Women who eat a lot of grilled, smoked and barbecued meats and develop breast cancer may be more likely to die from their cancer than those who eat less of these foods, a US study suggests.
A higher intake of barbecued, smoked or grilled meat before diagnosis was also associated with 23 per cent higher odds of death from all causes, the study found.
Of the three cooking options, smoking may be the worst. Routinely eating smoked beef, lamb and pork was tied to a 17 per cent greater risk of death from all causes and 23 per cent higher odds of dying from breast cancer.
"There are many carcinogens found in grilled or smoked meats," said lead study author Humberto Parada, a researcher at the University of North Carolina at Chapel Hill. "One of the most common are polycyclic aromatic hydrocarbons (PAH), which are formed during combustion of organic material."
Women may be exposed to these carcinogens by cigarette smoke or air pollution, which are associated with an increased risk of developing breast cancer, Parada said by email. Some research has suggested exposure to these chemicals through grilled or smoked meat can increase the risk of breast cancer, but the current study offers some of the first evidence suggesting it also influences survival odds.
"Grilling or smoking meats produces PAHs much more readily than other cooking methods, such as pan-frying," Parada said. "Several factors may influence the formation of PAHs including 'doneness' and meat type - higher fat content may result in the formation of more PAHs."
For the current study, researchers interviewed 1,508 women diagnosed with breast cancer about their eating habits in 1996 or 1997 and then questioned them again five years later.
After following half of the women for at least 17.6 years, there were 597 deaths including 237 fatalities from breast cancer.
Compared to women who consistently ate only small amounts of grilled, barbecued or smoked meat, women who consumed a lot of these foods both before and after their diagnosis were 31 per cent more likely to die during the study period, researchers report in the Journal of the National Cancer Institute.
Women who included poultry and fish in their diet before or after their breast cancer diagnosis were 45 per cent less likely to die during the study than women who didn't eat these foods.
Lower levels of saturated fats in chicken and fish relative to red meats might help explain this, Dr. Pagona Lagiou, a researcher at the University of Athens Medical School in Greece who wasn't involved in the study, said by email.
It's also possible that chicken and fish have a protective effect because women eat less red meat, said Carrie Daniel-MacDougall, a researcher at the University of Texas MD Anderson Cancer Center in Houston who wasn't involved in the study.
"Simply increasing fish or poultry intake, without reducing red meat intake, is likely to be less beneficial for cancer prevention," Daniel-MacDougall added by email.
One limitation of the study is that it relied on women to report how often they consumed different foods and didn't assess portion sizes or the number of times they ate meats each week, the authors note. The study also isn't an experiment, so it cannot prove that different types of meat influence survival odds with breast cancer.
Still, the findings suggest women should pay attention to how they cook their food to minimise their exposure to carcinogenic chemicals, said Dr. Mingyang Song, a researcher at Massachusetts General Hospital in Boston and Harvard University who wasn't involved in the study.
"These chemicals can be produced from wood smoke or when fat and juices from meat grilled directly over an open fire drip onto the fire, creating flames and smoke," Song said by email. "Generally, the fattier the meat is, the higher the chemical levels will be."