Vitamin C May Be a Potent Adjunct to Cancer Treatment

Story at-a-glance

  • Research shows vitamin C is selectively cytotoxic to cancer cells when administered intravenously in high doses, and has a number of heart and cardiovascular benefits
  • When given intravenously at high doses, vitamin C produces a pro-oxidant effect, thereby generating hydrogen peroxide, which is ultimately what kills the cancer cells
  • Normal tissues are not harmed by the high levels of hydrogen peroxide generated because healthy cells have several ways of effectively removing it, thereby preventing buildup to toxic levels. Cancer cells lack this ability


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

By Dr. Mercola

Vitamin C is one of the most well-established traditional antioxidants known and its potent health benefits have been clearly demonstrated over time — especially for the prevention and treatment of infectious diseases.

Research has also shown that vitamin C is selectively cytotoxic to cancer cells when administered intravenously (IV) in high doses, and has a number of heart- and cardiovascular benefits.

From my perspective, vitamin C is a very useful supplement that should be part of most cancer treatment protocols. Vitamin D is another crucial anti-cancer component I’ve written about on numerous occasions.

How Vitamin C Kills Cancer Cells

In order for vitamin C to effectively kill cancer cells, you need to have a very high concentration of vitamin C in your blood, and the only way to obtain these extreme levels is through IV administration, although using oral liposomal vitamin C can approach effectiveness at a fraction of the price, improved convenience and cost.

By bypassing the digestive tract, IV administration results in blood levels up to 500 times higher than what you can achieve through the oral route.

The mechanism behind vitamin C’s ability to selectively target cancer cells has to do with the generation of hydrogen peroxide, which is ultimately what kills the cancer cells. As reported by the University of Iowa:1

“In a new study2,3 … Buettner and his colleagues have homed in on the biological details of how high-dose vitamin C kills cancer cells. The study shows that vitamin C breaks down easily, generating hydrogen peroxide, a so-called reactive oxygen species that can damage tissue and DNA.

The study also shows that tumor cells are much less capable of removing the damaging hydrogen peroxide than normal cells …

‘Thus, cancer cells are much more prone to damage and death from a high amount of hydrogen peroxide,’ says Buettner, a professor of radiation oncology and a member of Holden Comprehensive Cancer Center at the University of Iowa.

‘This explains how the very, very high levels of vitamin C used in our clinical trials do not affect normal tissue, but can be damaging to tumor tissue.’”

The reason normal tissues are not harmed by the high levels of hydrogen peroxide generated is that healthy cells have several ways of effectively removing it, thereby preventing buildup to toxic levels.

One of the primary pathways of removal is the enzyme catalase, and the study found that cells with reduced catalase activity were indeed more prone to die when exposed to high amounts of vitamin C.

This provides a hint at which cancers are likely the best candidates for high-dose vitamin C therapy — tumors with low catalase levels are likely to be the most responsive, whereas tumors with high catalase levels would be the least responsive. Next, the research team wants to develop methods to measure catalase in tumors.

Vitamin C Lowers Inflammation in Cancer Patients, and More

Another way vitamin C benefits cancer is by lowering inflammation in your body, as shown in a 2012 study.4,5,6

As a general rule, chronic inflammation is a hallmark of cancer, and here they found that IV vitamin C treatment helps lower pro-inflammatory cytokines and C-reactive protein — two inflammatory markers — and that these improvements correlate with a reduction in tumor size.

It also helps lower the risk of metastasis. A positive response was noted in 75 percent of patients. This study was done by scientist at the Riordan Clinic, which is the successor to Linus Pauling and his work on vitamin C. There is likely no clinic in the world with as much experience with vitamin C as the Riordan Clinic.

Riordan carried out a 15-year-long research project called RECNAC (cancer spelled backwards), which showed vitamin C was selectively cytotoxic against cancer cells.

Other research7,8 done by scientists at the Lewis Cantley of Weill Cornel Medicine in New York found high doses of vitamin C helps kill and eliminate colorectal cancer cells with certain genetic mutations. Other studies9 have shown high-dose vitamin C can help slow the growth of prostate-, pancreatic-, liver- and colon cancer cells.

Human studies also show IV vitamin C can help improve symptoms associated with cancer and cancer treatment, such as fatigue, nausea, vomiting, pain and loss of appetite, and improve overall quality of life.

Vitamin C for Infectious Diseases

Vitamin C may be best known for its ability to combat infectious disease. Dr. Thomas Levy’s book, “Curing the Incurable,” details these benefits.

A perfect real-world example is the dramatic case of Allan Smith, who contracted a serious case of swine flu and was brought back from the brink of death using a combination of IV and oral vitamin C.

The case report was sent to me by Levy, who noted that, to his knowledge, vitamin C “has never failed to cure an acute viral syndrome.” According to Albert Szent-Gyorgyi (who won the Nobel Prize in 1937 for his discovery of vitamin C), “health” occurs when there is an ample flow and interchange of electrons in your cells.

Impaired or poor electron flow and interchange equals “disease,” and when the flow and interchange ceases entirely, your cells die. Oxidation, caused by free radicals in your body, involves the loss of electrons.

Antioxidants, both from your diet and endogenously produced, counter the disease process caused by oxidation (loss of electrons) by supplying electrons. Vitamin C is a major antioxidant, and according to Levy, perhaps the most important electron donor to maintain optimal electron flow in your cells.

In 2005, the Orthomolecular Medicine News Service (a non-profit and non-commercial informational resource), published findings that vitamin C is an effective treatment against the dreaded bird flu and other viruses.10

As with cancer, extremely high doses are needed though — upwards of 200,000 to 300,000 milligrams (mg) of vitamin C, given intravenously. The reason for this is because the avian flu appears to “consume vitamin C very rapidly, similar to an acute viral hemorrhagic fever, somewhat like an Ebola infection.”

A number of other studies and clinical experiences also attest to vitamin C as a potent treatment strategy against all sorts of infectious diseases, including influenza,11 encephalitis and measles.12

Vitamin C for Sepsis

Vitamin C in combination with thiamine (B1) and hydrocortisone has also been shown to be dramatically helpful in the treatment of severe sepsis and septic shock. Sepsis is a life-threatening condition triggered by a systemic infection, caused by bacteria, viruses or parasites that ultimately affects the function of vital organs. Hospital-acquired infections that progress to sepsis is a significant cause of death.

As many as half of all in-hospital deaths are related to sepsis,13 and recent research published in the Canadian Medical Association Journal proposes sepsis should be recognized as a distinct cause of death in hospitals around the world.14 The cost of treating sepsis is high, topping $24 billion in 2014, with nearly 25 percent of all hospital charges attributed to the treatment of sepsis. As reported by Dr. Malcolm Kendrick, the study in question:15

“… demonstrates that if you give vitamin C (along with hydrocortisone and thiamine) for just over two days in patients admitted with sepsis (blood poisoning) the mortality rate falls from 40 percent to 8.5 percent. The mortality rate in low income countries is normally around 60 percent. Now, this was a small study, but it seems robust. It represents an almost five-fold reduction in mortality … ”

Vitamin C Is Also Good for Your Heart, Blood Vessels, Lungs and Eyes

Other studies focused on vitamin C shows it helps:

  • Decrease risk of post-operative atrial fibrillation after heart surgery, thereby reducing the risk of stroke and heart failure. It also reduced the length of hospitalization after heart surgery. Oral administration reduced the length of hospital stay by 7 percent (less than half a day), whereas IV shortened it by 16 percent (1.5 days)16,17
  • Reduce high blood pressure — likely by protecting your body's supply of nitric oxide (NO), a molecule that relaxes blood vessels. In one study,18 both the systolic and diastolic (top and bottom) readings were inversely associated with ascorbic acid levels. Specifically, women with the highest levels of ascorbic acid had about 4.6 mm Hg lower systolic and just over 6 mm Hg lower diastolic blood pressure compared to those with the lowest ascorbic acid levels
  • Reduce your risk of chronic obstructive pulmonary disease (COPD), especially among smokers. In one study, heavy smokers with the highest vitamin C intake had a 77 percent lower risk of COPD than those with the lowest intake.19 The mechanism for this effect is thought to be related to vitamin C’s ability to improve levels of vascular endothelial growth factor, and boost proliferation of alveolar cells in your lungs
  • Prevent heart attacks, primarily by reducing inflammation20
  • Protect your vision by improving the function of your retinal cells, and reduce your risk for cataracts by fighting oxidative stress

Important Contraindication for IV Vitamin C Treatment

While the evidence strongly supports the use of IV vitamin C in high doses for infections, inflammation and even cancer, it’s important to get your glucose-6-phosphate dehydrogenase (G6PD) checked beforehand. G6PD is an enzyme your red blood cells need to maintain membrane integrity. High-dose IV vitamin C is actually a strong PRO-oxidant, and giving a pro-oxidant to a G6PD-deficient individual can cause hemolysis (rupturing) of their red blood cells.

So, administering IV vitamin C is not for the novice! I strongly recommend getting it done by an experienced practitioner who uses the Riordan protocol or some other protocol that ensures its done in a safe manner. Fortunately, G6PC deficiency is relatively uncommon.

People of Mediterranean- and African decent are at greater risk, but it’s rare even in those groups. Still, while it’s not a great concern that will prevent its use in most people, should you happen to be that rare person with a G6PC deficiency, the ramifications of barreling ahead with high dose IV vitamin C could be disastrous.

General Vitamin C Dosage Suggestions

Dr. Ronald Hunninghake — chief medical officer at the Riordan Clinic who has supervised 60,000 IV administrations of vitamin C — discusses the use of vitamin C for health and cancer protocols in the featured video. For cancer, research by the Riordan Clinic suggests you need a vitamin C blood level of around 300 to 400 mg/dl to achieve selective cytotoxicity against cancer cells.

To reach that post-IV saturation level, you’d need to administer somewhere between 25 to 50 grams of vitamin C intravenously. That’s up to 300 times the normal amount of vitamin C you’d get from eating a healthy diet. It’s important to understand that these extremely high levels are really only indicated for the treatment of cancers and infectious diseases, not for everyday, general health.

This is because vitamin C starts to have a pro-oxidant effect at these extreme levels — this is in fact what causes the hydrogen peroxide to be created in the first place. In other words, the hydrogen peroxide is a pro-oxidant effect of the vitamin C, so it needs to be used judiciously. You can learn more about using vitamin C as an adjunct to your cancer protocol on the Riordan Clinic’s website.21

For everyday health, I believe your best bet is to eat a varied whole food diet, rich in vitamin C and other antioxidants, to avoid causing a nutritional imbalance.

For example, taking large doses of vitamin C (ascorbic acid) on a regular basis lowers your copper level, so if you are already deficient in copper and take high doses of vitamin C, you can compromise your immune system. So, while temporarily taking mega-doses of vitamin C supplements to combat a case of the cold or flu is unlikely to cause a problem, for long-term, daily use, you’re probably going to be better off simply squeezing some lemon juice into a glass of water and/or eating a vitamin C-rich diet.

Also remember that vitamin C is a water-soluble vitamin, so when you do take a supplement, it’s best to divide your daily dose and take it three times a day. Also, if you’re sensitive to vitamin C, you may experience diarrhea. This is an indication that you need to lower your dosage.

Lastly, evidence suggests liposomal vitamin C provides better absorption, so it’s my personal favorite. I always bring some liposomal vitamin C with me when I travel in case I or someone I travel with gets sick, and then I use two to four capsules every hour until better.


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