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).