indicate that the intake of dietary silicic acid also influences the excretion of aluminium via the kidneys so that silicon appears to be profoundly involved in aluminium homeostasis. There are strong indications that silicic acid promotes copper utilization. The observed effects of silicon deficiency on collagen and osteogenesis may thus be due to low copper utilization. Whether reduced copper utilization is caused bg aluminium so that it is enhanced by silicic acid via the latter's interaction with Al is uncertain. Future research should include the interactions between Si Al and Cu.