yellow five does not shrink the male reproductive organs! it is just a myth that was created quite a while ago. mountain dew does contain yellow 5, it is in such small ammounts that if it did anything, you would have to drink a LOT of mountain dew.
if you do not beleve me, or you do not trust me, go to any of these sites and they will tell you;
mountain dew's response
the FDA's official response
nuketown.com
stayfreemagazine.org
straightdope.org