Americans trying to avoid cancer-causing substances in foods would benefit most from eating fewer calories and fats and more fruits and vegetables, a prestigious scientific panel concluded in a report issued yesterday. The panel suggested that people should worry far less about the risk of cancer from pesticide residues and food additives.
In a finding that is sure to appeal to anyone tired of washing vegetables in detergent to remove pesticides, a 20-member panel of the National Research Council, an arm of the National Academy of Sciences, confirmed that there were many natural and synthetic cancer-causing chemicals in foods, but it said their importance as cancer-causing agents was minimal compared with the overconsumption of calories and fat.
The report, "Carcinogens and Anticarcinogens in the Human Diet," based on an exhaustive review of scientific reports and other relevant information, said that about one-third of the 1.35 million new cancer cases in the nation each year could be traced to diet, but probably not to natural or synthetic chemicals in significant numbers.
"The great majority of individual naturally occurring and synthetic food chemicals are present in the human diet at levels so low," the report said, "that they are unlikely to pose an appreciable cancer risk."
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Food scientists and food industry representatives applauded the report.
Dr. Joyce A. Nettleton of the Institute of Food Technologists, most of whose members work in industry, said: "No responsible scientist in the food system would deny there are substances in the food supply that in theory could be nasty if consumed in excessive amounts, but bodies aren't piling up because of lethal substances in food. Diet-related health conditions are related to our overall habits, not to specific food chemicals present in minuscule amounts."
And Timothy Willard, a spokesman for the National Food Processors Association in Washington, said that the report was "in harmony with what the industry and scientists have said for years about food and health: that consumer and public health attention should focus on the real risks, rather than trivial and mostly hypothetical risks posed by synthetic or natural carcinogens."
In another segment of the food industry, Robert Scowcroft, executive director of the Organic Farming Research Foundation in Santa Cruz, Calif., said he did not expect the report to have much of an impact on organic foods, which are grown without pesticides.
Mr. Scowcroft said "what motivates people to buy organic are not just food safety issues but a desire for fresh foods and taste and to protect the environment and farm workers" from pesticides.
Al Meyerhoff, senior lawyer for the Natural Resources Defense Council, which has long championed a cleaner, safer environment, said that even though chemical carcinogens in foods were much less important than tobacco, alcohol and obesity as causes of cancer, "they can still cause thousands of cancers in consumers, and they should be avoided wherever possible."
The research council committee not only assessed the importance of the overall diet and carcinogenic chemicals, it also concluded that if any chemicals were important to human cancers, the naturally occurring carcinogens, which far outnumber the synthetic ones, probably made a greater contribution to the cancer risk.
Mr. Meyerhoff, reacting to this finding, said that little could be done about natural carcinogens but that "the more than 100 known man-made carcinogens in foods are avoidable and involuntary exposures."
About 6,000 chemicals, both synthetic and natural, are deliberately or inadvertently added to foods, whereas hundreds of thousands of chemicals -- perhaps a million -- are naturally present in foods. Coffee aroma alone consists of about 1,000 different chemicals.
Relatively few chemicals that occur naturally in foods have been tested for their cancer-causing potential, the committee noted, adding that natural food substances are not tested and regulated as are chemicals like pesticides and preservatives that are applied or added to foods.
More essential than ever.
Still, the committee, led by Dr. Ronald Estabrook, a biochemist at the University of Texas Southwestern Medical Center in Dallas, cited examples of several well-established natural carcinogens that are widely consumed in ordinary foods.
One is caffeic acid, most prominent by far in coffee but also found in notable amounts in apples, lettuce, peaches, pears, potatoes, tomatoes and citrus fruits. Caffeic acid causes cancer in laboratory animals, but its role, if any, in human cancer is unknown. Despite many studies exploring the relationship of coffee drinking to cancer in people, no link has been established.
"While some chemicals in the diet do have the ability to cause cancer, they appear to be a threat only when they are present in foods that form an unusually large part of the diet," Dr. Estabrook said. "The varied and balanced diet needed for good nutrition -- including fruits and vegetables -- seems to provide significant protection from the natural toxicants in our foods."
Might cancer result from eating vegetables and fruits containing caffeic acid or those contaminated by residues of possibly carcinogenic pesticides? The committee expressed strong doubts, noting that plant foods are major sources of substances that protect against cancer, including the antioxidant vitamins A, C and E and other natural chemicals, including isoflavonoids, phenolic acids and isothiocyanates.
The committee pointed out that little was known about the interaction of carcinogens and anticarcinogens in foods. Many foods have both. For example, broccoli contains arsenic, a carcinogen, and chlorogenic acid, which is converted in the body to caffeic acid, but it also has anticarcinogens: vitamin C, sulforaphane, indole and other isothiocyanates. And cooked beefsteak contains carcinogens like benzanthracene, heterocyclic amines and traces of arsenic and a fungal toxin, ochratoxin A. But it also has anticarcinogenic substances like linoleic acid and selenium.
Studies of different groups of people with different diets have strongly suggested that in a diet rich in fruits and vegetables, anticarcinogens are far more influential than natural and synthetic carcinogens. In the case of beef, natural and synthetic carcinogens and cancer promoters like fat appear to play a greater role. Several recent studies have found a strong link between the consumption of red meat and cancers of the prostate and colon.
Though nearly all that is known about the cancer risk of chemicals in foods comes from studies of laboratory animals exposed to very high doses of each suspect chemical, the committee urged caution in drawing conclusions from animal studies about cancer risks in humans. Animal studies have limitations, the report pointed out, because the bodies of animals and people might handle a chemical differently, and the effects of ingesting a single substance in isolation might differ from the effects of consuming it as part of a varied diet. Also, an animal study uses very large doses of a chemical that people are exposed to in only minute amounts.
Without studies more relevant to human exposures to back up laboratory findings, the committee said, few conclusions can be drawn about the risk to people of consuming chemicals that cause cancer in animals. The report stressed the need for better studies of synthetic chemicals and more studies of natural food chemicals that might be suspect carcinogens.
The committee said that to use laboratory studies to estimate the cancer risk to humans, better information was needed on human exposure to the chemicals -- what, how much and how often various sources of those chemicals are consumed.
The report also called for more research on natural anticarcinogens. Some of those might be added to foods to help protect people against cancer, the panel suggested.
Meanwhile, the committee said, "it is of utmost importance to continue recommending that the public consume diets rich in fruits and vegetables but low in fat and calories. The consumption of vitamins and minerals in a moderate, varied and balanced diet -- not as dietary supplements -- continues to be one of our best strategies for cancer prevention in people."
Source from : The NewYork Times