Silicon: A requirement in bone formation independent of vitamin D₁

Summary

Silicon has been reported to be involved in an early stage of bone formation as a result of earlier in vitro and in vivo studies in this laboratory. It is now possible to demonstrate that silicon exerts an effect on bone formation independent of the action of vitamin D. Day-old cockerels were fed Sideficient and Si-supplemented diets with adequate and no dietary vitamin D under trace element controlled conditions. At the end of 4 weeks chicks receiving dietary vitamin D₃ (600 IU) exhibited optimal rates of growth whereas the growth rates of chicks receiving D₂ (6000 IU) and no vitamin D were markedly depressed. There were no significant differences between growth of Si-deficient and Si-supplemented chicks on the same level of vitamin D. Skull and bone size was proportional to overall chick growth. However, all chicks on Sideficient diets irrespective of the level of dietary vitamin D had gross abnormalities of skull architecture, the overall skull appearance being narrower and shorter. The frontal area was narrower and the dorsal median line at the front parietal junction was depressed with a narrowing both posterior and laterally, stunting parietal and occipital areas. These abnormal areas showed fewer trabeculae and less calcification. Analyses of skull frontal bones for hexosamine, collagen, noncollagenous protein, and bone mineral demonstrated that the major difference was in collagen content, the Si-deficient skulls showing considerably less collagen at each level of vitamin D. These findings demonstrate that silicon has a significant effect on the bone matrix independent of vitamin D, and support the earlier postulate that silicon is involved in an early stage of bone formation.