What you should know about the popular supplement.

Vitamin D has been touted as a must-have vitamin in recent years as studies have shown that many Americans are deficient.

Getting vitamin D is important since it can help with calcium absorption and has roles in immune function and cell growth, among others. While the vitamin is found in some foods and can be obtained via ultraviolet light, nearly 50 percent of the population worldwide has insufficient levels, according to a 2012 study.

But understanding what’s the right amount of vitamin D for young children, pregnant women, and others, can be difficult.

This month, three studies shed more light on when pregnant women and babies should be getting vitamin supplements, and what’s the ideal amount