Vitamin D for respiratory infections in children under 6 Original paper

In this systematic review, when looking specifically at randomized controlled trials, supplemental vitamin D had no effect on the risk, severity, or duration of various respiratory infections in children.

The effect of supplementation with vitamin D on respiratory infections.

The outcomes included the duration and severity of respiratory infections and the risk of different types of respiratory infections (acute and recurrent, upper and lower). The respiratory infections included viral infections such as the common cold and influenza (but not COVID-19) and bacterial infections such as pneumonia.

A total of 2,189 children (ages 0–5; average ages of 2.2–4.8).

In this systematic review of 8 studies, 5 studies were randomized controlled trials (RCTs), 2 were case-control studies, and 1 was a prospective cohort study. Five studies were conducted in Canada, 2 in India, and 1 in China. The RCTs were described by the authors as good quality or excellent quality. The case-control studies were rated as good quality or fair quality. The cohort study was rated as fair quality.

The participants were given vitamin D for 3–12 months, at doses ranging from 400 IU per day to 2,000 IU per day. Some studies used initial one-time doses of 50,000–300,000 IU, with 400 IU per day given afterwards.

In the RCTs, other than increased serum vitamin D levels, there were no differences between vitamin D and placebo groups after vitamin D supplementation.

The case-control studies reported lower risks of pneumonia, upper respiratory infections, and lower respiratory infections with vitamin D supplementation. The prospective cohort study reported that the participants who supplemented with vitamin D recovered from acute respiratory infections quicker and had fewer acute respiratory infections.

Four studies reported the vitamin D insufficiency prevalence rates in their study populations. These rates widely varied; 6% to 75% of participants were vitamin D insufficient (defined in these studies as a level less than 20 or 30 nanograms per milliliter).