Vitamin D supplementation for improving bone mineral density in children

Abstract

Background: Results of randomised controlled trials (RCTs) of vitamin D supplementation to improve bone density in children are inconsistent. Objectives: To determine the effectiveness of vitamin D supplementation for improving bone mineral density in children, whether any effect varies by sex, age or pubertal stage, the type or dose of vitamin D given or baseline vitamin D status, and if effects persist after cessation of supplementation. Search methods: We searched the Cochrane Central Register of Controlled Trials (CENTRAL Issue 3, 2009), MEDLINE (1966 to present), EMBASE (1980 to present), CINAHL (1982 to present), AMED (1985 to present) and ISI Web of Science (1945 to present) on 9 August 2009, and we handsearched key journal conference abstracts. Selection criteria: Placebo-controlled RCTs of vitamin D supplementation for at least three months in healthy children and adolescents (aged from one month to Data collection and analysis: Two authors screened references for inclusion, assessed risk of bias, and extracted data. We conducted meta-analyses and calculated standardised mean differences (SMD) of the percent change from baseline in outcomes in treatment and control groups. We performed subgroup analyses by sex, pubertal stage, dose of vitamin D and baseline serum vitamin D and considered these as well as compliance and allocation concealment as possible sources of heterogeneity. Main results: We included six RCTs (343 participants receiving placebo and 541 receiving vitamin D) for meta-analyses. Vitamin D supplementation had no statistically significant effects on total body bone mineral content (BMC), hip bone mineral density (BMD) or forearm BMD. There was a trend to a small effect on lumbar spine BMD (SMD 0.15, 95% CI -0.01 to 0.31, P = 0.07). There were no differences in effects between high and low serum vitamin D studies at any site though there was a trend towards a larger effect with low vitamin D for total body BMC (P = 0.09 for difference). In low serum vitamin D studies, significant effects on total body BMC and lumbar spine BMD were approximately equivalent to a 2.6% and 1.7 % percentage point greater change from baseline in the supplemented group. Authors' conclusions: These results do not support vitamin D supplementation to improve bone density in healthy children with normal vitamin D levels, but suggest that supplementation of deficient children may be clinically useful. Further RCTs in deficient children are needed to confirm this. PLAIN LANGUAGE SUMMARY Vitamin D for improving bone density in children This summary of a Cochrane Review, presents what we know from research about the effect of vitamin D supplements on bone density in children. The review shows that in healthy children generally, vitamin D supplementation does not improve bone density at the hip, lumbar spine, forearm or in the body as a whole. Some of the evidence suggests that vitamin D supplements may improve bone density in children who have low levels of vitamin D but this is uncertain. We do not have precise information about side effects and complications but the available information suggests that vitamin D supplements are well tolerated. What is osteoporosis and what is vitamin D? Osteoporosis is a condition where bones are weak, brittle and break easily. The risk of osteoporosis and fractures (breaks) in later life depends on how much bone is built when a child and how much bone is lost when an adult. One way to prevent osteoporosis and fractures in later life is to build stronger bones when young. Vitamin D plays an important role in improving the body's absorption of calcium from food, reducing losses of calcium from the body and getting calcium deposited into to bone to improve the quantity of bone developed. Therefore it is thought that if vitamin D levels in the body are low in childhood, less bone will be developed and that improving vitamin D levels by supplements would result in more bone being developed. Bone density is a major measure of bone strength and the amount of bone mineral present at different sites and so is used to measure the effects of interventions, like vitamin D supplementation, to improve bone health.