Navigation Menu

Vitamin C — An Ingredient for Life

Author: Jian Gao, PhD
Editor: Mr. Frederick Malphurs
November 8, 2026 

Vitamin C is an essential micronutrient — we can’t live without, and we can’t make it inside our bodies. It is water-soluble — our bodies do not store it and whatever leftovers leave our body through the urine. Therefore, we need an ongoing supply of vitamin C from foods, such as citrus fruits, broccoli, and tomatoes. 

Vitamin C plays many vital roles in our body and deficiency is detrimental to our health and even can kill. It’s essential for the growth and repair of tissues in all parts of our bodies including our hearts. It helps to form an important protein, collagen, used to make skin, tendons, ligaments, and blood vessels. It helps to heal wounds and form scar tissue, repair and maintain cartilage, bones, and teeth, and aid in the absorption of iron. It is believed to be a key antioxidant that prevents or minimizes damage caused by free radicals.1,2 And countless studies have shown that how vitamin C plays a vital role in helping our immune system to function properly.3-6

One of the consequences of vitamin C deficiency is a disease called scurvy. Scurvy patients suffer from swollen and bleeding gums, loose teeth, hemorrhaging under the skin, and slowed healing of wounds, and death could, often did, quickly follow. It’s estimated that scurvy killed at least two million sailors during the Age of Exploration (between 1500 and 1800) before citrus fruits and lemon juice were widely recognized as cures.7

We tend to think scurvy is a thing of the past, but unfortunately that is not the case. A survey in a French hospital found 12% of hospitalized elderly patients had scurvy.8 Even in the general population, vitamin C deficiency isn’t rare: The Third National Health and Nutrition Examination Survey (NHANES) revealed 14% of males and 10% of females in the US had their plasma vitamin C levels below 11 µmol/L.9 Ten or fourteen percent doesn’t seem to be too high, but that’s because the threshold of 11 µmol/L is extremely low. The percentage of the population with less severe deficiency can be much higher given the reference range is 53.0-176.8 µmol/L.10 Vitamin C deficiencies are not rare in other countries either; for example, 14% of elderly people living at home and 40% of elderly people living in institutions in the UK,11 19% of males and 13% of females from India,12 23% of children and 39% of women in Mexico,13 and a study found 79-93% of men from Western Russia were deficient in vitamin C.14

So, the case isn’t closed, as the medical establishment believes. At the very least, we all need to remember this: Heaven forbid, if your loved ones, especially the elderly, become seriously ill, ask their doctors to check their vitamin C levels. A study published in 2017 in Critical Care found “one-third [of the critically ill] had vitamin C deficiency (i.e., < 11 μmol/L) … despite receiving recommended intakes via enteral and/or parenteral nutritional therapy (mean 125 mg/d).”15 This serious problem can be easily missed or ignored because the patients are believed to be given more than enough of vitamin C according to the standard set by the Food and Nutrition Board of the Institute of Medicine, National Academy of Sciences — the Recommended Dietary Allowance (RDA) is 90 mg for adult males and 75 mg per day for adult females.16         

Now, for ordinary people like you and me, do we get enough vitamin C from food, or do we need vitamin C supplementation? This is one of the most controversial and hotly debated questions among believers and nonbelievers. Recommendations for supplementation range from none at all among nonbelievers to over 10 grams per day from some alternative medicine doctors and even world-class scientists. The medical establishment generally believes that we get enough vitamin C from food and that taking too much can harm us.

How much is too much? “Here’s how you know what’s too much. You shouldn’t bypass the satiety level. Your stomach is only so big for a reason,” Dr. Paul Offit, an infectious disease and vaccine expert, warned about taking 1 gram of vitamin C (during the PBS special report interview). “You know, you’re not meant to eat eight cantaloupes. It’s a dangerous thing to do, to go against what nature intends.” The argument appears quite convincing.

On the other hand, believers argue that a gene mutation about 60 million years ago left humans unable to produce vitamin C, while most other animals can still produce it — and in large quantities. A 150-pound goat, for example, can produce 13 grams per day under normal conditions and up to ten times more during stress or illness.17,18

Adding to this concern, there has been significant loss of vitamin C and other micronutrients in crops due to soil depletion from intensive modern farming. Therefore, many believe supplementation is needed,2,19 including world-class scientists like Linus Pauling himself, the only winner of two undivided Nobel Prizes, who reportedly took 12 grams per day and lived to the age of 93.

What should we believe and do? Let’s first look at the existing scientific and empirical evidence about vitamin C and health.

Cardiovascular Diseases

Although not entirely consistent,20 most large-scale observational studies found vitamin C intake effective in reducing the risk of cardiovascular events (e.g., heart attack and stroke) and mortality.21-23 For example, the well-known Nurses’ Study, with 85,118 female participants and a 16-year follow-up, found total intake of vitamin C from both dietary and supplemental sources was inversely associated with coronary heart disease (CHD) risk: Participants in the  highest quintile of vitamin C intake experienced a 27% lower risk compared to those in the lowest quintile.24

Similarly, in the Doctors’ Study with 83,639 male physicians, the investigators found use of vitamin C supplements for a mean of 5.5 years was associated with a 12% and 14% reduction of cardiovascular disease (CVD) mortality and CHD mortality, albeit the results missed statistical significance.25 Another prospective study followed 20,649 British adults and found the participants in the top quartile of baseline plasma vitamin C concentrations had a 42% lower risk of stroke than those in the bottom quartile.26

The problem with observational studies, no matter how large they are, is confounding: those with higher vitamin C intake may also eat healthier and exercise more among other things they do. It’s hard to separate the effect of vitamin C from all other factors.

But on the other hand, randomized controlled trials (RCTs), hailed as the gold standard, can be very misleading too when used to assess the effects of dietary supplements on chronic diseases. As discussed in Your GPS for Health (Chapter 6), the effect of a micronutrient on chronic diseases is hard to detect by RCTs because, (1) the incubation period for chronic diseases is typically very long, whereas most RCTs last only a few years, (2) chronic diseases are typically multifactorial — micronutrient deficiency, especially vitamin C deficiency alone, is unlikely to be the major driver, and (3) the majority of the participants in the trials may not be deficient in the micronutrient that the trial was designed to test.

As expected, the RCTs on vitamin C showed inconsistent and disappointing results,27-30 just as succinctly summarized by a meta-analysis published in JAMA (Journal of the American Medical Association), “Treatment with beta carotene, vitamin A, and vitamin E may increase mortality. The potential roles of vitamin C and selenium on mortality need further study.”31

On the other hand, studies including RCTs have consistently shown that vitamin C supplementation improves endothelial function.32,33 The evidence on blood pressure is even stronger. Researchers from Johns Hopkins School of Medicine compiled 29 RCTs and found supplementation of vitamin C (median dose = 500 mg/d) reduced blood pressure. The reduction was small but statistically significant: 3.84 mm Hg (p < 0.01) for SBP (systolic blood pressure) and 1.48 mm Hg (p=0.04) for DBP (diastolic blood pressure).34 Subgroup analyses showed the effect was larger for those with a low baseline vitamin C level.

Cancer

Currently, there is a strong surge of interest in using vitamin C to treat cancer,35 as mounting evidence has unequivocally demonstrated that high doses of vitamin C can selectively inhibit cancer cell growth while leaving normal cells largely unaffected in laboratory and animal studies.36-46 Furthermore, researchers have also identified the underlying mechanisms: pro-oxidant activity, epigenetic modulation, signal transduction regulation, and immune regulation.47

The anticancer properties of vitamin C weren’t recognized until the mid-1970s when Linus Pauling and Ewan Cameron (a Scottish physician) published their findings from 100 terminal cancer patients who had been administered 10 grams of vitamin C intravenously per day for approximately 10 days, followed by 10 grams of oral vitamin C thereafter.48,49 Their study demonstrated significantly improved survival among these patients administered vitamin C compared with two retrospective cohorts of 1,000 patients who didn’t receive vitamin C.

To replicate these promising findings, researchers at the renowned Mayo Clinic carried out two randomized controlled trials: one involving 123 patients diagnosed with advanced malignancies50 and the other involving 100 patients diagnosed with advanced colorectal cancer.51 Both trials showed no significant survival advantage among patients who received 10 grams of vitamin C orally. The null findings of both studies, published in the prestigious New England Journal of Medicine, essentially relegated the use of vitamin C to treat cancer to the realm of alternative medicine.

The contradictory findings between the Cameron/Pauling studies and the Mayo studies remained a big puzzle until the mid-1990s, when the seminal work by Mark Levine and colleagues highlighted the dramatic differences between oral and intravenous (IV) administration of vitamin C.52 Vitamin C concentrations in human plasma and tissues are tightly regulated. Even at the maximum tolerated oral dose (about 18 g/day), plasma vitamin C concentrations can reach only about 220 μmol/L, whereas IV administration of 50–100 g can raise them to as high as 14,000 μmol/L.53

This is because oral intake of high doses of vitamin C is largely excreted in urine rather than absorbed into the bloodstream. And Cameron/Pauling studies used IV administration while the Mayo studies used oral administration.

The recognition of IV being more effective than oral administration sparked renewed interest.

 Although more studies are needed, early randomized trials of pharmacological doses of intravenous vitamin C (IVC) have largely shown improvements in patient tolerability, quality of life, and survival outcomes.54-59

However, all these trials combined vitamin C with conventional chemotherapy or radiation therapy rather than using vitamin C alone as a monotherapy. Research in this area is still at an early stage, with the optimal dosage of vitamin C and the types of cancer it may be most effective against still under active investigation.

In any event, do not count on vitamin C as a magic bullet against cancer. Although vitamin C can indeed inhibit cancer cell growth, it may be like using a garden hose or an under-sink fire extinguisher to fight a house fire. The most effective strategy and smartest policy are to prevent cancer from developing in the first place by addressing its root causes.

It is worth noting that the evidence for vitamin C’s preventive effects against cancer is more consistent than the evidence supporting its use as a cancer treatment. Epidemiological studies have shown that high vitamin C intake, especially from dietary sources, is associated with a lower risk of developing cancer. 60-65

Finally, doctors, patients, and especially caregivers or family members need to keep in mind that cancer patients are more likely to be deficient in vitamin C, and severe vitamin C deficiency can itself be fatal. Furthermore, cancer patients may need more vitamin C than healthy people do. In fact, the same dose of intravenously administered vitamin C results in a much lower circulating vitamin C level in cancer patients than in healthy individuals.66,67

Cold, Flu and Other Infections

For sure you or somebody you know takes vitamin C when getting a cold or flu. Just look at the ingredients of the popular Airborne — mostly vitamin C. Although vitamin C was used to treat common cold as early as in the 1940s, it didn’t catch much attention until 1970 when Dr. Linus Pauling published his book “Vitamin C and the Common Cold.”68 To substantiate his position, in 1971, he published a meta-analysis of the only four published double-blind randomized trials and concluded “that ascorbic acid [vitamin C], taken in the proper amounts, decreases the incidence of colds and related infections, and also decreases the severity of individual colds.”69

Ever since, numerous RCTs have been conducted to ascertain the effects of vitamin C on the common cold. Taken together, the findings were not as strong as hoped, as reflected in the most comprehensive 103-page report on vitamin C and the common cold, published by the Cochrane Database of Systematic Reviews.70 The review examined all placebo-controlled randomized trials (29 in total) in which participants took at least 200 mg of vitamin C daily. It concluded that prophylactic or preventive use of vitamin C did not substantially reduce the risk of developing a cold in the general population, but reduced the duration of colds by 8% in adults and 14% in children (18% when vitamin C intake was 1-2 g/day).

The vitamin C believers including Pauling believed the dosages were too small to be effective in these trials.2,71

Nevertheless, there was a bright spot in these trials — subgroup analyses of the trials involving marathon runners, skiers, and soldiers exposed to extreme physical exercise or cold environments showed prophylactic use of vitamin C in doses ranging from 0.25-1g/day reduced the incidence of cold by 52%. This is consistent with the observation that under stress humans and animals alike need a lot of vitamin C.71

Over the years, my personal experience has taught me that vitamin C is most effective when taken at the first sign of a cold or the flu, especially when combined with an oregano oil supplement. However, its effectiveness is harder to discern once the illness is in full swing.

In any event, colds and the flu are usually self-limiting illnesses that resolve on their own. However, when you have a serious infection for which no prescription drugs are effective, high-dose vitamin C may be a lifesaver. A total of 148 animal studies demonstrated that vitamin C can alleviate or prevent infections caused by bacteria and viruses. Evidence from human studies is also compelling.72-74 A recent study unequivocally demonstrated that intravenous infusion of vitamin C dramatically reduced Epstein-Barr virus (EBV) activity.75

EBV is generally benign, but it can persist and cause significant problems, including autoimmune diseases. For anyone suffering from a chronic viral infection for which conventional medicine offers no effective treatment, intravenous (IV) vitamin C may be worth discussing with your doctor. At IV doses, vitamin C is no longer simply a micronutrient; it is being used as a pharmacological agent. IV administration requires medical supervision and cannot be self-administered. Because most mainstream physicians do not offer this treatment, those interested in exploring it may need to seek physicians experienced in integrative or alternative medicine.

Detoxification

Vitamin C has another much-cherished trait ­— enhancing detoxification. Studies in both animals and humans have found vitamin C can help get rid of heavy metals such as lead from our bodies. 76-82

You might think, “Who cares about heavy metals?” after all, you’ve never worked in a factory that uses lead or mercury or lived near an industrial waste disposal site. But the problem is real: heavy metals such as lead and mercury can cause far more damage to our bodies than most of us realize. You don’t have to live in Flint, Michigan, to face heavy metal exposure, nor do you need excessive exposure to industrial waste to become ill. We are all exposed to these metals through various sources, including food such as fish, polluted air, dental fillings, and some vaccines. The problem is that our bodies’ ability to eliminate these metals varies greatly from person to person. Many people have difficulty eliminating them efficiently, and I personally know a few such individuals.

In addition to contributing to problems such as cardiovascular disease and cancer, heavy metals can trigger other conditions, including mental health problems and autoimmune diseases, some of which can be gravely serious. The real danger is that we assume our liver is doing its job of eliminating these metals from our bodies and that we are therefore fine, when in reality, we do not really know. Even if you ask your doctor to order a heavy metal test, a standard blood test generally reflects recent exposure.

If you suffer from unexplained chronic disorders, consider investigating long-term heavy metal exposure and possible accumulation in tissues and organs, despite the medical establishment often pooh-poohing such concerns. To do so, consult an experienced physician, often one practicing integrative or alternative medicine, who has access to specialized testing laboratories. For more information, see Chapter 12 of Your GPS for Health.

In addition to heavy metals, studies have also shown vitamin C supplementation helps detoxify pesticides and other manmade chemicals such as DDT and PCBs,83-90 which are ubiquitous in our food and environment. In animal models, researchers also demonstrated high-dose vitamin C reduces pesticide-induced DNA damage.91

DNA Damage from CT Scans and Other X-ray Imaging

Studies have also shown vitamin C supplementation protects DNA from radiation damage,92-94 and repair DNA damage after radiation exposure.95 In addition to the ‘traditional’ radicals created by radiation, vitamin C can counteract radiation-induced long-lived radicals (LLRs) that destabilize chromosomes and induce cancerous DNA mutations.96 This isn’t surprising because vitamin C is a strong antioxidant (donating electrons). Furthermore, vitamin C has also been shown to inhibit radiation-induced death of human blood cells.97 

These findings are instrumental to most of us. Millions of people are unknowingly exposed to excessive radiation in hospitals and doctors’ offices around the country. The main culprit is the computed tomography (CT) scans — a single CT scan subjects the patient to between 150 and 1,100 times the radiation of a conventional x-ray. “Many studies have shown that organ doses associated with routine diagnostic CT scans are similar to the low-dose range of radiation received by atomic-bomb survivors.”98

A study estimated approximately 29,000 new cancers could be related to CT scans performed in 2007 in the US alone.99 WebMD describes the situation this way: “Overall, your odds are very low — the chance of getting a fatal cancer from any one CT scan is about 1 in 2,000.”100 However, given that an estimated over 80 million CT scans are performed every year, 1 in 2,000 is tantamount to 40,000 new cancer cases due to CT scans.

Although there’s no consensus recommendation on how much vitamin C should be taken to reduce the radiation damage, some alternative medicine practitioners suggest 1-3 grams before and after CT scans or other radiation imaging, which can reduce DNA damage by up to 87%.

Safety and Side Effects

Nothing is safer than vitamin C, even with large doses — it’s regarded as safe as water.73 Actually too much water intake can be fatal — it can dilute the sodium concentration and cause the brain to swell. On the other hand, it’s hard to find any consequential side effect of taking giant doses of vitamin C; the most common side effect of vitamin C is diarrhea if the intake is excessive, which is commonly used to set the tolerable upper limit — diarrhea is an indication of vitamin C saturation. Many alternative medicine practitioners themselves purposely and regularly use vitamin C to induce diarrhea — a detox therapy called vitamin C flush or ascorbate cleanse. They believe the process can help get toxins out of the body, but there’s little research to prove or disprove its effectiveness. Intuitively, it might work for individuals who eat food loaded with manmade chemicals such as pesticides and food additives or experience severe bad bacteria overgrowth in the digestive system.

 The only “alleged” side effect of vitamin C is kidney stone formation. Calcium kidney stones are the most common type of stones. They are typically made of calcium and oxalate. The link between vitamin C and kidney stones has been suspected because vitamin C can be metabolized to oxalate.101 Oxalate is a natural chemical found abundantly in many plant foods such as beets, chocolate, spinach, rhubarb, tea, sweet potatoes, peanuts, rhubarb, Swiss chard, and most nuts, but low or not at all in animal products. Paradoxically, studies have found diets low in animal products and high in plant-based foods reduce risk of kidney stones.102

A few studies did find high intake of vitamin C was associated with elevated risk of kidney stones.103,104 But, for each study showing increased risk, there was another study finding vitamin C neutral or reducing the risk of kidney stones.105-107 It’s not surprising to see studies reaching contradictory findings — there are at least 60 established factors contributing to kidney stones72 — it is nearly impossible for observational studies to properly control for these confounders. As stated on the NIH website, “so it is not clear whether vitamin C actually plays a role in the development of kidney stones.”108 Nevertheless, those with compromised kidney functions should be careful with large doses of vitamin C.

Taken together, when it comes to safety, patients in studies consumed up to 10 grams daily for up to 3 years experienced no side effects.109 And don’t forget Linus Pauling himself, the renowned world class biochemist, reportedly taking 12 grams per day, lived to the age of 93. On balance, if you’re healthy and eat a lot of fresh vegetables and fruits, you probably get enough vitamin C under normal conditions. However, if you’re under stress (e.g., having a cold, flu or other illness, physically exhausted), you probably need more. If you’re not sure, try 1-2 grams each day for a month or two — you will know — in addition to the low frequency of colds and flu, your skin may look younger.

References

  1. Lykkesfeldt J, Michels AJ, Frei B. Vitamin C. Adv Nutr. 2014 Jan 1;5(1):16-8.
  2. Deruelle F, Baron B. Vitamin C: is supplementation necessary for optimal health? J Altern Complement Med. 2008 Dec;14(10):1291-8.
  3. Carr AC, Maggini S. Vitamin C and Immune Function. Nutrients. 2017 Nov 3;9(11):1211. doi: 10.3390/nu9111211. PMID: 29099763; PMCID: PMC5707683.
  4. Ang A, Pullar JM, Currie MJ, Vissers MCM. Vitamin C and immune cell function in inflammation and cancer. Biochem Soc Trans. 2018 Oct 19;46(5):1147-1159.
  5. Sorice A, Guerriero E, Capone F, et al. Ascorbic acid: its role in immune system and chronic inflammation diseases. Mini Rev Med Chem. 2014 May;14(5):444-52.
  6. Wintergerst ES, Maggini S, Hornig DH. Contribution of selected vitamins and trace elements to immune function. Ann Nutr Metab 2007;51:301–323.
  7. https://www.sciencehistory.org/distillations/the-age-of-scurvy
  8. Raynaud-Simon A, Cohen-Bittan J, Gouronnec A, et al. Scurvy in hospitalized elderly patients. J. Nutr. Health Aging 2010, 14, 407–410.
  9. Hampl JS, Taylor CA, Johnston CS. Vitamin C deficiency and depletion in the United States: the Third National Health and Nutrition Examination Survey, 1988 to 1994. Am J Public Health 2004;94:870-5.
  10. https://emedicine.medscape.com/article/2088649-overview
  11. Chiplonkar SA, Agte VV, Mengale SS, Tarwadi KV. Are lifestyle factors good predictors of retinol and vitamin C deficiency in apparently healthy adults? Eur J Clin Nutr 2002;56:96-104.
  12. Bates CJ, Prentice A, Cole TJ, et al. Micronutrients: highlights and research challenges from the 1994–5 National Diet and Nutrition Survey of people aged 65 years and over. Br J Nutr 1999;82:7-15.
  13. Villalpando S, Montalvo-Velarde I, Zambrano N, et al. Vitamins A, and C and folate status in Mexican children under 12 years and women 12–49 years: a probabilistic national survey. Salud Pu´blica de Me´xico 2003;45(Suppl 4):S508-19.
  14. Matilainen T, Vartiainen E, Puska P, et al. Plasma ascorbic acid concentrations in the Republic of Karelia, Russia and in North Karelia, Finland. Eur J Clin Nutr 1996;50:115-2.
  15. Carr AC, Rosengrave PC, Bayer S, et al. Hypovitaminosis C and vitamin C deficiency in critically ill patients despite recommended enteral and parenteral intakes. Crit Care. 2017 Dec 11;21(1):300. doi: 10.1186/s13054-017-1891-y.
  16. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoidsexternal link disclaimer. Washington, DC: National Academy Press, 2000.
  17. Chatterjee IB. Evolution and the biosynthesis of ascorbic acid. Science. 1973 Dec 21;182(4118):1271-2.
  18. Stone I. Homo sapiens ascorbicus, a biochemically corrected robust human mutant. Med Hypotheses. 1979 Jun;5(6):711-21.
  19. Davis DR, Epp MD, Riordan HD. Changes in USDA food composition data for 43 garden crops, 1950 to 1999. J Am Coll Nutr 2004;23:669-682.
  20. Morelli MB, Gambardella J, Castellanos V, et al. Vitamin C and Cardiovascular Disease: An Update. Antioxidants (Basel). 2020 Dec 3;9(12):1227. doi: 10.3390/antiox9121227. PMID: 33287462; PMCID: PMC7761826.
  21. Ye Z, Song H. Antioxidant vitamins intake and the risk of coronary heart disease: meta-analysis of cohort studies. Eur J Cardiovasc Prev Rehabil 2008;15:26-34.
  22. Knekt P, Ritz J, Pereira MA, O’Reilly EJ, Augustsson K, Fraser GE, et al. Antioxidant vitamins and coronary heart disease risk: a pooled analysis of 9 cohorts. Am J Clin Nutr 2004;80:1508-20.
  23. Chen GC, Lu DB, Pang Z, Liu QF. Vitamin C Intake, Circulating Vitamin C and Risk of Stroke: A Meta‐Analysis of Prospective Studies. J Am Heart Assoc. 2013 Dec; 2(6): e000329.
  24. Osganian SK, Stampfer MJ, Rimm E, et al. Vitamin C and risk of coronary heart disease in women. J Am Coll Cardiol 2003;42:246-52.
  25. Muntwyler J, Hennekens CH, Manson JE, et al. Vitamin supplement use in a low-risk population of US male physicians and subsequent cardiovascular mortality. Arch Intern Med 2002;162:1472-6.
  26. Myint PK, Luben RN, Welch AA, et al. Plasma vitamin C concentrations predict risk of incident stroke over 10 y in 20 649 participants of the European Prospective Investigation into Cancer Norfolk prospective population study. Am J Clin Nutr 2008;87:64-9.
  27. Shekelle P, Morton S, Hardy M. Effect of supplemental antioxidants vitamin C, vitamin E, and coenzyme Q10 for the prevention and treatment of cardiovascular disease. Evidence Report/Technology Assessment No. 83 AHRQ Publication No. 03-E043. Rockville, MD: Agency for Healthcare Research and Quality, 2003.
  28. Bleys J, Miller ER 3rd, Pastor-Barriuso R, et al. Vitamin-mineral supplementation and the progression of atherosclerosis: a meta-analysis of randomized controlled trials. Am J Clin Nutr 2006;84:880-7.
  29. Sesso HD, Buring JE, Christen WG, et al. Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians’ Health Study II randomized controlled trial. JAMA. 2008 Nov 12;300(18):2123-33. doi: 10.1001/jama.2008.600. Epub 2008 Nov 9. PMID: 18997197; PMCID: PMC2586922.
  30. Cook NR, Albert CM, Gaziano JM, et al. A randomized factorial trial of vitamins C and E and beta carotene in the secondary prevention of cardiovascular events in women: results from the Women’s Antioxidant Cardiovascular Study. Arch Intern Med. 2007 Aug 13-27;167(15):1610-8. doi: 10.1001/archinte.167.15.1610. PMID: 17698683; PMCID: PMC2034519.
  31. Bjelakovic G, Nikolova D, Gluud LL, et al. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis. JAMA. 2007 Feb 28;297(8):842-57.
  32. Ashor AW, Lara J, Mathers JC, Siervo M. Effect of vitamin C on endothelial function in health and disease: a systematic review and meta-analysis of randomised controlled trials. Atherosclerosis. 2014 Jul;235(1):9-20.
  33. Morelli MB, Gambardella J, Castellanos V, et al. Vitamin C and Cardiovascular Disease: An Update. Antioxidants (Basel). 2020 Dec 3;9(12):1227. doi: 10.3390/antiox9121227. PMID: 33287462; PMCID: PMC7761826.
  34. Juraschek SP, Guallar E, Appel LJ, Miller ER. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012 May;95(5):1079-88.
  35. Shenoy N, Creagan E, Witzig T, Levine M. Ascorbic Acid in Cancer Treatment: Let the Phoenix Fly. Cancer Cell. 2018 Nov 12;34(5):700-706.
  36. Abiri B, Vafa M. Vitamin C and Cancer: The Role of Vitamin C in Disease Progression and Quality of Life in Cancer Patients. Nutr Cancer. 2021;73(8):1282-1292.
  37. Ngo B, Van Riper JM, Cantley LC, Yun J. Targeting cancer vulnerabilities with high-dose vitamin C. Nat Rev Cancer. 2019 May;19(5):271-282.
  38. Szarka A, Kapuy O, Lőrincz T, Bánhegyi G. Vitamin C and Cell Death. Antioxid Redox Signal. 2021 Apr 10;34(11):831-844. doi: 10.1089/ars.2019.7897. Epub 2020 Aug 7. PMID: 32586104.
  39. Satheesh NJ, Samuel SM, Büsselberg D. Combination Therapy with Vitamin C Could Eradicate Cancer Stem Cells. Biomolecules. 2020 Jan 3;10(1):79. doi: 10.3390/biom10010079. PMID: 31947879; PMCID: PMC7022456.
  40. Lee SJ, Jeong JH, Lee IH, et al. Effect of High-dose Vitamin C Combined with Anti-cancer Treatment on Breast Cancer Cells. Anticancer Res. 2019 Feb;39(2):751-758.
  41. Zeng LH, Wang QM, Feng LY, et al. High-dose vitamin C suppresses the invasion and metastasis of breast cancer cells via inhibiting epithelial-mesenchymal transition. Onco Targets Ther. 2019 Sep 10;12:7405-7413.
  42. Kim TJ, Byun JS, Kwon HS, Kim DY. Cellular toxicity driven by high-dose vitamin C on normal and cancer stem cells. Biochem Biophys Res Commun. 2018 Feb 26;497(1):347-353.
  43. Yun J, Mullarky E, Lu C, et al. Vitamin C selectively kills KRAS and BRAF mutant colorectal cancer cells by targeting GAPDH. Science. 2015 Dec 11;350(6266):1391-6.
  44. Su X, Shen Z, Yang Q, et al. Vitamin C kills thyroid cancer cells through ROS-dependent inhibition of MAPK/ERK and PI3K/AKT pathways via distinct mechanisms. Theranostics. 2019 Jun 9;9(15):4461-4473.
  45. Su X, Shen Z, Yang Q, et al. Vitamin C kills thyroid cancer cells through ROS-dependent inhibition of MAPK/ERK and PI3K/AKT pathways via distinct mechanisms. Theranostics. 2019 Jun 9;9(15):4461-4473.
  46. Chen J, Qin F, Li Y, et al. High-Dose Vitamin C Tends to Kill Colorectal Cancer with High MALAT1 Expression. J Oncol. 2020 Nov 23;2020:2621308. doi: 10.1155/2020/2621308. PMID: 33293956; PMCID: PMC7714606.
  47. Zhao H, Fu W, Yang X, et al. High-dose vitamin C: A promising anti-tumor agent, insight from mechanisms, clinical research, and challenges. Genes Dis. 2025 Jun 27;13(2):101742. doi: 10.1016/j.gendis.2025.101742. PMID: 41403402; PMCID: PMC12704205.
  48. 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. 1976;73, 3685-3689.
  49. 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. 1978;75, 4538-4542.
  50. 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. 1979;301:687-690.
  51. 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. 1985;312:137-141.
  52. Levine M, Conry-Cantilena C, Wang Y, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proc Natl Acad Sci U S A. 1996 Apr 16;93(8):3704-9.
  53. Padayatty SJ, Sun H, Wang Y, et al. Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med. 2004;140:533-7.
  54. Bodeker KL, Smith BJ, Berg DJ, et al. A randomized trial of pharmacological ascorbate, gemcitabine, and nab-paclitaxel for metastatic pancreatic cancer. Redox Biol. 2024 Nov;77:103375. doi: 10.1016/j.redox.2024.103375. Epub 2024 Oct 2. PMID: 39369582; PMCID: PMC11491967.
  55. Petronek MS, Bodeker KL, Lee CY, et al. Iron-based biomarkers for personalizing pharmacological ascorbate therapy in glioblastoma: insights from a phase 2 clinical trial. J Neurooncol. 2024 Feb;166(3):493-501. doi: 10.1007/s11060-024-04571-z. Epub 2024 Jan 29. PMID: 38285244; PMCID: PMC13105400.
  56. Böttger F, Vallés-Martí A, Cahn L, Jimenez CR. High-dose intravenous vitamin C, a promising multi-targeting agent in the treatment of cancer. J Exp Clin Cancer Res. 2021 Oct 30;40(1):343. doi: 10.1186/s13046-021-02134-y. PMID: 34717701; PMCID: PMC8557029.
  57. Zasowska-Nowak A, Nowak PJ, Ciałkowska-Rysz A. High-Dose Vitamin C in Advanced-Stage Cancer Patients. Nutrients. 2021 Feb 26;13(3):735. doi: 10.3390/nu13030735. PMID: 33652579; PMCID: PMC7996511.
  58. Wang F, He MM, Xiao J, et al. A Randomized, Open-Label, Multicenter, Phase 3 Study of High-Dose Vitamin C Plus FOLFOX ± Bevacizumab versus FOLFOX ± Bevacizumab in Unresectable Untreated Metastatic Colorectal Cancer (VITALITY Study). Clin Cancer Res. 2022 Oct 3;28(19):4232-4239. doi: 10.1158/1078-0432.CCR-22-0655. PMID: 35929990; PMCID: PMC9527503.
  59. Fritz H, Flower G, Weeks L, et al. Intravenous vitamin C and cancer: a systematic review. Integr. Cancer Ther. 2014;13:280-300.
  60. Block G. Vitamin C and cancer prevention: the epidemiologic evidence. Am J Clin Nutr. 1991 Jan;53(1 Suppl):270S-282S.
  61. Block G. Vitamin C and cancer prevention: the epidemiologic evidence. Am J Clin Nutr. 1991 Jan;53(1 Suppl):270S-282S. doi: 10.1093/ajcn/53.1.270S. PMID: 1985398.
  62. Chen Z, Huang Y, Cao D, et al. Vitamin C Intake and Cancers: An Umbrella Review. Front Nutr. 2022 Jan 20;8:812394. doi: 10.3389/fnut.2021.812394. PMID: 35127793; PMCID: PMC8812486.
  63. Arshadi M, Ghazal N, Ghavidel F, et al. The association between vitamin C and breast cancer, prostate cancer and colorectal cancer: A systematic review and meta-analysis. Clin Nutr ESPEN. 2025;65:400-407. doi: 10.1016/j.clnesp.2024.12.001.
  64. Tran DV, Luu XQ, Tran HTT, Myung SK. Dietary and supplementary vitamin C intake and the risk of lung cancer: A meta‑analysis of cohort studies. Oncol Lett. 2023 Nov 10;27(1):10. doi: 10.3892/ol.2023.14144. PMID: 38034488; PMCID: PMC10688485.
  65. Zhong J, Li P, Zheng F, et al. Association between dietary vitamin C intake/blood level and risk of digestive system cancer: a systematic review and meta-analysis of prospective studies. Food Funct. 2024 Aug 12;15(16):8217-8237. doi: 10.1039/d4fo00350k. PMID: 39039956.
  66. Mikirova N, Casciari J, Riordan N, Hunninghake R. Clinical experience with intravenous administration of ascorbic acid: achievable levels in blood for different states of inflammation and disease in cancer patients. J Transl Med. 2013 Aug 15;11:191. doi: 10.1186/1479-5876-11-191.
  67. Carr AC, Cook J. Intravenous Vitamin C for Cancer Therapy – Identifying the Current Gaps in Our Knowledge. Front Physiol. 2018 Aug 23;9:1182. doi: 10.3389/fphys.2018.01182.
  68. Pauling L. Vitamin C and the Common Cold. W. H. Freeman and Company; First Edition edition. 1970.
  69. Pauling L. The significance of the evidence about ascorbic acid and the common cold. Proc Natl Acad Sci U S A. 1971;68:2678-81.
  70. Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews 2013, Issue 1. Art. No.: CD000980. DOI: 10.1002/14651858.CD000980.pub4.
  71. Hemilä H. Vitamin C and Infections. Nutrients. 2017 Mar 29;9(4):339. doi: 10.3390/nu9040339. PMID: 28353648; PMCID: PMC5409678.
  72. Levy TE. Curing the Incurable. Vitamin C, Infectious Diseases, and Toxins. 2011. LivOn Books. 2654 W. Horizon Ridge Pkwy, Henderson, NY 89052.
  73. Hickey S, Saul AW. Vitamin C: The Real Story, the Remarkable and Controversial Healing Factor. 2015. Basic Health Publication Inc. 28812 Top of the World Drive, Laguna Beach, CA 92651.
  74. Klenner FR. The treatment of poliomyelitis and other virus diseases with vitamin C. South Med Surg. 1949 Jul;111(7):209-14.
  75. Mikirova N, Hunninghake R. Effect of high dose vitamin C on Epstein-Barr viral infection. Med Sci Monit. 2014 May 3;20:725-32.
  76. Simon JA, Hudes ES. Relationship of ascorbic acid to blood lead levels. JAMA. 1999 Jun 23-30;281(24):2289-93.
  77. Cheng Y, Willett WC, Schwartz J, et al. Relation of nutrition to bone lead and blood lead levels in middle-aged to elderly men. The Normative Aging Study. Am J Epidemiol. 1998 Jun 15;147(12):1162-74.
  78. Dawson EB, Evans DR, Harris WA, et al. The effect of ascorbic acid supplementation on the blood lead levels of smokers. J Am Coll Nutr. 1999 Apr;18(2):166-70.
  79. Lihm H, Kim H, Chang H, Yoon M, Lee K, Choi J. Vitamin C modulates lead excretion in rats. Anat Cell Biol. 2013 Dec;46(4):239-45.
  80. Shawahna R, Zyoud A, Yahia EH, et al. Sub-chronic treatment with high doses of ascorbic acid reduces lead levels in hen eggs intentionally exposed to a concentrated source of lead: a pilot study. BMC Pharmacol Toxicol. 2020 Mar 2;21(1):17. doi: 10.1186/s40360-020-0389-4. https://doi.org/10.1186/s40360-020-0389-4
  81. The Role of Vitamin C in the Protection and Modulation of Genotoxic Damage Induced by Metals Associated with Oxidative Stress. 2017. IntechOpen, DOI: 10.5772/intechopen.68686. Available from: https://www.intechopen.com/chapters/55208
  82. Ali S, Awan Z, Mumtaz S, et al. Cardiac toxicity of heavy metals (cadmium and mercury) and pharmacological intervention by vitamin C in rabbits. Environ Sci Pollut Res Int. 2020 Aug;27(23):29266-29279.
  83. Gehin A, Guyon C, Nicod L. Glyphosate-induced antioxidant imbalance in HaCaT: The protective effect of Vitamins C and E. Environ Toxicol Pharmacol. 2006 Jul;22(1):27-34.
  84. Ghorbani Taherdehi F, Nikravesh MR, et al. Evaluating the Protective Role of Ascorbic Acid in Malathion-induced Testis Tissue Toxicity of Male Rats. Int J Prev Med. 2019 Apr 17;10:45. doi: 10.4103/ijpvm.IJPVM_253_17.
  85. Djeffal A, Messarah M, Boumendjel A, et al. Protective effects of vitamin C and selenium supplementation on methomyl-induced tissue oxidative stress in adult rats. Toxicol Ind Health. 2015 Jan;31(1):31-43.
  86. El-Gendy KS, Aly NM, Mahmoud FH, et al. The role of vitamin C as antioxidant in protection of oxidative stress induced by imidacloprid. Food Chem Toxicol. 2010 Jan;48(1):215-21.
  87. Khan PK, Sinha SP. Impact of higher doses of vitamin C in modulating pesticide genotoxicity. Teratog Carcinog Mutagen. 1994;14(4):175-81.
  88. Khan PK, Sinha SP. Ameliorating effect of vitamin C on murine sperm toxicity induced by three pesticides (endosulfan, phosphamidon and mancozeb). Mutagenesis. 1996 Jan;11(1):33-6.
  89. Khan PK, Sinha SP. Vitamin C mediated amelioration of pesticide genotoxicity in murine spermatocytes. Cytobios. 1994;80(323):199-204.
  90. Guo W, Huen K, Park JS, et al. Vitamin C intervention may lower the levels of persistent organic pollutants in blood of healthy women – A pilot study. Food Chem Toxicol. 2016 Jun;92:197-204.
  91. Khan PK, Sinha SP. Antimutagenic efficacy of higher doses of vitamin C. Mutat Res. 1993 Jan;298(3):157-61.
  92. Kanter M, Akpolat M. Vitamin C protects against ionizing radiation damage to goblet cells of the ileum in rats. Acta Histochem. 2008;110(6):481-90.
  93. Tao SM, Zhou F, Joseph et al. The effect of prophylactic oral vitamin C use on DNA double-strand breaks after abdominal contrast-enhanced CT: A preliminary study. Eur J Radiol. 2019 Aug;117:69-74.
  94. Konopacka M, Rzeszowska-Wolny J. Antioxidant vitamins C, E and beta-carotene reduce DNA damage before as well as after gamma-ray irradiation of human lymphocytes in vitro. Mutat Res. 2001 Apr 5;491(1-2):1-7.
  95. Konopacka M, Palyvoda O, Rzeszowska-Wolny J. Inhibitory effect of ascorbic acid post-treatment on radiation-induced chromosomal damage in human lymphocytes in vitro. Teratog Carcinog Mutagen. 2002;22(6):443-50.
  96. Waldren CA, Vannais DB, Ueno AM. A role for long-lived radicals (LLR) in radiation-induced mutation and persistent chromosomal instability: counteraction by ascorbate and RibCys but not DMSO. Mutat Res. 2004 Jul 13;551(1-2):255-65.
  97. Witenberg B, Kletter Y, Kalir HH, et al. Ascorbic acid inhibits apoptosis induced by X irradiation in HL60 myeloid leukemia cells. Radiat Res. 1999 Nov;152(5):468-78.
  98. Semelka RC, Armao DM, Elias J Jr, Huda W. Imaging strategies to reduce the risk of radiation in CT studies, including selective substitution with MRI. J Magn Reson Imaging. 2007 May;25(5):900-9.
  99. Berrington de Gonzalez A, Mahesh M, Kim KP, et al. Projected cancer risks from computed tomographic scans performed in the United States in 2007. Arch Intern Med. 2009 Dec 14;169(22):2071-7.
  100. https://www.webmd.com/cancer/can-ct-scans-lead-to-cancer (accessed 7/24/2021)
  101. Chalmers AH, Cowley DM, Brown JM. A possible etiological role for ascorbate in calculi formation. Clin Chem. 1986 Feb;32(2):333-6.
  102. Taylor EN, Fung TT, Curhan GC. DASH-style diet associates with reduced risk for kidney stones. J Am Soc Nephrol. 2009 Oct;20(10):2253-9
  103. Thomas LD, Elinder CG, Tiselius HG, et al. Ascorbic acid supplements and kidney stone incidence among men: a prospective study. JAMA Intern Med. 2013 Mar 11;173(5):386-8.
  104. Taylor EN, Stampfer MJ, Curhan GC. Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up. J Am Soc Nephrol 2004;15:3225-32.
  105. Curhan GC, Willett WC, Rimm EB, Stampfer MJ. A prospective study of the intake of vitamins C and B6, and the risk of kidney stones in men. J Urol 1996;155:1847-51.
  106. Curhan GC, Willett WC, Speizer FE, Stampfer MJ. Intake of vitamins B6 and C and the risk of kidney stones in women. J Am Soc Nephrol 1999;10:840-5.
  107. Schwille PO, Schmiedl A, Herrmann U, et al. Ascorbic acid in idiopathic recurrent calcium urolithiasis in humans–does it have an abettor role in oxalate, and calcium oxalate crystallization? Urol Res. 2000 Jun;28(3):167-77.
  108. https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/
  109. Bendich A, Langseth L. The health effects of vitamin C supplementation: a review. J Am Coll Nutr. 1995 Apr;14(2):124-36. doi: 10.1080/07315724.1995.10718484. Erratum in: J Am Coll Nutr 1995 Aug;14(4):398. Erratum in: J Am Coll Nutr 1995 Jun;14(3):218. PMID: 7790686.
Scroll to Top