Sunshine and Vitamin D

Photo by tarotastic. 

Having osteopenia encourages me to read regularly about factors that contribute to bone health.
I have written before about the role of calcium and exercise in building and  maintaining bone mass.
The body also needs adequate levels of Vitamin D in order to process calcium for proper bone health.
But it also essential for many other bodily functions, such as the following:
immune system, muscle function, cardiovascular function, respiratory system, brain development, and anti-cancer effects.
Unfortunately, many people are deficient in Vitamin D, which is most readily available from ultraviolet B rays from sunlight.
How does deficiency happen? For example, people may spend too much time indoors, they may live far from the equator, they may wear sunscreen and layers of clothing, they may have dark skin, or they might be overweight.
According to the National Institutes for Health, People ages 51 to 70 need 600 IU of daily Vitamin D.
People 71+ need 800 IU of daily Vitamin D.
Older adults are particularly at risk for osteomalacia (brittle bones) if they do not get enough Vitamin D.  In children, this condition has been called rickets.
People can take supplements or increase the number of Vitamin D rich foods they eat. However, sunlight has been the most reliable source for Vitamin D.  (I will address Vitamin D rich foods and supplements in future posts.) 
Most people need between 10 and 15 minutes of ultraviolet-rich light per day.  Here are some considerations:

• Sitting by a window is inadequate because the glass filters the UV rays. 
• Mid-day sun and early afternoon sun is better than morning or late afternoon sun. 
• The further away you live from the equator, the harder it is to get UV rays.
• If you have dark skin, you might need to 6 times the exposure.
• The more skin exposed, the better. 

Of course, you don't want to overdue sun exposure and increase your risk of skin cancer, so don't overdo it. 
So if the sun is out, consider taking a short walk during your lunch hour while wearing short sleeves.  Your bones will thank you. 
Related:
What Is Osteopenia? Calcium and Bone Density
Exercise to Increase Bone Density