You could be among the 42 percent of American adults who are low in vitamin D

Body needs vitamin D to build strong and healthy bones—but that’s not the only thing the sunshine vitamin has going for it

Vitamin D helps your body absorb calcium, plays a role in proper cell growth, and even reduces disease-causing inflammation

It’s often difficult to tell if newborns are deficient in D, but a sweaty forehead is one of the first noticeable symptoms

Being deficient in vitamin D can leave you feeling exhausted, even when you’re able to get enough sleep

Many things can make you feel down, but more and more research is linking true depression with a shortage of vitamin D

You stop building bone mass around age 30, and a lack of vitamin D can speed up or worsen osteoporosis

Certain fish—like salmon, swordfish, sardines, and tuna—will be your best sources, but you can also find vitamin D in eggs, cheese