Vitamin C in health, disease and supplements
What it found
A collection of papers looks at what vitamin C does in the body, from bones and sleep to cancer treatment.
It found mixed results, with benefits in some areas but not others.
What they found
Studies in people
Dialysis patients
In people on hemodialysis, giving vitamin C by mouth or vein brought its blood levels back to normal. This also reduced inflammation and oxidative stress markers, but patients with high ferritin levels may have more oxidative damage after treatment.
Bone density
Studies in people found that eating more vitamin C is linked to higher bone mineral density. Some observations suggest low vitamin C may be tied to osteoporosis, but more trials are needed to know if supplements help.
Sleep and exercise
In people, taking vitamin C did not improve physical performance in trained or untrained subjects, even at high doses. But it did improve sleep quality and reduced sleep disturbances and symptoms of sleep movement disorders.
Cancer treatment
Clinical trials in people with advanced cancer did not show that high-dose intravenous vitamin C has significant anti-cancer activity or boosts chemotherapy. It did improve quality of life and relieve pain, fatigue, nausea and sleep problems, so it might be used in palliative care.
Eye and skin
Vitamin C is concentrated in the eye and can absorb UV light, acting as a natural sunscreen. There is some evidence it may prevent nuclear cataract after vitrectomy, but this needs more study.
Pro-oxidant effects
In healthy people, vitamin C can sometimes act as a pro-oxidant, increasing markers of DNA damage in blood and urine. This may actually help by boosting DNA repair enzymes.
What the authors conclude
- They say that giving vitamin C to dialysis patients normalized levels and reduced inflammation and oxidative stress, but caution about high ferritin.
- They note that more controlled trials are needed to see if vitamin C can prevent osteoporosis or help as add-on therapy.
- They conclude that high-dose intravenous vitamin C should be considered for palliative care, not as an anti-cancer treatment.
How it was done
The authors wanted to gather current knowledge on vitamin C's role in various health conditions and resolve debates about its effects.
They put together 10 peer-reviewed papers, including nine reviews and one original study, covering topics like osteoporosis, sleep, exercise, oxidative stress in dialysis patients, eye cataract, skin, and high-dose infusions in cancer.
What it can’t tell you
- This is a summary of a collection of papers, not a single new study, so it cannot provide new data on cause and effect.
- Many findings come from different types of studies, so it is hard to draw firm conclusions about vitamin C's effects in all situations.
Who paid
- Conflicts
- The author declares no conflict of interest.
- Authors work at
- Medical University of Lodz, Poland
The paper
- Title
- Vitamin C in Human Health and Disease
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Nowak D (2021). Vitamin C in Human Health and Disease. Nutrients. doi:10.3390/nu13051595Free full textPubMed 34064549DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error