Humans, fruit bats, guinea pigs, and apes lack the enzyme to manufacture
vitamin C in the body and must  get it from their diet. So the question is how
much do we need. We can look to other mammals that manufacture vitamin c
in their bodies for that answer. Horses and dogs for instance produce 10 grams
per  day for every 150 lb. Of body weight. They produce even more under
stress. Since we have the same basic physiology and vitamin c is used in the
same way we can say we need the same about same which would be about
3 grams 3 times a day to mimic most other mammals. Possibly more
when under stress or in a  toxic environment. This makes the FDA's RDA of
vitamin C at 60 milligrams seem ridiculous. In fact it's just enough to prevent
scurvy and no where near the optimum amount.

Insider Net    
****Medical schools were started by the drug companies****