A clinical trial involving 109 people with pre-cancerous blood conditions and early-stage blood cancers has found that taking 1,000 mg of vitamin C daily was associated with significantly better overall survival than taking a placebo. The study, conducted by researchers from the University of Copenhagen, Van Andel Institute and collaborating institutions in Denmark and the United States, reported a 65% lower mortality hazard in an exploratory analysis after approximately three years of follow-up.
The findings have attracted attention because vitamin C is an inexpensive and widely available nutrient. However, the results should not be interpreted as evidence that taking vitamin C supplements reduces mortality among healthy people or prevents cancer generally. The research, known as the EVITA trial, was a relatively small Phase 2 study involving people with specific blood disorders. Its primary endpoint was not met, and researchers say a larger Phase 3 clinical trial is necessary to confirm the survival findings.
What Did the Vitamin C Trial Find?
The EVITA study, short for Epigenetics, Vitamin C, and Abnormal Hematopoiesis, investigated whether oral vitamin C supplementation could influence the progression of abnormal blood cells and improve clinical outcomes.
Researchers enrolled 109 adults diagnosed with clonal cytopenia of undetermined significance (CCUS) or lower-risk myeloid malignancies. These conditions can increase the risk of developing more serious blood cancers, including acute myeloid leukemia (AML).
Participants were randomly divided into two groups:
- Vitamin C group: 55 participants received 1,000 mg of oral vitamin C daily.
- Placebo group: 54 participants received a placebo without vitamin C.
The treatment period lasted 12 months, followed by longer-term monitoring of disease progression and survival.
The study found that participants receiving vitamin C had significantly better overall survival in an exploratory analysis.
| Trial detail | Findings |
|---|---|
| Study name | EVITA |
| Trial phase | Phase 2 |
| Total participants | 109 |
| Vitamin C group | 55 |
| Placebo group | 54 |
| Daily vitamin C dose | 1,000 mg |
| Treatment duration | 12 months |
| Follow-up | Approximately three years |
| Reported survival hazard ratio | 0.35 |
| Estimated reduction in mortality hazard | 65% |
The hazard ratio of 0.35 means the estimated hazard of death in the vitamin C group was 65% lower than in the placebo group during the analysed follow-up period. It does not mean that 65% fewer people will die in every population or that an individual can reduce their personal mortality risk by taking the supplement.
The Primary Endpoint Was Not Achieved
One of the most important details is that the trial did not achieve its primary endpoint.
Researchers initially wanted to determine whether vitamin C could change the growth rate of abnormal blood-cell clones. These abnormal cell populations can expand over time and may contribute to the development of blood cancers.
However, the researchers found no statistically significant difference in median clonal growth rates between the vitamin C and placebo groups.
The reported difference was -0.016, with a 95% confidence interval ranging from -0.096 to 0.064 and a p-value of 0.70.
This means the study did not demonstrate that vitamin C significantly slowed the growth of abnormal blood-cell populations.
The survival improvement emerged from an exploratory analysis of secondary outcomes. Although statistically significant, exploratory findings are generally considered less conclusive than results from a successful primary endpoint.
This distinction is important when interpreting the headline. The study provides an encouraging signal that deserves further investigation, not definitive evidence of a new cancer-prevention treatment.
Why Are Scientists Investigating Vitamin C and Leukemia?
Vitamin C is best known for its role in immune function, collagen production, wound healing and protection against oxidative damage.
However, researchers are also investigating its role in regulating how genes behave.
Vitamin C acts as a cofactor for enzymes called TET enzymes, which are involved in DNA demethylation and epigenetic regulation. These processes help regulate whether particular genes are active or inactive.
One of these enzymes, TET2, is particularly relevant to blood-cell development. Mutations in the TET2 gene are commonly associated with abnormal blood-cell production and certain forms of leukemia.
Researchers believe that restoring vitamin C levels could potentially support the normal activity of TET enzymes and influence the biological processes involved in the development of blood cancers.
The EVITA trial was designed partly around this biological theory.
However, the findings do not establish that vitamin C directly prevents leukemia by repairing TET2 mutations. More research is needed to understand the biological mechanisms behind the observed survival difference.
Vitamin C Group Experienced Fewer Serious Adverse Events
The trial also reported differences in serious adverse events between the two groups.
Among participants receiving vitamin C, 18 out of 55 experienced serious adverse events, compared with 30 out of 53 participants in the placebo group for whom the relevant data were available.
| Outcome | Vitamin C group | Placebo group |
|---|---|---|
| Participants with serious adverse events | 18 | 30 |
| Percentage | 33% | 57% |
The researchers also observed differences in inflammatory cytokine patterns, which are connected to the body’s immune and inflammatory responses.
These findings provide additional information about the potential biological effects of vitamin C in this particular patient population.
However, the small sample size means that the safety findings should not be treated as proof that high-dose supplementation is risk-free for everyone.
Who Were the Participants in the Study?
The trial did not recruit healthy adults from the general population.
Instead, it focused on people with two specific categories of blood conditions.
Clonal cytopenia of undetermined significance (CCUS) is a condition in which a person has low blood-cell counts and detectable genetic changes in blood-forming cells. It can increase the risk of developing a blood cancer, although progression is not inevitable.
Myelodysplastic syndromes (MDS) are a group of disorders in which bone marrow produces abnormal or insufficient blood cells. Some forms can progress to acute myeloid leukemia.
These conditions require specialist medical monitoring because their progression and treatment needs vary considerably between individuals.
The researchers were investigating whether vitamin C could become a relatively accessible intervention for patients who have limited options for preventing disease progression.
The results cannot automatically be applied to people without these conditions.
Does This Mean Everyone Should Take 1,000 mg of Vitamin C?
No. The study does not establish that healthy people should start taking 1,000 mg of vitamin C every day.
For adults, the recommended daily intake is approximately 90 mg for men and 75 mg for women under US dietary reference guidelines. Vitamin C can be obtained from fruits and vegetables, including oranges, guavas, lemons, amla, strawberries, peppers and broccoli.
The US adult tolerable upper intake level is 2,000 mg daily from all sources. This is a safety limit, not a recommended daily target.
Taking large amounts of vitamin C can cause diarrhoea, nausea and abdominal cramps. People with kidney disorders or a history of certain kidney stones should be particularly cautious. High-dose vitamin C can also increase iron absorption, which may be problematic for people with iron-overload disorders.
People receiving cancer treatment should discuss supplements with their treating medical team because vitamin C may interact with certain treatments.
The 1,000 mg dose in the EVITA trial was studied under controlled clinical conditions. It should not be treated as a general prescription for cancer prevention or longer life.
Researchers Call for a Larger Phase 3 Trial
The researchers say the findings justify further investigation through a larger Phase 3 clinical trial.
A larger study could help determine whether the survival advantage observed in EVITA is reproducible across a broader group of patients.
It could also clarify which patients are most likely to benefit, whether vitamin C has different effects across specific blood disorders and how changes in biological markers relate to long-term outcomes.
Professor Kirsten Grønbæk of the University of Copenhagen, who led the international trial, has described the findings as promising but preliminary. The research team has emphasised that it is too early to make definitive treatment recommendations.
The study was published in the journal Cancer in 2026.
The Bigger Picture
The EVITA trial adds to growing scientific interest in cancer interception, an approach that attempts to intervene before a disease develops into an advanced or aggressive form. Rather than treating established cancer, researchers are investigating whether biological changes associated with early disease can be influenced before progression occurs.
Vitamin C is particularly interesting because it is inexpensive, widely available and has established biological functions. However, a promising result in a small trial is not enough to establish a new medical treatment. The failure to meet the primary endpoint makes independent confirmation especially important.
For the wider medical community, the research offers a reason to investigate vitamin C’s role in early-stage blood disorders more closely, but not a reason to replace established medical monitoring or treatment.
Looking Ahead
The next major step will be a larger Phase 3 trial to determine whether the survival benefit observed in EVITA can be confirmed. Researchers will need to establish whether the effect is consistent, identify which patients may benefit and better understand the relationship between vitamin C, TET enzymes and abnormal blood-cell development.
Until stronger evidence becomes available, people should not take high-dose vitamin C supplements to prevent leukemia or reduce mortality. The current findings are promising for a specific group of patients, but they do not establish a general health benefit for everyone. The distinction between an encouraging clinical signal and a proven treatment will be central to understanding what this research ultimately means.
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