Comment: Nutritional rickets is highly prevalent in countries such as Mongolia, Tibet and China1 where winter sunlight is reduced and there is no universal vitamin D supplementation. Paradoxically, rickets is also prevalent in developing countries in the tropics and subtropics where sunlight is unlikely to be a limiting factor. Low calcium intakes (including vegetarian diets), prolonged breast feeding, and covering of the skin may all contribute.2,3

Published reports and clinical experience in Sydney suggest an increase in prevalence of rickets, especially in infants and mothers in immigrant populations2,4-7 Other Western countries have reported similar findings. The vitamin D deficiency described by Johnson and Willis in an infant in Perth highlights a high-risk group — infants of mothers who are veiled. Treatment of associated nutritional deficiencies, especially iron deficiency,4,5 and giving a minimum of 300 000 IU of vitamin D over 6–8 weeks, should resolve the rickets. Data on the epidemiology of vitamin D deficiency in these high-risk groups in Australia and other Western societies are lacking and should be the subject of future research.

The major source of vitamin D and its circulating form, 25-hydroxyvitamin D3 (25OHD3), in children and adults is the skin. It is estimated that exposure to sunlight for 15 minutes three times per week normalises 25OHD3 levels.8 Dark skin, increasing age, sun protection agents, and the angle of the sun in winter will attenuate this increase in 25OHD3.8 Neonates acquire their vitamin D3 stores from their mothers via the placenta, with only a small amount transferred in breast milk.9

By screening high-risk pregnant women, specifically veiled women and those with dark skin,10,11 prevention of most cases of infant rickets is possible. Levels of 25OHD3 should be measured and, if low, the mother should receive 4000 IU of vitamin D daily until 25OHD3 levels are normal. There is currently no recommendation for routine supplementation of vitamin D in infants, and most cereals and foods are not fortified with vitamin D. However, infant formulas are supplemented with 200 IU of vitamin D per litre. It is estimated that sufficient vitamin D levels to prevent rickets could be achieved if 400 IU of vitamin D were provided daily as part of a multivitamin supplement to high-risk infants.