Vitamin D3 is the primary raw material to make active and useable vitamin D.  Vitamin D3 is produced when our body is exposed to sunlight (ultraviolet B radiation sunlight).  Our bodies are amazingly efficient when it comes to producing vitamin D3; brief sunlight exposure of the arms and face will enable our body to produce 200 international units (IU) of vitamin D3. The precise amount of vitamin D3 produced will vary depending on factors such as skin type, geographical location, season, and time of the day.  For example, an individual will produce 400 IU of vitamin D3 in Boston, Massachusetts within 8 minutes of sunshine whereas the same individual may only need 6 minutes if they are in Miami, Florida.  Not a huge difference but something to celebrate if you are reading this from South Beach.

Correction of vitamin D deficiency is quite simple with the use of over-the-counter vitamin D supplementation.  The American Geriatrics Society recommends vitamin D dose of 800 to 1000 IU by oral supplementation daily to reduce the risk of falls and fractures.  Most pharmacies carry vitamin D in doses of 400 IU to 2000 IU per tablet. Other formulations such as a liquid formulation is available for children and an injection for people with gastrointestinal absorption issues.  People with kidney or liver disease will need to see a specialist because the over-the-counter vitamin D is the inactivated form and in the presence of kidney or liver disease, our body cannot convert this inactivated form to its active metabolite (our liver and kidneys convert vitamin D to its active form). There are virtually no side effects with vitamin D because it is a natural hormone.  The Institute of Medicine recommends an upper limit of 4000 IU of vitamin D per day.   In cases where there is vitamin D toxicity, calcium levels may be too high but this is extremely rare.

Vitamin D can come from our diet but there are very few foods in nature that contain vitamin D (e.g. fatty fish liver is the best source but who wants to eat that).  The best sources of Vitamin D in nature come from fatty fish (salmon, tuna, mackerel) and small amounts are also found in cheese, egg yolks, sardines and fortified foods.