Related topics: •  Food Rx: Eating Right to Stay Healthy •  Guidelines on Nutrition and Physical Activity for Cancer Prevention

Yes. At least one-third of cancer deaths each year are linked to a poor diet, along with obesity and inactivity. Of course, nothing can guarantee that you won't get cancer, but next to quitting smoking, eating a healthy diet is one of the best things you can do to tip the odds in your favor.

In addition, fruits and vegetables are packed with minerals, antioxidants, and other substances that may have a protective effect against oral, stomach, colon, esophageal, and lung cancers, according to the American Cancer Society. There is some evidence that a diet high in fruits and vegetables may help prevent cancer of the colon, pancreas, and prostate as well.

Why – or even whether -- certain types of food may help protect us from cancer is an ongoing mystery. The American Cancer Society cautions against getting too excited about the latest news story touting this or that vitamin or special food. The truth is we have a general idea of what might help and what to avoid, but researchers are still investigating how the complicated compounds in foods act in the human body. Still, you can't go wrong if you follow some general guidelines for a healthy diet.

Start by loading up on fruits and vegetables. For one thing, filling up on fruits and vegetables every day may help you avoid higher fat foods that are more likely to pack on excess weight. This is important because obesity has been linked to increased risk for colorectal cancer as well as cancer of the esophagus, breast, endometrium, and kidneys.

Variety in food is key. Researchers aren't sure which of the many compounds in fruits and vegetables might play a role in warding off cancer, so try to choose a colorful array of foods. The substances in fruits and vegetables that give them their unique colors are often the same elements that scientists think may give them their protective properties, so the more colorful your selection, the better.

The National Cancer Institute recommends getting two to five servings of fruits and two to eight servings of vegetables each day. A serving is about half a cup. There’s no guarantee that your produce shelf will keep you from getting cancer, but studies continue to look at some tantalizing possibilities.

•Cruciferous vegetables such as broccoli, cauliflower, cabbage, and brussels sprouts contain compounds that have been linked to a lower risk of cancer. In particular, a substance called sulforaphane -- which is found in higher concentrations in broccoli sprouts than in mature broccoli or other vegetables -- may prompt the body to produce higher levels of certain cancer-fighting enzymes.

•Garlic contains allyl sulfur compounds that may help rid the body of cancer-causing chemicals and boost the immune system. According to the American Cancer Society, some studies suggest that people who eat a lot of garlic may have a lower risk of stomach, prostate, and colorectal cancer.

•Lycopene, the antioxidant that gives tomatoes, apricots, guava, watermelon, papaya, and pink grapefruit their color, shows promise as a cancer fighter. Lycopene is particularly prevalent in tomatoes, and studies show that for cooked tomato products wind up putting more lycopene in your bloodstream than raw tomatoes do. People who eat a lot of tomatoes seem to have a lower risk of prostate, lung, and stomach cancers.

Some studies suggest that green tea may help protect against cancer of the skin, esophagus, stomach, colon, pancreas, lung, bladder, prostate, and breast. That's quite a claim for a simple cup of tea. But unfortunately it's more complicated than that. Lab studies of animals and cell cultures show that green tea seems to act against cancer cells, but those results don't extend to human studies. Most human studies are observational -- that is, they look at a large population that drinks a lot of green tea and compare that group's risk of cancer to another group that doesn't drink green tea. The results of these studies have been inconclusive, and the American Cancer Society currently does not find enough evidence to recommend green tea for either preventing or treating cancer.

Fiber is the part of fruits, vegetables, grains, and legumes that the body can't digest. It keeps your intestinal tract running smoothly, and early studies suggested it might help prevent colon cancer. However, larger studies -- including a well-known Harvard study that followed over 80,000 female nurses for 16 years -- found no real connection between fiber consumption and a reduced risk for either colon cancer or polyps (which are thought to lead to colon cancer.) Still, fiber benefits your body in other ways (like reducing your risk of heart disease and diabetes to name just a couple) so it's a good idea to make sure you get enough of it in your diet -- at least 20 to 35 grams a day for adults.

For starters, it's just not possible to pack all of the possibly beneficial compounds found in a head of broccoli into a pill. We still don’t know how the many elements in food may interact with each other and the body to benefit health, so it's a good idea to get your nutrition from food, not supplements. However, because many people do not get enough of the key vitamins that help to prevent chronic diseases, the Harvard School of Public Health says that taking a daily multivitamin makes sense for most adults. Also, people with restricted diets, pregnant women, postmenopausal women and some women of childbearing age may benefit from various supplements to make sure they're at least getting their minimum requirements. If you're not sure whether you should be taking vitamins or supplements, check with your doctor.

Experts used to think that a diet generally high in fat was a risk factor for a variety of cancers. Now they're not so sure. After careful review of the evidence, an expert panel concluded in 2007 that there is limited evidence of a link between a high fat diet and lung cancer and postmenopausal breast cancer. It also found evidence that animal fat may be a cause of colorectal cancer. Whatever food choices you make, you should get less than 35 percent of your daily calories from fat. Fats like olive oil, canola oil, and omega-3 fatty acids are actually healthy for you, however.

Drink alcohol in moderation, if at all. Drinking raises your risk of cancer of the mouth, larynx (voice box), pharynx (throat), esophagus, liver, and breast. It may also increase the risk of colon and rectal cancer. If you're a man, hold the line at two drinks a day. If you're a woman, your body metabolizes alcohol differently, so you need to limit yourself to no more than one can of beer, one glass of wine, or one ounce of hard liquor a day. If you are a woman at high risk for breast cancer, you might want to avoid alcohol entirely. The American Cancer Society cautions that even a few drinks per week can increase a woman's breast cancer risk.

Go easy on processed meats like hot dogs and lunch meat. They contain nitrite -- a preservative that's been linked to an increased risk of colorectal and stomach cancer. The American Cancer Society also suggests avoiding smoked foods, fish and meat that have been preserved by salting, and pickled vegetables, due to the risk of exposure to cancer-causing agents in them. Though it's important to cook meat thoroughly, it's equally important that you not overdo it. Some studies suggest that frying, broiling, or grilling meats at very high temperatures produces substances in the meat that may increase the risk of colorectal cancer.

If you follow these diet tips from the American Cancer Society, you may not get a free pass when it comes to cancer, but you will be fortifying your body with nutrients that might well give you an edge.

•Eat a variety of fruits and vegetables every day. Try adding fruit to a green salad, add chopped vegetables to soups, salads, and casseroles, or fix a stir-fry with plenty of vegetables mixed in.

•Choose whole grains -- like whole wheat pasta and oatmeal -- instead of processed grains and sugars.

•Limit your intake of red meat, especially high-fat and processed meats. Trim fat before cooking meat, and eat poultry with the skin removed.

•Cook without using added fat by roasting, baking, steaming or poaching. Avoid deep-fat frying or overcooking meats.

•Use reduced-fat dairy products.

•Limit your alcohol intake.

•Drink at least 8 cups of water a day. Water dilutes the concentration of cancer-causing agents in the urine and rids your body of them faster, possibly reducing your risk of bladder cancer

-- Nancy Montgomery is a senior editor for Consumer Health Interactive.

Further Resources

Roberta Larson Duyuff, MS, RD, CFCS, The American Dietetic Association's Complete Food &Nutrition Guide. Chronimed Publishing, 1996, 1998.

Varro E. Tyler, PhD. Herbs of Choice: The Therapeutic Use of Phytomedicinals. Pharmaceutical Products Press, 1994.

References

Michael Potter, MD, an attending physician and associate clinical professor at the University of California, San Francisco, who is board-certified in family practice.

First published March 21, 2008
Copyright © 2008 Consumer Health Interactive

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