Barbecue-cooked meat represents a significant cancer risk, according to Danish researchers.
Their findings, published in the journal PLOS ONE, suggest that on a population level exposure is considerably higher than the level deemed acceptable by the World Health Organisation.
The scientists, led by Lea Sletting Jakobsen of the Technical University of Denmark, approached the risk assessment using a probabilistic population model to estimate how age, sex and weight affect exposure to polycyclic aromatic hydrocarbons (PAHs), which are produced when meat is grilled or barbecued.
The findings suggest that people with lower body weight could be at highest risk, and that men may be more susceptible than women, but the results are not clear cut.
PAHs are produced when food is heated. They are also found throughout the environment and in tobacco smoke, and have been identified as genotoxins: that is, they can cause mutations to DNA and lead to cancer.
The most studied PAH is called benzo[a]pyrene (BaP). It has been classified as a group-1 human carcinogen by the International Agency for Research on Cancer (IARC).
“In principle there is no safe limit for BaP, because one particle or one molecule could actually initiate a carcinogenic process,” explains Jakobsen.
Because it’s impossible to avoid BaPs completely, the WHO has set an acceptable limit for risk of cancer from the compound at one case per million. The researchers’ results estimate an average cancer risk of 6.8 cases in 100,000 – well above the WHO figure.
PAHs are formed through the incomplete combustion of organic matter at high temperatures. This is thought to include fat, carbohydrate and protein when exposed to heat above 200 degrees Celsius, peaking between 500 and 900 degrees.
They can also form when fat drips onto a flame or charcoal, producing smoke which can result in the compounds adhering to the outside of the meat.
Danes love barbecues. But the country’s National Food Authority advises them to limit consumption barbecued meat and avoid charring it.
“However, the output of such risk assessment does not provide information on which sub-groups of the population could be higher risk, or of the variability and uncertainty of these estimates,” the authors write.
So Jackobsen and colleagues set out to quantify peoples’ cancer risk and identify subgroups that might be at higher risk to better inform public health recommendations.
Using a local population database, they created a statistical model to simulate people’s exposure to barbecued meat, including fish. The analysis factored in BaP concentrations from 407 samples.
Cancer risk was assessed by adapting dose-response data from tumours formed in mice exposed to comparable levels of BaP in coal tar mixtures. The results showed a very wide variation.
“So in that sense you would say that the barbecuing behaviour we have in Denmark at the moment is actually of concern,” says Jakobsen.
“But the uncertainty ranges in three orders of magnitude, so that of course complicates the message.”
Indeed, the calculated average risk varied from one to 4074 extra lifetime cases of cancer.
Males of lower body weight were at higher risk, but this can’t be confirmed because “the difference due to sex and body weight between subgroups are dwarfed by the uncertainty,” Jakobsen and colleagues write.
Co-author Stylianos Georgiadis explains that the uncertainty in the model derives from the translation of risk assessment from animals to humans, and suggests that’s where the research needs to focus.
To further complicate the picture, it is difficult to do epidemiological, population-based, studies, “because you are exposed to the compound from so many different sources,” says Jakobsen.
Then there’s different origins of cancer risk. “It’s not easy to allocate the risk of cancer piece by piece,” explains Georgiadis. “On the other hand, it’s very complicated to deal with them all at the same time.”
Georgiadis wants people and policy-makers to be aware of these uncertainties in scientific research.
Would their findings encourage the researchers to limit their barbecued meat consumption?
“From my research on risk assessment in foods,” says Jakobsen, “I would say that eating a varied diet is the best you can do.”