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Grilled, smoked and barbecued meats may increase breast cancer mortality

MeatsWomen 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% 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% greater risk of death from all causes and 23% 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. 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% more likely to die during the study period, researchers report.

Women who included poultry and fish in their diet before or after their breast cancer diagnosis were 45% 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. 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 Centre 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.

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 in the report.

"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. "Generally, the fattier the meat is, the higher the chemical levels will be."

Abstract
Background: Grilled, barbecued, and smoked meat intake, a prevalent dietary source of polycyclic aromatic hydrocarbon (PAH) carcinogens, may increase the risk of incident breast cancer. However, no studies have examined whether intake of this PAH source influences survival after breast cancer.
Methods: We interviewed a population-based cohort of 1508 women diagnosed with first primary invasive or in situ breast cancer in 1996 and 1997 at baseline and again approximately five years later to assess grilled/barbecued and smoked meat intake. After a median of 17.6 years of follow-up, 597 deaths, of which 237 were breast cancer related, were identified. Multivariable Cox regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality as related to prediagnosis intake, comparing high (above the median) to low intake, as well as postdiagnosis changes in intake, comparing every combination of pre-/postdiagnosis intake to low pre-/postdiagnosis intake. All statistical tests were two-sided.
Results: High prediagnosis grilled/barbecued and smoked meat intake was associated with increased risk of all-cause mortality (HR = 1.23, 95% CI = 1.03 to 1.46). Other associations were noted, but estimates were not statistically significant. These include high prediagnosis smoked beef/lamb/pork intake and increased all-cause (HR = 1.17, 95% CI = 0.99 to 1.38, Ptrend = .10) and breast cancer–specific (HR = 1.23, 95% CI = 0.95 to 1.60, Ptrend = .09) mortality. Also, among women with continued high grilled/barbecued and smoked meat intake after diagnosis, all-cause mortality risk was elevated 31% (HR = 1.31, 95% CI = 0.96 to 1.78). Further, breast cancer–specific mortality was decreased among women with any pre- and postdiagnosis intake of smoked poultry/fish (HR = 0.55, 95% CI = 0.31 to 0.97).
Conclusion: High intake of grilled/barbecued and smoked meat may increase mortality after breast cancer.

Authors
Humberto Parada Jnr, Susan E Steck, Patrick T Bradshaw, Lawrence S Engel, Kathleen Conway, Susan L Teitelbaum, Alfred I Neugut, Regina M Santella, Marilie D Gammon

[link url="http://www.reuters.com/article/us-health-meat-breast-cancer-idUSKBN1532Y1"]Reuters Health report[/link]
[link url="https://academic.oup.com/jnci/article-abstract/109/6/djw299/2804985/Grilled-Barbecued-and-Smoked-Meat-Intake-and?redirectedFrom=fulltext"]Journal of the National Cancer Institute abstract[/link]

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