One of the fat-soluble vitamins, although technically not a vitamin because it can be synthesized by the skin when exposed to sunlight (Ultraviolet B radiation).
Vitamin D is involved in the regulation of at least 800 genes.
Vitamin D deficiency is common and perhaps the most widespread deficiency in developed nations – estimated 75% of Americans
Role in disease states
- Osteoporosis (adults) and Rickets (children)
- Immunity; infection
- Teeth and Gum disease
- Cancer – Adequate levels associated with lower risk of breast cancer, colon cancer, and prostate cancer.
Getting Vitamin D
Studies have shown that our bodies use about 4,000 IU (International Units) per day. Dietary sources account for only 5-10% of that total, so either the rest must come from the sun, or this imbalance results in sub-optimal Vitamin D levels.
- Far and away, fatty fishes are the best source.
- The next most reliable source is milk fortified with Vitamin D.
- Fair-colored skin – 20 minutes in sun can produce 20,000 IU of Vitamin D. In comparison, a large piece of fatty fish may contain 1,000 IU.
- Nature’s design: Northern climates have less intense sun but access to fatty fish (salmon, sardines, etc) containing large amounts of Vitamin D.
- Factors decreasing Vitamin D synthesis: clothing, dark skin complexion, aging
- Shadow rule: Optimal time of day for sun exposure is when the length of your shadow is less than your height.
- Most people require supplementation, usually in the form of Vitamin D3 (cholecalciferol)
- How much to take is determined by multiple factors. Determining the appropriate dose may require measurement of your 25-hydroxy Vitamin D level.
Can one get too much Vitamin D?
Yes, it is possible, albeit very rare. The safe range of Vitamin D levels (the therapeutic index) for Vitamin D is quite large.