Sustained levels of ascorbic acid are toxic and immunosuppressive for human T cells

Ascorbate (vitamin C) can protect from oxidative damage to DNA and lipids that may lead to aging, cancer, and other dysfunctions. However, we find that purified human T cells deteriorate if maintained in ascorbate in culture for 18 hrs. or more; viability and Il-2 synthesis are over 90% curtailed by ascorbate at 50 micrograms/ml. T cell proliferation and adhesion are severely suppressed at 10-25 micrograms/ml. Dihydro-ascorbate was much less toxic or suppressive. The suppressive effect of ascorbate appears irreversible, since removal of ascorbate after 18 hrs. did not restore the mitogenic response. Although moderate dietary levels of ascorbate often reach 250-1000 mg or more daily and appear beneficial, our data caution against sustained megadoses of ascorbate for treatment of patients with AIDS and cancer.