For cancer prevention, AICR advises eating no more than 3 ounces a day of red meat (pork, beef or lamb). It is preferable to choose fish or poultry. Research continues to support this advice. A recent review by British scientists of 13 studies in Cancer Epidemiology, Biomarkers & Prevention concluded that the risk of colorectal cancer is increased by 12-17 percent for every 100 grams (about 4 ounces) of red meat (beef, pork and lamb) consumed daily.

Processed meat, however, appears to be a much greater cancer risk. The British review noted a 49 percent increased risk when 25 grams of processed meat (about half a hot dog) is consumed daily. And in 2001, the European Prospective Investigation into Nutrition and Cancer (EPIC), the largest study ever into diet and cancer, reported that a high consumption of processed meats correlates with increased colorectal cancer risk.

Nitrite: The Food Preservative

Scientists consider the increased risk from eating meat to come from the formation of N-nitroso compounds – NOCs – in the gut during digestion. Studies have shown that eating chicken instead of meat has no effect on NOC formation, which agrees with the lack of a link between colorectal cancer risk and chicken consumption in population studies.

The increased risk from processed meats is thought to come from nitrite, usually sodium nitrite, which is added as part of the curing process. Nitrite is used because it develops flavor and color and retards spoilage. Although regulations govern the amount of nitrite used, mounting evidence indicates that nitrite can combine with amines, which may be byproducts of amino acids formed by reactions with sugars in meat – even before consumption – to form nitrosamines, a form of NOC. Most nitrosamines are known carcinogens in test animals.

AICR-funded researcher Sidney Mirvish, Ph.D., at the University of Nebraska Medical Center, is studying how processed meat leads to NOC formation and, eventually, cancer. "It may be possible to adjust the manufacture of processed meats to reduce their levels of NOCs, thereby reducing their ability to cause colon cancer," Dr. Mirvish says.

In his studies, mice were fed either a plain diet, one with hot dogs or one with sautéed beef. The level of NOCs excreted in the feces was high in the mice fed hot dogs or beef compared to the mice on a plain diet, with the highest level in the mice fed hot dogs. The results show that the NOC levels in hot dogs are about 10 times higher than those in fresh meat. Levels, however, vary among brands as well as for a single brand purchased at different times.

Future Work

Although further work is needed to establish whether NOCs in the colon from fresh red meat or processed meats actually induce cancer, the focus of Dr. Mirvish's future work is lowering levels of NOCs from processed meat. He warns, "Consumption of nitrite-cured meat has also been linked in several studies with brain cancer in children and in one study with leukemia in children."


Reference

Mirvish, SS et al. Total N-Nitroso compounds and their precursors in hot dogs and in the gastrointestinal tract and feces of rats and mice: possible etiologic agents for colon cancer. J Nutrition. 2002; 132(11S):3526S-3529S.