Guinea pigs.
The scientists were able to measure the serum Vit C level in animals that make there own C and extrapolate it to what a hundred twenty pound human would need.
Are you ready?
Somewhere between 5-6 thousand milligrams per day.
Also, if you're interested on the nutritional side, I can only urge you to read about some of the recent discoveries about Vitamin D. Reductions of some forms of cancer by 50 percent.
And if 1000mg is 1G then I'm around 1 to 2 g short for a 120 lb man, and I have 55 more pounds than that.
Yup, way more than the RDA of 60mg.
I've read of people taking up to 40K mg. A doctor and big proponent of C perscribed as much to a pregnant woman, and relatively speaking her delivery was about as painless and quick as such a thing can be (but what do I know, I'm a guy) Or up to the point were the bowels start to complain and then backing off. And the Vit. D thing I just read in the paper, but its been suggested for some time. Fortunately D is made in the body by exposure to sunlight, so while I'm not a tanning fanatic, I get a fair amount, and I love milk which is enhanced with D as well. And thanks, Guinea pigs was the one I couldn't remember. Adding to that little factoid is; that among the 4 mammals, humans are the ONLY carnivores that do not produce C naturally.