Skip Navigation

Search Knowledgebase

High-Dose Vitamin C (PDQ®): Complementary and alternative medicine - Health Professional Information [NCI]

This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http://cancer.gov or call 1-800-4-CANCER.

High-Dose Vitamin C

Overview

This complementary and alternative medicine (CAM) information summary provides an overview of the use of high-dose vitamin C (also known as ascorbate or L-ascorbic acid) as a treatment for people with cancer. This summary includes a brief history of early clinical trials of high-dose vitamin C; reviews of laboratory, animal, and human studies; and current clinical trials.

This summary contains the following key information:

  • Vitamin C is an essential nutrient with antioxidant functions at normal physiologic concentrations.
  • High-dose vitamin C has been studied as a treatment for cancer patients since the 1970s.
  • Laboratory studies have reported that high-dose vitamin C has pro-oxidant properties and decreased cell proliferation in prostate, pancreatic, hepatocellular, colon, mesothelioma, and neuroblastoma cell lines.
  • Two studies of high-dose vitamin C in cancer patients reported improved quality of life and decreases in cancer-related side effects.
  • Studies of vitamin C combined with other drugs in cancer patients have shown mixed results.
  • Intravenous vitamin C has been generally well tolerated in clinical trials.

Many of the medical and scientific terms used in this summary are hypertext linked (at first use in each section) to the NCI Dictionary of Cancer Terms, which is oriented toward nonexperts. When a linked term is clicked, a definition will appear in a separate window.

Reference citations in some PDQ CAM information summaries may include links to external Web sites that are operated by individuals or organizations for the purpose of marketing or advocating the use of specific treatments or products. These reference citations are included for informational purposes only. Their inclusion should not be viewed as an endorsement of the content of the Web sites, or of any treatment or product, by the PDQ Cancer CAM Editorial Board or the National Cancer Institute.

General Information

Vitamin C is an essential nutrient that has antioxidant functions, is a cofactor for several enzymes, and plays an important role in the synthesis of collagen.[1] A severe deficiency in vitamin C results in scurvy, which is associated with malaise, lethargy, easy bruising, and spontaneous bleeding.[2] One of the effects of scurvy is a change in collagen structure to a thinner consistency. Normal consistency is achieved with administration of vitamin C.

In the mid-20th century, a study hypothesized that cancer may be related to changes in connective tissue, which may be a consequence of vitamin C deficiency.[3] A review of evidence published in 1974 suggested that high-dose ascorbic acid may increase host resistance and be a potential cancer therapy.[4]

Vitamin C is synthesized from D-glucose or D-galactose by many plants and animals. However, humans lack the enzyme L-gulonolactone oxidase required for ascorbic acid synthesis and must obtain vitamin C through food or supplements.[1]

References:

1. Naidu KA: Vitamin C in human health and disease is still a mystery? An overview. Nutr J 2: 7, 2003.
2. Padayatty S, Espey MG, Levine M: Vitamin C. In: Coates PM, Betz JM, Blackman MR, et al., eds.: Encyclopedia of Dietary Supplements. 2nd ed. New York, NY: Informa Healthcare, 2010, pp 821-31.
3. McCORMICK WJ: Cancer: a collagen disease, secondary to a nutritional deficiency. Arch Pediatr 76 (4): 166-71, 1959.
4. Cameron E, Pauling L: The orthomolecular treatment of cancer. I. The role of ascorbic acid in host resistance. Chem Biol Interact 9 (4): 273-83, 1974.

History

The earliest experience of using high-dose vitamin C (intravenous [IV] and oral) for cancer treatment was by a Scottish surgeon, Ewan Cameron, and his colleague, Allan Campbell, in the 1970s.[1] This work led to a collaboration between Cameron and the Nobel Prize–winning chemist Linus Pauling, further promoting the potential of vitamin C therapy in cancer management.[2,3] As a result, two clinical trials on oral vitamin C were conducted in the late 1970s and early 1980s.[4,5]

(Refer to the Human Studies section of this summary for more information about these early studies.)

Pharmacokinetic studies later revealed substantial differences in the maximum achieved blood concentrations of vitamin C based on the route of administration. When vitamin C is taken orally, plasma concentrations of the vitamin are tightly controlled, with a peak achievable concentration less than 300 µM. However, this tight control is bypassed with IV administration of the vitamin, resulting in very high levels of vitamin C plasma concentration (i.e., levels up to 20 mM).[6,7] Further research suggests that pharmacologic concentrations of ascorbate, such as those achieved with IV administration, may result in cell death in many cancer cell lines.[8]

Health care practitioners attending complementary and alternative medicine conferences in 2006 and 2008 were surveyed about usage of high-dose IV vitamin C in patients. Of the 199 total respondents, 172 had administered vitamin C to patients. In general, IV vitamin C was commonly used to treat infections, cancer, and fatigue.[9]

References:

1. Cameron E, Campbell A: The orthomolecular treatment of cancer. II. Clinical trial of high-dose ascorbic acid supplements in advanced human cancer. Chem Biol Interact 9 (4): 285-315, 1974.
2. Cameron E, Pauling L: Supplemental ascorbate in the supportive treatment of cancer: Prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A 73 (10): 3685-9, 1976.
3. Cameron E, Pauling L: Supplemental ascorbate in the supportive treatment of cancer: reevaluation of prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A 75 (9): 4538-42, 1978.
4. Creagan ET, Moertel CG, O'Fallon JR, et al.: Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer. A controlled trial. N Engl J Med 301 (13): 687-90, 1979.
5. Moertel CG, Fleming TR, Creagan ET, et al.: High-dose vitamin C versus placebo in the treatment of patients with advanced cancer who have had no prior chemotherapy. A randomized double-blind comparison. N Engl J Med 312 (3): 137-41, 1985.
6. Padayatty SJ, Sun H, Wang Y, et al.: Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med 140 (7): 533-7, 2004.
7. Hoffer LJ, Levine M, Assouline S, et al.: Phase I clinical trial of i.v. ascorbic acid in advanced malignancy. Ann Oncol 19 (11): 1969-74, 2008.
8. Verrax J, Calderon PB: Pharmacologic concentrations of ascorbate are achieved by parenteral administration and exhibit antitumoral effects. Free Radic Biol Med 47 (1): 32-40, 2009.
9. Padayatty SJ, Sun AY, Chen Q, et al.: Vitamin C: intravenous use by complementary and alternative medicine practitioners and adverse effects. PLoS One 5 (7): e11414, 2010.

Laboratory / Animal / Preclinical Studies

In Vitro Studies

Numerous studies have demonstrated that pharmacological doses of ascorbic acid (0.1–100 mM) decrease cell proliferation in a variety of cancer cell lines.[1,2,3,4,5] Specifically, decreases in cell proliferation after ascorbic acid treatment have been reported for prostate,[6]pancreatic,[7,8]hepatocellular,[9]colon,[10]mesothelioma,[11] and neuroblastoma [12] cell lines.

The potential mechanisms through which treatment with high-dose ascorbic acid may exert its effects on cancer cells have been extensively investigated. Several studies have demonstrated that the in vitro direct cytotoxic effect of ascorbic acid on various types of cancer cells is mediated through a chemical reaction that generates hydrogen peroxide.[1,7] Reviewed in [13,14] Treating colon cancer cells with 2 mM to 3 mM of ascorbic acid resulted in downregulation of specificity protein (Sp) transcription factors and Sp-regulated genes involved in cancer progression.[10] One study suggested that ascorbate-mediated prostate cancer cell death may occur through activation of an autophagy pathway.[6]

Differences in chemosensitivity to ascorbate treatment in breast cancer cell lines may depend on expression of the sodium -dependent vitamin C transporter 2 (SVCT-2).[15]

Research has suggested that pharmacological doses of ascorbic acid enhance the effects of arsenic trioxide on ovarian cancer cells,[16] gemcitabine on pancreatic cancer cells,[8] and combination treatment of gemcitabine and epigallocatechin-3-gallate (EGCG) on mesothelioma cells.[17]

Findings from one study reported in 2012 suggested that high-dose ascorbate increases radiosensitivity of glioblastoma multiforme cells, resulting in more cell death than from radiation alone.[18]

However, not all studies combining vitamin C with chemotherapy have shown improved outcomes. Treating leukemia and lymphoma cells with dehydroascorbic acid (the oxidized form of vitamin C that increases levels of intracellular ascorbic acid) reduced the cytotoxic effects of various antineoplastic agents tested, including doxorubicin, methotrexate, and cisplatin (relative reductions in cytotoxicity ranged from 30% to 70%).[19] In another study, multiple myeloma cells were treated with bortezomib and/or plasma obtained from healthy volunteers who had taken vitamin C supplements. Cells treated with a combination of bortezomib and volunteers' plasma exhibited lower cytotoxicity than did cells treated with bortezomib alone.[20]

Animal Studies

Studies have demonstrated tumor growth inhibition after treatment with pharmacological ascorbate in animal models of pancreatic cancer,[1,7,8]liver cancer,[3] prostate cancer,[21]sarcoma,[22] mesothelioma,[11] and ovarian cancer.[4]

The effects of high-dose ascorbic acid in combination with standard treatments on tumors have been investigated. In a mouse model of pancreatic cancer, the combination of gemcitabine (30 or 60 mg /kg every 4 days) and ascorbate (4 g /kg daily) resulted in greater decreases in tumor volume and weight, compared with gemcitabine treatment alone.[8] According to a study reported in 2012, ascorbate enhanced the cancer cell–killing effects of photodynamic therapy in mice injected with breast cancer cells.[23]

Using N-acetylcysteine (NAC) and vitamin C, researchers showed in 2007 that these compounds, both thought to act predominantly as antioxidants, may have antitumorigenic actions in vivo by decreasing levels of hypoxia -inducible factor (HIF)-1, a transcription factor that targets vascular endothelial growth factor (VEGF) and plays a role in angiogenesis.[24]

There have also been reports of animal studies in which vitamin C has interfered with the anticancer activity of various drugs. In a study reported in 2008, administration of dehydroascorbic acid to lymphoma-xenograft mice prior to doxorubicin treatment resulted in significantly larger tumors than did treatment with doxorubicin alone.[19] Treating multiple myeloma xenograft mice with a combination of oral vitamin C and bortezomib resulted in significantly greater tumor volume than did treatment with bortezomib alone.[20]

References:

1. Chen P, Stone J, Sullivan G, et al.: Anti-cancer effect of pharmacologic ascorbate and its interaction with supplementary parenteral glutathione in preclinical cancer models. Free Radic Biol Med 51 (3): 681-7, 2011.
2. Chen Q, Espey MG, Krishna MC, et al.: Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues. Proc Natl Acad Sci U S A 102 (38): 13604-9, 2005.
3. Verrax J, Calderon PB: Pharmacologic concentrations of ascorbate are achieved by parenteral administration and exhibit antitumoral effects. Free Radic Biol Med 47 (1): 32-40, 2009.
4. Chen Q, Espey MG, Sun AY, et al.: Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice. Proc Natl Acad Sci U S A 105 (32): 11105-9, 2008.
5. Frömberg A, Gutsch D, Schulze D, et al.: Ascorbate exerts anti-proliferative effects through cell cycle inhibition and sensitizes tumor cells towards cytostatic drugs. Cancer Chemother Pharmacol 67 (5): 1157-66, 2011.
6. Chen P, Yu J, Chalmers B, et al.: Pharmacological ascorbate induces cytotoxicity in prostate cancer cells through ATP depletion and induction of autophagy. Anticancer Drugs 23 (4): 437-44, 2012.
7. Du J, Martin SM, Levine M, et al.: Mechanisms of ascorbate-induced cytotoxicity in pancreatic cancer. Clin Cancer Res 16 (2): 509-20, 2010.
8. Espey MG, Chen P, Chalmers B, et al.: Pharmacologic ascorbate synergizes with gemcitabine in preclinical models of pancreatic cancer. Free Radic Biol Med 50 (11): 1610-9, 2011.
9. Lin ZY, Chuang WL: Pharmacologic concentrations of ascorbic acid cause diverse influence on differential expressions of angiogenic chemokine genes in different hepatocellular carcinoma cell lines. Biomed Pharmacother 64 (5): 348-51, 2010.
10. Pathi SS, Lei P, Sreevalsan S, et al.: Pharmacologic doses of ascorbic acid repress specificity protein (Sp) transcription factors and Sp-regulated genes in colon cancer cells. Nutr Cancer 63 (7): 1133-42, 2011.
11. Takemura Y, Satoh M, Satoh K, et al.: High dose of ascorbic acid induces cell death in mesothelioma cells. Biochem Biophys Res Commun 394 (2): 249-53, 2010.
12. Hardaway CM, Badisa RB, Soliman KF: Effect of ascorbic acid and hydrogen peroxide on mouse neuroblastoma cells. Mol Med Report 5 (6): 1449-52, 2012.
13. Du J, Cullen JJ, Buettner GR: Ascorbic acid: chemistry, biology and the treatment of cancer. Biochim Biophys Acta 1826 (2): 443-57, 2012.
14. Levine M, Padayatty SJ, Espey MG: Vitamin C: a concentration-function approach yields pharmacology and therapeutic discoveries. Adv Nutr 2 (2): 78-88, 2011.
15. Hong SW, Lee SH, Moon JH, et al.: SVCT-2 in breast cancer acts as an indicator for L-ascorbate treatment. Oncogene 32 (12): 1508-17, 2013.
16. Ong PS, Chan SY, Ho PC: Differential augmentative effects of buthionine sulfoximine and ascorbic acid in As2O3-induced ovarian cancer cell death: oxidative stress-independent and -dependent cytotoxic potentiation. Int J Oncol 38 (6): 1731-9, 2011.
17. Martinotti S, Ranzato E, Burlando B: In vitro screening of synergistic ascorbate-drug combinations for the treatment of malignant mesothelioma. Toxicol In Vitro 25 (8): 1568-74, 2011.
18. Herst PM, Broadley KW, Harper JL, et al.: Pharmacological concentrations of ascorbate radiosensitize glioblastoma multiforme primary cells by increasing oxidative DNA damage and inhibiting G2/M arrest. Free Radic Biol Med 52 (8): 1486-93, 2012.
19. Heaney ML, Gardner JR, Karasavvas N, et al.: Vitamin C antagonizes the cytotoxic effects of antineoplastic drugs. Cancer Res 68 (19): 8031-8, 2008.
20. Perrone G, Hideshima T, Ikeda H, et al.: Ascorbic acid inhibits antitumor activity of bortezomib in vivo. Leukemia 23 (9): 1679-86, 2009.
21. Pollard HB, Levine MA, Eidelman O, et al.: Pharmacological ascorbic acid suppresses syngeneic tumor growth and metastases in hormone-refractory prostate cancer. In Vivo 24 (3): 249-55, 2010 May-Jun.
22. Yeom CH, Lee G, Park JH, et al.: High dose concentration administration of ascorbic acid inhibits tumor growth in BALB/C mice implanted with sarcoma 180 cancer cells via the restriction of angiogenesis. J Transl Med 7: 70, 2009.
23. Wei Y, Song J, Chen Q, et al.: Enhancement of photodynamic antitumor effect with pro-oxidant ascorbate. Lasers Surg Med 44 (1): 69-75, 2012.
24. Gao P, Zhang H, Dinavahi R, et al.: HIF-dependent antitumorigenic effect of antioxidants in vivo. Cancer Cell 12 (3): 230-8, 2007.

Human / Clinical Studies

Early Ascorbate-Only Trials

In the early 1970s, a consecutive case series was conducted in which 50 advanced cancer patients were treated with large doses of ascorbic acid.[1] These patients began ascorbic acid treatment after conventional therapies were deemed unlikely to be effective. Patients received intravenous (IV) ascorbic acid (10 g /day for 10 consecutive days; some patients received higher doses), oral ascorbic acid (10 g/day), or both. The subjects exhibited a wide variety of responses to treatment, including no or minimal response, tumor regression, and tumor hemorrhage. However, the authors noted that lack of controls prevented definitive assignment of any beneficial responses to the ascorbic acid treatment. A case report published in 1975 detailed one of the patients who had experienced tumor regression.[2] Diagnosed with reticulum cell sarcoma, the patient exhibited improvement in well-being and resolution of lung masses after being treated with ascorbic acid. When the patient's daily dose of ascorbic acid was reduced, some of signs of the disease returned; however, remission was achieved again after the patient reverted to the higher initial dose.

A larger case series of terminal cancer patients treated with ascorbate was reported in 1976. In this study, 100 terminal cancer patients (50 of whom were reported on previously) [1] were treated with ascorbate (10 g/day for 10 days IV, then orally) and compared with 1,000 matched controls from the same hospital. The mean survival time for ascorbate-treated patients was 300 days longer than that of the matched controls.[3,4]

Two studies tried to reproduce earlier results. These studies were randomized, placebo-controlled trials in which cancer patients received either 10 g oral vitamin C or placebo daily until signs of cancer progression. At the end of each study, no significant differences were noted between the two ascorbate-treated and placebo-treated groups for symptoms, performance status, or survival.[5,6]

Recent Ascorbate-Only Trials

One study reported three case reports of cancer patients who received IV vitamin C as their main therapy. During vitamin C therapy, the patients used additional treatments, including vitamins, minerals, and botanicals. According to the authors, the cases were reviewed in accordance with the NCI Best Case Series guidelines. Histopathologic examination suggested poor prognoses for these patients, but they had long survival times after being treated with IV vitamin C.[7] Vitamin C was given at doses ranging from 15 g to 65 g, initially once or twice a week for several months; two patients then received it less frequently for 1 to 4 years.

Two studies demonstrated that IV vitamin C treatment resulted in improved quality of life and decreases in cancer-related side effects in cancer patients.[8,9]

Studies have shown that vitamin C can be safely administered to healthy volunteers or cancer patients at doses up to 1.5 g/kg and with screening to eliminate treating individuals with risk factors for toxicity (e.g., glucose -6-phosphate dehydrogenase deficiency, renal diseases, or urolithiasis). These studies have also found that plasma concentrations of vitamin C are higher with IV administration than with oral administration and are maintained for more than 4 hours.[10,11]

Ascorbate-Combination Trials

A phase I study published in 2012 examined the safety and efficacy of combining IV ascorbate with gemcitabine and erlotinib in stage IV pancreatic cancer patients. Fourteen subjects entered the study and planned to receive IV gemcitabine (1,000 mg /m2 over 30 minutes, once a week for 7 weeks), oral erlotinib (100 mg daily for 8 weeks), and IV ascorbate (50 g/infusion, 75 g/infusion, or 100 g/infusion 3 times per week for 8 weeks). Minimal adverse effects were reported for ascorbic acid treatment. Five subjects received fewer than 18 of the planned 24 ascorbate infusions and thus did not have follow-up imaging to assess response. Three of those patients had clinically determined progressive disease. All of the other nine patients had repeat imaging to assess tumor size, and each met the criteria for having stable disease.[12]

A number of studies have included IV ascorbic acid treatment (1,000 mg) with arsenic trioxide regimens, with mixed results. The combination therapies were well tolerated and suggested beneficial effects in multiple myeloma patients, although the specific contribution of vitamin C could not be determined.[13,14,15,16] However, similar combination regimens resulted in severe side effects and disease progression in patients with acute myeloid leukemia,[17]refractory metastatic colorectal cancer,[18] and metastatic melanoma.[19]

Current Clinical Trials

Check NCI's list of cancer clinical trials for cancer CAM clinical trials on ascorbic acid that are actively enrolling patients.

General information about clinical trials is also available from the NCI Web site.

References:

1. Cameron E, Campbell A: The orthomolecular treatment of cancer. II. Clinical trial of high-dose ascorbic acid supplements in advanced human cancer. Chem Biol Interact 9 (4): 285-315, 1974.
2. Cameron E, Campbell A, Jack T: The orthomolecular treatment of cancer. III. Reticulum cell sarcoma: double complete regression induced by high-dose ascorbic acid therapy. Chem Biol Interact 11 (5): 387-93, 1975.
3. Cameron E, Pauling L: Supplemental ascorbate in the supportive treatment of cancer: Prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A 73 (10): 3685-9, 1976.
4. Cameron E, Pauling L: Supplemental ascorbate in the supportive treatment of cancer: reevaluation of prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A 75 (9): 4538-42, 1978.
5. Creagan ET, Moertel CG, O'Fallon JR, et al.: Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer. A controlled trial. N Engl J Med 301 (13): 687-90, 1979.
6. Moertel CG, Fleming TR, Creagan ET, et al.: High-dose vitamin C versus placebo in the treatment of patients with advanced cancer who have had no prior chemotherapy. A randomized double-blind comparison. N Engl J Med 312 (3): 137-41, 1985.
7. Padayatty SJ, Riordan HD, Hewitt SM, et al.: Intravenously administered vitamin C as cancer therapy: three cases. CMAJ 174 (7): 937-42, 2006.
8. Vollbracht C, Schneider B, Leendert V, et al.: Intravenous vitamin C administration improves quality of life in breast cancer patients during chemo-/radiotherapy and aftercare: results of a retrospective, multicentre, epidemiological cohort study in Germany. In Vivo 25 (6): 983-90, 2011 Nov-Dec.
9. Yeom CH, Jung GC, Song KJ: Changes of terminal cancer patients' health-related quality of life after high dose vitamin C administration. J Korean Med Sci 22 (1): 7-11, 2007.
10. Padayatty SJ, Sun H, Wang Y, et al.: Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med 140 (7): 533-7, 2004.
11. Hoffer LJ, Levine M, Assouline S, et al.: Phase I clinical trial of i.v. ascorbic acid in advanced malignancy. Ann Oncol 19 (11): 1969-74, 2008.
12. Monti DA, Mitchell E, Bazzan AJ, et al.: Phase I evaluation of intravenous ascorbic acid in combination with gemcitabine and erlotinib in patients with metastatic pancreatic cancer. PLoS One 7 (1): e29794, 2012.
13. Abou-Jawde RM, Reed J, Kelly M, et al.: Efficacy and safety results with the combination therapy of arsenic trioxide, dexamethasone, and ascorbic acid in multiple myeloma patients: a phase 2 trial. Med Oncol 23 (2): 263-72, 2006.
14. Berenson JR, Matous J, Swift RA, et al.: A phase I/II study of arsenic trioxide/bortezomib/ascorbic acid combination therapy for the treatment of relapsed or refractory multiple myeloma. Clin Cancer Res 13 (6): 1762-8, 2007.
15. Qazilbash MH, Saliba RM, Nieto Y, et al.: Arsenic trioxide with ascorbic acid and high-dose melphalan: results of a phase II randomized trial. Biol Blood Marrow Transplant 14 (12): 1401-7, 2008.
16. Berenson JR, Boccia R, Siegel D, et al.: Efficacy and safety of melphalan, arsenic trioxide and ascorbic acid combination therapy in patients with relapsed or refractory multiple myeloma: a prospective, multicentre, phase II, single-arm study. Br J Haematol 135 (2): 174-83, 2006.
17. Welch JS, Klco JM, Gao F, et al.: Combination decitabine, arsenic trioxide, and ascorbic acid for the treatment of myelodysplastic syndrome and acute myeloid leukemia: a phase I study. Am J Hematol 86 (9): 796-800, 2011.
18. Subbarayan PR, Lima M, Ardalan B: Arsenic trioxide/ascorbic acid therapy in patients with refractory metastatic colorectal carcinoma: a clinical experience. Acta Oncol 46 (4): 557-61, 2007.
19. Bael TE, Peterson BL, Gollob JA: Phase II trial of arsenic trioxide and ascorbic acid with temozolomide in patients with metastatic melanoma with or without central nervous system metastases. Melanoma Res 18 (2): 147-51, 2008.

Adverse Events

Intravenous high-dose ascorbic acid has been generally well tolerated in clinical trials.[1,2,3,4,5,6,7]Renal failure following ascorbic acid treatment has been reported in patients with preexisting renal disorders.[8]

Case reports have indicated that patients with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency should not receive high doses of vitamin C because of the risk of developing hemolysis.[9,10,11]

Vitamin C may increase bioavailability of iron, and high doses of the vitamin are not recommended for patients with hemochromatosis.[12]

Drug Interactions

When administered in high doses, vitamin C may result in adverse interactions with some anticancer agents. These interactions have primarily been detected in preclinical studies. A 2013 phase I clinical study evaluated the safety of combining pharmacological ascorbate with gemcitabine in stage IV pancreatic cancer patients. The combination therapy was well tolerated by patients, and no significant adverse events were reported.[13]

In vitro and in vivo animal studies have suggested that combining vitamin C with bortezomib interferes with the drug's ability to act as a proteasome inhibitor and blocks bortezomib-initiated apoptosis.[14,15,16] This interference occurred even with the oral administration of vitamin C (40 mg /kg /day) to animals. Studies in cell culture and performed by adding blood plasma from healthy volunteers given oral vitamin C (1 g /day) also showed a significant decrease in bortezomib's growth inhibitory effect on multiple myeloma cells. Another study found similar results. When given at orally achievable concentrations (equivalent to 1 g/day, a dose frequently used by patients), vitamin C was shown to decrease the efficacy of bortezomib on multiple myeloma cells and blocked its inhibitory effect on 20S proteasome activity.[16] However, a study that utilized mice harboring human prostate cancer cell xenografts failed to find any significant effect of oral vitamin C (40 mg/kg/day or 500 mg/kg/day) on the tumor growth inhibitory action of bortezomib.[17]

Several studies have been performed to assess the potential synergistic or inhibitory action of vitamin C on certain chemotherapy drugs, with variable results. A series of studies in cell culture and in animals bearing tumors has shown that when given at high concentrations or dosages, dehydroascorbic acid (an oxidized form of vitamin C) can interfere with the cytotoxic effects of several chemotherapy drugs.[18] However, dehydroascorbic acid is generally present only at low concentrations in dietary supplements and fresh foods.

References:

1. Padayatty SJ, Sun H, Wang Y, et al.: Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med 140 (7): 533-7, 2004.
2. Hoffer LJ, Levine M, Assouline S, et al.: Phase I clinical trial of i.v. ascorbic acid in advanced malignancy. Ann Oncol 19 (11): 1969-74, 2008.
3. Chen Q, Espey MG, Sun AY, et al.: Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice. Proc Natl Acad Sci U S A 105 (32): 11105-9, 2008.
4. Monti DA, Mitchell E, Bazzan AJ, et al.: Phase I evaluation of intravenous ascorbic acid in combination with gemcitabine and erlotinib in patients with metastatic pancreatic cancer. PLoS One 7 (1): e29794, 2012.
5. Abou-Jawde RM, Reed J, Kelly M, et al.: Efficacy and safety results with the combination therapy of arsenic trioxide, dexamethasone, and ascorbic acid in multiple myeloma patients: a phase 2 trial. Med Oncol 23 (2): 263-72, 2006.
6. Berenson JR, Matous J, Swift RA, et al.: A phase I/II study of arsenic trioxide/bortezomib/ascorbic acid combination therapy for the treatment of relapsed or refractory multiple myeloma. Clin Cancer Res 13 (6): 1762-8, 2007.
7. Qazilbash MH, Saliba RM, Nieto Y, et al.: Arsenic trioxide with ascorbic acid and high-dose melphalan: results of a phase II randomized trial. Biol Blood Marrow Transplant 14 (12): 1401-7, 2008.
8. Padayatty SJ, Sun AY, Chen Q, et al.: Vitamin C: intravenous use by complementary and alternative medicine practitioners and adverse effects. PLoS One 5 (7): e11414, 2010.
9. Campbell GD Jr, Steinberg MH, Bower JD: Letter: Ascorbic acid-induced hemolysis in G-6-PD deficiency. Ann Intern Med 82 (6): 810, 1975.
10. Mehta JB, Singhal SB, Mehta BC: Ascorbic-acid-induced haemolysis in G-6-PD deficiency. Lancet 336 (8720): 944, 1990.
11. Rees DC, Kelsey H, Richards JD: Acute haemolysis induced by high dose ascorbic acid in glucose-6-phosphate dehydrogenase deficiency. BMJ 306 (6881): 841-2, 1993.
12. Barton JC, McDonnell SM, Adams PC, et al.: Management of hemochromatosis. Hemochromatosis Management Working Group. Ann Intern Med 129 (11): 932-9, 1998.
13. Welsh JL, Wagner BA, van't Erve TJ, et al.: Pharmacological ascorbate with gemcitabine for the control of metastatic and node-positive pancreatic cancer (PACMAN): results from a phase I clinical trial. Cancer Chemother Pharmacol 71 (3): 765-75, 2013.
14. Zou W, Yue P, Lin N, et al.: Vitamin C inactivates the proteasome inhibitor PS-341 in human cancer cells. Clin Cancer Res 12 (1): 273-80, 2006.
15. Llobet D, Eritja N, Encinas M, et al.: Antioxidants block proteasome inhibitor function in endometrial carcinoma cells. Anticancer Drugs 19 (2): 115-24, 2008.
16. Perrone G, Hideshima T, Ikeda H, et al.: Ascorbic acid inhibits antitumor activity of bortezomib in vivo. Leukemia 23 (9): 1679-86, 2009.
17. Bannerman B, Xu L, Jones M, et al.: Preclinical evaluation of the antitumor activity of bortezomib in combination with vitamin C or with epigallocatechin gallate, a component of green tea. Cancer Chemother Pharmacol 68 (5): 1145-54, 2011.
18. Heaney ML, Gardner JR, Karasavvas N, et al.: Vitamin C antagonizes the cytotoxic effects of antineoplastic drugs. Cancer Res 68 (19): 8031-8, 2008.

Changes to This Summary (03 / 21 / 2013)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Adverse Events

Added text about a 2013 phase I clinical study that evaluated the safety of combining pharmacological ascorbate with gemcitabine in stage IV pancreatic cancer patients; the combination therapy was well tolerated by patients, and no significant adverse events were reported (cited Welsh et al. as reference 13).

Added text about a study that found that vitamin C given at orally achievable concentrations decreased the efficacy of bortezomib on multiple myeloma cells and blocked its inhibitory effect on 20S proteasome activity.

This summary is written and maintained by the PDQ Cancer Complementary and Alternative Medicine Editorial Board, which is editorially independent of NCI. The summary reflects an independent review of the literature and does not represent a policy statement of NCI or NIH. More information about summary policies and the role of the PDQ Editorial Boards in maintaining the PDQ summaries can be found on the About This PDQ Summary and PDQ NCI's Comprehensive Cancer Database pages.

About This PDQ Summary

Purpose of This Summary

This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the use of high-dose vitamin C in the treatment of people with cancer. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.

Reviewers and Updates

This summary is reviewed regularly and updated as necessary by the PDQ Cancer Complementary and Alternative Medicine Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).

Board members review recently published articles each month to determine whether an article should:

  • be discussed at a meeting,
  • be cited with text, or
  • replace or update an existing article that is already cited.

Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.

The lead reviewer for High-Dose Vitamin C is:

  • Jeffrey D. White, MD (National Cancer Institute)

Any comments or questions about the summary content should be submitted to Cancer.gov through the Web site's Contact Form. Do not contact the individual Board Members with questions or comments about the summaries. Board members will not respond to individual inquiries.

Levels of Evidence

Some of the reference citations in this summary are accompanied by a level-of-evidence designation. These designations are intended to help readers assess the strength of the evidence supporting the use of specific interventions or approaches. The PDQ Cancer Complementary and Alternative Medicine Editorial Board uses a formal evidence ranking system in developing its level-of-evidence designations.

Permission to Use This Summary

PDQ is a registered trademark. Although the content of PDQ documents can be used freely as text, it cannot be identified as an NCI PDQ cancer information summary unless it is presented in its entirety and is regularly updated. However, an author would be permitted to write a sentence such as "NCI's PDQ cancer information summary about breast cancer prevention states the risks succinctly: [include excerpt from the summary]."

The preferred citation for this PDQ summary is:

National Cancer Institute: PDQ® High-Dose Vitamin C. Bethesda, MD: National Cancer Institute. Date last modified <MM/DD/YYYY>. Available at: http://www.cancer.gov/cancertopics/pdq/cam/highdosevitaminc/healthprofessional. Accessed <MM/DD/YYYY>.

Images in this summary are used with permission of the author(s), artist, and/or publisher for use within the PDQ summaries only. Permission to use images outside the context of PDQ information must be obtained from the owner(s) and cannot be granted by the National Cancer Institute. Information about using the illustrations in this summary, along with many other cancer-related images, is available in Visuals Online, a collection of over 2,000 scientific images.

Disclaimer

The information in these summaries should not be used as a basis for insurance reimbursement determinations. More information on insurance coverage is available on Cancer.gov on the Coping with Cancer: Financial, Insurance, and Legal Information page.

Contact Us

More information about contacting us or receiving help with the Cancer.gov Web site can be found on our Contact Us for Help page. Questions can also be submitted to Cancer.gov through the Web site's Contact Form.

Last Revised: 2013-03-21

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.

Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.