VITAMIN D
Vitamin D is a fat-soluble hormone that is responsible for enhancing intestinal absorption of calcium and promotes bone mineralization. In humans, there are two important forms: vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol). D2 is synthesized by plants and D3 is created when skin is exposed to ultraviolet-B rays from the sun and is often referred to as the “sunshine vitamin”.
Deficiency has been linked to:
- Osteoporosis
- Rickets
- Osteomalacia
- Autoimmune diseases like multiple sclerosis and rheumatoid arthritis
- Some cancers
Some sequelae of vitamin D deficiency include fatigue and porous bones which can result in fractures. Deficiency is common in northern latitudes where sun exposure is sporadic and in those with minimal exposure to sunshine. It is also found to be higher in African Americans which recent studies indicate may be related to a decrease in the binding protein.
It is difficult to get enough vitamin D from your diet. Although many foods are fortified, they provide vitamin D2, which is less well utilized by the body than D3. Good dietary sources include fortified foods, eggs, and oily fish such as salmon, tuna, mackerel and sardines. Daily exposure to sunlight is helpful at least two to three times per week between 11 am and 3 pm.
The US Institute of Medicine Recommended Dietary Allowance of vitamin D is 400 IU (10 mcg) per day for children younger than 1 year of age, 600 IU (15 mcg) per day for children at least 1 year of age and adults up to 70 years, and 800 IU (20 mcg) per day for older adults. In 2008, the American Academy of Pediatrics increased the recommended minimum daily intake of vitamin D to 400 IU (10 mcg) daily for all infants and children, including adolescents. No adverse effects have been seen with supplemental vitamin D intakes up to 10,000 IU daily.