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What's the Beef?

Carcinogenicity from cooked meats

Melissa Lock

Fall 2005

carcinogen carcinogenicity cook meat hca heterocyclic amine    Research shows that chicken may not necessarily be a healthier alternative to beef. Whether you eat chicken, beef, or pork, chances are that any type of cooked meat contains a number of chemical carcinogens. Worldwide research indicates that cooking meats at high temperatures creates carcinogenic chemicals that are absent in uncooked meats. These chemicals called heterocyclic amines (HCAs), form in a variety of meats including pork, beef, fish, and fowl.

    The National Toxicology Program, a division of the National Institutes of Health, has recently added three HCAs (2-ami- no-3,4-dimethlimidazo[4,5-f]quinoline (MeIQ), 2-amino-1-methyl-6-phenylimid- azo[4,5-b]pyridine (PhIP), and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx)) to their list of potential human chemical carcinogens. Although the cooking methodology, type of food preparation, and cooking time all contribute to the amount of carcinogens produced in the meat, these chemicals are primarily the result of cooking at high temperatures.

    HCAs, produced by cooking muscle meats, are formed from their amino acid precursors. Researchers at the Lawrence Livermore National Laboratories in Livermore, California, mixed phenylalanine and creatine (both naturally present in animal muscle) to reflect the proportion of both amino acids normally present in raw beef. By dry-heating the mixture at 200C, the researchers found that PhIP was produced in similar amounts to those amounts formed from cooking beef on a grill. Another study conducted by the National Cancer Institute’s research labs found that the amount of HCAs increased threefold in meats when the cooking temperature was raised from 200C to 250C. Michael Malfatti, PhD, who has been investigating HCAs at the laboratories for over 13 years, articulates that “the correlation is that the longer and hotter you cook your food, the more HCAs are formed. Therefore, the more heat that is applied, the more HCAs will be formed.”

    Since frying, broiling, and barbequing involve cooking at very high temperatures, they are considered to be the cooking methods that produce the largest amounts of HCAs. Dr. Malfatti emphasizes that “any cooking method that uses high temperatures [from] 200 C - 300 C will form them.” Other methods of cooking that involve lower temperatures (e.g. basting and roasting) produce a lower amount of HCAs.

    Cooking meats in water is a different story. “Stewing, poaching, and boiling produce little to no amounts of HCAs because they involve cooking temperatures at or below 100C. You can never make the temperature go higher than the boiling point of water,” says Leonard Bjeldanes, PhD, of the University of California, Berkeley. “Because it can’t heat up as high, the metabolic activation of these carcinogens will not occur.” It is important, however, to point out that this does not include pressure cooking, which does allow water to boil over 100C.

    So what do HCAs actually do? HCAs are known to cause irreversible damage to DNA. Dr. Malfatti confesses that although many researchers have dedicated their entire careers to studying the multi-step mechanism, it is still not yet fully understood. “HCAs are pro-carcinogens, which means they need to be metabolized to become bioactive. Once metabolized, the bioactive metabolites can bind to DNA and cause mutations. If you get enough mutations and cell proliferation, tumors can form.”

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