Another study has shown people who eat more meat have a high risk of cancer. This time, it's kidney cancer, researchers reported Monday.
And it's not just people who eat red meat, as many other studies have shown. People who eat more so-called white meat, such as chicken, have the higher risk, too.
Dr. Xifeng Wu and colleagues at The University of Texas MD Anderson Cancer Center in Houston studied 659 patients just diagnosed with kidney cancer and compared them to 699 similar people without cancer.
They wanted to break down not just the link, but to tease out the factors that might explain it. They looked at what kinds of meat people ate, how they cooked it, as well as people's genetic makeup to see if certain genes made them more susceptible.
People who said they ate the most grilled meat — red meat and chicken alike — had a higher risk of kidney cancer, they reported in the journal Cancer. And those with two genetic mutations that already put people at higher risk of kidney cancer were most affected by the grilled meat risk.
People with kidney cancer also ate fewer fruits and vegetables than people who didn't have it.
"Although previous studies have linked meat intake with an increased risk of (kidney cancer), to the best of our knowledge the underlying mechanism for this association remains unclear," they wrote.
Cancer experts have long known that grilling or barbecuing meat can make it carcinogenic. Burning or charring meat creates cancer-causing substances.
In this case, the two culprits Wu's team looked for were 2-amino-1-methyl-6-phenyl-imidazo(4,5-b) pyridine (PhIP for short ) and amino-3,8-dimethylimidazo(4,5-f) quinoxaline (MeIQx for short).
"Kidney cancer is among the 10 most common cancers in both men and women," the American Cancer Society said. The group projects that more than 61,000 Americans will be diagnosed with kidney cancer this year and 14,000 will die of it.
"For reasons that are not totally clear, the rate of new kidney cancers has been rising since the 1990s, although this seems to have leveled off in the past few years," the American Cancer Society added in a statement on its website.
"Part of this rise was probably due to the use of newer imaging tests such as CT scans, which picked up some cancers that might never have been found otherwise."
Wu's team also wonders whether an increase in eating meat might explain some of it.
"The American/Western dietary pattern consists largely of red and processed meats, and the results of the current study suggest that the association between this dietary pattern and cancer may be in part explained by exposure to meat cooking mutagens," they wrote.
Last month, the International Agency for Research on Cancer (IARC) released a controversial report that stated definitively that processed meats such as sausages and bacon cause cancer and that red meat probably does.
This study fits in with the studies that undergird the IARC's pronouncement.
Outside experts said it will be important to find out just what the risk is and what people can do about it.
"Once we have identified more genes we will likely be able to identify a subset of the population that is at particularly high risk to develop kidney cancer if they eat meat and processed meat," said Dr. Ulrike Peters of the Fred Hutchinson Cancer Research Center in Seatlle.
"However, overall recommendations to limit intake of red and processed meat will remain for the entire population."