Cochrane review finds that Vitamin D helps rickets  – downloaded Feb 2010
Interventions for the prevention of nutritional rickets in term born children
Although only a few studies with different results exist, preventive measures against nutritional rickets appear reasonable in high risk groups until new data become available.
Rickets is a disease which affects the bone of growing children. Calcium and phosphate are important elements which form the bone. In nutritional rickets, initially the availability of calcium is diminished, later disturbances in phosphate occur. The shortage of calcium may be caused by limited intake or limited resorption in the gut. The latter is highly regulated by vitamin D, which can be synthesised from the skin after sun exposure or can be acquired from dietary sources, for example cod liver. Therefore, shortage of calcium, vitamin D or both may lead to nutritional rickets, which is mainly characterized by deformed bones, bone pain, convulsions or delayed development. Since the 1930s supplementation of vitamin D is used for the prevention of rickets in children, mainly in high-income countries; several other measures like supplementation of calcium or longer exposure of the skin to sunlight are also used. Over the time many factors have changed, for example nutrition, which provides calcium, air pollution, through which sun light is absorbed leading to a diminished synthesis of vitamin D in the skin, or social issues, for example child labour, again leading to limited sun exposure. Because of these changes we looked for studies conducted in the last 50 years which investigated patient-relevant outcomes. As patient-relevant outcomes we defined the occurrence of rickets, adverse effects of the intervention, mortality, health-related quality of life and costs.
Four trials enrolled approximately 1700 participants and lasted between nine months and two years. Study participants were aged from one month to 15 years. There were different results on the occurrence of nutritional rickets in different settings. Adverse effects were investigated in one study only.
Considering the partial high frequency of nutritional rickets, the obvious way of action of supplementation of vitamin D or calcium and the favourable risk-benefit ratio, preventive measures are reasonable in high risk groups like infants and toddlers. New studies investigating main and side effects of preventive measures against nutritional rickets in different age groups and in different countries are indicated.