Was Linus Pauling Right About Vitamin C and Cancer After All?

Linus Pauling won two unshared Nobel Prizes and helped establish our modern understanding of the chemical bond. Late in his career, he became convinced that megadoses of vitamin C could treat cancer, a claim that made him, in the eyes of much of mainstream medicine, a cautionary tale. When he died of cancer himself at 93, it seemed to confirm the verdict: brilliance in one field doesn’t guarantee wisdom in another.

Fifty years later, the picture looks less clear-cut.

Where Pauling’s story went wrong

In the 1970s, Pauling teamed up with Scottish physician Ewan Cameron and gave terminally ill cancer patients very large doses of vitamin C, first intravenously, then as tablets. Compared with similar patients who didn’t receive it, their treated group reportedly lived longer and felt better, in some cases by several times.

Two subsequent Mayo Clinic trials tried to confirm this and found nothing: patients taking vitamin C tablets lived no longer than those who didn’t. For most oncologists, that settled the question, and Pauling’s crusade was filed away as a well-meaning mistake.

The detail everyone missed

Here’s the twist: Pauling and Cameron’s original patients received vitamin C by IV, while the Mayo Clinic trials tested tablets only, and that difference turns out to matter enormously. The gut can only absorb so much vitamin C; past a certain dose, swallowing more tablets barely raises blood levels at all. An intravenous drip bypasses that limit entirely, pushing blood concentrations tens or even hundreds of times higher than any pill could achieve.

At those extreme concentrations, vitamin C stops behaving like a vitamin and starts behaving more like a drug. At ordinary levels it’s a straightforward antioxidant, neutralizing harmful molecules and protecting cells. But at very high levels, especially in and around tumors, it can flip roles and help generate hydrogen peroxide, a reactive compound that damages cells.

Cancer cells appear to be unusually vulnerable to this effect. They divide rapidly, often in poorly oxygenated tissue, already generate excess reactive molecules of their own, and have overstretched internal repair systems. A sudden pulse of hydrogen peroxide can be enough to push them over the edge, damaging their DNA and energy-producing machinery. Healthy cells, under less baseline stress, tend to tolerate it far better, making high-dose IV vitamin C, in effect, a weak but somewhat selective chemotherapy-like agent, achievable only at doses tablets simply can’t reach.

What the newer evidence actually shows

Human evidence remains early and mixed. Small trials have delivered high-dose IV vitamin C to patients with difficult cancers, ovarian, pancreatic, and brain tumors among them, generally finding it can be given repeatedly without serious side effects, though caution is warranted for anyone with poor kidney function or certain inherited conditions.

Some studies suggest pairing vitamin C infusions with chemotherapy may modestly extend survival or ease side effects; others show no benefit at all. The trials are still too small and inconsistent to draw firm conclusions. The one relatively consistent signal is quality of life, patients receiving vitamin C alongside chemotherapy often report less fatigue, pain, and nausea, which matters even short of a cure.

Laboratory work also points to subtler roles: vitamin C influences enzymes involved in how DNA is chemically marked and read, and in how cells respond to low oxygen, both relevant to cancer biology. Some experiments show high vitamin C levels making cancer cells less aggressive and more sensitive to treatment, and there are early hints it may help the immune system recognize tumors, though that remains speculative.

Partly right, not vindicated

So was Pauling right? The fairest reading is that he was partly right, for reasons he didn’t fully understand, and that he overstated the case. Tablets don’t help, and vitamin C is nowhere near the universal remedy he once claimed. But his instinct that very high, intravenously delivered doses might behave differently in the body than everyday supplementation has held up.

What’s still missing are large, definitive randomized trials proving that IV vitamin C meaningfully extends survival for most cancer patients. Until that evidence exists, it belongs in clinical trials and carefully supervised medical settings, not in wellness clinics selling it as an immune boost.

Original papers:
Cameron & Pauling (1976), “Supplemental ascorbate in the supportive treatment of cancer,” PNAS
Padayatty et al., “Vitamin C pharmacokinetics: implications for oral and intravenous use”
Source article: Stebbing, J., “Vitamin C and cancer: was Nobel laureate Linus Pauling on to something?”, The Conversation (2026) 

Source: Was Linus Pauling Right About Vitamin C and Cancer After All?