To know about the effects of vitamin D deficiency, it is important to understand what vitamin D does in the body and how it functions. As more research is done, we are learning that vitamin D in not only a fat-soluble vitamin, but also acts as a steroid structure hormone. This means that the effects of vitamin D are more far-reaching than previously thought.
Functions of Vitamin D
Vitamin D is most often associated with bone health. It also helps with the regulation of calcium and phosphate. The idea that it functions as a hormone comes from many years of research linking vitamin D regulation with parathyroid hormone regulation. Areas of function that are still being researched include immune function, cell growth, mood regulation and decreased risk for fall fractures in the elderly.
Deficiency Signs and Symptoms
It is difficult to know when to look for deficiency and how best to know based on signs. To get a true idea of where your vitamin D level is, it is helpful to get a blood test to look for active forms of vitamin D (1,25 OH). This test can be done at any medical lab, and can be ordered by your doctor. In children, vitamin D deficiency is a condition called rickets, where there is bowing of the bones, especially in the legs, poor tooth enamel, overall muscle spasms, or even "floppy baby" syndrome, where the baby doesn't move well. This problem is more common in third world countries. In adults the same condition is called osteomalacia. There is often not such obvious signs as bowing of the legs, but there is still muscle weakness and an increased risk for fractures. A 2008 review study of vitamin D research done by the International Journal of Circumpolar Health found that vitamin D deficiency can even be linked to diseases like cancer, multiple sclerosis and type I diabetes. This same study also noted that those living in the northernmost areas of the Earth need to supplement vitamin D during the winter, since sunlight is not as readily available.
Sources of Vitamin D
The best source of vitamin D is through UVB sunlight. This can mean anywhere from 10-30 minutes of sunlight without sunscreen, depending on the color of your skin. The darker your skin, the longer it will take to absorb the light and have your body synthesize the vitamin D. If sunlight is not an option based on work or where you live, fatty fishes like tuna and salmon (100 g serving size of fish) will give you 5-16 mcg of vitamin D. Butter, eggs and fortified milk and cereals also have vitamin D in them. The recommended daily allowance for vitamin D is 5-15 mcg or 400-600 IU (international units) per day currently. There is much research showing that much higher values of vitamin D can be taken without side effects, especially if there is immune compromise. Studies have been done looking at doses of 10,000 IU a day when sick or deficient. Once re-testing of vitamin D levels have shown normal values, supplementation of 1,000 IU a day has recently been found to be safe and effective by the Journal of the American Family Physician.
References
- Journal of American Board Family Medicine; Vitamin D: An Evidence-Based Review; Nov.-Dec. 2009
- International Journal of Circumpolar Health; Vitamin D and Living in Northern Latitudes---An Endemic Risk Area for Vitamin D Deficiency.; Huotari A, and Herzig KH; June 2008
- American Family Physician; Recognition and Management of Vitamin D Deficiency; Bordelon P., et al.; Oct 2009
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