Something that many of the US President's have in common is the graying of their hair while in office.  So, naturally you would think it would come from the stress of the job. 

But it doesn't.  The most common cause is genetics & timing. 

Most US presidents are in office during their late 40s, 50, and 60s... which are the "graying" years for most.  It's when our bodies melanin production slows down.  And if you're genetically pre-disposed to have low levels... then you're heading for gray-ville.  Thank your parents for that!

You can read the entire article HERE.