Notice that the vitamin D helped more and more as the studies were probably having higher doses of vitamin D
The analysis did not appear to consider dosage level, including studies which had just 133 IU daily dose.
Strange that vitamin D did WORSE than the placebo in 2005 - How might it be possible that taking vitamin D for only 3 months would DECREASE BMD?
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Laurie Barclay, MD
October 5, 2010 — Use of vitamin D supplements may not improve bone density in healthy children with normal vitamin D levels, but vitamin D–deficient children may benefit, according to the results of a systematic review reported online October 6 in the Cochrane Database of Systematic Reviews.
"Results of randomised controlled trials (RCTs) of vitamin D supplementation to improve bone density in children are inconsistent," write Tania Winzenberg, from the Menzies Research Institute in Hobart, Tasmania, and colleagues.
The goal of this review was to assess the efficacy of vitamin D supplementation for improving bone mineral density (BMD) in children. The reviewers also examined whether results varied in subgroups based on sex, age, pubertal stage, or baseline vitamin D status. Finally, they evaluated the effects of type or dose of vitamin D and whether effects were maintained after supplementation was stopped.
To identify placebo-controlled randomized controlled trials determining bone density outcomes with vitamin D supplementation for at least 3 months in healthy participants aged 1 month to younger than 20 years, the reviewers searched the Cochrane Central Register of Controlled Trials (CENTRAL Issue 3, 2009), MEDLINE (1966 - present), EMBASE (1980 - present), CINAHL (1982 - present), AMED (1985 - present), and ISI Web of Science (1945 - present). In addition, they manually searched key journal conference abstracts and reference lists.
Two authors determined the risk for bias and extracted data. Standardized mean differences of the percent change from baseline in outcomes were calculated in treatment and control groups. Six randomized controlled trials, in which 343 participants received placebo and 541 received vitamin D, were included in the meta-analyses.
Total body bone mineral content (BMC), hip BMD, and forearm BMD were not statistically significantly affected by vitamin D supplementation, but there was a small, nonsignificant effect on lumbar spine BMD (standardized mean difference, 0.15; 95% confidence interval, –0.01 to 0.31; P = .07).
There were no differences in effects between studies of high and low serum vitamin D levels at any site, but there was a trend towards a larger effect with low vitamin D levels for total body BMC (P = .09 for difference). In studies of low serum vitamin D levels, the supplemented group had significant effects on total body BMC and lumbar spine BMD of approximately a 2.6% and 1.7 % percentage point greater change from baseline.
"Vitamin D supplementation had no statistically significant effects on bone density at any site in healthy children," Dr. Winzenberg said in a news release. "There was, however, some indication that children who had low levels of vitamin D in their blood might benefit from supplementation. We now need randomised controlled studies focused on vitamin D deficient children to confirm if vitamin D supplements would help this particular group."
The review authors have disclosed no relevant financial relationships.
Cochrane Database Syst Rev. Published online October 6, 2010.