Vitamin D, which often is called the "sunshine vitamin," is typically associated with bone health, yet researchers are finding that it can fulfill multiple roles in promoting health and preventing disease.

"Nutritionally speaking, Vitamin D is actually a hormone; about 10 percent is typically derived from foods, and about 90 percent is produced within the body as a result of skin coming in contact with direct sunlight," said Sandy Procter, Kansas State University Research and Extension nutrition specialist.

As a health-promoting hormone, Vitamin D binds to receptor cells in the body that control a wide range of hormone- and gene-expressing processes, said Procter, who cited research findings highlighting health benefits from the vitamin. Vitamin D:

  • Strengthens the immune system to help the body fend off infections and diseases.
  • Helps prevent autoimmunity, an abnormal response of the immune system in which the body attacks its own cells and tissues. Researchers are exploring the connection between Vitamin D deficiency and autoimmune diseases such as multiple sclerosis and rheumatoid arthritis.
  • Regulates a number of genes in prostate, colon and breast cancer. Studies suggest that a Vitamin D deficiency might affect the outcome of a diagnosis of cancer, and may also be a factor in causing the cancer.
  • Appears to be a factor in improving the body's sensitivity to insulin, which, in addition to lowering the risk of diabetes, may prevent or delay the onset of the disease and reduce complications from it in those who already have it.
  • In related news, a recently reported study in Finland linked higher vitamin D levels to a lower risk of Parkinson's disease.

Even with health benefits identified and research continuing on Vitamin D, three out of four Americans fall short of the recommended Adequate Intake values identified by the Institute of Medicine, Procter said.

Many experts believe that the current recommendations, such as the daily recommendation for adults ages 19-50 (200 International Units), are not enough to prevent health consequences, she added.

Widespread deficiencies of the vitamin are being identified in many Americans. The reasons given for the shortfall include more time being spent indoors; lesser air quality (smog, for example); recommended use of sunscreen (to reduce damage to skin from overexposure to the sun); seasonal weather, such as a lack of sunshine in winter months; obesity, in which fat cells interfere with body processes in forming and storing Vitamin D; aging, during which the body's ability to process Vitamin D declines; darker skin color, which translates into lesser absorption through the skin, and breastfeeding.

If, for example, a mother is low in Vitamin D, the infant will likely experience a similar deficiency due to low levels of vitamin D in the breast milk, and that's why it is now recommended that breastfed infants receive 400 IU (international units) of supplemental vitamin D beginning shortly after birth, Procter said.

Since 2000, a recurrence of rickets, a disease attributed to a deficiency in Vitamin D that is characterized by the softening and curving of bones resulting in bowed legs, an enlarged head, rib cage, joints or deformed pelvis particularly noted in African American infants and children, prompted the American Academy of Pediatrics to recommend (in 2008) that all infants, children and adolescents need 400 IU of vitamin D a day. 

The change in the recommendation doubles the previous recommendation, said Procter, who explained that current knowledge about Vitamin D is being reviewed by an Institute of Medicine Committee and recommendations are expected to be updated in fall, 2010.