2.3. Sample Size Considerations
We estimated that a sample size of 140 per group would enable the detection of an effect size of 0.5 (90% power and 5% type 1 error rate) for the comparison of differences in IGF1 or IGFBP3 concentration between any 2 groups. Given the limited literature on the effect of micronutrient supplementation on these aforementioned biomarkers, this sample size was informed by the estimated effect size of the intervention on other biomarkers, such as plasma zinc and ferritin.