In the past month, the world press has been awash with stories about an amazing new breakthrough in cancer prevention. This had to do with a 30,000 person Chinese study (J Nat Cancer Inst, Sept 15 1993) proving that certain nutritional supplements could protect people from many types of cancer by as much as one fifth. This study is important, because it was so carefully designed and backs up scores of similar, if smaller, studies on humans. But the message it contains is hardly new.

The Chinese study (see box, p 2) is only the latest of already weighty evidence about vitamins and cancer treatment generated from numerous similar research conducted in many countries over the past decade.

Most research like the Chinese study has centred on the role of antioxidants in preventing or treating cancer. Antioxidants protect the body from damage caused by harmful molecules called free radicals. Besides respiration, the body's cells use oxygen to metabolize (and literally "burn") food for its energy, and also for immune activity, to burn away germs and toxins. As American nutritional specialist Leo Galland puts it, "This process of combustion creates tiny bonfires in the cells, and these fires give off 'sparks' that can start fires in undesirable places, damaging cell membranes and destroying essential fatty acids." These sparks, called free radicals, also are created from many other sources (ultraviolet radiation, smoke pollution, heavy metals, rancid fatty acids or overheating of oils, such as in fast food restaurants). These free radicals wreak havoc by destroying cell membranes, causing genetic damage, depressing immune function, hardening the arteries, disrupting hormone regulation, contributing to diabetes and other systemic disorders and, of course, causing the growth and spread of cancer.

But we're now learning that damage from free radicals can be prevented and even reversed if there are sufficient concentrations in the body of free radical scavengers, called antioxidants what Galland calls the body's own "fire brigade" which "snuff these sparks before they start too many fires." These include the antioxidant vitamins: vitamin A and beta-carotene, B2 (riboflavin), B3 (nicotinic acid), vitamin C and vitamin E and selenium.

Besides the Chinese study, extensive evidence supports the ability of individual antioxidants to prevent cancer. For instance, in the December 1991 issue of the American Journal of Clinical Nutrition, Dr G Block of the University of California, Berkeley, concluded that "approximately 90 epidemiologic studies have examined the role of vitamin C or vitamin C-rich foods in cancer prevention, and the vast majority have found statistically significant protective effects. . . ."

But even if modern medicine is coming around to the notion that cancer can be prevented by diet and nutrients, it is less willing to use these tools to fight cancer that is already there. Most oncologists aren't aware of (or don't accept) the massive research during the past decade on the treatment of cancer using nutritional supplements. A recent survey of the literature for the Bristol Cancer Help Centre has been compiled into a database of 3000 research studies. This research is not the work of fringe organizations, but of prestigious scientists and laboratories published in mainstream medical journals.