What’s the story in your region?
By Allan R. Handysides
Cancer is a major global disease. It’s estimated that about 13 million new cases and 7.6 million deaths from cancer occurred in 2008. This is an increase from 2003, when the World Health Organization’s World Cancer Report noted about 10 million new cases and some 6 million deaths.1
No region of the world is cancer-free. Age-standardized cancer rates allow identification of particular geographic variations, but not all databases are of the same quality. Generalizations, however, can usually be made with some degree of reliability.
Regional differences in cancer rates are very distinct. The United States rates high, with some 334 cases of cancer per 100,000 men. Australia and New Zealand, with 356.8 per 100,000, has worse statistics. Northern Europe at 303.5 and Western Europe at 337.4 per 100,000 also have high rates. The risk of dying from cancer is even higher in Central and Eastern Europe. Women in the same regions also have high rates of cancer, particularly breast cancer.
The lowest cancer rates occur in Central and West Africa, and South-Central Asia for men and Central and North Africa for women.2
Affluent societies carry a higher burden of cancer, usually related to tobacco smoking and other factors associated with a Western lifestyle.
In developing countries, 25 percent of tumors are associated with chronic infections such as hepatitis B (liver cancer), human papilloma viruses (cervical cancer), and Helicobacter pylori (stomach cancer).
In some Western countries there has been a decline in cancer mortality rates, because fewer people are smoking. Worldwide, lung cancer is the most common, followed by breast cancer and then colon cancer.
Cancer deaths are most often related to lung, stomach, and liver cancer. The increase in the world’s population is responsible for some of the gross increase in cancer statistics.
Because some cancers are more amenable to treatment, cancer of breast, prostate, and uterine/cervix, for example, are the cause of death in only a minority of patients so affected.
Causes of Cancer
Many factors impact the prevalence of human cancer. These range from cancer-inducing agents, or carcinogens, to chronic infections, dietary and lifestyle factors, alcohol consumption, and genetic susceptibility. Some 20 percent of cancers are associated with chronic infections.
The most hazardous human carcinogens include tobacco, asbestos, aflatoxins, and ultraviolet light.
Tobacco smoke is irrefutably causally associated with lung cancer. Less recognized is the association of tobacco with laryngeal, pancreatic, kidney, bladder, and—in conjunction with alcohol—oral and esophageal cancer.
The age a person begins to smoke affects incidence of cancer. Adults aged 55 to 64 who smoke 21 to 39 cigarettes per day and commenced smoking before age 15 are three times more at risk to die of lung cancer than those who started after age 25.
Certain varieties of tobacco (e.g., black tobacco) may be more dangerous than others, but there is no safe tobacco.3
The World Cancer Report 2003 listed alcohol as second in its summary of cancer causes. Heavy alcohol consumption causes cancer of the oral cavity, pharynx, larynx, esophagus, and liver, and increases the risk of breast and colorectal cancer. A causal relationship between alcohol and colon and rectal cancer is also strongly suggested, and the risk of head and neck cancers in heavy drinkers is some five to 10 times higher than in nondrinkers.
The risk correlates to the amount of alcohol consumed. Changing patterns of consumption suggest increases in less developed countries with a decrease in more developed countries. The actual carcinogenic effect of habitual drinking, however, is likely underestimated.
Alcohol is estimated to be involved in causing 3 percent of all cancers (4 percent in men and 2 percent in women). Of course, apart from its carcinogenic effects, alcohol is associated with a plethora of other problems.
Some industries expose workers to a variety of chemicals. The first cases of occupational cancer were identified in the eighteenth century among chimney sweeps, who developed scrotal cancer.4 Currently there are about 25 chemicals, or groups of chemicals, for which occupational exposure has been established as carcinogenic risk.
In developed countries most such risks have been eliminated, especially for asbestos, crystalline silica, and heavy metals, but there are hazardous materials that are probably carcinogens that bring the total to nearly 50 potentially carcinogenic chemicals. Awareness of such dangers is helpful in assuring vigilance and regulation of industries.
Some agents occur in the general environment, such as chronic hepatitis B and C viruses, aflatoxins, radon, and solar radiation. Diesel exhaust has been implicated in lung and bladder cancer.
The environment, with its polluted soil, water, and air, is responsible for up to 4 percent of all cancers.5 The “environment” that we create with smoking, drinking alcohol, dietary factors, lack of exercise, and excessive sun exposure may be implicated in the majority of human cancers.6
Unavoidable nonoccupational toxic substances to which we are environmentally exposed include the following:
♦ Asbestos, one of the best-documented causes of cancer, specifically mesothelioma. Asbestos dust may contaminate not only the workplace but the homes of asbestos workers when transported on their clothes.
♦ Air pollution, which includes industrial work materials, not the least of which are vehicular emissions. These emissions may contain such products as benzene, toluene, xylenes, and acetylene—all known carcinogens. Urban populations have a higher risk than rural populations. Very high lung cancer rates have been noted in nonindustrial workers living at home. Studies show that nonsmoking Chinese women, for example, are exposed to indoor air pollution from their cooking and heating practices. Vapors from hot oil may contribute to such cancers, along with the smoke of their heating source and fuel.7
♦ Water pollution, which can be combated with chlorination to reduce bacterial and viral problems. The chlorinating process, however, may produce harmful chlorination by-products. Studies suggest a causal relationship between chlorinated water and bladder cancers.8
Contaminated water is a source of arsenic exposure, which links to skin cancer, lung cancer, and cancer of other organs. High arsenic levels have been found in drinking water in several areas of Argentina, Bangladesh, Chile, India, Mexico, Mongolia, Taiwan, Alaska, and other parts of the United States.9
Not only the environment but also our food may be contaminated. Even natural foods can be infected with natural molds that can produce toxins such as aflatoxins. Residual pesticides can also be a problem.
In Africa and Asia fungal growth and aflatoxin production are recognized problems. Animals consuming such foodstuffs, in turn, become problematic. When such contaminants are antibiotics, hormonal growth promoters, pesticides, and heavy metals, they may be concentrated in the meat, milk, or eggs.
Organochlorines, such as DDT, have been associated with increased risk of pancreatic and breast cancers, lymphoma, and leukemia. Attempts to correlate polychlorinated biphenyls (PCBs) with breast cancer have proved conclusive.10
Infection Agents and Cancer
Ellen White spoke of cancerous effects of flesh foods in unpublished testimonies in 1896. In 1905 she spoke of flesh that was “filled with tuberculosis and cancerous germs.”11 It was not until Peyton Rous in 1911 published “Transmission of Malignant New Growth by Means of a Cell-free Filtrate” that an infection link to cancer was first documented in scientific literature.12 Only in the 1980s did advances in molecular biology permit the detection of very small quantities of an infectious agent in biological specimens. Since then at least eight different viruses, four parasites, and one bacterium have been causally linked to cancer.
Hepatitis B and C and the human papilloma viruses are transmitted by sexual means and blood contamination. The Epstein-Barr virus is also transmitted by human-to-human contact, as is HIV infection. The human T-cell lymphotropic virus causes lymphoma/leukemia, and is similarly transmitted by human-to-human contact.
Human herpes virus 8 (HHV-8) has been associated with Kaposi’s sarcoma. Helicobacter pylori are associated with stomach cancer. Parasites of the liver fluke families, acquired by eating raw or undercooked fish, have been associated with liver cancer. As yet there is no evidence of animal viruses causing human cancer, but the concept of a cancer germ was dismissed in medical literature until the past few decades.
Diet and Nutrition
It’s been estimated that some 30 percent of human cancers are related to diet and nutrition. The incidence of various cancers differs by world region. There are many potential causes of such variation, but cancers of the breast, colorectum, prostate, endometrium, ovary, and lung are generally more common in developed countries. Cancer of the digestive tract is more frequent in developing countries.
The most consistent finding is the association of reduced risk of various cancers with the eating of fruits and vegetables. The Adventist Health Studies support these findings, particularly showing that meat eaters experience a threefold to fourfold increased risk for colon cancers. There is a consistent association between red meat (pork, beef, and lamb) and processed meat, with increased risks being noted in many studies.
Simple sugar (mono- and disaccharides) may be associated with increased colorectal cancer. The higher carbohydrate content of a vegetarian diet, with its complex carbohydrates, appears to offer a protective effect.
Fat has been the focus of most hypotheses about dietary factors and cancer. Studies on ratios of polyunsaturated and monounsaturated fats have, as yet, not yielded clear data, although olive oil is associated with reduced risk.
A Gift From God
The Adventist health message of healthful eating, exercise, fresh air, rest, and trust in God is a gift to us from our loving, merciful Creator to help us to live full, healthy lives while we await His soon return. Let’s thank and praise Him for this bountiful gift.
1 World Health Organization, World Cancer Report 2008, www.iarc.fr/en/publications/pdfs-online/wcr/2008/.
2 International Journal of Cancer 127, no. 12 (Dec. 15, 2010): 2893-2917.
3 World Health Organization, World Cancer Report 2003, pp. 22-28.
4 P. Pott, ed. Chirurgical Observations (London: Hawes, Clark, and Collins, 1775).
5 Harvard Report on Cancer Prevention. Volume 1: Cancer Causes and Control 7 (suppl.): 53-59.
6 L. Tomatis, A. Aitio, N. E. Day, E. Heseltine, J. Kaldor, A. B. Miller, D. M. Parkin, E. Riboli, eds.,Cancer: Causes, Occurrence, and Control, IARC Scientific Publication, no. 100 (Lyon: IARC Press, 1990).
7 “Carcinogens in Food: Priorities for Regulatory Action,” Human Experimental Toxicology15:739-746.
8 “Chlorination, Chlorination By-products, and Cancer: A Meta-analysis,” American Journal of Public Health 82:955-963; Drinking Water and Cancer. Cancer Causes and Control 8:292-308.
10 Relevance to Human Cancer of N-Nitroso Compounds, Tobacco Smoke, and Mycotoxins,IARC Scientific Publications, no. 105 (Lyon: IARC Press, 1991).
11 Ellen G. White, The Ministry of Healing (Mountain View, Calif.: Pacific Press Pub. Assn., 1905), p. 313.
12 Peyton Rous, in Journal of the American Medical Association 56 (1911): 198.
Allan R. Handysides, a board-certified gynecologist,
is director of the General Conference Health Ministries Department.