Review Requested for Recommended Dietary Allowance For Vitamin C

With newly published research reports showing that higher concentrations of vitamin C can be achieved in the blood plasma than previously thought possible, antioxidant researchers have penned their names to a plea for a scientific re-evaluation of the Recommended Dietary Allowance (RDA) for vitamin C.

A dozen prominent antioxidant researchers, authors, and clinicians say the prevalent belief that 200 milligrams of oral vitamin C, an amount that can be obtained by eating five servings of selected fresh fruits and vegetables, can saturate the blood plasma and additional amounts are excreted in the urine, has now been disproved. Two recently published papers indicate that blood plasma levels of ascorbic acid can be raised three times greater than a flawed 1996 study indicates. One of the published studies shows that blood plasma concentrations of vitamin C continue to rise with a single 1000 milligrams dose of supplemental vitamin C.

Drs. Steve Hickey and Hilary Roberts, pharmacology graduates of the University of Manchester in England assert the initial studies used to determine the blood plasma saturation point for vitamin C failed to calculate for the half life of this vitamin. In their newly published book, Drs. Hickey and Roberts show that the original calculations used to establish the RDA were performed 12 hours, or 24 half lives, after oral consumption of vitamin C and are therefore invalid. (Ascorbate: The Science of Vitamin C, 264 pages, referenced, ebook:

In addition to Drs. Hickey and Roberts, the list of researchers calling for a re-evaluation of the RDA for vitamin C includes: Thomas E. Levy MD, JD, author of Vitamin C, Infectious Diseases, and Toxins: Curing the Incurable (Philadelphia, PA: Xlibris Corporation; 2002); Robert F. Cathcart III, MD, a practicing physician and advocate of high oral-dose vitamin C therapy; Richard Passwater PhD, antioxidant researcher and author of Supernutrition; Patrick Holford, London, author of the Optimum Nutrition Bible; Dr Archie Kalokerinos, M.D., Graduate Sydney University, Australia, author of Vitamin C: Nature's Miraculous Healing Missile; Joel M. Kaufman, PhD, Professor of Chemistry Emeritus, University of the Sciences in Philadelphia, special interest in medicinal chemistry; Professor Ian Brighthope, Managing Director, Nutrition Care Pharmaceuticals Pty Ltd, Australia; Hugh D. Riordan, M.D., Director - Bio-Communications Research Institute, Wichita, Kansas; and Abram Hoffer, M.D., PhD., F.R.C.P., a practicing physician, advocate of nutritional medicine and editor of the Journal of Orthomolecular Medicine.

The written plea was sent to the Institutes of Medicine, Food & Nutrition Board, which establishes the Recommended Dietary Allowances for essential nutrients. ]



As health professionals who have been involved in vitamin C research, it has recently come to our attention that higher blood plasma concentrations of vitamin C can be achieved through oral intake than previously thought possible. , This scientific revelation has ramifications upon the current Recommended Dietary Allowance for vitamin C and personal health regimens for consumers. It is apparent the current published advice, that the blood plasma concentration for vitamin C is saturated at 200 milligrams oral consumption, must be revised. Furthermore, it is apparent the RDA for vitamin C needs immediate re-evaluation. We urge the scientific community and other responsible health authorities to take timely action to correct misinformation concerning oral dosing of vitamin C and to join an effort to re-evaluate the RDA for vitamin C.


Steve Hickey Ph.D., Metropolitan University of Manchester, England.
Co-author, Ascorbate, The Science of Vitamin C,, 2004.
ISBN 1-4116-0724-4 Telephone from USA: 011 44 161 962 5495

Hilary Roberts, Ph.D., graduate University of Manchester, England. Co-author, Ascorbate, The Science of Vitamin C,, 2004. ISBN 1-4116-0724-4

Professor Ian Brighthope, Managing Director, Nutrition Care Pharmaceuticals Pty Ltd,
25 - 27 Keysborough Avenue, Keysborough Victoria 3173 Australia,
Phone: +613 9769 0811, Fax: +613 9769 0822

Robert F. Cathcart III, M.D., advocate of high-dose vitamin C therapy; 127 Second Street, Suite 4, Los Altos, California 94022; Telephone: 650-949-2822; FAX: 650-949-5083

Abram Hoffer, M.D., PhD., F.R.C.P. ; Editor-in-chief of the Journal of Orthomolecular Medicine; Suite 3 - 2727 Quadra St ; Victoria, British Columbia V8T 4E5 Canada; Telephone: 250-386-8756; Fax 604-386-5828; email: [email protected]

Patrick Holford, London, founder of the Institute for Optimum Nutrition (ION) and the Brain Bio Centre; author of The Optimum Nutrition Bible, Tel: +44 (0)20 8871 2949 ex 22, Fax: +44 (0)20 8874 5003; Websites:
(USA), (UK), email: [email protected]

Dr Archie Kalokerinos, M.D., Graduate Sydney University. He is a Life Fellow of the Royal Society for Health, a Fellow of the International Academy of Preventive Medicine, Fellow of the Australasian College of Biomedical Scientists, and a Member of the New York Academy of Sciences. He has authored Vitamin C: Nature's Miraculous Healing Missile (1993). Currently he is semi-retired, living in Tamworth, New South Wales. Address: 20 Kennedy Close, Cooranbong, Australia, NSW 2265; Telephone: 61 2 4977 2957; Email: [email protected]

Joel M. Kauffman, PhD, Professor of Chemistry Emeritus, University of the Sciences in Philadelphia, Emeritus Professor of organic chemistry, MIT. Special interest in medicinal chemistry. 65 Meadowbrook Rd. Wayne, PA 19087-2510. Telephone: 215- 596-8839. Email: [email protected]

Thomas Edward Levy, M.D., J.D., Tulane University School of Medicine, 1972-76-M.D.; Fellowship in Cardiology, 1979-81, Tulane Univ. Affiliated Hospitals; author, Vitamin C, Infectious Diseases, and Toxins: Curing the Incurable, Philadelphia, PA: Xlibris Corporation; 2002. Telephone: 800-331-2303, 719-548-1600; Fax 719 572-8081 or email to [email protected]

Dr. Richard A. Passwater, Ph.D., antioxidant researcher, author "Supernutrition," Berlin, Maryland. Email: [email protected] Telephone: 410-641-7411.

Hugh D. Riordan, M.D., President - The Center for the Improvement of
Human Functioning Int'l, Inc., Director - Bio-Communications Research Institute,
3100 North Hillside Avenue, Wichita, KS 67219 U.S.A., Phone: 316-682-3100,
Fax: 316-682-5054, e-mail: [email protected], website:

Andrew W. Saul, PhD, Contributing Editor, Journal of Orthomolecular Medicine, Number 8 Van Buren Street, Holley, New York 14470 USA. Email: [email protected]


Padayatty SJ, Sun H, Wang Y, Riordan HD, Hewitt SM, Katz A, Wesley RA, Levine M., Vitamin C pharmacokinetics: implications for oral and intravenous use, Annals Internal Medicine, April 6, 140: 533-37, 2004.
National Institute of Diabetes and Digestive and Kidney Diseases, the National Cancer Institut, and the Clinical Center, National Institutes of Health, Bethesda, Maryland 20892-1372, USA.

BACKGROUND: Vitamin C at high concentrations is toxic to cancer cells in vitro. Early clinical studies of vitamin C in patients with terminal cancer suggested clinical benefit, but 2 double-blind, placebo-controlled trials showed none. However, these studies used different routes of administration. OBJECTIVE: To determine whether plasma vitamin C concentrations vary substantially with the route of administration. DESIGN: Dose concentration studies and pharmacokinetic modeling. SETTING: Academic medical center. PARTICIPANTS: 17 healthy hospitalized volunteers. MEASUREMENTS: Vitamin C plasma and urine concentrations were measured after administration of oral and intravenous doses at a dose range of 0.015 to 1.25 g, and plasma concentrations were calculated for a dose range of 1 to 100 g. RESULTS: Peak plasma vitamin C concentrations were higher after administration of intravenous doses than after administration of oral doses (P < 0.001), and the difference increased according to dose. Vitamin C at a dose of 1.25 g administered orally produced mean (+/-sd) peak plasma concentrations of 134.8 +/- 20.6 micromol/L compared with 885 +/- 201.2 micromol/L for intravenous administration. For the maximum tolerated oral dose of 3 g every 4 hours, pharmacokinetic modeling predicted peak plasma vitamin C concentrations of 220 micromol/L and 13 400 micromol/L for a 50-g intravenous dose. Peak predicted urine concentrations of vitamin C from intravenous administration were 140-fold higher than those from maximum oral doses. LIMITATIONS: Patient data are not available to confirm pharmacokinetic modeling at high doses and in patients with cancer. CONCLUSIONS: Oral vitamin C produces plasma concentrations that are tightly controlled. Only intravenous administration of vitamin C produces high plasma and urine concentrations that might have antitumor activity. Because efficacy of vitamin C treatment cannot be judged from clinical trials that use only oral dosing, the role of vitamin C in cancer treatment should be reevaluated.

Polidori MC, Mecocci P, Levine M, Frei B., Short-term and long-term vitamin C supplementation in humans dose-dependently increases the resistance of plasma to ex vivo lipid peroxidation, Archives Biochemistry Biophysics, March 423: 109-15, 2004.

Institute of Biochemistry and Molecular Biology I, Heinrich-Heine University, Duesseldorf, Germany.

To assess the effects of short-term and long-term vitamin C supplementation in humans on plasma antioxidant status and resistance to oxidative stress, plasma was obtained from 20 individuals before and 2h after oral administration of 2g of vitamin C, or from eight subjects enrolled in a vitamin C depletion-repletion study using increasing daily doses of vitamin C from 30 to 2500 mg. Plasma concentrations of ascorbate, but not other physiological antioxidants, increased significantly after short-term supplementation, and increased progressively in the long-term study with increasing vitamin C doses of up to 1000 mg/day. Upon incubation of plasma with a free radical initiator, ascorbate concentrations were positively correlated with the lag phase preceding detectable lipid peroxidation. We conclude that vitamin C supplementation in humans dose-dependently increases plasma ascorbate concentrations and, thus, the resistance of plasma to lipid peroxidation ex vivo. Plasma and body saturation with vitamin C in humans appears desirable to maximize antioxidant protection and lower risk of oxidative damage.

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