A daily dose of vitamin C may help people with precancerous blood conditions or early-stage blood cancers live longer, according to a clinical trial that found encouraging results.
The study, EVITA phase 2, a follow-up to the EVITA trial from 2016, included 109 patients with either clonal cytopenia of undetermined significance (CCUS), a precancerous blood condition, or myelodysplastic syndrome (MDS), a blood disorder that can develop into acute myeloid leukemia (AML), an aggressive type of blood cancer.
Researchers randomly assigned participants to take either 1,000 mg of oral vitamin C daily for 12 months or a placebo containing no vitamin C. Neither the patients nor the clinical staff knew who had received the supplement until the study ended. None of the participants were receiving cancer treatment during the trial.
The authors noted that more than half of the participants had insufficient levels of vitamin C at the beginning of the study. Among those who received the supplement, blood vitamin C levels returned to normal.
Patients taking vitamin C also experienced fewer adverse events during the study and its follow-up period. Researchers additionally observed changes in certain cytokines, molecules that help cells communicate, including immune cells. These changes were associated with more favorable outcomes and may point to effects on inflammatory processes involved in the growth and progression of abnormal blood cells.
"In our trial, we see that vitamin C correlates with a change in inflammatory signaling that aligns with a better outcome," Kirsten Grønbæk, a hematologist and professor at the University of Copenhagen who led the study, told Newsweek. However, she added that researchers believe multiple factors are likely contributing to the findings.
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One of the most encouraging results emerged from an exploratory analysis of survival. In an exploratory analysis, participants who received vitamin C were significantly more likely to be alive after approximately three years of follow-up than those who received placebo.
However, according to the researchers, Vitamin C did not significantly slow the expansion of abnormal blood cells. The trial also did not establish that the supplement prevents leukemia or definitively improves survival.
"Importantly, we did not see significant differences in baseline characteristics between the participants in the placebo group compared to the vitamin C group," Grønbæk said.
The findings build on research into vitamin C's role in regulating gene activity and normal cell development. Scientists are particularly interested in its relationship with TET2, an enzyme that helps regulate genes and maintain normal cellular function. Mutations affecting TET2 are frequently found in leukemia and related blood disorders. Vitamin C supports TET2 activity, raising questions about whether supplementation could help restore normal gene regulation in blood cells at risk of becoming cancerous.
The EVITA trial did not establish whether this mechanism explains the observed results.
Dr. Lucy Hooper, a private GP and co-founder of Coyne Medical, who was not involved in the research, said there is a plausible biological explanation for the results because vitamin C acts as an important cofactor for TET2, which is frequently disrupted in myeloid blood disorders and cancers.
She noted previous studies have found vitamin C deficiency can impair TET enzyme activity, while restoring vitamin C can improve its function and suppress abnormal blood cell proliferation.
"However, this was a relatively small trial. Although 109 patients were recruited, only 44 completed the full 12 months of vitamin C treatment. Importantly, the trial did not meet its primary endpoint, which was to demonstrate a reduction in the growth of abnormal blood cell clones," she said.
"The researchers did find an improvement in survival, which is certainly interesting, but this was an exploratory finding rather than the primary outcome the study was designed to investigate. So I think these results are encouraging enough to justify further research, but we need to be careful not to overinterpret them."
The study was conducted at four hospitals in Denmark and the United States by an international research team led by Professor Grønbæk. Its results were published in the American Cancer Society journal, Cancer.
The researchers see the findings as a potential step toward cancer interception, an approach that aims to intervene before cancer becomes established. For patients with precancerous blood conditions, who are often monitored for signs of disease progression, such an approach could eventually offer another avenue for care.
Still, the team emphasizes that larger studies are needed. A phase 3 clinical trial will be necessary to determine whether vitamin C reliably improves patients' outcomes.
Grønbæk said preparations for such a study are already underway and that researchers hope to launch a phase 3 trial in early 2027, while also investigating the biological mechanisms that could explain the survival difference between the vitamin C and placebo groups.
"At the 2026 American Society of Hematology Annual Meeting in December, we are going to present additional data from subgroup analyses," she added.
For now, the results offer a promising research lead, not a proven treatment. Although daily vitamin C corrected levels and was associated with a possible survival benefit, scientists have yet to establish whether the supplement can change the course of these blood conditions or prevent leukemia.
According to Hooper, if confirmed in larger trials, the potential impact could be significant.
"If something as simple as correcting a vitamin deficiency could help reduce that risk or improve survival, that would be a very welcome development. Vitamin C is inexpensive, widely available and generally well tolerated," she said.
However, she also cautioned that the wider context of research into vitamin C and cancer needs to also be considered.
"There have even been studies in breast cancer patients suggesting that taking antioxidant supplements during chemotherapy may be associated with worse outcomes, including an increased risk of recurrence.
"So, we shouldn’t assume that because vitamin C may be beneficial in one particular group of patients, it will necessarily be beneficial in other cancers, or at different stages of the disease."
Reference:
Grønbæk et al. Oral vitamin C supplementation in patients with clonal cytopenia of undetermined significance or lower‐risk myeloid malignancies: Results from EVITA, a phase 2 randomized, placebo‐controlled trial. Cancer, 2026; 132 (19) DOI: 10.1002/cncr.70549; https://pubmed.ncbi.nlm.nih.gov/42764731/