People who eat large amounts of meat cooked at high temperature or over an open flame - and are also genetically susceptible - may have a higher risk of kidney cancer, according to a new study.
Animal muscle, cooked at high temperatures, produces substances called heterocyclic amines and polycyclic aromatic hydrocarbons, which can cause changes in DNA that may increase cancer risk, according to the National Cancer Institute.
Population studies have not found a definite link between cooked meat and cancer in humans, but studies using detailed food questionnaires have found that increased consumption of well done, fried or barbequed meats is tied to an increased risk of cancer of the colon, pancreas and prostate.
"A few previous studies have looked at kidney cancer and these carcinogens, but this is the first study to find an association between one of these specific mutagens (MeIQx) and kidney cancer risk," said senior author Dr. Xifeng Wu of The University of Texas MD Anderson Cancer Center in Houston.
MeIQx is one of the heterocyclic amines formed by high temperature cooking.
"This is also the first study to look at genetic variants along with consumption of these carcinogens in relation to kidney cancer risk," Wu told Reuters Health by email.
The researchers compared the dietary patterns and genetic risk profiles of 659 people newly diagnosed with renal cell carcinoma to 699 people without the cancer.
Cancer patients tended to eat more red and white meat, and more of the carcinogenic "char" chemicals caused by grilling, pan frying or barbequing, than people without the cancer.
People with two gene variants, one involving lipid signaling in the cells and another which encodes for the activation of other genes when oxygen levels are low, appeared to be more susceptible to the cancer-causing chemicals in cooked meat.
These are common gene variants, but their effect on cancer risk was very small, Wu said.
Those in the cancer group also tended to consume more calories, less fruit, and were more often obese, according to a report scheduled for publication in the journal Cancer. The researchers only surveyed non-Hispanic white adults, so the results may not apply to other racial and ethnic populations, Wu said.
Heterocyclic amines and polycyclic aromatic hydrocarbons have been shown to cause cancer in laboratory studies of mice and rats, and have been associated with several cancer types in humans, Wu said.
"The kidney is responsible for filtering harmful toxins from the body, exposure to these carcinogens through diet would impact kidney cancer risk," she said.
Although certain compounds in the study increased kidney risk by two-fold, the lifetime risk of kidney cancer is still low for most people, she said.
"The recent news on the carcinogenicity of red meat resulted from an existing body of literature on this topic, which focused primarily on cancer of the bowel and colon," Wu said.
"The evidence for some other cancers, such as kidney cancer, is not as clear," she said. "More studies are necessary to understand the role of meat and these meat -cooking mutagens in kidney cancer."
According to the U.S. National Institutes of Health, in 2012 there were roughly 376,000 people living with kidney cancer in the U.S., and every year, about 16 new cases are diagnosed per every 100,000 people.