Giving vitamin D supplements to kids who don’t have enough of it can boost their vitamin D blood levels, but it doesn’t always help them grow taller, develop faster during puberty, or feel better if they have asthma.

Taking vitamin D might help kids between 1 and 15 years old get fewer colds and lung infections, but scientists aren't totally sure yet.

Taking 2000 IU of vitamin D daily for 12 weeks raises vitamin D levels in the blood of young, healthy men who were initially deficient, but this change is not linked to changes in testosterone, estradiol, cortisol, or SHBG levels.

Scientists use your genes to guess how much vitamin D you’ve had over your life, and since these genes don’t change much as you grow, they can help estimate your vitamin D levels even when you were a kid—even though the data was collected from adults.

Being taller doesn’t cause your body to have more or less vitamin D—any link you see between height and vitamin D is probably because taller people spend more time outside or have bigger bodies, not because height directly affects vitamin D.