- Miguel Trancoso Treviño
- BBC Future
Do you spend a lot of time in the kitchen preparing food? Do you like barbecue from hot skewers or well-made grilled beef? Scientists believe that your health is threatened by a number of risks – from exposure to toxic chemicals emitted to an increased risk of lung cancer. How to avoid all this?
“The only reason we evolved as humans is because we started cooking our own food. [на огне]”- says with conviction Jenna Macchioki, an immunologist from the University of Sussex (England). – When we ate only raw foods, we had to eat constantly, because the body was deprived of nutrients all the time.”
This view is popular among biologists. There is a strong list of evidence that confirms that human evolution is directly related to the use of fire.
When our distant ancestors began cooking food on the fire, they facilitated the digestion and absorption of nutrients from food, which eventually helped to widen the gap between the amount of energy expended to digest food and the amount of energy received. from food. eaten. And, of course, they had to chew less.
It is believed that thanks to culinary skills, not only did the size of our jaws decrease, but our brains also increased – we were able to afford the energetic activity of neurons.
In addition, cooking on fire kills many potentially dangerous bacteria in food, protecting us from food poisoning.
And yet, despite all the obvious benefits of such cooking, let us ask ourselves: is it possible for food processing at high temperatures to pose hidden health risks?
Raw food diets are becoming more and more popular all over the world and we are seeing a trend towards the invention and use of new ways of cooking. And scientists, meanwhile, are exploring all aspects of hot dishes with growing skepticism.
Acrylamide: Excessive cooking increases the risk of cancer
Not all cooking methods are the same for all foods.
For foods high in starch, the main danger comes from acrylamide, a chemical used in the production of polymers, but produced quite naturally, for example, when frying potatoes – generally, whenever food is cooked at high temperatures for long time.
The ingredients of carbohydrate-rich dishes (potatoes, cereals, cakes and pastries, coffee, etc.) are particularly vulnerable – the reaction of these products to temperature is easily perceived by the formation of an appetizing crust, which darkens, like a burn.
Acrylamide has long been suspected of being carcinogenic, although most evidence comes from animal studies.
In any case, Jenna Macciochi (and nutritionists) advises to refrain from frequent consumption of foods high in acrylamide, paying special attention to industrially processed foods.
In particular, the UK Food Standards Authority recommends that you stop cooking at the golden brown stage and do not store potatoes in the refrigerator if you plan to cook them later at a high temperature (cooling the potatoes releases sugars, which, in combination with amino acids, form acrylamide when heated).
In general, the basic idea is not to overcook. However, the dangers do not stop there.
“Things like acrylamide in food are just one of the many dangers of the modern diet,” warns Macciochi, who studies how diet and lifestyle affect the human immune system. “On its own, it is unlikely to cause cancer, but if a person is not eating properly, this is something we need to do to reduce the risks.”
Combustion products and lung cancer
Cooking at high temperatures affects not only what we end up eating, but also what we inhale.
Initially, stoves themselves were a major cause of disease in developing countries where people cooked over fires using wood, charcoal and agricultural waste. Indoor tobacco, according to the WHO, causes death – up to 3.8 million deaths a year.
However, the use of certain food ingredients in cooking also leads to air pollution in the home.
A 2017 study published in the Journal of Cancer Research and Clinical Oncology found evidence that inhaling combustion products from cooking with vegetable oil increased the risk of lung cancer.
Scientists analyzed 23 studies of 9,411 cases of cancer in China and concluded that not only the lack of good ventilation in the kitchen increases the risk of cancer, but also different cooking methods, each of which has its own consequences for the human body. For example, frying in a pan increases the risk of lung cancer, while frying does not.
Other studies provide evidence that inhaling vegetable oil combustion products during pregnancy can lead to weight loss in newborns.
In 2017, Taiwanese scientists compared the amount of aldehydes (many of which are toxic to humans) released by different cooking methods. The study authors believe that sunflower oil combustion products and methods such as deep frying and sautéing have a higher risk of aldehyde release, while low-unsaturated vegetable oil (such as palm or canola) in combination with milder methods does not give such aldehyde tumors (and such aldehydes that are harmful).
Fried meat and diabetes
Meat lovers should think about how they cook it and how often they eat it.
Several studies have found that cooking red meat over an open fire, as well as at high oven temperatures, can lead to an increased risk of diabetes among women who eat meat in the US (it was not clear why they were women and not men were at risk).
Another study found an association between high-temperature cooking or fire and type 2 diabetes in those who ate red meat, as well as those who ate chicken and fish, regardless of gender and consumption.
It is important to note that none of these studies took into account lifestyle elements – for example, the regularity of exercise or aspects of a person’s diet, for example, sugar intake. So it is quite possible that all this will play a role.
However, scientists have suggested the use of alternative methods (such as steam cooking) that do not appear to be associated with a risk of diabetes.
In the last century, cooking techniques have evolved and become more diverse, moving away from the old primitive ways. Microwave ovens, electric hobs and toasters are now found in almost every home – the need for an open fire has disappeared.
More and more scientists are recommending the use of a microwave oven – of course, depending on what you cook.
For example, a recent study in Spain found that one of the safest ways to cook mushrooms is in the microwave.
With this method, the level of antioxidants in the product is significantly increased, helping to protect cells from damage. But when you cook or fry mushrooms, the amount of antioxidants decreases.
Scientific evidence shows that the best way to preserve the vitamins and nutrients when cooking vegetables is to cook them for a short time and use as little liquid as possible.
In this sense, the microwave is a good way, because it wastes less useful in it, as opposed to, say, boiling, in which all the useful ingredients are put into the water.
“Steaming vegetables instead of boiling them in water is also much better. Problems arise every time you cook something for a long time using high temperatures – this reduces the nutritional properties or produces some of the unwanted acrylamide compounds,” he said. Macciocchi.
Another problem with frying, or any other cooking method that uses vegetable oil, is what happens after heating with some fat.
It turns out that under the influence of high temperature, various chemical reactions occur in the oil and you run the risk of ending up with a completely different ingredient compared to what you started cooking.
But this is not the case with all types of oils. For example, olive oil (as opposed to, say, coconut oil) very quickly reaches the point where it quickly begins to lose its nutritional and beneficial properties and produce harmful compounds such as aldehydes.
However, Macciochi recommends the use of olive oil in most cases, as it is very useful. You just do not need to use it for long-term cooking something.
And yet, despite the fact that some cooking methods carry certain risks to our health, completely abandoning cooked food in favor of raw food can be much more harmful.
According to a German study, people who followed a raw food diet for several years were found to have lost about 9 pounds (in men) and 12 pounds (in women) in weight.
By the end of the study, a significant percentage of these men were underweight and about a third of women had stopped menstruating. The authors conclude, which sounds scientifically restrained: “a very strict diet with raw foods can not be recommended for long-term use.”
“Ultimately, cooking meat and foods high in carbohydrates is a good way to increase nutrient availability, as opposed to a raw food diet,” notes Jenna Macciochi. “Think of a raw potato. It is very difficult to extract nutrients from it, not to mention that this process is unlikely to bring you pleasure.
Apparently, our ancestors knew what they did when they changed from raw to cooked food.
More articles on similar topics – on the site BBC Future.