Carcinogenic foods

[Guest guest]

Wow, well now, here's a real eye opener! Thankfully, this list isn't that long! Probably good to be aware of which foods we need to eat a little less of....

http://mathforum.org/~josh/alfalfa.html

Doctors now agree that a majority of human cancers are caused by agents we eat and breathe. Many of us have taken this to heart, and are thinking about our diet, reading the labels on the food we buy, and changing our eating habits to lessen the risk. Information about what's good and what's bad comes from many sources: newspapers and magazines, advice from doctors, and tips from our friends. There are foods we avoid, perhaps with a passion - but how many of us have a really sound foundation for our beliefs about what causes cancer and what doesn't? Recently, a list was published of some of the worst carcinogens in the typical American diet. The results have raised a lot of eyebrows, and I for one have changed some eating habits to which I had long been committed. A few years back, Science, the journal of the American Association for the Advancement of Science, devoted an entire issue to risks in our everyday lives: how we measure them, how we minimize and avoid them. One of the articles was primarily about cancer and diet, by Bruce Ames, a biochemistry professor at the University of California, Berkeley. It is from this article and an earlier article, also by Ames, that this summary is taken. Ames had been for many years a vocal advocate of strict government regulation of carcinogens in the diet. This political role prompted him to do a quantitative investigation: what were the greatest risks, the substances that should be top priorities of the regulatory agencies of the Department of Agriculture and the Food and Drug Administration? He compiled a list that contained a big surprise, and has led him to do an about face in the kind of policies he had been advocating. The worst offenders as it turned out - the substances which cause the most deaths - are not DDT and BHT and EDB and Temic. The list is filled with items like mushrooms, black pepper, celery and potatoes. Long before people started manufacturing chemicals to protect vegetables from insect pests, the vegetables themselves had an interest in killing insects. Many common plants have evolved their own internal chemical factories, and synthesize poisons to keep insects away. Some of these substances are far more carcinogenic (in tests on mice and rats) than anything the FDA has ever let through. Yet they slip through a legal loophole: They are GRAS, (Generally Recognized As Safe), and no government agency has the authority to regulate them. Yet if the same standards were applied that are used for, say, a new beetle spray submitted by Dow Chemical, they would fail with flying colors. Basil leaves pose a far greater risk than BHT, and pepper is more dangerous than PCB's. Ames's list is ordered according to the seriousness of the risk, as best he can judge from best he can judge from experiments on rats and mice. The ordering reflects not only the potency and concentration of carcinogens in various foods, but also the quantities that the average American ingests. At the top of the list, almost in a class by itself, is alcohol. Of the substances that we consume orally (cigarettes specifically excluded), alcohol is, for the average American, probably the greatest single cause of cancer, simply because of the quantities that we as a society consume. Other substances are more surprising: Mushrooms are particularly bad, especially when uncooked. Potatoes contain large quantities of solanine, which is a teratogen (induces birth defects) in mice, and is toxic to humans in quantities not far above a dinner portion. There's an amusing story about potato breeders, ever searching for more insect-resistant strains, who several years ago cultivated a variety that needed no pesticides. The only trouble was, people became sick when they ate it. It seems that the insect resistance resulted from high concentrations of the same chemicals that are toxic to humans. Many of us avoid bacon and hot dogs because they contain nitrates and nitrites, which react chemically with essential proteins in the body and turn them into mutagens and carcinogens. What a dirty trick for mother nature to load her celery, beets, lettuce, spinach, and radishes with the same nitrates! Celery also protects itself with psoralen, a chemical that causes cancer and birth defects in mice. When the celery is bruised or diseased, it protects itself from attack by manufacturing up to 100 times as much psoralen as is present in healthy celery. Farm workers have been known to develop skin irritation just from handling bruised celery. Many of the chemical problems listed are associated with oxidation. Oxygen is, of course, very useful to our bodies, but it is also a highly reactive chemical agent, and our bodies are in a continual struggle to keep the oxygen that is ubiquitous inside and outside our bodies from attacking the chemical agents that are essential for life function. (It has even been speculated that the aging process itself may result principally from accumulation of oxidation damage in the body's vital chemical libraries.) Oxidized carcinogens may be introduced into the body in two ways: First, our foods may become rancid with age, or they may be burnt (even just browned!) in cooking, and many nutrients are turned to poisons as they combine with oxygen. Second, we may consume substances that create free oxygen (in the form of peroxides) when they are digested. For example, alcohol, rhubarb, coffee, canavanine from alfalfa sprouts, and psoralen from celery are thought to act in this way. Yes, alfalfa sprouts are on the list too. Just a few years ago, I consumed sprouts by the bowlful (though it always felt to me like eating grass) just because I thought they were the healthiest food nature had to offer. Fortunately, they were not hard to give up. Here's a list I've abstracted from Ames's two articles. It's depressingly long, and listed in alphabetical order because the information supplied is not specific enough to order the list by seriousness of the threats. FOOD CHEMICAL AGENT COMMENTS Alfalfa Sprouts Canavanine Up to 1.5% of dry weight Alcohol ->Acetaldehyde Basil Estragole Potent carcinogen and teratogen Beets Nitrates Metabolize to nitrosamines. Black Pepper Piperine, safrole Up to 10% by weight Burnt anything Even lightly browned toast is significant. Celery Psoralen Especially when bruised or diseased. Cocoa Theobromine Causes chromosome damage; also sexual dysfunction in male rats Coffee Chlorogenic acid Preliminary evidence for association and burnt material with many organ cancers. Comfrey Symphytine Quite potent and dangerous. Cottonseed oil Sterculic acid Mushrooms Hydrazines Raw worse than cooked. Mustard Allyl Isothiocyanate Causes cancer and chromosome damage in rodents, even at low dosage Potatoes Solanine Peeling helps. Sprouted eyes are worst. Peanut Butter Aflatoxin From mold in peanuts and grains. Radishes Nitrates Rancid and burnt oxidized lipids Important because we consume so much fats and oils

Root beer Safrole Found in large concentrations, but in "Natural" root beer only. Spinach nitrates, Especially damaged leaves. oxalic acid

An updated version of this list, with mixed food and non-food carcinogens ranked in an order that reflects their relative importance as public health hazards is available on line from Ames's Berkeley lab: http://potency.lbl.gov/herp.html. Though we've been focusing on problem with vegetables, meat incidentally, is not the answer. The animals we eat are likely to be less careful than we about carcinogens in their diets, and animal tissues absorb and concentrate many of these substances. So what are we to make of this list? First, we should look on it not as one more reason to feel guilty about what we eat, but as an opportunity. It invites us to stop worrying about some risks, and focus on others. We already have a generous life expectancy, perhaps we are quite healthy and robust, and this new data beckons us with the probability of a yet longer and healthier life. Look first at the products that you eat habitually, perhaps daily. Does it make sense to reserve these for special treats? Coffee, alcohol, and perhaps even chocolate are special cases because it is so difficult, once we have become used to them in our lives, to cut them out. But it is just those things that we consume habitually that usually offer the least active pleasure, and we cling to them merely to avoid the temporary pain of giving them up. I know people, and I'm sure you do too, who say that one week after they gave up coffee they had more energy than they could remember having in years. or major modifications of our lifestyles. Buy potatoes when they are fresh, keep them in a dark place, don't store them too long, peel them and remove the eyes before serving. Don't scrape your burnt toast, but throw it away and set the toaster on "lighter" for the next batch. Buy cooking oil when it's fresh and keep it in the refrigerator. Perhaps the commercial brands with added antioxidant are on balance a healthier bet. Don't put mushrooms in salad. Eat mustard and pepper in moderation. Don't buy bruised celery on sale for half price. There are more precautions we can take without adopting obsessions And there are affirmative things we can do as well. The same articles discuss some foods that apparently have anti-carcinogenic properties. Cruciferous vegetables (broccoli, cabbage, Brussels sprouts, and cauliflower) contain chemicals that seem to protect against cancer. Vitamin E helps prevent the process of oxidation that corrupts our body chemistry. Vitamin C and Beta Carotene (associated with Vitamin A) act similarly, and seem in some studies to be associated with protection from cancer. Experts do not yet agree whether doses in excess of the recommended daily allowance afford added protection. The trace mineral selenium is essential to the body's protective de-oxygenation process, though large quantities of this element are toxic. High fiber diets are associated with lower rates of stomach cancer, probably because they shorten the time between ingestion and elimination, so there is less opportunity for foods to putrify in our intestines. Eating less of everything is a sure-fire way to cut your intake of "natural" carcinogens. But calorie-cutting has benefits far beyond what you might expect from this alone: The hungry body invokes a powerful adaptive response that makes you more energetic, more resistant to infection, less susceptible to cancer and heart disease. In lab experiments, hunger has been shown to slow the aging process in every respect, and evidence is accumulating that the trick works as well in humans. Far below your medical "ideal weight" is probably the healthiest place to be, but you don't have to torture yourself to feel the benefits: every pound that you lose adds to your life expectancy. How much of this could portly Ben lin have known, when Poor counseled: "To lengthen thy life, lessen thy meals."? A couple of technical footnotes: 1 - How do they know which substances are how carcinogenic? Almost entirely through tests on rats and mice. Studies on humans are impractical because there is just no way to find two large groups of people who on the whole live identical lifestyles except that one group eats potatoes while the other doesn't. The rodent studies are probably only a rough indication of carcinogenicity in humans, but it's all we have, and it's the same evidence that forms the basis for regulation of man-made pesticides and preservatives. 2 - But how do we know people haven't evolved ways to cope with the carcinogens that occur naturally in food? This would be a comforting thought, but probably it won't get us off the hook, for two reasons. First, many of the foods mentioned above have not been in the human diet for such a long time. Potatoes, for example, have only been widely eaten for a few hundred years, far too short a time for evolution to have had any effect. Second, cancer is a disease of old age. Evolution has had, unfortunately, very little motivation for extending people's lives beyond, say, 50 years, because childrearing is over and done with. Ames stops short of recommending drastic dietary changes for all of us. His basic message can be quite liberating: stop worrying about most chemical pesticides and food additives: the threat from "natural" poisons and carcinogens that we consume every day is probably some 10,000 times as great. But we are also free to shift our diets, moderating our intake of the most blatant offenders, take supplements of vitamins E, A, and C and selenium, and enjoying cabbage, broccoli, and high-fiber foods more often.