By: Yoon Hang Kim, MD, MPH

Board Certified in Preventive Medicine | 

 Osher Fellow Graduate University of Arizona Integrative Medicine Fellowship| 

Institute of Functional Medicine Scholarship Recipient

www.yoonhangkim.com

www.directintegrativecare.com

Introduction: A Controversial Therapy Whose Time May Have Come

Few therapies in oncology have endured a more turbulent scientific journey than high-dose intravenous vitamin C (IVC). From its passionate championing by two-time Nobel laureate Linus Pauling in the 1970s, through its apparent debunking by the Mayo Clinic in the 1980s, to its remarkable scientific rehabilitation by National Institutes of Health (NIH) pharmacokinetics researchers in the early 2000s, the story of ascorbate in cancer care is one of missed opportunities, methodological misunderstandings, and ultimately, of meticulous science catching up to clinical intuition.

Today, in 2026, the landscape has shifted dramatically. A landmark randomized phase II trial from the University of Iowa, published in Redox Biology in November 2024, demonstrated that adding high-dose IVC to standard chemotherapy doubled overall survival in patients with metastatic pancreatic cancer—from a median of eight months to sixteen months. The trial was stopped early because of the magnitude of benefit. Major cancer centers including MD Anderson Cancer Center and Memorial Sloan Kettering Cancer Center now acknowledge IVC as a generally well-tolerated investigational adjunctive therapy. The National Cancer Institute’s Physician Data Query (PDQ) classifies IV vitamin C as a complementary and investigational modality warranting further study.

This article provides a comprehensive, evidence-based review of IVC in oncology. It is written from the perspective of an integrative physician who believes that cancer care demands an “all hands on deck” approach—one that combines the best of conventional oncology with rigorously evaluated complementary therapies. The purpose is not to advocate for IVC as a standalone cancer cure, but rather to place the current evidence in its proper context so that clinicians and patients can make informed decisions.

Historical Context: From Pauling to the Riordan Clinic

The Cameron–Pauling Era (1971–1978)

The modern story of vitamin C and cancer begins with Scottish surgeon Ewan Cameron, who hypothesized in the early 1970s that ascorbate could inhibit tumor invasion by strengthening the extracellular matrix through collagen synthesis and inhibiting hyaluronidase. Cameron began treating terminally ill cancer patients at Vale of Leven Hospital in Scotland with intravenous ascorbate, starting at 10 grams per day. He contacted Linus Pauling, who was already advocating megadose vitamin C for various conditions. Together, they published their seminal 1976 paper in the Proceedings of the National Academy of Sciences reporting that 100 terminal cancer patients treated with intravenous vitamin C followed by oral maintenance survived approximately four times longer than 1,000 matched historical controls.

The Cameron–Pauling studies were groundbreaking in concept but fundamentally flawed in design. There was no randomization, no blinding, and the control patients were retrospectively selected. The patient groups were not well matched for disease stage, performance status, or timing of the “terminal” designation. As critics later pointed out, the vitamin C–treated patients may have been designated terminal at an earlier stage of their disease, creating an artificial survival advantage. Nevertheless, the core observation—that something interesting was happening with intravenous, not merely oral, ascorbate—would prove prophetic.

The Mayo Clinic Trials and the “Death” of Vitamin C Therapy (1979–1985)

Charles Moertel and colleagues at the Mayo Clinic conducted two prospective, double-blind, placebo-controlled trials that appeared to settle the question definitively. Published in the New England Journal of Medicine in 1979 and 1985 respectively, both trials used 10 grams per day of vitamin C administered orally and found no survival benefit. The medical community concluded that Pauling had been wrong, and the idea was largely abandoned for two decades.

However, there were crucial differences between the Cameron–Pauling and Mayo Clinic protocols that were not fully appreciated at the time. First, Cameron and Pauling had administered vitamin C both intravenously and orally, whereas the Mayo Clinic studies used only the oral route. Second, the Mayo Clinic trials discontinued vitamin C when disease progressed, whereas Cameron and Pauling continued treatment throughout the patient’s life. Third—and most critically—the pharmacokinetic implications of these different routes of administration were unknown in the 1980s.

The Riordan Clinic: Pioneering IVC Research in Wichita, Kansas

While the mainstream medical community moved on, a small group of researchers refused to abandon the vitamin C hypothesis. Among the most consequential was Dr. Hugh Riordan, a psychiatrist with a deep commitment to root-cause medicine who founded the Riordan Clinic (originally the Center for the Improvement of Human Functioning) in Wichita, Kansas, in 1975. With the support of philanthropist Olive W. Garvey, Riordan built what would become one of the preeminent centers for IVC research and clinical application.

Dr. Riordan became one of the first physicians in the United States to systematically administer high-dose intravenous vitamin C to cancer patients. When a 70-year-old patient with metastatic renal cell carcinoma that had spread to his liver and lungs came to the clinic in the early 1980s requesting IV ascorbate infusions—having read Pauling’s research—Riordan began treatment at 30 grams twice per week. Fifteen months later, the patient’s oncologist reported no signs of progressive cancer.

This case galvanized the Riordan Clinic’s cancer research program, which would grow to encompass in vitro cell line studies, animal models, pharmacokinetic analyses, and ultimately clinical trials. The Riordan research team—including Neil H. Riordan, PhD, Joseph Casciari, PhD, and Nina Mikirova, PhD—demonstrated that at millimolar concentrations achievable only by intravenous administration, ascorbate is preferentially toxic to cancer cells while leaving normal cells unharmed. More than 60 cancer cell lines were tested. The team published extensively, including in the British Journal of Cancer (2001), the Puerto Rico Health Sciences Journal (2005), and the Journal of Translational Medicine (2013). The Riordan Clinic holds patents on treating cancer with vitamin C (U.S. patents 6,448,287; 6,436,411; 6,284,786) that predate the turn of the century.

The Riordan IVC Protocol—which has become the most widely adopted clinical framework for IVC administration in integrative oncology—specifies slow infusion of ascorbate at doses of 0.1 to 1.0 grams per kilogram of body weight, two to three times per week, titrated upward based on post-infusion plasma levels. The protocol incorporates mandatory pre-screening for glucose-6-phosphate dehydrogenase (G6PD) deficiency, renal function assessment, and monitoring parameters. The Riordan Clinic has administered over 40,000 IVC treatments and reports that serious side effects are rare when the protocol is followed. The Clinic continues to host the annual IVC Symposium and IVC Academy (IVCandCancer.org), training physicians worldwide.

The Pharmacokinetic Revolution: Why Route of Administration Matters

The pivotal breakthrough that rehabilitated IVC as a scientifically credible cancer therapy came not from oncology, but from basic pharmacokinetics. In 2004, Sebastian Padayatty, Mark Levine, and colleagues at the NIH published a landmark study in the Annals of Internal Medicine that fundamentally changed the understanding of vitamin C’s behavior in the human body.

The key finding was breathtaking in its simplicity: when vitamin C is taken orally, plasma concentrations are tightly controlled by at least three mechanisms—intestinal absorption, tissue accumulation, and renal reabsorption. Even at the maximum tolerated oral dose of 3 grams every four hours, pharmacokinetic modeling predicted peak plasma concentrations of only about 220 micromoles per liter (µmol/L). However, when the same researchers administered a 50-gram intravenous dose, the predicted peak plasma concentration was approximately 13,400 µmol/L—roughly 60-fold higher. The 2004 paper explicitly included Hugh Riordan as a co-author, bridging the NIH’s pharmacokinetics expertise with the Riordan Clinic’s clinical experience.

This finding retroactively explained why the Mayo Clinic trials had failed: oral vitamin C simply cannot achieve the plasma concentrations needed for anti-cancer activity. The Cameron–Pauling studies, which used intravenous administration initially, were testing a fundamentally different intervention than the oral-only Mayo Clinic trials. The two sets of investigators were, in pharmacologic terms, testing different drugs.

Mechanisms of Action: How Pharmacologic Ascorbate Fights Cancer

The mechanisms by which high-dose IVC exerts anti-cancer effects are multifaceted and continue to be elucidated. Rather than a single pathway, pharmacologic ascorbate appears to operate through at least four distinct and potentially synergistic mechanisms.

Mechanism 1: Pro-Oxidant Hydrogen Peroxide Generation

The most extensively studied mechanism was definitively characterized by Qi Chen, Mark Levine, and colleagues at the NIH in a series of three landmark papers published in the Proceedings of the National Academy of Sciences (PNAS) in 2005, 2007, and 2008. At pharmacologic concentrations achievable only intravenously (millimolar range), ascorbate paradoxically functions as a pro-oxidant rather than an antioxidant. Through a process involving iron and copper catalysis, high-dose ascorbate donates an electron to molecular oxygen, generating the ascorbate radical and, subsequently, hydrogen peroxide (H₂O₂) in the extracellular fluid surrounding tumors.

In the 2005 PNAS study, Chen et al. demonstrated that normal cells were unaffected by ascorbate concentrations up to 20 millimolar (mM), whereas five of ten cancer cell lines tested had EC50 values below 4 mM—concentrations readily achievable with intravenous administration. The cytotoxicity was completely abrogated by catalase (an enzyme that degrades H₂O₂), confirming that hydrogen peroxide was the effector molecule. In the 2007 study, the team demonstrated in vivo that parenteral ascorbate produced sustained ascorbate radical and H₂O₂ formation selectively within the interstitial (extracellular) fluid, with concentrations four to twelve times higher than in blood. The 2008 study showed that pharmacologic ascorbate decreased the growth of aggressive tumor xenografts (glioblastoma, pancreatic, and ovarian) in mice by 41 to 53 percent.

The selectivity of this mechanism—killing cancer cells while sparing normal cells—is believed to arise from differences in antioxidant defense capacity. Tumor cells frequently have lower catalase activity, reduced glutathione peroxidase levels, and diminished superoxide dismutase expression compared to normal cells. As Frei and Lawson noted in their 2008 PNAS commentary, the dose-dependent effects of H₂O₂ on cell function—from growth stimulation at very low concentrations to growth arrest, apoptosis, and necrosis at higher concentrations—may be shifted to the left in tumor cells, making them exquisitely vulnerable.

Mechanism 2: Epigenetic Modulation via TET Enzymes and Histone Demethylases

A newer and equally compelling mechanism involves vitamin C’s role as an essential cofactor for the ten-eleven translocation (TET) family of dioxygenases (TET1, TET2, TET3), which catalyze the stepwise oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC)—the process of active DNA demethylation. In a landmark 2013 study published in Nature, Blaschke and colleagues showed that vitamin C promotes TET-dependent DNA demethylation in embryonic stem cells. Vitamin C also serves as a cofactor for the Jumonji C (JmjC) domain-containing histone demethylases, particularly JHDM1a/b (KDM2A/B), which remove methyl groups from histone lysine residues.

This epigenetic dimension is particularly relevant in hematological malignancies. TET2 loss-of-function mutations are prevalent in acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and certain lymphomas, occurring in approximately 10–30 percent of patients. Loss of TET2 function leads to DNA hypermethylation and aberrant gene silencing that drives malignant transformation. A 2017 study in Nature by Agathocleous et al. demonstrated that ascorbate regulates hematopoietic stem cell function and that its depletion accelerates leukemogenesis. Clinical studies have shown that vitamin C supplementation can boost DNA demethylation in TET2 mutation carriers, raising the possibility that IVC could partially compensate for TET2 dysfunction. A 2019 case report in Blood Cancer Journal documented clinical remission following ascorbate treatment in a patient with AML harboring TET2 and WT1 mutations.

Mechanism 3: HIF-1α Suppression and Anti-Angiogenesis

Hypoxia-inducible factor 1-alpha (HIF-1α) is a master transcriptional regulator that enables tumors to adapt to low-oxygen environments by promoting angiogenesis, glycolysis, and immune evasion. The prolyl hydroxylases (PHDs) that mark HIF-1α for proteasomal degradation are Fe(II)- and α-ketoglutarate-dependent dioxygenases that require ascorbate as a cofactor. Vitamin C deficiency impairs PHD activity, stabilizing HIF-1α even under normoxic conditions. High-dose ascorbate restores PHD function, suppressing HIF-1α-driven gene expression. Additionally, Mikirova et al. at the Riordan Clinic demonstrated anti-angiogenic effects of high-dose ascorbate in aortic ring and Matrigel plug assays, published in the Journal of Angiogenesis Research (2012) and the Journal of Translational Medicine (2008).

Mechanism 4: Synergy with Chemotherapy and Radiation

Preclinical data suggest that pharmacologic ascorbate can sensitize cancer cells to DNA-damaging agents by increasing intratumoral oxidative stress. The University of Iowa group has demonstrated synergistic effects between IVC and gemcitabine in pancreatic cancer models, between IVC and radiation in glioblastoma models, and between IVC and standard chemoradiation in non-small cell lung cancer. Importantly, meta-analyses of clinical studies have concluded that antioxidant supplementation does not interfere with the cytotoxicity of chemotherapy regimens, and pharmacologic IVC appears to enhance rather than diminish chemotherapeutic efficacy in the cell lines and animal models studied.

Clinical Evidence: From Case Reports to Randomized Trials

Early Clinical Observations and Phase I Trials

In 2005, the Riordan Clinic published a pilot clinical study of continuous intravenous ascorbate in terminal cancer patients in the Puerto Rico Health Sciences Journal. While the study was small and uncontrolled, it demonstrated the feasibility and safety of the approach. In 2006, Padayatty et al. at the NIH reported three well-documented cases—renal cell carcinoma, bladder carcinoma, and B-cell lymphoma—in which patients treated with high-dose IVC experienced sustained tumor regression beyond what conventional therapy would predict.

Multiple phase I trials from the University of Iowa and other centers (including Jeanne Drisko’s work at the University of Kansas) confirmed that IVC at doses up to 1.5 g/kg is safe and well tolerated when standard precautions are observed, including G6PD screening and renal function monitoring. These studies also generated pharmacokinetic data showing that target plasma concentrations in the 20–30 mM range are consistently achievable.

The University of Iowa Pancreatic Cancer Trial (2024)

The most compelling clinical evidence to date comes from the University of Iowa’s randomized phase II trial, led by Joseph Cullen, MD, and published in Redox Biology in November 2024 (Bodeker et al., 2024; doi: 10.1016/j.redox.2024.103375). In this trial, 34 patients with stage IV metastatic pancreatic ductal adenocarcinoma (PDAC) were randomized 1:1 to receive either standard chemotherapy alone (gemcitabine plus nab-paclitaxel) or the same chemotherapy with concomitant IVC at 75 grams three times weekly.

The results were striking: median overall survival was 16 months in the IVC-plus-chemotherapy group versus 8 months in the chemotherapy-only group, a doubling of survival that led to early termination of the trial. Progression-free survival extended from approximately 4 months to 6 months. Post-infusion plasma ascorbate levels in the IVC group were approximately 500-fold higher than in the control group. Crucially, IVC did not add measurable toxicity. In fact, Dr. Cullen reported that patients in the vitamin C arm appeared to tolerate chemotherapy better, received higher cumulative doses for longer periods, and reported fewer side effects.

It is worth noting that in an earlier University of Iowa phase I trial combining high-dose IVC with radiation for locally advanced pancreatic cancer, three of fourteen patients achieved long-term survival exceeding nine years—far beyond the typical survival range for this disease.

Glioblastoma

Results from a University of Iowa phase II trial in glioblastoma multiforme (GBM), published in Clinical Cancer Research in 2024, showed that patients receiving high-dose IVC in combination with standard chemoradiation (temozolomide plus radiation) survived approximately five months longer than those receiving chemoradiation alone. For a disease with a median survival of only 14.6 months, this is clinically meaningful. The lead researcher, Bryan Allen, MD/PhD, noted that high-dose vitamin C appeared not only to impair cancer cells but also to protect normal tissue from radiation-induced damage.

Non-Small Cell Lung Cancer

A University of Iowa phase II trial in non-small cell lung cancer is nearing completion as of 2025, and earlier phase I data have been encouraging. All three major Iowa trials—pancreatic cancer, glioblastoma, and lung cancer—were funded by a 2018 National Cancer Institute grant, lending institutional credibility to the research program.

Quality of Life and Supportive Care

Beyond tumor-directed outcomes, a substantial body of observational and interventional data supports IVC’s role in improving cancer-related quality of life. Multiple studies—including those from the Riordan Clinic, as well as independent groups in Germany, Korea, and Canada—report that IVC at supportive doses (5–25 grams, one to three times per week) is associated with reduced fatigue, pain, nausea, and appetite loss; improved functional status; and reductions in inflammatory markers such as C-reactive protein (CRP) and pro-inflammatory cytokines. The National Cancer Institute’s PDQ summary on IV vitamin C notes two clinical series in which IVC was associated with improved quality of life and decreased cancer-related toxicities.

Systematic Reviews and the Current Evidence Landscape

Systematic reviews—including those from the Cochrane Collaboration and the Canadian College of Naturopathic Medicine—generally conclude that while there is no definitive, replicated evidence that IVC improves survival in unselected cancer populations, the safety profile is well established, quality-of-life benefits are consistently observed, and selected tumor types (particularly pancreatic cancer and glioblastoma) show promising signals that warrant phase III confirmation.

Dosing, Protocols, and Practical Implementation

Two Distinct Clinical Paradigms

It is essential to distinguish between two fundamentally different clinical applications of IVC, as they target different goals and use different dose ranges.

Supportive Care / Quality-of-Life Dosing

Doses of 5–25 grams infused over 30 to 120 minutes, one to three times per week, are used primarily to replenish the profound vitamin C depletion that is nearly universal in cancer patients, reduce inflammation, mitigate chemotherapy side effects, and improve functional status. This approach does not aim to achieve pharmacologic (pro-oxidant) plasma levels and is analogous to high-dose nutritional support.

Pharmacologic / Anti-Tumor Dosing

Doses of 0.5–1.5 g/kg body weight (typically 50–100 grams absolute dose in adults), infused two to three times per week, aim to achieve plasma concentrations in the millimolar range (target: 20–30 mM post-infusion) sufficient to generate cytotoxic levels of hydrogen peroxide in the tumor microenvironment. This is the approach used in the University of Iowa trials and represents a true pharmacologic intervention.

The Riordan IVC Protocol: A Practical Framework

The Riordan IVC Protocol, developed over decades of clinical experience at the Riordan Clinic in Wichita, Kansas, provides the most widely used framework for clinical implementation. Key elements include the following.

Pre-treatment screening: G6PD enzyme activity (absolute contraindication for high-dose IVC if deficient), comprehensive metabolic panel with renal function (creatinine, eGFR), complete blood count, urinalysis (for oxalate), and baseline vitamin C plasma levels.

Dose titration: Treatment typically begins at 15 grams and is gradually increased over several sessions (25g, then 50g, then 75g, then up to 100g if tolerated) based on post-infusion plasma ascorbate levels. The target post-infusion plasma level is 350–400 mg/dL (approximately 20–23 mM).

Infusion parameters: Ascorbate is diluted in sterile water (not lactated Ringer’s or normal saline at high doses, to avoid excessive sodium/osmolar load) and infused over 90 to 180 minutes depending on dose and patient tolerance. Infusion rates are typically 0.5–1.0 g/minute.

Frequency and duration: Two to three times per week, continuously, without lapses. The Riordan Clinic emphasizes that continuous treatment without interruption is critical for maintaining anti-tumor pressure. Treatment is typically continued until tumor stabilization or no detectable cancer for 12 months, at which point frequency is tapered.

Monitoring: Post-infusion plasma ascorbate levels at regular intervals, renal function monitoring, complete metabolic panels, and awareness that IVC can cause false-positive glucose readings on point-of-care glucometers (electrochemical method) at doses of 15 grams and above, which may persist for up to eight hours post-infusion. Venous blood analyzed by the hexokinase method in a clinical laboratory gives accurate results.

Safety Profile and Contraindications

Overall Safety

High-dose IVC has been repeatedly demonstrated to be safe when administered with appropriate screening and monitoring. A 2010 survey of approximately 300 integrative and orthomolecular medicine practitioners found that roughly 10,000 patients had received IVC at an average dose of 0.5 g/kg without significant adverse effects. The Riordan Clinic’s experience with over 40,000 treatments, the University of Iowa’s three phase I–II trials, and multiple independent studies collectively support a favorable safety profile.

Common minor side effects include transient thirst (due to osmotic diuresis), mild nausea, and occasionally light-headedness during infusion. Rarely, patients may experience venous irritation at the infusion site.

Absolute and Relative Contraindications

Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency: This is the most critical safety concern. G6PD-deficient erythrocytes lack the capacity to generate sufficient NADPH to maintain glutathione in its reduced form, making them vulnerable to oxidative hemolysis when exposed to the pro-oxidant hydrogen peroxide generated by high-dose ascorbate. Multiple case reports document severe hemolytic anemia, methemoglobinemia, acute kidney injury, and even death in G6PD-deficient patients receiving doses of 30 grams or more. G6PD screening is mandatory before initiating high-dose IVC, particularly in populations of African, Mediterranean, Middle Eastern, and Southeast Asian descent where G6PD deficiency prevalence is highest. Importantly, qualitative G6PD screening may yield false-negative results during acute hemolysis due to reactive reticulocytosis, so baseline testing before any IVC administration is essential.

Renal Insufficiency and Oxalate Nephropathy: Ascorbate is metabolized to oxalate, and high-dose IVC increases urinary oxalate excretion. Patients with significant renal impairment (eGFR below 30–40 mL/min), a history of calcium oxalate nephrolithiasis, or known hyperoxaluria are at risk for oxalate crystal deposition and acute kidney injury. Renal function should be monitored throughout treatment.

Iron Overload Conditions: Because the pro-oxidant mechanism of IVC involves iron-catalyzed Fenton chemistry, patients with hemochromatosis or other iron overload states may experience amplified oxidative stress. Caution is warranted.

Heart Failure and Fluid-Sensitive States: High-dose IVC involves infusion of substantial fluid volumes and osmolar loads. Patients with uncontrolled congestive heart failure should be managed carefully with adjusted infusion rates and volumes.

Timing of IVC Relative to Chemotherapy and Radiation

One of the most common clinical questions regarding IVC is whether it should be given on the same day as chemotherapy, and whether its antioxidant properties might blunt the cytotoxicity of oxidative-stress-dependent chemotherapeutic agents. The evidence on this point is reassuring but nuanced.

At pharmacologic (pro-oxidant) concentrations, IVC generates oxidative stress within tumors, which is mechanistically synergistic rather than antagonistic with DNA-damaging agents such as gemcitabine, carboplatin, and paclitaxel. This is supported by the University of Iowa’s pancreatic cancer trial, in which IVC was given concomitantly with chemotherapy (not on separate days) and doubled survival.

Nevertheless, because of theoretical concerns and in the absence of definitive timing data for all regimens, most integrative oncology groups—including MD Anderson Cancer Center’s integrative medicine program—recommend a conservative approach: administering IVC on non-chemotherapy days when possible, or allowing several drug half-lives between IVC and curative-intent chemotherapy infusions, and ensuring that IVC has cleared from the plasma before the next chemotherapy cycle. The Riordan Clinic protocol similarly advises that IVC not be given within 24 hours of certain chemotherapy regimens, though the specific timing window depends on the chemotherapeutic agent’s pharmacokinetics.

For palliative-intent chemotherapy—where the goal is symptom control and survival extension rather than cure—the evidence increasingly supports concomitant administration, as demonstrated in the Iowa pancreatic cancer trial.

Clinical Decision-Making: When IVC May Be Reasonable and When to Avoid It

Potentially Reasonable (with Informed Consent and Oncologist Collaboration)

Advanced or metastatic solid tumors where prognosis is poor and standard therapy is palliative in intent, particularly pancreatic cancer, glioblastoma, and other tumors where early-phase data support benefit. Patients who are highly symptomatic from disease or treatment toxicity and where quality-of-life improvement is a major therapeutic goal. Patients with adequate renal function, confirmed G6PD sufficiency, and no contraindications. Patients who are interested in participating in clinical trials evaluating IVC.

Use with Caution or Generally Avoid

Curative-intent regimens (such as adjuvant chemotherapy for early-stage breast or colorectal cancer) where even a theoretical risk of reduced efficacy is unacceptable—unless within a clinical trial specifically evaluating IVC in that setting. Patients with G6PD deficiency, significant renal impairment, a history of oxalate nephrolithiasis, iron overload states, or uncontrolled heart failure. Any clinical scenario in which IVC would substitute for, rather than complement, evidence-based standard of care.

Future Directions and the Path to Phase III

The University of Iowa’s pancreatic cancer results represent the strongest clinical signal to date and provide compelling rationale for a large, multi-institutional phase III trial. However, as Dr. Cullen has candidly noted, obtaining pharmaceutical industry funding for such a trial is challenging because ascorbic acid is inexpensive, unpatentable, and offers no commercial return on investment. Public funding through the National Cancer Institute and philanthropic support may be essential.

Key unanswered questions include the optimal dose and frequency of IVC for different tumor types; the ideal timing of IVC relative to specific chemotherapy and immunotherapy agents; whether particular molecular subtypes (such as KRAS-mutant colorectal cancers, which were shown by Yun et al. in a 2015 Science paper to be preferentially killed by high-dose vitamin C) predict response; the role of IVC in combination with emerging immunotherapies; and the duration of treatment needed.

The epigenetic dimension of IVC’s activity—particularly its role as a TET enzyme cofactor—opens additional avenues of investigation in hematological malignancies, where TET2 mutations are common and vitamin C deficiency is prevalent. Clinical trials combining IVC with hypomethylating agents (such as azacitidine) in AML and MDS are underway.

Conclusion

The story of intravenous vitamin C in oncology is a story of science’s capacity for self-correction. What was prematurely dismissed due to a pharmacokinetic misunderstanding has, over four decades, been rebuilt on a foundation of rigorous cell biology, animal models, pharmacokinetics, and now randomized controlled trials. The contributions of Linus Pauling and Ewan Cameron, of Hugh Riordan and his team in Wichita, of Mark Levine and Qi Chen at the NIH, and of Joseph Cullen and Bryan Allen at the University of Iowa represent a continuum of intellectual courage and scientific persistence.

IVC is not a cancer cure. It is, however, an increasingly well-characterized pharmacologic intervention with a defined mechanism of action, a strong safety profile, reproducible quality-of-life benefits, and now, randomized trial evidence of survival improvement in selected cancers. It deserves to be evaluated with the same rigor applied to any other adjunctive oncologic therapy—neither dismissed because of its origin in complementary medicine nor embraced uncritically beyond what the evidence supports.

As the Riordan Clinic has long advocated, cancer requires an “all hands on deck” approach. Intravenous vitamin C, when used judiciously, under proper medical supervision, and in collaboration with the patient’s oncology team, represents one more hand on that deck.

Credentials:

Yoon Hang Kim, MD, MPH, FAAMA 

• Board-Certified Preventive Medicine Physician
• Integrative Medicine Fellowship, University of Arizona (Andrew Weil Program)
• Institute of Functional Medicine Scholarship Recipient

I'm a preventive medicine physician with over 25 years of clinical experience in integrative and functional medicine. My Master of Public Health with a concentration in Health Promotion provides a strong foundation in nutrition science and evidence-based lifestyle interventions.

Relevant experience includes serving as Chief Wellness Officer at Memorial Hospital, where I developed lifestyle medicine programs including nutritional interventions, and as Enterprise Medical Director of Integrative Medicine at WellMed/Optum, overseeing wellness initiatives for 30,000 patients.

I've authored 28+ peer-reviewed articles on integrative therapies, serve on the editorial board of Explore journal, and am a peer reviewer for the Journal of Alternative and Complementary Medicine. My clinical approach emphasizes evidence-based supplementation as part of comprehensive wellness strategies.

I can be reached at drkim@georgiaintegrative.com or 678.373.8034 (text preferred).

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