The Vitamin D Council recommends between 5,000 and 10,000 IU of vitamin D daily for adults because their research suggests that this is the optimum amount the body needs for overall good health. Vitamin D is important to support healthy functioning of the heart, lungs, brain, muscles and bones.
A person can ensure that their vitamin D intake is sufficient by getting enough sun exposure, and by taking a vitamin D supplement. The body manufactures its own vitamin D when a person exposes their skin to sunlight.
When the body is not getting enough vitamin D, the person can suffer from vitamin D deficiency, which causes multiple problems, such as rickets and osteomalacia. These conditions cause the bones to become brittle and thin. Vitamin D deficiency has also been linked to cancer, diabetes, high blood pressure, depression and some autoimmune diseases.