Many years ago it was suggested that taking large amounts of vitamin C supplements might help people who had cancer. But research trials, which looked at giving very high doses of vitamin C as tablets, did not show any benefit. Some enthusiastic supporters of alternative therapies continued to claim that vitamin C could help treat cancer but there was no good evidence for this.

However, recently researchers in the USA have discovered that cancer cells grown in the laboratory can be killed by high doses of vitamin C. This has renewed interest in studying vitamin C. New trials are being run to look at whether it can help to treat cancer in humans.

Unfortunately, there have been many occasions in cancer research when chemicals have looked effective against cancer cells in the lab, but haven’t been of any benefit when tested in patients. It is likely that the same will be true for ultra-high dose vitamin C therapy.

The doses of vitamin C that worked against cancer cells in the lab can’t be achieved in a person by taking the drug by mouth. Instead the vitamin C needs to be given into a vein (intravenously), through a drip. The trials will test giving Vitamin C in this way. High doses of intravenous vitamin C can cause serious side effects, including kidney damage and even kidney failure. So these trials are important both to discover if vitamin C given in this way is effective and to be sure that it is safe.

At present it's too soon to say what the tests will show, but certainly there is no reason to believe that taking vitamin C supplements (as tablets or as a drink) is of any value.

References

• Chen Q et al. Pharmacologic ascorbic acid concentrations selectively kill cancer cells: Action as a pro-drug to deliver hydrogen peroxide to tissues. Proceedings of the National Academy of Sciences of the United States, 2005;
  102: 13604-13609
• McAllister CJ et al. Renal failure secondary to massive infusion of vitamin C. JAMA 252; 1684. 1984
• Creagan ET et al. Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer. A controlled trial. New England Journal of Medicine. 1979 ;301(13):687-690.