The dose makes the poison (or the cure). According to the article they gave daily injections containing 300 oranges worth of vitamin C (which google tells me is over 15 grams of vitamin C, an order of magnitude larger than the daily recommended dose for adult humans).
Certainly being skeptical is still warranted, as OP is correct, there are significant differences in how this particular compound is handled species to species. However, simply that mice produce ascorbic acid does not imply that they produce it in quantity great enough to impact this kind of tumor.
Certainly being skeptical is still warranted, as OP is correct, there are significant differences in how this particular compound is handled species to species. However, simply that mice produce ascorbic acid does not imply that they produce it in quantity great enough to impact this kind of tumor.