Vitamin D is found in many dietary sources, such as fish, eggs, fortified milk and cod liver oil. The sun also contributes significantly to the daily production of vitamin D, and as little as 10 minutes of exposure is thought to be enough to prevent deficiencies. The term "vitamin D" refers to several different forms of this vitamin. Two forms are important in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is synthesized by plants. Vitamin D3 is synthesized by humans in the skin when it is exposed to ultraviolet B (UVB) rays from sunlight. Foods may be fortified with vitamin D2 or D3.
In a new study, researchers evaluated 3,705 well-functioning men and women aged 70-79 years-old who were participating in the Health, Aging and Body Composition Study. Over a six-year period, the team measured subjects' vitamin D levels and mobility status semi-annually to determine if the two may be linked. The participants performed tasks such as walking a quarter of a mile, climbing 10 steps or engaging in other everyday tasks to determine their level of physical function.
The results suggested that people who had lower vitamin D levels had about a 30 percent greater risk of experiencing mobility limitations and about a twofold greater risk of disability, compared to those who had higher levels of vitamin D.
The scientists concluded that increasing vitamin D intake may help older adults maintain mobility and prevent the development of physical disability. More research is needed to better understand these findings.
The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. It is used, alone or in combination with calcium, to increase bone mineral density and decrease fractures. Recently, research also suggests that vitamin D may provide protection from osteoporosis, hypertension (high blood pressure), cancer and several autoimmune diseases.
For more information about vitamin D, please visit Natural Standard's Foods, Herbs & Supplements Database.