It has become popular in recent years to try to block out sunlight, especially the ultra-violet rays.  We make eyeglasses that block out the UV rays.  We have windows on our homes and cars that block out  UV rays.  Now we have a vacuum cleaner that uses UV rays to kill germs.  Huh?  Wouldn't it be better to just open a few windows and let real sunlight with plenty of natural UV rays in to kill those germs and freshen the air?  
    And dermatologists told us to hide from sunlight as much as possible to prevent skin cancer.  The result is a big increase in vitamin D deficiency.  And sunlight was never the root cause of the cancer anyway.  The real cause is the chemicals in the food we eat, the water we drink and the air we breathe that build up in our skin and the fat layer just below the skin which often turn carcinogenic when exposed to sunlight.
    Man always seems to want to invent things to "fix" nature.  Then he has to invent something else to fix the problems caused by the first invention.   Then something else to fix the problems caused by that invention, and on and on.  Meanwhile, the longest lived peoples in the world are eating fresh grown vegetables, fish and a little meat, getting exercise regularly, socializing, and getting outdoors into the sunlight.