Most people think of vitamin C as something for a winter cold. For decades, it has been one of the cheapest supplements on the shelf. But for one group of patients, it may now mean something very different.
In a phase 2 trial published in 2026 in the journal Cancer, researchers followed 109 adults with precancerous or low-risk blood cancers. Half took 1,000 mg of oral vitamin C every day for a year. The others got a placebo.
After roughly three years of follow-up, 11 people in the vitamin C group had died. In the placebo group, the number was 24. That translated to about a 65 percent lower risk of dying on vitamin C.
The patients had either clonal cytopenia of undetermined significance (CCUS) or lower-risk myelodysplastic syndrome. These are bone-marrow conditions in which the body produces faulty blood cells. In some people, the condition eventually progresses to acute myeloid leukemia.
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The trial missed its own main goal
The researchers, led by Kirsten Grønbæk at the University of Copenhagen, had set out to see whether vitamin C would slow the growth of abnormal cells. It did not. On that primary measure, vitamin C and placebo looked the same.
The survival benefit turned up as a secondary finding. Even so, the gap between the two groups was wide. The team at the Van Andel Institute in Michigan also saw changes in inflammatory signaling molecules called cytokines.
Those shifts went in a direction linked to better outcomes.
Side effects also leaned in vitamin C's favor. Serious events occurred in roughly a third of people on vitamin C. In the placebo group, about half had a serious event. Stomach complaints were more common in the vitamin C group.
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What this does not mean for your supplement shelf
A phase 2 trial is designed to spot signals, not to prove benefit. The researchers were clear that patients should not read this as a reason to start high-dose vitamin C on their own.
"These exciting preliminary findings lay the groundwork for a larger clinical trial to explore vitamin C as a possible way to improve patient outcomes," said Grønbæk.
Anyone with CCUS or an early blood disorder should talk to their doctor before starting any supplement. The next step for the researchers is a larger phase 3 trial that can confirm, or rule out, the survival effect.
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This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.