High dose Vitamin C has been shown to help fatigue, viral illness (influenza), some forms of cancer, and inflammatory conditions (arthritis, fibromyalgia).
The benefits of long-term vitamin C consumption in excess of the U.S. government recommended daily allowance (RDA) are widely acknowledged and include reduced risks of cancer, cardiovascular disease, and cataracts. Higher than RDA vitamin C intakes have been associated with increases in HDL cholesterol, decreases in LDL cholesterol oxidation, decreased blood pressure, and decreased cardiovascular mortality. Vitamin C enhances non-heme iron absorption in individuals with low iron status. Helpfulness has been reported for severe attacks of ulcerative colitis, advanced human cancer, and reticulum cell sarcoma. Doses in these reports ranged from 50 to 150 gm intravenous per day, with no adverse effects reported.