Although the recent Chinese study into cancer has grabbed the headlines, many earlier tests had already pointed the way to a nutritional approach.
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.
Much of the data concerns work on cells or animals [in the latter case, work that WDDTY does not support editor] and some of the work on people is preliminary. Nevertheless, the existence of this copious research is all the more reason to wonder why the medical profession continues to treat the use of nutritional therapy for cancer as anything other than a feel good adjunct to the "real" treatment radiation, chemotherapy or surgery when that treatment hasn't made any headway in terms of improving survival statistics since the time of our grandparents (New Eng J Med; 1986; 314: 1226-32).
Vitamin A/Beta Carotene
Fat soluble vitamin A, vital to eye and retina function (whence its name retinol is derived), protects the mucous membranes of the mouth, nose, throat and lungs from damage, and as an immune system enhancer, reduces risk of infection and cancer. Researchers have proposed that retinol may have a potential benefit in reducing cancer risk because of its role in maintaining cell integrity and on evidence that certain retinoids stop the growth of chemically induced tumours in laboratory animals.
These days, most scientists concur that the benefits have more to do with beta carotene, which the body metabolizes into vitamin A. Carotenoids such as beta carotene are made into vitamin A by the body which only makes what it needs. While you can overdose on fat soluble vitamin A, found in liver and fish, large doses of water soluble beta carotene, found in carrots and broccoli, are non toxic and constitute an extremely potent source of antioxidant activity.
Almost every study of nutrition and cancer shows a relationship between low levels of vitamin A and cancer, including the otherwise conservativelyinterpreted results of the recent Harvard's Nurses' Health study of 90,000 women with breast cancer (New England Journal of Medicine, 22 July 1993).
Work in the laboratory on cell lines and animals has shown that vitamin A/beta carotene also has a direct toxic effect upon cancer cells. Researchers at Harvard School of Dental Medicine found that beta-carotene or vitamin E quickly altered and slowed proliferation of breast, oral, lung and skin human tumour cell lines (isolated cells in the laboratory) (J Oral Maxillofac Surg; Apr 1992).
Of the human studies that are available, a number have showed that beta carotene and vitamin A can help reverse precancerous lesions. One Canadian study showed that with tobacco chewers from Kerala, India given vitamin A for six months, oral precancerous lesions completely disappeared in slightly more than half and virtually all experienced a reduction of the abnormal cells. Beta carotene produced similar results. Vitamin A also completely suppressed the formation of new lesions (Am J Clin Nutr, Jan 1991).
According to American health writer Gary Null (Healing Your Body Naturally, Four Walls Eight Windows 1992) studies done at the Sloan-Kettering Institute in Manhattan have found that a vitamin A derivative caused a remission in 80 per cent of subjects with leukaemia with far greater results than among those receiving chemotherapy as well.
Perhaps more research has been performed on vitamin C than on any other nutrient, largely due to the interest of twice Nobel Prize laureate research scientist Linus Pauling. In addition to being a potent antioxidant, vitamin C enhances antiviral and anti bacterial immune function. Most studies of stomach and esophageal cancers have shown that the diets of the adult patients are low in vitamin C-rich foods (Epidemiology, Cancer Causes Control 2:325-57,1991). The Chinese trial showed no evidence of reduced cancer among the group given vitamin C alone; however, it may be that the doses only twice the US Recommended Daily Allowance were too low, far lower than doses recommended by Pauling and others for therapeutic purposes. A Canadian study, which performed a combined analysis of data from 12 studies of diet and breast cancer, predicted that dietary changes including vitamin C could prevent about a fifth of all breast cancers (Howe et al, J Natl Cancer Inst; Apr 4 1990).
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).
Perhaps most important of all are those studies that examine all the anti oxidants working in tandem. In a way, the Chinese results, where only the group with the highest number of antioxidants had improved cancer survival, suggests that antioxidant nutrients rely on an interaction with each other to produce the best results.
Although much of the laboratory and clinical evidence is spectacular, some of the studies that have been done to treat human cancer patients with nutrients have been small or inconclusive. In a companion trial done in the same province of China on 3000 people with esophageal cancer there was no significant survival difference between the group given 26 vitamins and those given a placebo. Again, this may be because treatment requires megadoses, and the study group was only receiving two or three times the RDA. While epidemiologic evidence consistently shows that people eating lots of fresh fruit and vegetables reduce their risks of cancer by as much as a half (Epidemiology, Cancer Causes Control 2:325-57, 1991), we still have much to learn about the dosage in treating people once they have the disease.
Sandra Goodman, Ph.D. has compiled the Nutrition and Cancer Database for the Bristol Cancer Help Centre which laypersons and professionals may contact on (0272) 743216.