Not getting enough vitamin D, also called a vitamin D deficiency, can cause your bones to become thin, brittle, bent or bowed during growth. More study is needed to understand how vitamin D levels affect chronic illness.

The recommended amount of vitamin D a day for adults is 600 international units, also called IU. That goes up to 800 IU a day for people older than age 70.

Some groups are at risk for vitamin D deficiency. Those at risk of vitamin D deficiency include people who have obesity, people who have Black or brown skin, and people who are older than 65. Infants who are breastfed for a long time without taking a vitamin D supplement also are at risk. People with inflammatory bowel disease or other conditions that limit how the body handles fat from the diet also may not get enough vitamin D. And a vitamin D deficiency is a risk for people who follow an eating pattern that doesn't include foods with vitamin D or for people who have limited sun exposure.

Foods high in vitamin D include fatty fish, such as salmon or trout. Foods with vitamin D added, called fortified, are another source of vitamin D. These include milk and yogurt. Some plant milks, such as soy, almond and oat milk, have vitamin D added, as do some cereals. Some mushrooms are treated with ultraviolet light, which gives them more vitamin D.

It's possible to get too much vitamin D. This mainly happens if you take supplements. Studies haven't shown that high levels of vitamin D help health more. In fact, too much vitamin D has been linked to health issues.

If you're concerned about getting enough vitamin D, talk with your healthcare professional about your diet and whether a vitamin supplement might be right for you.