In the 1970's. Nobel laureate Linus Pauling conducted some very widely publicized studies of high-dose vitamin C as a method of extending the life of terminally ill cancer patients. In his study of 2000 people with terminal cancer, those who received 10 grams of vitamin C daily lived 5 to 20 times as long as those who did not. That is, most of the study volunteers taking vitamin C lived an average of 120 days, rather than 42 days, and 10 per cent of those taking vitamin C lived as long as 2-1/2 years. The vitamin C was administered by intravenous drip for the first 10 days and then taken in tablet form.
This study did not find that vitamin C cured cancer. It did find that vitamin C extended the very end of life in almost all cases. Follow-up research, unfortunately, found no benefit in increasing the dose to more than 10 grams a day, nor did patients live as long as they did in Dr. Pauling's trial.
That was not the end of the story. Thirty years later, Canadian doctors tried administering all the vitamin C intravenously. They found that 25 times more vitamin C reached cancer cells when the supplement was administered by IV compared to giving the vitamin by mouth. In the scientists' own words,
"Recent evidence shows that oral administration of the maximum tolerated dose of vitamin C (18 g/d) produces peak plasma concentrations of only 220 μmol/L, whereas intravenous administration of the same dose produces plasma concentrations about 25-fold higher. Larger doses (50–100 g) given intravenously may result in plasma concentrations of about 14 000 μmol/L. At concentrations above 1000 μmol/L, vitamin C is toxic to some cancer cells but not to normal cells in vitro."
In other words, you simply can't get enough vitamin C to fight cancer into your body if you take the vitamin by mouth. You have get it intravenously. When vitamin C is given intravenously, however, at least in the cases of advanced kidney cancer, advanced lung cancer, and advanced bladder cancer the doctors treated, remission occurred and lasted four, nine, and ten years after a terminal diagnosis.