As enjoyable as it is to cook a stir-fry, there is good reason to believe it might be exposing you to a cancer risk. In fact, a slow but steady stream of research now suggests inhaling cooking fumes, especially oily ones, may be hazardous. Homemakers, wok-tossers and barbecue enthusiasts, read on.
The first studies supporting a link between cooking fumes and lung cancer were published in 2000 by separate research groups in Taiwan and Singapore. The Taiwanese work, published in the American Journal of Epidemiology, studied 645 women to show lung cancer risk increased with the average number of meals cooked per day. This risk peaked at about threefold for women who cooked all three meals daily. The risk was increased further, up to sixfold, for women who did not use a fume extractor in their kitchen. Because most Taiwanese meals involve frying in oil, this study concluded the aerosolization of harmful particles was the most likely culprit.
The Singapore study, published in Cancer Epidemiology, Biomarkers and Prevention, looked at 1,069 women, demonstrating cooking increased the lung cancer risk of smokers. Smoking women who said they prepared meals by stir-frying daily were found to have double the cancer risk. Those who said they stir-fried meat daily were found to have an additional 70 percent risk while those who said their kitchens were “regularly filled with oily fumes” had an additional 170 percent risk.
In 2013, a second Taiwanese study of 865 women showed nonsmokers who were exposed to heavy tobacco smoke at work had a 3.6 times higher lung cancer risk. Much to their surprise, they also found that nonsmokers who did not receive such exposure at work but cooked more than twice daily had a nearly identical increase in risk: 3.3 times higher.
A Chinese study published in 2014 in collaboration with UCLA examined the lifestyles of 5,967 women and found good kitchen ventilation had a protective effect against lung cancer: reducing risk by 14 percent. The following year, a study published by Yale researchers looked at the lung cancer rates of 71,000 non-smoking women in Shanghai. This work found that poor kitchen ventilation resulted in a 49 percent increase in lung cancer risk.
Given the daily prevalence of stir-frying in Asia, it is not surprising that most research on this topic has thus far originated in Asia. Some important questions do, however, remain unanswered. For example, does it matter what you are frying? The 2000 Singapore study would suggest meat is perhaps worse than other foods, but this has yet to be confirmed through other studies.
Another question is whether the type of oil matters. A sizable body of research suggests certain oils might be better than others with certain industrial processes being more likely to produce carcinogens. Another question is the degree of protection afforded by kitchen ventilation. In many Asian countries, poor and average households have only a window or small fan. How might this affect risk compared to a state-of-the-art ventilation system in an upscale restaurant?
In terms of identifying the carcinogens at play, there are plenty of candidates. A few studies have already shown Chinese women who cook more often tend to have more carcinogens in their blood and urine, raising the need for more research. Equally important are considerations for food industry workers who grill or fry as a daily occupation. Workers in Korean restaurants who cook meat over open flames may be at risk as well, pointing to the need for better awareness and, perhaps, new safety standards.
Justin Fendos is a professor at Dongseo University in Busan and associate director of the Tan School at Fudan University in Shanghai. -- Ed.