Cancer Today Origins, Prevention, and Treatment (1984) / Chapter Skim
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Diet and Cancer
Diet and Cancer
Pages 49-80
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From page 49... ...
This chapter is based on the presentation given by Anthony B Miller, National Cancer Institute of Canada, University of Toronto, at the 1983 annual meeting of the Institute of Medicine.
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From page 50... ...
Later epidemiological studies revealed that workers who handled aniline dye faced an increased risk of bladder cancer. More recently, the incidence of lung cancer in coastal regions of the United States has been linked to exposure to asbestos in the shipbuilding industry during World War II.
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From page 51... ...
Recently, suspicion has turned to both the intended and unintended products of industrialization, such as industrial chemicals or pollution from oil and gas consumption. So far, the fear that the environment has become increasingly carcinogenic has not been confirmed by epidemiological studies.
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From page 52... ...
Nonetheless, when numerous epidemiological studies repeatedly turn up the same associations, the weight of evidence becomes difficult to ignore. That is what happened with smoking and cancer some 20 years ago.
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From page 53... ...
Other migrants to Israel who came from Western European countries, the United States, and Canada -- where colorectal cancer is much more prevalent -- showed very little increase. A similar pattern occurs for breast cancer -- Asian and African migrants and those born in Israel show a marked increase, while the incidence for migrants from Western nations remains stable.
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From page 54... ...
TABLE 5 -- 2 Comparison of Rates of Breast Cancer Among Native and Migrant Jewish Females Ages 35-64, in Israel Native Country . Increase in Incidence (percent)
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From page 55... ...
The Seventh Day Adventists abstain from tobacco and alcohol, and roughly half of them are lacto-ovovegetarians -- that is, they eat dairy products but no meat. In several studies, Roland Phillips and his colleagues at Loma Linda University in California have found that this diet seems to protect against colorectal cancer: Seventh Day Adventists had lower rates of both this diet-related cancer and smoking-related cancers than did a control group of comparable age, sex, and social status.
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From page 56... ...
Some inverse relationships also came to light: gastric cancer with meat, animal protein, and fat; cervical cancer with protein and fruit. Kenneth Carroll of the University of Western Ontario calculated that there was a strong correlation worldwide between per capita total fat intake and age-adjusted mortality from breast cancer.
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From page 57... ...
Miller of the National Cancer Institute of Canada and the University of Toronto. He and his colleagues collected dietary intake data on six nutrients from 400 breast cancer cases and 400 controls.
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From page 58... ...
Jay Lubin and his colleagues at the National Cancer Institute and the Cross Cancer Institute in Edmonton, Alberta, have found that risk of breast cancer increases significantly with frequent consumption of beef and other red meat, pork, and desserts -- all of which reflect fat consumption. Colorectal Cancer A greater number of case-control studies have explored the relation of diet and colorectal cancer.
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From page 59... ...
When fat intake is increased from 10 to 40 percent of total calories in the diet of laboratory animals, tumor incidence in various tissues also rises. On the positive side, the consumption of some ingredients in high-fiber foods, such as cellulose and bran, has been shown to inhibit the induction of colon cancer by certain chemical carcinogens, but not consistently.
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From page 60... ...
Dietary Guidelines Despite the uncertainties about the role of diet in cancer, many scientists believe that sufficient evidence exists to recommend preliminary dietary guidelines for reducing the risk of cancer. After a two-year study of diet and cancer, a committee of the National Research Council (National Academy of Sciences)
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From page 61... ...
If the population had been persuaded to stop smoking when the association with lung cancer was first reported, approximately 30 percent of today's cancer deaths could have been prevented. Many scientists, including the NRG committee, now believe that it may eventually be possible to define a diet that will significantly reduce the incidence of cancer in the United States.
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From page 63... ...
In recent history, food additives and contaminants such as chemicals used in food processing or residues of pesticides have engendered the greatest concern as possible health hazards. In the past two decades, many food additives have been tested for toxicity -- although only a small number have so far been tested for carcinogenicity.
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From page 64... ...
These studies reveal that mutagens and potential carcinogens are ubiquitous in the human diet -- they can be found in celery, peanuts, hamburgers, and toast, for instance. Yet the magnitude of the risk they pose is not at all clear.
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From page 65... ...
The mechanisms by which they act are not known, nor is it clear if these chemicals have the same inhibitory effect in the living human body as they do in the laboratory. Nonetheless, the laboratory findings are intriguing in light of several epidemiological studies suggesting that certain foods protect against cancer.
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From page 66... ...
The following examples, drawn from the work of Bruce Ames, illustrate the diverse sources of these naturally occurring mutagens and carcinogens. Edible mushrooms contain a group of chemicals known as hydrazines, many of which are mutagenic and some of which are carcinogenic in laboratory animals.
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From page 67... ...
Many of these pyrrolizidine alkaloids are extremely potent carcinogens, causing lung and other tumors in laboratory animals. Plants containing pyrrolizidine alkaloids sometimes contaminate forage crops and food grains, resulting in acute or chronic poisoning in livestock.
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From page 68... ...
PAHs have since been detected in a variety of cooked or smoked foods, including coffee. In the past few years, it has been learned that many burned or browned foods are rife with mutagens and potential carcinogens.
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From page 69... ...
In the past few years, reseachers have found that french fries, toast, caramelized sugar, the crust of French bread, and other browned foods all contain highly mutagenic -- but as yet unidentified -- chemicals. Anticarcinogens Epidemiological studies suggest that some foods, including cabbage and other cruciferous vegetables and some components of dietary fiber, protect against cancer.
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From page 70... ...
Epidemiological studies are rare, however, because vitamin E is so prevalent in common foods, such as vegetable oil, whole grain cereals, and eggs, and thus it is difficult to distinguish its effect from those of other compounds in the foods. The mineral selenium, which is present in seafood, organ meats, and grains, as well as in drinking water, has been shown to protect against cancer in laboratory studies and to a limited extent in epidemiological studies.
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From page 71... ...
If active oxygen forms do prove to be involved in carcinogenesis, as Ames suspects, then one approach to cancer prevention may be to adjust the dietary intake of antioxidants, he says. At present, the optimum level of dietary antioxidants is not known, and excessive consumption of several of them, including vitamin A and selenium, can be toxic.
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From page 72... ...
It may be prudent to determine which pesticides -- natural or synthetic -- pose the greatest health hazard, Ames suggests. Questions of relative risk aside, it is far easier to minimize the occurrence of intentional additives and industrial contaminants in foods than it is to control the natural risk factors in diet.
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From page 73... ...
In the past 25 years, FDA has specifically sought to eliminate possible cancer-causing substances from foods. The focus has been on exogenous chemicals -- food additives, coloring agents, industrial contaminants, natural contaminants, and the like.
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From page 74... ...
As outlined in Chapter 6, recent studies suggest that a typical, everyday diet may pose a greater cancer risk than do food additives and contaminants, at least at current levels. In the past 20 years, epidemiologists have found that the foods people eat strongly influence the probability of their developing certain types of cancer.
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From page 75... ...
By contrast, food additives are typically thought to cause at most 5 percent of all cancers, and environmental pollutants no more than 2 percent. These are preliminary estimates at best.
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From page 76... ...
Such controls could be revived and modified to reflect new understanding of dietary risk factors, suggests Merrill. For example, FDA could set a limit on the amount of saturated fat allowed in processed foods.
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From page 77... ...
Both the American Cancer Society and the federal government embarked on new efforts in 1984 to alert the public to the risks and benefits of certain dietary patterns. The federal cancer prevention effort, led by the Department of Health and Human Services, will focus on diet, smoking, and to a lesser extent, occupational safety.
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From page 78... ...
Surprisingly little is known about the quantity and types of foods people eat, or the exact composition of those foods. Even less is known about why people select certain foods, or why they change their eating habits, as they often do spontaneously.
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From page 79... ...
Perhaps most relevant to the diet and cancer issue is our experience with programs designed to prevent heart disease. In the recent Multiple Risk Factor Intervention Trial, a 7-year study conducted by the National Heart, Lung, and Blood Institute involving 13,000 men at high risk for heart attack, half of the group was given "special intervention" to help them reduce the factors that contribute to the risk of heart attack.
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From page 80... ...
Such programs will always be imperfect tools for preventing cancer, but as the accumulating evidence about diet and cancer makes clear, any effort toward prevention will have to emphasize consumer self-protection.
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