A new study suggests that high vitamin D levels in the blood may be linked to decreased risk for disease.
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 measured blood levels of vitamin D in 1,621 Caucasian men and women over the age of 65. All subjects had participated in the Cardiovascular Health Study since the 1990s. Over a period of 11 years, the scientists studied the link between these individuals' vitamin D levels and any serious medical conditions, including hip fractures, heart attacks and cancer.
The results suggested that the risk of these diseases increased when the level of vitamin D fell below 20 nanograms per milliliter of blood. Additionally, the scientists discovered that the risk of developing serious medical conditions changed with the seasons. In the spring and summer, when subjects had more exposure to vitamin D from sunlight, their vitamin D blood levels tended to be higher than in fall and winter.
The researchers concluded that maintaining adequate levels of vitamin D in the blood may help reduce the risk of serious illness. The authors emphasized that more studies are 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.
Rickets and osteomalacia are classic vitamin D deficiency diseases. In children, vitamin D deficiency causes rickets, which results in skeletal deformities. In adults, vitamin D deficiency can lead to osteomalacia, which results in muscular weakness in addition to weak bones. Populations who may be at a high risk for vitamin D deficiencies include the elderly, obese individuals, exclusively breastfed infants and those who have limited sun exposure. Also, individuals who have fat malabsorption syndromes (e.g., cystic fibrosis) or inflammatory bowel disease (e.g., Crohn's disease) are at risk.
For more information about vitamin D, please visit Natural Standard's Foods, Herbs & Supplements Database.