Cooling in hot weather: do popular methods work?
According to forecasts, in many US states hot and suffocating August is expected. Those who do not have an air conditioner at home or in the office will look for ways to cool themselves, often resorting to popular advice.
Edition with the BBC tried to look from a scientific point of view at the five very common people's councils suffering from the heat, to find out from the effectiveness.
1. Drink cold drinks and abstain from hot
Drinking more in the heat is right. It is very important in such conditions to help your kidneys and prevent dehydration. But there has long been a debate about what kind of liquid to drink - ice or hot.
The theory behind the choice of the hot, is this: you heat yourself up from the inside, start to sweat more, which eventually cools you.
The human body is able to excrete up to two liters of sweat per hour, and this is a very effective way to lower its temperature.
But if the lost amount of fluid is not compensated, then soon you will be dehydrated - and because of this, some experts recommend that you completely abandon hot drinks in the heat.
In addition, they emphasize that it is better to avoid tea or coffee, because these drinks contain caffeine, increasing dehydration. However, very little evidence that a moderate amount of caffeine acts as a diuretic.
Indeed, some studies support the notion that cold drinks are better in hot weather.
Experiments were conducted, in particular, during which participants were subjected to severe physical exertion, and then their body temperature was measured as they were given either hot or cold drinks. It was found that the latter more effectively cool the body.
However, there is at least one possible problem with such studies - the method used to measure temperature.
Brave volunteers were given rectal thermometers. As noted by Olli Jay, a graduate student at the Department of Physiology of Thermal Control of the University of Ottawa (Canada), drunk cold liquid fell straight into the stomach, which is not very far from the supplied thermometer. It is not surprising, therefore, that the temperature quickly fell.
When a team of researchers led by Olli Jay took readings using eight thermometers placed in different parts of the body, it was found that hot drinks cool the body morebecause, as already noted, they increase perspiration.
So hot drinks in the heat help better. There is, however, a situation in which they are useless: if the humidity is very high or you are so dressed that sweat does not have the ability to evaporate. In this case, use cold drinks.
Verdict: This is a myth. Hot drinks will cool you down faster - unless the humidity is too high.
2. Use a fan
The breeze from the rotating fan is definitely a relief. But we must take into account that the fan does not cool the air, it just moves it, and the air flow created by it helps the normal heat exchange of our body - including the evaporation of sweat that appears on the skin from the heat.
Fans are used everywhere. There was even a casewhen three patients with heat stroke were cooled downwardly from the propeller of the light helicopter.
However, there are different opinions on the cooling efficiency of the fans.
In 2012, the authors Cochrane Analytical Reviews (which usually collect all existing primary research on a particular topic, and then evaluate them using strict rules to establish whether or not there is convincing evidence regarding a particular method or treatment) decided to test the effectiveness of the fans and with acute shortages of randomized controlled trials.
Most studies were observational, observant, without the intervention of scientists. Some of them found that the fans help, others noted that if the air temperature is very high, then the situation is only getting worse.
In general, it is believed that a fan can help if the air temperature is not higher than 35 degrees Celsius. If it is higher, then blowing the body with such air will only increase the thermal load and may lead to thermal shock.
So if the room is too hot, then the use of fans even accelerates dehydration.
In addition, fans are less effective at high humidity. In this case, though the air moves, it is filled with moisture, which makes it difficult to evaporate the sweat from human skin.
However, until randomized controlled studies are conducted, we cannot know for sure what effect the fans have.
And such studies are not easy to plan. Scientists will need to prepare everything for the moment when the next wave of heat comes - and the required temperatures may have to wait several years.
What we know for sure so far is that fans are not always a lifesaver. Let's say during the heat of the year 1999 in Cincinnati 17 people died, and ten of them used fans, which were turned on when these people were found dead.
Of course, we don't know - maybe they would die even faster without the fans. Or maybe they just bought fans because they lived in very hot buildings.
Verdict: Need more data. But if the temperature has passed for plus 35 Celsius, it is better to turn off the fan.
3. Strong heat is dangerous only for older people.
It is true that during especially hot days it gets to hospitals more people and many of them are elderly.
The body temperature at which our body feels most comfortable and works normally is between 36 and 37,5 degrees Celsius.
Thermoreceptors on our skin, deep tissues and organs immediately detect an increase in temperature - even by one degree. If the ambient temperature is higher than body temperature, we begin to sweat to cool down.
In addition, we release heat by sending more blood to our hands and feet (which is why they can be so hot at night).
Both of these methods of thermoregulation require more active work from our heart. Therefore, older people sometimes have heart attacks or heart attacks.
Unlike how a cold snap affects the health, the majority of deaths from heat occur already in the first days of its arrival.
Another problem with older people is that they are not always able to understand in time that they are overheating and their body is dehydrated.
However, all this does not mean that the heat is dangerous only for the elderly. Children and people with chronic illnesses are also at risk - just like anyone with mobility difficulties, which prevents them from simply walking up to a window and opening it, fetching water or making hot tea to replace the loss of fluid from sweating.
When it is hot day and night, our body is very difficult to cool. Heat in Europe 2003 of the yearby some estimates, caused the death of at least 30 thousands of people, and some experts cite the number in 70 thousands. Of the 15 thousands who died in France, 1321 people were at the age not exceeding 64 of the year.
Verdict: Not true. Elderly people, of course, should be especially careful in the heat, but so should many others.
4. Need to open all windows
Opening a window is the first thing most of us think of when it's hot. But this can have the opposite effect.
It is necessary to open the windows only when the air outside is cooler than in the room (and this is how it usually happens at night).
During the heat of the day, you should keep your windows closed. Less sunlight gets into the room, so the temperature is not so high.
Even if by creating a draft you can achieve some blowing through your home or office, it will only work if the air is not too hot - otherwise you will not be able to cool down.
Moreover, if the content of pollen in the air is high, then such ventilation will only exacerbate allergies in those who suffer from it.
Verdict: This is not true if the air temperature outside the window is higher than in the room. But the windows open at night will make your life easier during the heat.
5. Need to drink beer
In the 1958 film The Hard Way to Alexandria, the character played by John Mills dreams of an ice cold beer under the scorching sun of the African desert. At the end of the film, after all the adventures and difficulties endured, he sits in a bar, they bring him the coveted beer, he takes a sip and says the famous words: “Worth waiting for” (“It was worth waiting for”).
You don’t need to drive a truck through the desert in North Africa to have a beer at sunset. But will it help cool? Not always.
If it's just one glass, then the beer is unlikely to hurt you. In various studies, scientists offered participants physical activity in order to get them sweat, and then gave them beer - including non-alcoholic ones.
In one of 1985 research year such an experiment took place in an atmosphere of high humidity, and the "urinary peak" occurred after drinking beer. This is not good because it indicates that the body is losing rather than retaining fluid.
However, it should be emphasized that the difference in the results of those who drank non-alcoholic beer, and those who drank the usual, was extremely small.
Other, more recent research yielded similar results. Although regular water and refreshing drinks for athletes were more effective in compensating for fluid loss, beer also showed surprisingly good results.
Another study by Spanish scientists, in which participants spent 40 minutes on a running simulator, has shown: Both water and beer to the same extent helped to compensate for the loss of fluid.
And this is strange - because we know that people go to the toilet more often when they drink beer. Perhaps when the body becomes dehydrated and needs fluid, it leaves as much of the beer as it needs.
These are, however, small studies that did not pay attention to how the body temperature behaved, so we cannot say for sure if the beer cooled the body and, if so, how effectively.
But they demonstrated that one or perhaps two glasses of beer would replace fluid loss rather than worsen it. So, probably, the hero of the movie "The Hard Way to Alexandria" was right, a pint of beer was worth the wait.
Verdict: This is true - at least when it comes to one or two glasses.
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