The renewed interest comes from research into high doses of vitamin C given intravenously, rather than through ordinary tablets.
Scientists say intravenous treatment can produce much higher levels of vitamin C in the blood and may cause biological effects that cannot be achieved by taking supplements.
The story dates back to the 1970s, when American scientist Linus Pauling, a two time Nobel Prize winner, worked with Scottish doctor Ewan Cameron to investigate high doses of vitamin C in patients with advanced cancer.
Their early work suggested that some patients receiving large amounts of vitamin C lived longer and experienced an improved quality of life.
However, two major trials conducted by the Mayo Clinic later found no survival benefit from vitamin C pills.
Scientists now believe the difference between intravenous vitamin C and tablets may help explain the conflicting results.
When vitamin C is taken orally, the digestive system limits how much can enter the bloodstream.
Intravenous administration, however, can raise blood concentrations to levels many times higher than those reached through tablets.
At very high concentrations, vitamin C may behave differently from its usual role as an antioxidant.
Laboratory studies suggest it can help generate hydrogen peroxide, a reactive substance that can damage cells.
Cancer cells may be particularly vulnerable because they are already under stress and may have weaker systems for dealing with such damage.
Researchers have tested intravenous vitamin C in small studies involving patients with difficult to treat cancers, including ovarian, pancreatic and brain tumors.
Some studies suggest that combining vitamin C infusions with chemotherapy could help certain patients live longer or experience fewer treatment related side effects.
Other studies, however, have found no clear benefit. Researchers say the studies remain too small and varied to provide firm conclusions.
One of the more consistent findings has involved quality of life. Some patients receiving vitamin C alongside chemotherapy have reported less fatigue, pain and nausea.
Scientists are also investigating whether high levels of vitamin C could affect cancer cell growth, DNA regulation, responses to low oxygen and the immune system.
These findings are still being studied and some remain preliminary.
Researchers therefore say Pauling was partly right to believe vitamin C could have a role in cancer treatment, but he overstated its benefits and was wrong to promote vitamin C tablets as a powerful cancer cure.
For now, large and definitive clinical trials have not shown that high dose intravenous vitamin C can extend the lives of most cancer patients.
Scientists say it should remain an experimental treatment studied in clinical trials or carefully supervised medical settings, rather than a replacement for established cancer therapies.
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