Millions of parents worry about their children getting sick with acute respiratory infections. A massive review looked at whether giving vitamin D supplements could help prevent these illnesses in children under five and pregnant women. The study combined data from hospitals, day-care centers, and homes to see if taking vitamin D made a real difference.
The analysis showed that vitamin D might lead to a small drop in the proportion of children needing a healthcare visit for a cold. However, it probably does not reduce the average number of visits per child. When comparing high doses to low doses, the results were similar, suggesting the amount taken does not change the outcome.
Safety was also a major focus. The researchers looked for a condition called hypercalcaemia, where calcium levels in the blood get too high. No cases were found in pregnant women. For children, the risk of this condition was little to no different whether they took vitamin D or a placebo. Overall, the supplement appears safe.
The evidence for a slight benefit is considered low certainty, meaning the results are not fully proven. The evidence showing no benefit for reducing the average number of visits is of moderate certainty. This review helps doctors decide on supplementation policies for pregnancy and early childhood without overstating the benefits.