|June 1998 U.S. Edition|
BEAT THE HEAT
David Schardt & Leila Corcoran
It may look like a garbled computer message, but its actually bad news for beef and chicken lovers, especially with the summer cookout season around the corner.
The snippets are shorthand for half a dozen potentially cancer-causing chemicals called HCAs, or heterocyclic amines, which are created when meat, poultry, and fish are cooked at high temperatures.
"We know these compounds can probably cause cancer in humans," says Elizabeth Snyderwine, Chief of the Chemical Carcinogenesis Section at the National Cancer Institute (NCI) in Bethesda, Maryland. "What we dont know yet is how significant a problem they are in the American diet."
Until theres more evidence, "it makes sense to avoid (HCAs) when we can," says Mark Knize of the Lawrence Livermore National Laboratory in Livermore, California.
How much HCAs are created depends on how long the food cooks, at what temperature, and how its prepared.
"Meat and poultry produce the most HCAs because they contain the most amino acids and creatine, which are converted into HCAs," says Lawrence Livermores James Felton. "Seafood produces much less, and plant foods like veggieburgers, fruits, and vegetables little or none."
Grilling, barbecuing, broiling, and pan-frying are more likely to produce HCAs than baking or roasting, because they generate more heat. A propane gas grill set on high can reach 640 F, while a typical roasting temperature is 350 .
Cooking with liquidboiling, steaming, poaching, or stewing, for examplegenerates no HCAs because the temperature never tops the boiling point of water. Ditto for microwaving, so long as the food is not overcooked or dried out.
NCI epidemiologist Rashmi Sinha says that well-done beef, pork, and chicken produce the most HCAs, particularly if theyve been grilled or barbecued.
"But nowadays, with bacterial infections, you dont want to tell people to eat rare meat," she says. "You want to cook it thoroughly, but not at a very high temperature."
(Interestingly, people who frequently eat chicken have lower rates of colon cancer.1 Researchers dont know why.)
While charred meat and poultry contain more HCAs, you cant always predict which meats have the most. For example:
PAHs: Another Grill Menace
Whenever fat drips on a flame, heating element, or hot coals, chemicals called PAHs (polycyclic aromatic hydrocarbons) form. The PAHs waft up in the smoke and can land on the food. They can also form directly on food when its cooked to a crisp.
"If you throw a steak or hamburger on the grill and let it get really brownthe fats dripping off it and flames and smoke are shooting upthats the stuff you dont want to do," says the NCIs Rashmi Sinha.
As many as 12 of the 18 PAHs found in cooked food cause cancer in laboratory animals. But proof that they cause cancer in humans is still elusive. The key to preventing PAHs: Stop the fat from dripping on the heat source (see "Avoiding HCAs and PAHs").
The Smoking Gun
People who eat more meat have a higher risk of colon and prostate cancer. Is that because they eat more saturated fat, fewer fruits and vegetables, or more or less of something else? No one knows. Could it be because they consume more HCAs and PAHs? Most research has centered on HCAs.
Only one study has asked people how much meat they ate and how they cooked it, and then waited to see who got cancer.
Among 10,000 Finns monitored for 24 years, women who reported eating the most fried meat had a 77 percent greater risk of developing cancer of the breast, endometrium, or ovary than women who ate the least. But men who ate more fried meat had no greater cancer risk than men who ate less. (The researchers didnt ask about grilled or broiled meat.)
And six studies have found that people with breast, colon, stomach, or other cancers had eaten more fried or well-done meats than similar people without cancer.
But being diagnosed with cancer may have biased their reporting.
Case Not Closed
"It seems very plausible that HCAs cause cancer," says Knize. "But its still a long way from proof."
First, "the level of HCAs in food can vary by two-hundred fold or more, since it depends so much on cooking conditions," points out Lawrence Livermores James Felton.
Second, people vary in their susceptibility. About half of all Caucasians in the U.S. inherit a slow-acting form of an enzyme called NAT2, and that makes them less susceptible to developing cancer from carcinogens like HCAs.
Put these two factors together "and you could have a thousand times greater risk of cancer than your neighbor who eats the same food," says Felton.
Lawrence Livermore has an NCI grant to work on the HCA puzzle. In the meantime, "I think were on really safe ground to say that well-done or very-well-done meat is not good for you," says Sinha.
|Avoiding HCAs and PAHs
Heres how to minimize your exposure
to HCAs and PAHs. Some of the tips will also help keep harmful bacteria at bay:
WHAT TO COOK
HOW TO PREPARE IT
HOW TO COOK IT
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