Vitamin D has been called the Sunshine Vitamin. Most people can make some vitamin D if they get enough mid-day sunshine, but there are problems. The atmosphere blocks the UV light which triggers vitamin D conversion in the skin. The sun needs to be high off the horizon so that enough UV light gets through to you.
You should protect yourself from sunburn and skin cancer risk, with clothing, hat, and sunblock. Unfortunately that will prevent you from making vitamin D. That is why more people in South Florida and Southern California are Vitamin D deficient than in Iowa.
In Iowa we cannot get ANY vitamin D from the sun from September through April. Over half of Iowans are deficient in September. Over 85% of Iowans are deficient by the end of March. In South Florida and Southern California the year-round average for persons over 50 was 80% in a recent shopping mall survey.
The ability to make Vitamin D varies from person to person, and it diminishes with age. In general, darker skinned individuals are more likely to be deficient, but some very pale people also fail to make enough vitamin D. Even in the tropics some individuals cannot make enough vitamin D from unprotected exposure to the sun. This leads to Vitamin D Deficiency.
Without enough Vitamin D your body cannot absorb enough Calcium and you develop Osteoporosis. Test for Vitamin D level to see if you have enough or if you need to take Vitamin D supplements.
Jay Ginther, MD
2008 / Revised November 2010