<PSA>...and boost your vitamin D level! 60% of the US population is deficient and it gets worse in the winter (which is one reason flu cases increase seasonally.) Your body will make vitamin D on its own in response to direct sunlight (but not through glass.) You can also buy inexpensive D3 supplements. Many high end multivitamins already include it.</PSA>

http://www.scientificamerican.com/blog/60-second-science/pos...