Daily vitamin C was linked to better survival in a 109-person phase 2 trial of people with precancerous blood disorders

In a randomised, double-blind, placebo-controlled phase 2 trial of 109 people with two precancerous blood conditions, those given 1,000 milligrams of vitamin C by mouth every day for a year were significantly more likely to be alive after about three years than those given a placebo. The survival result was an exploratory analysis, not the trial’s main question, and the main question came back negative. The researchers themselves call it a signal that needs a larger trial.

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Kirsten Grønbæk, a hematologist and professor at the University of Copenhagen who led the trial, said it is too early to make definitive recommendations based on the results. Peter A. Jones of the Van Andel Institute, a co-corresponding author, described the team as cautiously optimistic that the findings could one day translate into a simple way to protect people at risk of leukemia.

The EVITA Trial in Clonal Cytopenia and Lower-Risk MDS

The study, called EVITA, was published in CANCER, the American Cancer Society journal, in volume 132, issue 19, with Stine Ulrik Mikkelsen of the University of Copenhagen and Copenhagen University Hospital-Rigshospitalet as first author. The Van Andel Institute’s release is dated Sept. 21, 2026; ScienceDaily’s repost appeared Oct. 20, so the research is about a month old. This was a human trial, not an animal or laboratory study, though it is small and was designed to test something other than survival.

Participants had clonal cytopenia of undetermined significance (CCUS) or myelodysplastic syndrome (MDS), conditions in which blood-forming cells carry mutations and which can progress to acute myeloid leukemia. None were receiving cancer treatment when enrolled. CancerNetwork’s report on the paper describes the population as CCUS or lower-risk MDS, randomised one to one to vitamin C or placebo, and notes that patients with prior kidney stones were excluded. Sites were Copenhagen University Hospital-Rigshospitalet, Copenhagen University Hospital-Herlev, Aalborg University Hospital and Keck Hospital of USC.

The trial launched in 2017, after a 2016 pilot study of whether oral vitamin C could raise blood levels. More than half of participants were short of vitamin C at the start, and levels returned to normal in the supplement group.

The placebo was indistinguishable from the vitamin C capsules in appearance, taste and smell, and neither participants nor study staff knew the assignments until the trial ended. Follow-up continued beyond the 12-month treatment period, which is where the roughly three-year survival comparison comes from. Mikkelsen said the early pilot work was critical for developing the trial.

The survival figures, and their exploratory status

CancerNetwork reported the exploratory overall survival result as a hazard ratio of 0.35 (95% confidence interval 0.17 to 0.71; P = .0025) favoring vitamin C. A hazard ratio of 0.35 would mean a much lower rate of death in the vitamin C arm, but the interval is wide, and a result chosen after the primary endpoint was missed is hypothesis-generating. The news releases give no survival percentages or death counts per arm, and the CCUS and MDS split was not reported. The hazard ratio figure comes from that secondary report; the paper itself could not be opened.

The primary endpoint, a reduction in the growth rate of the abnormal blood-cell clones, was not met: vitamin C did not significantly slow the expansion of abnormal cells, the measure commonly used to track progression toward leukemia. Participants on vitamin C had fewer adverse events during the trial and follow-up, and cytokine levels, the immune signaling molecules the team measured, shifted in ways linked with more favorable outcomes. CancerNetwork also said gastrointestinal adverse effects, mainly gastritis, occurred in 3 of 54 patients.

Mechanism, Confounding and the Phase 3 Question

Vitamin C supports TET2, an enzyme that regulates gene activity and is frequently mutated in leukemia and related blood disorders, and the release points to earlier cancer-model experiments. Those experiments do not establish that vitamin C caused the survival difference. CancerNetwork reported that the mechanism behind the survival difference is unclear, and that the investigators tried to exclude differences between the groups without explaining the result. HCPLive likewise noted that additional analyses are ongoing.

Casey O’Connell, lead clinician at USC’s site and holder of the Lawrence and Jane Kelly Chair in Hematology, noted in the release that no one wants to hear that they have a condition that increases leukemia risk, and that the trial was an effort to address the factors that drive leukemia development in people already carrying these diagnoses. In the release Jones said the team is exploring whether vitamin C may help restore normal epigenetic function in blood cells at risk of becoming leukemia, an explanation that remains a hypothesis rather than a result. The next step the investigators describe is a phase 3 trial with all-cause mortality as the primary endpoint. The work was funded by the Van Andel Institute through the VAI-SU2C Epigenetics Dream Team, the Danish Cancer Society and Greater Copenhagen Health Science Partners.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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