You Can Prevent Cancer

Tip the odds in your favor with these supportive suggestions.


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According to the American Cancer Society, smoking causes one-third of the 500,000 annual U.S. cancer deaths. Another third is attributable to poor diet and sedentary living. The final third’s causes remain controversial. The implications of this breakdown are clear: Don’t smoke, and embrace the diet and active lifestyle that help prevent what just this year became the nation’s leading killer. (For decades, heart disease was number one — now it’s number two.)

Unfortunately, eating and exercising to reduce cancer risk are easier said than done. In most households, Mom no longer spends her day preparing meals the American Cancer Society would applaud. Most adults have jobs and time-consuming commutes. They come home exhausted, so meal preparation gets short shrift and convenience is king. As a result, according to the U.S. Department of Agriculture, restaurants — often fast-food places — now supply one-third of Americans’ calories, almost double the proportion of 30 years ago. Meanwhile, according to the Centers for Disease Control and Prevention, fewer than half of Americans are as physically active as health experts recommend. But with some planning and determination, it’s not all that difficult to embrace a cancer-preventive diet and lifestyle.

Eat More Fruits and Vegetables

Many people imagine cancer as an alien that invades our bodies inexplicably and consumes us from the inside out. But cancer is no alien. The biochemical processes that produce it are at work in our bodies from the moment we’re conceived. They’re part of what helps us grow; but in cancer, growth spins out of control — or more precisely, burns out of control. Slow burning is how we metabolize food. Metabolism is fueled by oxygen. But some of the body’s oxygen molecules turn into nasty electrically charged ions called free radicals that become so highly chemically reactive that they damage our DNA. To repair and prevent free radical damage, the body marshals compounds known as antioxidants, among them vitamins A, C and E, and the mineral selenium. A mountain of research shows that ingesting anything that promotes free radical creation — for example, cigarette smoke — boosts cancer risk. But ingesting antioxidant nutrients reduces risk.

Antioxidant nutrients are found overwhelmingly in fruits and vegetables. As fruit and vegetable consumption increases, cancer risk decreases. The classic study was published in 1992 by an epidemiologist at the University of California, Berkeley, who analyzed every prior study published that correlated diet and cancer risk, some 200 studies in all. Compared with people who ate few fruits and vegetables, those who ate the most had only half the cancer risk. Since then, many more studies have corroborated this finding.

As a result, the National Cancer Institute recommends eating at least five — and preferably nine — servings of fruits and vegetables a day. (See “What’s a Serving?” on Page 22.) Currently, most Americans eat only about three daily servings of fruit and vegetables, so we’ve got a way to go, but the goal is within reach. Once you get the hang of it, it’s not difficult to get at least five. Have one or two pieces of fruit or fruit juice with breakfast — for example, raisins on cereal and a glass of orange juice. Have a vegetable and salad at lunch. Snack on fruit or vegetables (carrot sticks, bell pepper slices, etc.). Have a vegetable and salad with dinner. And have some fruit for evening snacks — instead of ice cream, try fruit sorbet.

Now for two fine points: First, french fries and other deep-fried vegetables (for example, vegetable tempura) don’t count toward your five to nine servings. Deep frying means loads of fat, which negates vegetables’ cancer-preventive benefits (see below).

Second, all plant foods help prevent cancer, but two categories are particularly beneficial: highly colorful fruits and vegetables (blueberries, beets) and cruciferous veggies (broccoli, cauliflower, Brussels sprouts). The pigments that give plant foods their color are potent antioxidants. The crucifers also are high in antioxidants.

Should You Buy Organic Produce?

One of the rationales behind consuming organic food goes something like this: Pesticides are carcinogenic; therefore, it makes sense that eating food grown using pesticides — and containing pesticide residues — might increase cancer risk. (Other valid reasons include the better flavor of organic foods, the health of the soil and support of alternatives to corporate agribusiness and the chemical industry.) According to a 2003 article in Alternative Medicine Alert, Americans now buy 40 times more organic produce than they did in 1986, almost $8 billion a year. Considerable evidence, including a study published in Occupational and Environmental Medicine in 2003, shows that farmers occupationally exposed to large doses of pesticides have an increased risk of some cancers, notably non-Hodgkin’s lymphoma.

Other research shows that compared with children who eat commercially grown food, those who eat organic have lower levels of pesticides in their bodies. But to date, there are no compelling studies showing that eating organic food reduces cancer risk. All the studies demonstrating that fruits and vegetables significantly reduce cancer risk used conventionally grown produce. So eat organic if you want to (I do) and certainly reduce your exposure to pesticides of all kinds, but don’t expect organic food to be the magic bullet that immunizes you against cancer. Currently, the best evidence shows that any plant foods, even those grown using pesticides, help reduce cancer risk.

Use Antioxidant Herbs

Notice that two of the top antioxidant foods mentioned on Page 21 are also considered herbs — garlic and onion. Several other herbs also are rich in antioxidants, notably tea and turmeric.

Among herbs, garlic has the best evidence of cancer-preventive action. Research at the MD Anderson Cancer Center in Houston shows that garlic reduces the risk of bladder cancer. National Cancer Institute researchers, in a study published in the Journal of the National Cancer Institute in 2002, have found that garlic and its close botanical relative, onion, help prevent prostate cancer. Chinese researchers have correlated garlic and onion consumption with reduced risk of esophageal and stomach cancers. And a study of 42,000 Iowa women published in the Journal of Epidemiology in 1994 showed that compared with people who ate the least garlic, those who ate the most had a 32 percent lower risk of colon cancer.

Tea (primarily green tea) has been shown to reduce the risk of several cancers: bladder, breast, colon, esophageal and pancreatic. Research on the cancer-preventive activity of turmeric is in its infancy, but there is no doubt that this herb is a potent antioxidant. One study, published in Cancer Research in 1999, shows the herb reduces the risk of colon cancer.

Eat Less Meat

Meat is problematic for several reasons. First, it tends to displace plant foods from the diet. Meat has low levels of antioxidants, so diets heavy on meat tend to be low in cancer-preventive antioxidants. Red meat also is high in animal (saturated) fat. This type of fat (as opposed to fish oils, vegetable oils and the fats found in plant foods) has been found to increase risk of several cancers: colon, prostate, uterine and breast. Cooking meats (especially grilling) introduces potent carcinogens (heterocyclic amines) into them. Finally, a gram of fat contains twice as many calories as a gram of protein or carbohydrate. Because meat is high in fat, it’s also high in calories, which promotes weight gain — and obesity is a risk factor for several cancers (see “Watch Your Weight” on Page 24).

Meat is fundamental to most Americans’ diets, and eating less can be difficult — serving less can elicit howls of protest from the family. An excellent way to cut back on meat — without anyone noticing — is to use soy-based substitutes. In casseroles, pasta sauces, soups and sloppy Joes, it’s hard to tell the difference between ground beef and soy substitute. Other suggestions: Instead of red meat, serve dishes made with fish, or skinless chicken or turkey breasts. Serve pizza topped with vegetables instead of meat (and go easy on the cheese). Or serve tomato-based vegetable sauces over pasta.

Eat Less Fast Food and Junk Food

Fast food (burgers, pizza, french fries) and junk food (ice cream, doughnuts, etc.) are high in fat, which contributes to weight gain, a key risk factor for cancer. They’re also low in plant material, so they tend to displace foods containing cancer-­preventive antioxidants. Sure, there’s a little lettuce on a Big Mac. But it’s overwhelmed by the beef, cheese and high-fat special sauce. If you haven’t seen Morgan Spurlock’s documentary Supersize Me, rent the video or DVD. The protagonist eats nothing but fast food for a month, gains 20 pounds and develops a host of health problems. Before the month is up, his doctor is so appalled by Spurlock’s physical deterioration that he begs him to stop. (I played the DVD for my kids. It made a big impression on them.)

Get Regular Exercise

To prevent cancer, the American Cancer Society recommends 45 minutes of moderate exercise at least five days a week. Activities that qualify include walking, dancing, bike riding, yoga, roller or ice skating, baseball, volleyball, tennis, golf, soccer, gardening, lawn mowing — you get the idea. A University of Toronto analysis shows that regular exercise reduces the risk of breast, colon, prostate, testicular and uterine cancers, and possibly lung cancer. The Toronto researchers found that regular exercisers have an approximately 46 percent lower cancer risk compared to people who live sedentary lives.

Why exercise reduces risk of cancer isn’t entirely clear. However, this much is known: Exercise speeds the movement of food through the colon, limiting the body’s exposure to any carcinogens food contains. Exercise also reduces the amount of estrogen in women’s bloodstreams, reducing the risk of breast cancer.

Watch Your Weight

Carrying extra pounds goes hand-in-hand with physical inactivity, along with a high-fat diet heavy on meats, fast foods and junk foods and lacking in plant foods. So it should come as no surprise that being overweight is also associated with increased cancer risk, particularly for cancers of the colon, esophagus, kidney, gallbladder, pancreas and uterine endometrium. The cancer-preventive lifestyle — a plant-based diet and regular exercise, with a minimum of high-calorie, high-fat meats, fast foods and junk foods — is also the lifestyle recommended for long-term weight control, so as you reduce the pounds, you also reduce your cancer risk. Good news all around.

Do Vitamin and Mineral Supplements Help?

Consume Alcohol in Moderation

Moderate alcohol consumption — two drinks a day for men, one for women — is not a risk factor for cancer. But drinking any more than that has been associated with cancers of the mouth, throat, larynx, esophagus, breast and liver, and possibly colon. Excessive alcohol has a direct cancer-promoting effect throughout the digestive tract. It increases the risk of breast cancer because it increases blood levels of estrogen.

Vitamins A, C and E, the mineral selenium and many other nutrients are potent antioxidants, so it stands to reason that taking them as supplements would reduce cancer risk. But it’s not that simple. Over the past 20 years, a number of studies have shown that supplementation with antioxidants reduces risk of some cancers. The most persuasive report was a Cornell study that followed 1,312 adults who took a placebo or selenium (200 micrograms a day) for up to 10 years. The selenium group showed a significant decrease in cancer deaths, particularly with cancers of the lung, colon and prostate.

Overall, though, the evidence in favor of a cancer-preventive effect for supplements is nowhere near as consistent nor as compelling as the evidence for fruits and vegetables. In fact, one noted study, published in the New England Journal of Medicine in 1994, showed that beta-carotene supplements, which convert to vitamin A in the body, increased the risk of lung cancer in smokers. The current thinking is that taking a few isolated antioxidants in supplements is simply not as effective for cancer prevention as eating the much broader natural mix of antioxidants found in plant foods. Take a multivitamin if you want to (I do), but instead of splurging on exotic supplements, you’re more likely to prevent cancer if you splurge on blueberries, blackberries, strawberries and cherries — which taste better, too.

For some quick, simple, antioxidant-rich recipes, visit our website at

Beyond Cancer Prevention: Bonus Benefits

The cancer-preventive diet and lifestyle not only help prevent cancer, they also help prevent heart disease, stroke, diabetes and Alzheimer’s disease. Like cancer, all of these conditions are the result of free radical damage that an active life and a diet high in antioxidants help prevent. So take a nice long walk down to your favorite produce store. Load up on delicious fruits and vegetables — and antioxidant herbs. Then walk home and enjoy them. With every step, and with every bite, you’re likely to live longer — and healthier.

San Francisco-based health writer Michael Castleman is the author of 10 consumer health guides. Visit his website at

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