Vitamin D deficiency — when the level of vitamin D in your body is too low — can cause your bones to become thin, brittle or misshapen. The role of vitamin D and insulin resistance, high blood pressure, and immune function — and how these relate to heart disease and cancer — is under investigation.
Although the amount of vitamin D adults get from their diet is often less than what's recommended, exposure to sunlight can make up for the difference. For most adults, vitamin D deficiency is not a concern. However, some groups — particularly people with dark skin and adults older than age 65 — may not get enough vitamin D in their diet or get enough sunlight for their bodies to produce it.
The recommended dietary allowance (RDA) for adults is 600 IU of vitamin D a day. That goes up to 800 IU a day for those older than age 70. To meet this level, choose foods that are rich in vitamin D. For example, choose fortified foods such as milk and yogurt and fatty fish such as salmon, trout, tuna and halibut.
Don't over do it, though. Very high levels of vitamin D have not been shown to provide greater benefits. In fact, too much vitamin D has been linked to other health problems.
If you're concerned about whether you're getting enough vitamin D, talk to your doctor about your diet and whether a vitamin supplement might benefit you.