High doses of vitamin C injected into the blood stream could be a safe and potentially effective form of cancer treatment, research suggests.
Vitamin C infusions up to 1,000 times higher than recommended intake levels selectively targeted tumour cells, increasing their death rate and sensitising them to radiation and chemotherapy, scientists found.
They also appeared to be safe, producing mild side effects such as frequent bathroom trips and a dry mouth.
Eleven brain cancer patients were given three infusions of vitamin C a week for two months followed by a further two per week for seven months while receiving standard radiotherapy and chemotherapy.
Tests showed that iron in their tumours reacted with the vitamin to form highly reactive and destructive "free radical" hydrogen peroxide molecules.
The free radicals were thought to cause selective DNA damage in cancerous, but not healthy, cells. This in turn was expected to lead to enhanced cancer cell death as well as sensitisation to radiation and chemotherapy drugs.
US researcher Dr Garry Buettner, from the University of Iowa, said: "This paper reveals a metabolic frailty in cancer cells that is based on their own production of oxidizing agents that allows us to utilise existing redox active compounds, like vitamin C, to sensitise cancer cells to radiation and chemotherapy."
The findings are published in the journal Cancer Cell.
The safety study sets the stage for larger Phase II trials investigating whether high-dose vitamin C injections can extend the lifespan of cancer patients.