At present we really don't understand how vitamin C works, but some of the studies suggest that something in its chemistry, rather than its properties as a vitamin, inhibit a variety of cancers breast, liver and leukaemias. In the case of oestrogen dependent breast cancer, vitamin C has the ability to lower the concentration of toxic hormonal substances produced by oestrogens.
The Linus Pauling Institute in California proved a similar inhibiting factor on breast cancer tumours inplanted in mice (Am J Clin Nutr, Dec 1991), and the University of Texas in Galveston demonstrated vitamin C's ability to decrease oestrogen induced tumour growth in hamster kidneys by half (Am J Clin Nutr, Dec 1991).
Vitamin E has a particular antioxidant role on cell membranes, at times working in tandem with vitamin C, and interacting with vitamin A, the B-complex vitamins and selenium. It prevents toxic interaction with fats and oxygen in cells and so plays a vital role in maintaining the cell's integrity and use of oxygen. As an immune system enhancer, vitamin E especially protects against lung damage from pollution. In a Boston animal study vitamin E prevented oral tumour formation in hamsters by galvanizing the immune system to destroy developing tumour cells (J Oral Pathol Med, Feb 1990).
The largest controlled human study in Italy to date has shown that the risk of stomach cancer was more closely linked to low intake of vitamin E than any other nutrient (Int J Cancer 45:896-901, 1990), and a national study of over 1000 American patients showed that vitamin E supplements reduced the risk of oral cancer by half (Am J Epidemiol 135: 1083-1092, 1992). As for treatment, of 43 patients at the Anderson Cancer Center in Houston, Texas with precancerous oral lesions treated with vitamin E, nearly half improved and a fifth showed evidence of cell improvement after six months (J Natl Cancer Inst, Jan 6 1993).
Selenium, whose best source is seafood, works in partnership with vitamin E to protect against cancer and to prevent cell membrane damage. This mineral detoxifies heavy metals, protects against environmental and chemical sensitivities, and enhances the body's antibacterial and antiviral defences. The variety of animal and human studies point to its ability to inhibit colon, cervical, breast and liver cancers. A study in Finland, for instance, found that blood levels of selenium were significantly lower in men who went on to develop stomach cancer (J Natl Cancer Insti 82: 864-868, 1990).
In American Health Foundation research selenium inhibited colon and breast cancer in rats (Cancer Res, May 1 and Oct 15, 1992).
And research at Nehru University, New Delhi, India administering selenium in drinking water reduced cervical cancer incidence by half in mice(Oncology; 1992; 49(3): 237-40).
Essential Fatty Acids
In all the attention focused on antioxidants, doctors tend to overlook the role of essential fatty acids in protecting and treating cancer and maintaining a healthy immune system. Fats are broadly divided into saturated and polyunsaturated. There are two kinds of EFAs called "essential" because the body needs them but cannot manufacture them itself: omega-6 linoleic acid and gamma linolenic acid (present in Evening Primrose oil) and the omega-3 alpha linolenic acid family (found in fish and linseed oils). Broadly speaking, these acids get metabolized into hormone like substances called prostaglandins, which regulate the activity of the white blood cells in the immune system. We're not sure how EFAs kill tumour cells but it may involve the ability of fatty acids to bind to protein and so prevent the toxic action of tumour cells (Nutrition,Sept-Oct, 1992).