The symptoms of vitamin D deficiency are important to be aware of, because if you’re not getting enough of this nutrient it could lead to soft bones, known as rickets in children, and osteomalacia in adults.

So why do we need vitamin D? According to a spokesperson from the Academy of Nutrition and Dietetics, this fat-soluble nutrient aids in the absorption of calcium and phosphorus in our bodies, bringing these minerals to our bones and teeth and helping to regulate how much calcium remains in our blood.

“Together with calcium, vitamin D helps protect against the loss of bone mass,” they say. “It also helps muscles to function and allows the brain and body to communicate through nerves. The immune system also uses vitamin D to help fight off invading bacteria and viruses.”

Registered dietitian Jen Bruning, a spokesperson for the Academy of Nutrition and Dietetics, also adds: “There may also be a role for vitamin D in inflammation reduction as well as helping to control the growth of cancer cells and preventing depression.”

The body naturally produces vitamin D when exposed to sunlight, but we can also get it from certain foods and the best vitamin D supplements. But research in the National Institutes of Health found that 42% of Americans aren’t getting enough vitamin D, and people with darker skin need longer to synthesize enough of it.

In this article, experts explain more about the symptoms of vitamin D deficiency and what you can do to avoid it.

What causes vitamin D deficiency?

Bruning told Live Science: “Estimates suggest that around 1 billion people worldwide have a vitamin D deficiency. In many adults, this may not present with any clear signs or symptoms.”