Eat to tip the odds in your favor
By Elaine Magee, MPH, RD
WebMD Weight Loss Clinic - Expert Column
Don't you wish there were a diet that could assure you a life free from cancer? Most experts agree it doesn't exist -- yet. But there is a way to eat and live that could put the odds of preventing cancer in your favor.
The dietary habits that tend to increase our cancer risk come down to too much and too little: Too much red meat, alcohol, fried foods, refined carbohydrates and sugars, and too much body fat; too few phytochemical-rich plant foods and too little exercise. (Of course, you already know you shouldn't smoke or get too much sun.)
To decrease our risk, for example, we want to eat whole grains (such as whole wheat, barley, and oats) and plenty of fruits and vegetables. Many fruits and vegetables have cancer-fighting potential. For example, lycopene, a phytochemical found in cooked tomatoes and tomato products, has been shown to slow the growth of breast, lung, and endometrial tumors and to reduce prostate, stomach, and pancreatic cancer risks.
Randall Oyer, MD, chairman of medical oncology at John Muir Medical Center in Walnut Creek, Calif., isn't afraid to say that nutrition plays a role in cancer prevention, but he cautions against making a connection within a short time frame. "What a person has been eating a year before they were diagnosed with breast cancer, for example, probably isn't as relevant as what they've been eating a decade or two before," he explains.
And most cancer researchers admit there's stronger scientific evidence for a link between diet and colon cancer, for example, than for one between diet and breast cancer -- the cancer that so many women fear the most. But we're learning more every day.
In the past year, scores of studies have been published on diet and breast cancer alone. And more and more of this research is distinguishing between the effects that certain nutrients have on women before menopause and after.
In my opinion, future studies also should look at the differences between types of fat and types of carbohydrates. Some studies have suggested that higher-fiber, high-phytochemical plant foods (which are rich in carbohydrates) may have protective effects, while refined carbohydrates and sugars may have negative ones. Others have suggested that olive oil (and monounsaturated fat) and omega-3 fatty acids may help reduce breast cancer risks.
Should It Really Be "10-a-Day"?
Although some earlier scientific studies failed to find a link between eating vegetables and fruits and reduced risk for some types of cancers, more recent ones are reversing that trend.
For example, a recent study in Northern Italy suggested that raw vegetables may help protect against both breast and prostate cancer. Other research has indicated that cruciferous vegetables (like broccoli, cauliflower, and cabbage) may play a role in reducing breast-cancer risks in premenopausal women. One of the benefits of cruciferous veggies may be their abundant supply of isothiocyanates. These phytochemicals may help increase certain enzymes that detoxify cancer-promoting chemicals.
While we're on the subject of broccoli, another phytochemical in this vegetable recently made medical news. A report from the University of Illinois at Urbana-Champaign was the first to show how the isothyiocyanate found in broccoli, brussels sprouts, and kale -- called sulphoraphane -- can block late stages of the cancer process. Using human breast cancer cells in the lab, researchers were able to hinder the growth of the cancer -- much like certain drugs do.
Various fruits and vegetables have also been scientifically linked with prevention of colon, mouth, esophageal, lung, and stomach cancers. Population studies have repeatedly suggested that certain types of produce -- dark green vegetables; tomatoes; citrus; cruciferous vegetables such as broccoli and cabbage; and carotene-rich ones such as carrots and cantaloupe -- reduce overall cancer risk.
More and more studies are being done all the time. But obviously, fruits and vegetables are very important to our health in general. It's hard to argue with those food choices!
Bottom line: Strive to eat 10 servings (about 1/2 cup is a serving) of fruits and vegetables a day, choosing carotene-rich produce, dark green vegetables, cruciferous vegetables, tomatoes, and citrus when possible.
Specific Nutrients or Foods with an Anti-Cancer Connection
Flaxseed. This sesame-like seed has three things going for it. Ground flaxseeds contain soluble fiber, alphalinolenic acid (a form of healthy omega-3 fatty acid), and are the richest source of lignans (phytoestrogens that function like antioxidants) on the planet. These are not to be confused with flaxseed oil, which contains just the oils from flaxseed, not the fiber or plant estrogens.
Studies in rats have shown a reduction in the number and growth of breast tumors. And encouraging results from the first human flaxseed-breast cancer study were presented at the San Antonio Breast Cancer Symposium in December 2000. The study showed that adding a reasonable amount of flaxseed (the study used a muffin containing 25 grams of flaxseed) for about 38 days reduced tumor growth in people with breast cancer -- similar to benefits seen with the drug tamoxifen.
Further, one more recently published study found that premenopausal women whose diets contained the most lignans were 34% less likely to get breast cancer than women whose diets had the least lignans. (Other good sources of lignans include whole grains, strawberries, cantaloupe, onions, grapefruit, winter squash, and carrots.)
Bottom line: Although more research needs to be done, adding a tablespoon of ground flaxseed to your smoothie, muffin, or meatloaf, a few times a week may be helpful. (At the least, it increases the fiber and the plant omega-3 fatty acid content of your diet.)
Soy. The scientific battle over whether soy increases or decreases breast cancer risks continued this year. Increasingly, experts are suggesting that early exposure to soy -- such as during the teenage years -- may help protect women from developing breast cancer later on. Many questions remain on breast cancer and soy, but studies that are going on now may shed more light on this issue.
Still, adding soy to your diet has been shown to lower cholesterol. It may also reduce bone loss in postmenopausal women; our government is spending about $10 million to research this potential benefit.
Bottom line: At the very least, soy foods provide high-quality protein. So a couple of servings per day seem like a good idea.
Dietary Fat's Cancer Connection
Dietary Fat. Several new studies support the theory that higher-fat diets may increase breast cancer risks. But while the relationship between a high-fat diet and breast cancer is still in question, that's not the case for other cancers. The American Cancer Society says high-fat diets are associated with an increased risk of colon, rectal, prostate, and endometrial cancers. It also says the consumption of meat -- especially red meat -- has been linked to colon and prostate cancers. And gram for gram, fat has more than twice the calories of carbohydrates and protein, meaning excessive amounts are likely to cause weight gain.
But there may be an advantage to eating a lower-fat, higher-carbohydrate diet that has more to do with detecting breast cancer than preventing it. There is evidence that such a diet may decrease breast tissue density, making mammograms easier to read.
Bottom line: Avoid high fat meals to decrease the risk of colon, prostate, and endometrial cancers; to possibly decrease breast-tissue density; and to discourage weight gain.
Folic Acid. Judith Christman, PhD, with the University of Nebraska Medical Center, is studying how diets lacking in folic acid encourage the cancer process. "When diets lack folic acid," explains Christman, "the structure of the cell's genetic material becomes disrupted. If cells misread normal or read damaged genetic information and reproduce, cancer can develop."
If you drink alcohol, you've got another reason to eat foods rich in folic acid. A recent Mayo Clinic study reported that women who consumed the lowest amount of folic acid and the highest amount of alcohol had a 59% higher risk of breast cancer than women who never drank and whose folic acid intake was above the median.
If you're getting plenty of fruits and vegetables, including beans and peas, as well as fortified breads and cereals, you're likely meeting the recommended daily allowance for folic acid (400 micrograms).
Bottom line: Eat plenty of fruits, vegetables, beans, and peas (especially lentils and pinto beans, collard greens, spinach, and other dark-green vegetables).
Many of us fear cancer more than any other disease. But any anti-cancer diet should parallel, as much as possible, dietary guidelines aimed at preventing disease in general.
Here are some smart-eating guidelines based on the Dietary Guidelines for Americans, published by the departments of Health and Human Services and Agriculture, as well as on what researchers know and suspect about diet and cancer.
- If you drink alcohol, limit it to one drink a day. Even better, try less than three drinks a week. And make sure you're eating enough foods with folic acid (see above).
- Keep extra weight off by exercising almost every day (consult your doctor before starting an exercise program) and trying not to overdo fat and sugar.
- Aim for nine to 10 servings (about 1/2 cup each) of a variety of fruits and vegetables a day. Try to include a cup of dark green vegetables and a cup of an orange fruit and/or vegetable.
- Eat fish two to three times a week, to take the place of meats high in saturated fats and as a source of omega-3 fatty acids.
- Eat beans (including soybean products) three times a week to take the place of red meat and as a source of folic acid (in lentils and pinto beans), fiber, and assorted phytochemicals.
- Have several servings of whole-grain foods each day.
- Find satisfying substitutes for foods you love to eat that are lower in calories, lower in fat, and higher in nutrients including fiber.
- Choose lean meats and low-fat dairy products and substitute canola and olive oil for butter, lard, and margarines high in trans fats.
Looking for some delicious ways to prepare foods full of potentially cancer-fighting nutrients? Try these two recipes.
Broccoli Parmesan Pasta
1 tablespoon olive oil
1 teaspoon minced garlic
1 cup broccoli florets, lightly steamed or microwaved
2 cups cooked and well-drained angel hair pasta (or other cooked pasta)
Salt to taste
Couple of pinches of crushed pepper flakes (or to taste)
1/8 cup shredded Parmesan cheese
- Heat oil in medium nonstick skillet over medium heat. Saute garlic until lightly golden, stirring often (about 1-2 minutes). Add broccoli and pasta and saute, stirring occasionally, for 2-3 minutes.
- Add salt and red pepper flakes to taste.
- Sprinkle Parmesan cheese over the top. Turn off heat and let rest about a minute before serving.
Yield: 2 servings
Per serving: 300 calories, 11.5 g protein, 47 g carbohydrate, 8.5 g fat (1.5 g saturated fat, 5.1 g monounsaturated fat, 1.2 g polyunsaturated fat), 2 mg cholesterol, 6 g fiber, 59 mg sodium. Calories from fat: 25%.
Raw Veggies & Hummus Platter (Chickpea and Garlic Spread)
I'm always looking for fun ways to enjoy an assortment of raw vegetables. Instead of dipping the veggies in the usual ranch dressing, try a dip with an ethnic twist -- hummus.
15-ounce can garbanzo beans (about 1 1/2 cups drained)
1 teaspoon bottled minced garlic
3 tablespoons low-fat plain yogurt (add more if desired)
1/4-1/2 teaspoon salt (optional)
4 tablespoons fresh lemon juice
1/4 cup tahini paste (sesame butter, made from ground sesame seeds)
1 tablespoon finely chopped fresh parsley
4 green onions, finely chopped, the white and part of the green
3 tablespoons finely chopped red bell pepper
Pepper to taste
2 cups broccoli florets (raw, or lightly cooked then cooled)
2 cups cauliflower florets (raw or lightly cooked then cooled)
2 cups green beans (lightly cooked and cooled) or raw snap peas
- In a colander, drain and rinse the garbanzo beans. Place them in a food processor. Add the garlic, yogurt, salt if desired, lemon juice, tahini, and parsley.
- Pulse mixture in the food processor, scraping sides often with the spatula, until smooth. Stir in green onions and red bell pepper, and spoon into serving bowl.
- Make a platter by setting the bowl of hummus in the center of a large plate. Surround the bowl with the assorted vegetables.
Note: You can make this without a food processor. Just mash the garbanzo beans, garlic, yogurt, and salt (if desired) with a potato masher until fairly smooth. With a spoon, beat in the lemon juice a few tablespoons at a time. Slowly beat in the tahini and parsley, then onions and red bell pepper.
SOURCES: International Journal of Cancer, July 2003; June 2004; July 2004; and 2004; 111, 440-443. Breast Cancer, Jan. 12, 2004. AACN Clinical Issues, January-March 2004. Cancer Epidemiology, Biomarkers and Prevention, April 2004. American Journal of Clinical Nutrition, May 2004. Journal of Nutrition, May 2004; September 2004. Journal of Epidemiology, May 2001. Journal of Cancer Causes and Control, Vol. 13. Mark Messina, PhD, adjunct associate professor, nutrition department, Loma Linda University; president, Nutrition Matters Inc., Port Townsend, Wash.
Published September 2004.
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