Why Vitamin C Might Protect You Against Cancer

For decades, Nobel prize winning biochemist Linus Pauling advocated high-dose vitamin C to help prevent cancer. For the most part, doctors dismissed his ideas as unproven. But more recent research suggests that vitamin C might protect people from certain types of cancer or help in treating it. Some of the research requires a mental leap from mice to humans, but other studies are based on clinical trials. How might it work?

High-Dose Intravenous Vitamin C Treats Pancreatic Cancer

Q. I read your article about using vitamin C to treat cancer. High-dose intravenous vitamin C appears to have pro-oxidative activity, rather than the antioxidant activity it exerts when taken orally. This may explain its devastating effect upon cancer cells. Research was published in Nutrients (May 21, 2020).

It is unfortunate that the U.S. medical establishment appears to be so biased against vitamin C therapy. Perhaps that’s because its use does not generate large profits as many pharmaceutical drugs do.

A. Cancer researchers at the University of Iowa studied the effects of high-dose intravenous vitamin C against stage IV metastatic pancreatic cancer (Redox Biology, Nov. 2024).  The randomized trial compared standard cancer treatment to standard treatment plus IV vitamin C. When vitamin C was added, it doubled median overall survival time from 8 months to 16 months. Patients did not experience serious adverse reactions.

German oncologists took note of these results and used them to treat a 43-year-old man whose metastatic intestinal cancer was not responding to standard chemotherapy (Redox Biology, Sep. 2025). When they added high-dose vitamin C to his next round of treatment, the tumor regressed, resulting in clinical benefit for the patient.

To provide some context, scientists presented a report about a new anticancer drug at the most recent meetings of the American Society of Clinical Oncology. The results from a clinical trial of daraxonrasib produced a standing ovation and headlines around the world. This breakthrough improved overall median survival for metastatic pancreatic cancer from 6.7 months to 13.2 months (New England Journal of Medicine, May 31, 2026).

How Vitamin C Might Protect People Against Cancer

What about prevention? A study published several years ago in the journal Nature shows that vitamin C may help reduce the likelihood of leukemia (Nature, Aug. 21, 2017). Stem cells require a lot of ascorbate, also known as vitamin C. These are the cells that lead to the development of all the cells that circulate in the blood.

When levels of ascorbate fall, the epigenome is damaged. At that point, the stem cells become more likely to transform into leukemia cells instead of ordinary white blood cells. This research was carried out in mice and confirmed in test-tube studies. Other scientists, working independently, have confirmed this effect (Frontiers in Genetics, May 4, 2021).

Should You Take Vitamin C?

As a result, this research suggests that people who might be at higher risk for leukemia should be especially conscientious about getting adequate amounts of vitamin C from their diet or from supplements.

Where Will You Find Vitamin C?

Many fruits and vegetables are rich in ascorbate, which might help explain why a diet rich in fresh produce has been linked to a lower risk of cancer. The best sources include blueberries; broccoli and cauliflower; cantaloupe and other melons; citrus fruits such as grapefruit, oranges and tangerines; cranberries; green and red peppers; mango; papaya; pineapple; raspberries; spinach and other dark green leafy vegetables; strawberries; sweet potatoes; tomatoes; and watermelon.