This new review assessed the effects of oral vitamin D supplementation on linear growth and other health outcomes among infants and children under five years of age.
It includes 75 randomised controlled trials (RCTs) or quasi-RCTs comparing oral vitamin D supplementation, with or without other micronutrients, to no intervention, placebo, a lower dose of vitamin D or the same micronutrients alone (and not vitamin D) in infants and children under five years of age who lived in any country. A total of 12,122 participants took part in the studies, most of which were conducted in India, USA and Canada.
The results were as follows.
Vitamin D supplementation versus placebo or no intervention
Compared to placebo or no intervention, vitamin D supplementation probably improves length/height-for-age z-score (1 study, 1258 participants; moderate-certainty evidence); however, the evidence is very uncertain about its effects on:
· linear growth (mean difference (MD) 0.66 cm, 95% confidence interval (CI) −0.37 to 1.68; 3 studies; 240 participants, low-certainty evidence);
· stunting (1 study, 1247 participants; moderate-certainty evidence);
· developing hypercalciuria (risk ratio (RR) 2.03, 95% CI 0.28 to 14.67; 2 studies, 68 participants; high-certainty evidence); and
· developing hypercalcaemia (RR 0.82, 95% CI 0.35 to 1.90; 2 studies, 367 participants; very low-certainty evidence).
Vitamin D supplementation (higher dose) versus vitamin D (lower dose)
The evidence is very uncertain about the effect of higher-dose vitamin D supplementation, compared to a lower dose of vitamin D, on:
· linear growth (MD 1.00, 95% CI −2.22 to 0.21; 5 studies, 283 participants);
· L/HAZ (MD 0.40, 95% CI −0.06 to 0.86; 2 studies, 105 participants; low-certainty evidence);
· hypercalciuria (RR 1.16, 95% CI 1.00 to 1.35; 6 studies, 554 participants; low-certainty evidence); and
· hypercalcaemia (RR 1.39, 95% CI 0.89 to 2.18; 5 studies, 986 participants; low-certainty evidence)
No studies included in this comparison evaluated stunting.
Vitamin D supplementation (higher dose) + micronutrient(s) versus vitamin D (lower dose) + micronutrient(s)
Supplementation with a higher dose of vitamin D plus micronutrients, compared to a lower dose of vitamin D with the same micronutrients:
· probably makes little to no difference to:
o linear growth (1 study, 25 participants; moderate-certainty evidence); or
o developing hypercalcaemia (RR 1.00, 95% CI 0.90, 1.11; 2 studies, 126 participants; moderate-certainty evidence); and
· may make little to no difference to developing hypercalciuria (1 study, 86 participants; low-certainty evidence).
An additional four studies in this comparison measured hyperphosphataemia and three studies measured kidney stones. However, these studies reported no occurrences, and therefore were not included in the analyses for these outcomes. No studies included in this comparison evaluated L/HAZ or stunting.
The authors concluded that oral vitamin D supplementation probably slightly improves length/height-for-age z score compared to placebo, but may result in little to no difference in linear growth, stunting or adverse effects compared to placebo, no intervention, or lower dose vitamin D, with or without micronutrients. However, the evidence is very uncertain.
The evidence is current to December 2019. Read the full review here on the Cochrane Library.