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updated 8/26/2005 11:46:24 AM ET 2005-08-26T15:46:24

A large European study recently reported a strong link between eating high amounts of red meat and an increased risk of colorectal cancer. This finding supports and extends the results of several previous studies. However, for consumers who want to apply these findings to best protect their health, questions remain about specific food choices.

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The study shows that after an average of almost five years, people who ate the most red meat and processed meat had a 35 percent greater risk of developing colorectal cancer than those who ate the least amounts.

The cancer risk actually rises with fairly small amounts of these foods. Eating more than about five-and-a-half ounces of red meat and processed meat per day put people in the most at-risk group. A smaller change in risk was even seen with 10 ounces per week. The meats responsible include beef, pork, lamb and veal, plus sausage, ham, bacon and cold cuts.

Not all studies support a link between red meat and colon cancer, but what scientists call the “preponderance,” meaning a convincing majority, do. A study of more than 148,000 Americans released earlier this year tracked people for 9 to 19 years. Those who ate the most red and processed meats faced a 13 to 15 percent increase in the risk of colon cancer.

There are several factors to consider when trying to discern how red meat raises cancer risk. The high saturated fat content is a major contributor to heart disease. It may affect cancer development as well. But merely choosing lean red meats and reduced-fat processed meats does not appear to remove the cancer risk.

Cancer-causing substances, known as heterocyclic amines (HCAs), form when meat is grilled, broiled, or fried at high temperatures. Because HCAs form on poultry and fish cooked at high temperatures, too, HCAs alone do not explain the greater risk from red meat.

Another problem particular to processed red meats is the presence of nitrites, which can be converted to carcinogenic N-nitroso compounds (NOCs) in the colon. In fact, some NOCs may already be present in the meat. Nitrites don’t account for all of the risk posed by processed red meats, however, since not all of these meats contain them.

Not too late to cut back
The higher colon cancer risk from red meat may be due to its levels of the heme form of iron. Heme iron is only found in animal foods, and the amount in beef is about twice that in chicken and fish. It has a different chemical form than the iron in plant foods and supplements. Heme iron seems to damage the lining of the colon and cause abnormal cell growth. One study shows that increasing red meat leads to more NOCs in the colon. Red meat’s heme iron produces more NOCs than iron from plant foods.

What should you do?

The American Institute for Cancer Research’s expert panel report, Food, Nutrition and the Prevention of Cancer, recommends limiting red meat consumption to three ounces a day or less. Choose poultry and stew it or bake it to avoid HCA formation.

Prepare fish two times a week since studies show it offers protective benefits, apparently through its special omega-3 fat. Since none of the risks connected with red meat apply to plant-based dishes, make meatless entrées with beans, nuts, or seeds for protein.

If you continue to include red meat in your diet, choose lean cuts and stick to the recommend 3 ounces or less a day. Even if you’ve eaten large amounts of red meat your entire life, studies suggest that changing your eating pattern now can have a positive effect within a few years.

When you eat any kind of animal protein, however, make sure the focus of your meals is vegetables, fruits, whole grains and beans, which are the source of many health-promoting nutrients and phytochemicals.

Nutrition Notes is provided by the American Institute for Cancer Research in Washington, D.C.

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