You’re depressed
Having the blues may be linked to an insufficient amount of vitamin D. According to the Vitamin D Council, vitamin D receptors have been found in many parts of the brain, including in areas linked to depression. Results from studies have been mixed—some researchers have found significant improvements in mood after supplementing with D, while others have not—but that could depend on the severity of the depression as well as the vitamin D deficiency. For example, researchers from Columbia University found that taking vitamin D supplements was effective for those who sufferred from clinically significant depression.

Your bones hurt
Adults who don’t get enough vitamin D often have aches and pains in their muscles and bones, especially in the winter. Their joints are also a little stiffer in the morning. “Many aches and pains are symptoms of the classic vitamin D deficiency, osteomalacia,” says Sonya Angelone, MS, RDN, spokesperson for the Academy of Nutrition and Dietetics. Soft bones are more likely to bow and fracture than ones that are healthy and hard. Here are some other simple ways to boost your bone health.