Injections of vitamin C could halve the growth of cancerous tumours, research suggested yesterday. A study in the United States found that the vitamin could prove useful in treating cancers for which few other options currently exist.
However, experts warned that the benefits of the vitamin had yet to be demonstrated in human patients.
For the latest study, researchers from the National Institutes of Health in Bethesda, Maryland, examined the effects of vitamin C on cells grown in laboratories. Two hours of exposure to the vitamin significantly cut the survival of ovarian, pancreatic and brain tumour (glioblastoma) cancer cells.
Similar results were seen when cancer-ridden mice were injected with vitamin C. The therapy halved the growth of aggressive tumours, killing cancer cells while leaving healthy tissue unharmed.
It is thought the discovery could provide a new lifeline for patients with a poor prognosis and few other options.
Tackling cancer with vitamin C would also have the added advantage of being cheap compared with many of the very expensive cancer treatments.
Usually the body keeps a tight rein on high vitamin C levels in the blood. But the scientists found that the mechanism can be by-passed if the vitamin is injected straight into the blood instead of passing through the digestive system. When this is done it releases the powerful anti-cancer potential of the vitamin, according to the researchers writing in the journal Proceedings of the National Academy of Sciences.
The experiments showed that high levels of vitamin C in the blood generate hydrogen peroxide, which is lethal to tumours. The chemical forms in the spaces between cancer cells, damaging membranes, upsetting metabolism and scrambling the DNA of the tumour.
Even the growth of aggressive cancers was held back in the experiments. But healthy tissues appeared to resist the effects.
The use of high-dose vitamin C as an alternative cancer treatment has a long history dating back to the 1970s. Patients have taken the vitamin both by mouth and intravenously, but with mixed results in scientific trials. For this reason, claims that vitamin C can treat cancer have been dismissed by conventional cancer experts. But the new investigation, led by Dr Qi Chen, may help to start changing attitudes towards this approach.
The scientists said: "Pharmacologic concentrations of ascorbate (the chemical name for vitamin C] decreased tumour volumes 41-53 per cent in diverse cancer types known for both their aggressive growth and limited treatment options."
Dr Alison Ross, science information officer at Cancer Research UK, said: "This is encouraging work but it's at a very early stage because it involves cells grown in the lab and mice."