Is vitamin C one of the best cancer fighters and antioxidants known to man or does it actually cause cancer at relatively high doses, as a recent study suggests?

It's interesting to see just how far we've come, that a suggestion that vitamin C actually has pro oxidant properties and so is potentially carcinogenic should now be considered almost heretical in the quarters of nutritional medicine.

A disbelieving scientific community was finally won round to to Vitamin C's benefits in September, 1990, at the National Institutes of Health meeting, when scientist after scientist presented their research findings. Dr Balz Frei of Berkeley said he considered vitamin C "the most effective antioxidant in human blood plasma", and that some of the chemical reactions that cause cancer simply could not take place if vitamin C was present. Dr E Niki from the University of Tokyo stated that harmful free radicals are destroyed faster by vitamin C than by any other antioxidant.

Dr Gladys Block of the National Cancer Institute in the US reviewed the evidence of 46 studies. Thirty three of the studies concluded that vitamin C had a protective effect against cancer, and that people with high levels of vitamin C in their diet had half the chance of contracting cancer as those who had a low intake.

A year later and the magazine Science finally accepted that perhaps the argument for vitamin C was gaining "a little respect".

But respect is always a dangerous thing when it comes to medicine, and so the challenge from the University of Leicester is at least healthy for opening up the debate again. A research team, headed by Ian Podmore, gave a group of 30 healthy volunteers (16 females and 14 males aged between 17 and 49) either a placebo or 500 mg a day of vitamin C supplements. Unfortunately we know nothing else about these "healthy" volunteers, such as if they were smokers or heavy drinkers or vegetarians. It is a serious omission, and one often committed by scientists who still do not understand the significance of lifestyles.

Using gas chromatography mass spectometry technology, the researchers analysed the blood of the participants and found that, among those taking the supplements, there was a significant increase in the DNA markers that suggested greater pro oxidisation.

The research team's concern was about the antioxidant qualities of vitamin C above the 500 mg daily amount; below that they say that the supplement may well still have a positive effect (Nature, 9 April, 1998).

The Leicester study was certainly not the first to suggest that vitamin C causes cancer. Dr S Fukushima of Nagoya City University Medical School concluded nearly 15 years ago that an extremely high dose of sodium L-ascorbate around 5 per cent amplified the effects of bladder carcinogens under experimental conditions, "while a high dose (1 per cent) does not" (Cancer Res, 1983; 43: 4454-7).

But that was testing the sodium salt of the vitamin. When the more common ascorbic acid was tested, Fukushima reported that doses of 5 per cent did not cause cancer or promote bladder cancer (Cancer Res Fund, 1985; 16: 159-68).

So could it be that the Leicester researchers were testing sodium salt rather than ascorbic acid? Again, they do not say.

Certainly it has been proven that vitamin C has a paradoxical effect in cell cultures from cancer patients with acute nonlymphocyctic leukaemia and preleukaemia it enhanced cell growth in one third of all patients, but this does not apply to the Leicester study because the volunteers were all healthy.

In conventional medical circles, the jury's still out over whether vitamin C can, as Pauling and more recently Canadian biochemist Abram Hoffer maintain, improve survival rates once cancer has taken hold. Neither Pauling nor his original colleague Dr Ewan Cameron thought that vitamin C on its own could be a primary cancer therapy (research has shown, for example, that its effects are magnified when taken with vitamin K).

What was beginning to be accepted in conventional circles was the protective quality of the vitamin, and it is this which the Leicester team is questioning, as have other researchers before them.

Most of the other objections have eventually been disproved will the Leicester study suffer the same fate? Certainly it must be remembered that a test among 15 people half of the 30 original participants were given a placebo is hardly grounds to make nutritional medicine take a backward step. But, as all the best medical studies say, it's worthy of further research. . . but any chance of a nutritional expert on the research team next time?

!ABryan Hubbard