According to a new study, giving cancer patients high doses of vitamin C during their treatment may weaken cancer cells and make them more vulnerable to the effects of chemotherapy and radiation. 93 percent of the people in the study receiving vitamin C infusions responded to chemotherapy and radiation, compared to 40 percent who usually do. Moreover, more than 30 percent of the people getting the vitamin C also showed signs of their tumors shrinking. Usually, only 15 to 19 percent of people receiving chemo and radiation see their tumors get smaller.