ON THE MECHANISMS UNDERLYING THE ESSENTIALITY OF SILICON INTERACTIONSWITH ALUMINUM 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 w eight gains and pathological changes in the formation and structures o f collagenous connective tissue and bone. The biochemical mechanisms u nderlying the effects of silicon deficiency have until recently been o bscure, with no evidence for any organic binding of silicon. Recent st udies have shown that silicic acid, Si(OH)(4), the form in which silic on exists in physiology, interacts with aqueous aluminium species to f orm hydroxyaluminosilicates that can have low bio-availability and tox icity. It is now established that the gastro-intestinal absorption of aluminium is greatly reduced in the presence of silicic acid. More rec ent studies indicate that the intake of dietary silicic acid also infl uences the excretion of aluminium via the kidneys so that silicon appe ars to be profoundly involved in aluminium homeostasis. There are stro ng indications that silicic acid promotes copper utilization. The obse rved effects of silicon deficiency on collagen and osteogenesis may th us be due to low copper utilization. Whether reduced copper utilizatio n is caused bg aluminium so that it is enhanced by silicic acid via th e latter's interaction with Al is uncertain. Future research should in clude the interactions between Si Al and Cu.