Short answer: not in the way researchers hoped — but a new trial turned up a surprise worth watching.
I recently presented a 2026 study to colleagues that tested a simple idea. Could a daily vitamin C tablet slow down early, slow-growing blood disorders that sometimes turn into leukaemia? The trial, called EVITA, was run by Danish and US researchers and published in the journal Cancer.
The headline that will travel is "vitamin C cut deaths by two-thirds". The real story is more interesting, and more cautious. Here it is in plain language.
Who was this study about?
The trial included people with early or "lower-risk" myeloid conditions. These are disorders of the bone marrow, the factory that makes your blood cells.
In all of them, a single blood stem cell picks up a genetic change and starts copying itself a little too successfully. Over years, its offspring (a "clone") can take up more and more of the marrow. The conditions included were:
- CCUS (clonal cytopenia of undetermined significance): a clone is present and blood counts are a bit low, but it isn't a cancer.
- Lower-risk MDS (myelodysplastic syndrome): the marrow makes blood cells that don't work or mature properly.
- Early CMML (chronic myelomonocytic leukaemia): a slow-growing condition with too many of one type of white cell.
A minority of people with these conditions go on to develop acute myeloid leukaemia (AML). For most, the current approach is "watch and wait" with regular blood tests. That is why a cheap, safe tablet that slowed things down would be so appealing.
Why would vitamin C help?
Think of your DNA as a long instruction manual. Cells stick small chemical "off" tags on pages they don't need. To grow into mature, working blood cells, stem cells must peel some of those tags off again.
The main "eraser" for this job is an enzyme called TET2. Damage to TET2 is one of the most common genetic changes in these conditions, and it helps the abnormal clone thrive. TET2 can't work without a helper, and that helper is vitamin C.
Most people with a faulty TET2 still have one working copy. The theory was simple: top up vitamin C, and that remaining copy might work harder, slowing the clone.
How the trial worked
This was a well-designed "gold standard" study: people were assigned by chance, and nobody knew who was getting the real tablet.
The main thing the researchers measured was whether the abnormal clone grew more slowly with vitamin C. They also tracked blood counts, disease progression and safety.
What the trial found
The main question got a clear answer: vitamin C did not slow the growth of the abnormal clone.
- Many people were low in vitamin C to begin with. More than half of participants had deficient or borderline levels at the start.
- The tablets worked as a supplement. Blood vitamin C in the treated group rose to the "topped-up" level the body can hold and stayed there. The placebo group stayed flat.
- The clone didn't shrink or slow down. This was the trial's main goal, and the two groups looked the same.
- No change in the DNA "tags" either. The chemical marks vitamin C was supposed to help remove did not change measurably.
- No clear difference in progression. Nine people on placebo and five on vitamin C progressed to a more advanced disease. With numbers this small, that gap could easily be chance.
- It was safe. Side effects were mild: some stomach upset, and one kidney stone in a person who had had stones before.
So, as an anti-leukaemia treatment, vitamin C didn't do what the science predicted. Then came the twist.
The surprise: fewer deaths
When the researchers followed everyone for about three years, fewer people had died in the vitamin C group: 11 compared with 24. On paper, that is roughly a two-thirds lower risk of death.
Look at what people died of. Very few deaths were from leukaemia. Most were from serious bacterial infections, and that is where the gap was biggest. During the treatment year, pneumonia was also far less common with vitamin C.
This fits with what we already know: vitamin C matters for the white cells that fight infection. So if the effect is real, vitamin C may have helped by fixing a deficiency and supporting the immune system, not by attacking the disease.
Why doctors aren't celebrating yet
A two-thirds drop in deaths from a vitamin would be remarkable. Most proven treatments for these conditions don't come close. That alone is a reason for caution.
None of this means the finding is wrong. It means it is a strong lead rather than an answer. The right next step is a larger trial designed specifically to test survival and infections, ideally in people who start out low in vitamin C.
What does this mean if you have one of these conditions?
Vitamin C is not a treatment for MDS, CMML or CCUS, and this trial doesn't change that. But it is a useful reminder that nutrition matters.
- Avoiding deficiency is sensible for everyone. Fruit and vegetables such as capsicum, kiwifruit, citrus, berries and broccoli are excellent sources. If your diet is limited, a modest supplement is reasonable.
- Don't take it as a cancer treatment. There is no evidence it slows the disease itself.
- Check first if you receive regular blood transfusions. Vitamin C increases iron absorption, and transfused patients often carry too much iron already. If you take iron-removing medicine, your doctor may allow only a small dose, and only at the right time.
- Check first if you have had kidney stones or kidney disease. High-dose vitamin C can add to stone risk.
- Blood tests for vitamin C are tricky. The sample has to be processed within minutes, so not every lab offers it. Ask your haematologist before ordering one.
Most importantly, talk to your haematologist before starting any supplement. Some interact with your treatment or blood tests.
The bottom line
- Vitamin C was meant to slow the abnormal clone. It didn't.
- It was safe, and it fixed a deficiency that turned out to be common.
- Fewer people died in the vitamin C group, mostly because of fewer serious infections. That is intriguing but not yet proven.
- A larger trial, designed to test survival and infections directly, is the right next step.
Until then: eat well, avoid deficiency, don't treat vitamin C as a leukaemia cure, and check with your haematologist before adding supplements.
This article is general information and not personal medical advice.