With the official start of summer just one week away and an estimated 50% of the world population at risk of vitamin D deficiency, it's important to consider what this seasonal change may mean for you  commencing or continuing a Vitamin D supplementation regimen. For much of the country, this is the time of year when the sun shines and people head outside to soak up its warm rays. An individual is capable of endogenously producing greater that 10,000IU of vitamin D daily, but what factors actually influence production and is continued supplementation necessary in these warmer, brighter months? Let's take a closer look...

There are many factors affecting vitamin D production in the body, the most well known being the angle of the sun's rays. The angle of the sun's rays is affected by the time of day, season and latitude. These factors in turn determine the amount of UVB exposure that reaches the skin and, ultimately, stimulates vitamin D production in the body. UVB rays are the portion of light that stimulate vitamin D production and are diffused during the early and latter parts of the day, during winter months and incrementally in latitudes north of the equator. Skin type is another factor when considering vitamin D production by the body. Individuals with darker skin pigmentation require longer sun exposure time for vitamin D synthesis. The combined factors of skin type, latitude and season must all be factored into determining the necessary length of sun exposure time for an individual to produce optimal amounts of vitamin D.

At noon in Miami, an individual with skin type III (fair with mild burning potential) would require approximately 6 minutes to synthesize 1000 IU of vitamin D in summer and 15 minutes in winter. Skin type V (dark-toned skin with rare burning) would need around 15 and 29 minutes, respectively.

At noon in Boston during summer, skin type III would require approximately 1 hour and skin type V, 2 hours to synthesize 1000 IU of D. During the winter months in Boston vitamin D production is not possible.

In addition to the factors discussed above, many people use sunscreens that, even at a minimal sun protection factor of 8, can block 95% of UVB rays. Optimal vitamin D production necessitates 40% of the entire skin surface be exposed when outdoors with the torso having the largest capacity for production and the face the least. For those individuals under the age of 20 and over the age of 60, vitamin D production can take quadruple the amount of time than it does for the rest of the population! Other culprits blocking UVB rays include clouds, air pollution and glass; the warm sun may be a welcome sight through the office window, but it's not contributing to vitamin D production without direct skin exposure. UVB tanning beds are a viable direct exposure option, however they are costly and overuse is associated with accelerated aging of the skin and increased risk of skin cancers. Just as outdoor exposure does not require tanning or reddening of the skin to stimulate vitamin D production, neither does exposure by tanning beds.

Consideration of all of these factors in addition to baseline testing and monitoring of your Vitamin D levels  will ensure optimal vitamin D health.