In fact, these seemingly different questions roughly illustrate the same thing: frying with vegetable oil brings fumes, and everyone can be victimized by them. In fact, the severity of the soot problem is again related to the variety of fats and oils, and to specific cooking methods.
Smoke exposure and lung cancer risk
The delicious stir-fry dishes that Chinese people are used to eating are often associated with smoky, greasy, dirty backrooms, and with cooks whose faces, hair, and even bodies are covered in the smell of soot. In fact, fumes do not only mean damage to the skin and pollute the environment, it also has great health hazards. The reason why pregnant women hate fumes so much is precisely because embryos in early pregnancy are particularly sensitive to harmful substances. Expectant mothers at this time the sensitivity of the sense of smell rises significantly, is instinctively trying to stay away from the oil smoke and other harmful substances, to avoid them endangering the fetus. Even if they are not pregnant, ordinary people do not like the smell of strong fumes because their bodies know they are harmful.
In our country, lung cancer is the number one most prevalent cancer among men and the second most prevalent cancer among women. Intriguingly, 15 percent of men with lung cancer and 53 percent of women with lung cancer don't smoke - but they usually fry a lot. Scientific studies have long found that cooking fumes are one of the most important causative factors for lung cancer, especially among women who don't smoke, and it's a factor that can't be ignored.
U.S. researchers combed through 29 population-based research studies. Eighteen of the 22 epidemiologic studies all found a correlation between grease smoke exposure and lung cancer risk. Another four studies found theoretical evidence linking carcinogenic air pollutants in kitchens to human health. Two studies found a correlation between the amount of 1-hydroxypyrene (1-OHP, 1-hydroxypyrene, an indicator of the metabolism of polycyclic aromatic hydrocarbons (PAHs) in the body) in urine samples from male restaurant workers and indicators of DNA damage. There was also a retrospective study from the UK that found that an occupational history of being a chef carried an increased risk of lung cancer. In other words, although there is no long-term cohort follow-up, there are now a number of studies suggesting that regular exposure to grease fumes increases the risk of lung cancer. In addition, women who have been engaged in Chinese cooking for a long period of time have an increased prevalence of respiratory diseases and decreased lung ventilation capacity. These views have been generally recognized by researchers at home and abroad.
Which oils produce the most carcinogens when heated
Many people will ask the question: Which oils produce the most carcinogens when heated at high temperatures? What kind of oil is most likely to emit fumes?
A recent science news report in the Daily Telegraph said that chemical analysts at the University of De Montfort found that fats rich in polyunsaturated fatty acids, such as corn oil and sunflower oil, produce the most aldehyde carcinogens when cooked. With them to cook a "fish and chips" fast food, carcinogenic aldehydes content than the World Health Organization's relevant health standards 100 to 200 times higher. In contrast, if you switch to olive oil, butter or coconut oil, the amount of harmful substances produced will be greatly reduced.
In fact, studies have long confirmed that cooking fumes produced by soybean oil, sunflower oil and lard contain the aldehyde carcinogens t-t-2, 4-DDE, t-t-2-NDE,
t-2, CA and t-2-UDA. t-t-2, 4-DDE is most abundant in cooking oils produced by soybean oil, which is 85% higher than that of sunflower oil. These substances are genotoxic and cytotoxic to human lung epidermal cells and significantly reduce the activity of various antioxidant enzymes and increase the production of reactive oxygen species.
These studies show that polyunsaturated fatty acids, which are often advertised as "polyunsaturated fatty acids," are in fact unstable to heat and are more likely to produce toxic carcinogens when heated at high temperatures. They are also susceptible to thermo-oxidative polymerization reactions, generating a "sticky" substance that makes the range hood difficult to clean and leaves the kitchen covered with a layer of dirt that can't be wiped off. In contrast, the lard heat temperature sex better, produce oxidized polymer is a little less, so the stove "less sticky".
So it's important to choose a fat that oxidizes less easily, is slightly more thermally stable, and has a higher smoke point. Compared to clear oils, crude oils from "clay presses" have more impurities and produce more fumes at the same temperature. Leftover oil from a single cooking session or from deep-frying is more likely to emit smoke than fresh, clarified oil. It's not wise to use them often, and don't assume that frying in "home" or "traditional" oil is healthier.
How to stay away from cancer risk
A study of 61 Army cooks found that after five days of exposure to cooking fumes, their urinary levels of 1-hydroxypyrene, a marker of PAH metabolites, 5-hydroxydeoxyguanine, a marker of DNA damage, and isoprostane, a marker of oxidative stress, were significantly higher than those of the soldiers who were not exposed to cooking fumes. . Moreover, there was a significant correlation between the log concentrations of PAH metabolites, oxidative stress metabolites and DNA damage markers in their blood. Simply put, after staying in an environment with lots of grease and smoke for several days, there was an increase in carcinogens in the blood of the cooking soldiers, a rise in the level of damage to genetic material, and an increase in substances that promote aging. These studies suggest that if the frequency of stir-frying can be reduced, the proportion of cooking methods such as steaming, cooling and blanching can be elevated, and the proportion of stir-frying dishes can be reduced, the cooks can reduce the degree of victimization.
The study also found that the state of indoor ventilation is related to lung cancer risk. Not only is cigarette smoke a source of PM2.5, but so is grease smoke. A single cigarette can greatly exceed the PM concentration in a house, and grease smoke from next to a frying pan can easily raise PM2.5 values to over 200. The more harmful substances people inhale from indoors, the more their bodies are damaged, so timely and effective ventilation is very important to reduce grease pollution.
The "overcooked" cooking method produces more carcinogens
Of course, not everyone who cooks will develop lung cancer under the same air pollution conditions. Numerous studies have found that there is a genetic basis for susceptibility to lung cancer. For people with susceptibility genes, being in the midst of air pollution for a long period of time may add to the problem and increase the risk of lung cancer. Since we are not sure whether we have super anti-pollution genes, it is wiser to take the initiative to stay away from oil smoke pollution. Because unrefined oil and leftover oil contain more impurities and have a low smoke point, more fumes will be released when stir-frying.
2. When stir-frying, reduce the proportion of soybean oil, corn oil, sunflower oil (such oils contain more unsaturated fatty acids), and prioritize the use of more heat-stable oils, such as refined tea seed oil, refined olive oil, canola oil and other monounsaturated fatty acid-based cooking oil. If high-temperature stir-frying and deep-frying is really necessary, it is recommended to choose oils that are highly saturated and more stable to heat, such as palm oil and coconut oil.
3. Reduce the proportion of dishes that require high-temperature heating by frying, stir-frying, braising, drying and other fats, and increase the number of cooking methods such as steaming, boiling, stewing, blanching, and cold mixing. For example, a steamed fish in black bean sauce, a boiled seaweed broccoli, a cold wood ear cucumber, an onion and carrot fried shredded pork. This way the dishes are also hearty and nutritionally balanced, but then there is much less fumes than 4 stir-fries.
4. Reduce the temperature of the oil for stir-frying. Given that the smoke point of pure oil and grease are now up to 190 ℃ or more, there is no obvious smoke when you can reach the temperature of normal frying. As long as you see a bit if smoke, immediately put the dishes in, the temperature is just right. In fact, how to judge the oil smoke, with a piece of onion skin or garlic can test out: around a lot of bubbles, but will not immediately change color. Eliminate the "overcooking" method of cooking in the pot. This method not only creates fumes, but also exposes ingredients to direct heat, which creates more carcinogens.
5. Buy a pot with a thicker body and a larger heat capacity. Due to the large thermal capacity of the pot, it takes time to heat up, so that the pot is not so thick and smoky before you have time to put in your dishes. It takes a few times to get used to this type of pan, and you may not be able to time your dishes well at first. But once you get used to it, you'll enjoy the happiness of less fumes, and the dishes are more refreshing and tasty.
6. Buy a range hood with strong suction. Pay attention to the installation of a reasonable height from the stove, not too far, to ensure that the suction is strong enough, 1 meter away from the stove can not be smelled frying.
7. Open the range hood before the stovetop fire, wait until the end of the stir-fry and then continue to smoke for 5 minutes, to ensure that not fully combusted exhaust and fumes are fully absorbed. At the same time, open nearby windows to allow fresh air to flow in.
8. Put on a hat and a long-sleeved jacket when doing stir-frying and deep-frying, then change out of the jacket in time and wash it regularly. Wash your hands and face after leaving the kitchen.
9. When using an air fryer to bake fat-containing foods (such as grilled fish, chicken wings, ribs, etc.), be careful to place the air fryer next to the range hood. Because of the high temperature hot air to "dry fry" fat-containing food will also produce a certain amount of smoke, which inevitably contains fat heat produced by harmful substances.
10. At present, there is a lot of research at home and abroad on the hazards of PM2.5 for pregnant mothers and children, and it is recommended that pregnant women and breastfeeding mothers should not cook smoky food and stay away from smoky kitchens. Fried food should also eat less, according to foreign research results, eat more fried food may increase the risk of children suffering from asthma, allergies and other diseases in the future.