• Cold foods only very temporarily help lower body temperature, according to our partner The Conversation.

  • The feeling of refreshment provided by cold liquids is more likely due to a rehydration effect.

  • The analysis of this phenomenon was carried out by Peter Poortvliet, postdoctoral researcher in neuroscience at the University of Queensland (Australia).

All over the world, summer is synonymous with water activities, cold drinks and, of course, ice cream.

While most of us agree that ice cream and cold drinks are refreshing summer pleasures, do they actually help cool us down?

To find out, you need to know a little more about how the body controls temperature under different conditions.

The process of maintaining optimal body temperature is called thermoregulation.

It involves a delicate balance between heat production and loss.

Humans are warm-blooded or endothermic, which is a scientific way of saying that we can control our body temperature independent of the environment.

We can do this because our body is constantly producing heat as a byproduct of internal chemical processes (metabolism).

How does it all work?

The metabolism is necessary for the proper functioning of our body.

It includes the digestive processes involved in breaking down nutrients in food, absorbing and transporting these nutrients to cells, and converting them into building blocks or energy for physical activity.

A good ice cream often gives a feeling of refreshment © Lindsay Moe / Unsplash

These chemical reactions can generate heat. It is beneficial when it is cold, but when the outside temperatures rise, we must avoid overheating. While it may seem logical that the introduction of a cold food, such as ice cream, into the stomach helps to reduce the temperature, its initial cooling effect is quickly replaced by the heat generated by the digestive processes necessary for the decomposition of the stomach. its nutrients. Digestion of high calorie foods leads to an increase in body temperature.

Ice cream is therefore not the best option for cooling off, but what about cold drinks?

The transfer of heat between a cold drink and the digestive system can directly influence the temperature.

But, this is only momentary and depends on the quantity and caloric content of the liquid ingested.

A small amount of liquid will lose its cooling effect fairly quickly as it is warmed by the surrounding organs.

And large amounts of cold fluids will cause blood flow to slow down, making heat transport less efficient.

Cold drinks are very popular in summer © Kaizen Nguy N / Unsplash

As you can imagine, drinks with a high calorie content, such as soda, will have an effect similar to that of ice cream and will jump-start our metabolism soon after ingestion.

Yet we have the impression of cooling off

The cooling effects of cold liquids are most likely explained by their rehydration effects.

If heat builds up, the body will attempt to lose excess heat by carrying it away from vital organs to the skin surface where it is transferred directly to our environment by convection and radiation.

For this to happen, the ambient temperature must be lower than our own temperature, otherwise the opposite is happening and the heat is transferred to our body.

Just like the heat radiated by the sun on a hot summer day.

Sweating causes evaporative cooling © Hans Reniers / Unsplash

Sweating is the most efficient way for our body to lose heat.

Sweating occurs when an increase in the body's core temperature is detected by the brain, which responds by stimulating sweat glands spread all over the body to produce sweat.

Sweat on the surface of the skin evaporates, causing the skin to cool (also called evaporative cooling).

The blood that circulates near the surface of the skin cools in the process and helps reduce core temperature.

On average, an adult can lose up to half a liter or a liter of sweat per day, but in hot environments this amount can reach almost a liter and a half per hour.

This is why it is essential to keep the body hydrated in hot weather.

Drink hot to cool down

Alcoholic drinks - here, beer - reduce the ability to sweat © Paloma A / Unsplash

What about alcoholic drinks?

Many people jump on a cold beer on a hot summer day in an attempt to cool off.

But alcohol is a diuretic, which means it loses water in your body and thus reduces your ability to lose heat through sweat.

Surprisingly, hot drinks can be a great way to cool off.

While not intuitive, consuming a hot beverage triggers a sweating response in receptors in the mouth and throat, allowing the body to cool off without having to ingest a large amount of hot liquid.

Some ingredients in spicy foods have the same effect;

they also trigger a sweating reaction which allows the body to cool off.

This is why these types of foods are popular in hot climates.

Our file "CANICULE"

So, while cold treats can be satisfying and certainly refreshing, a better way to cool off is to spice things up, sweat, and most importantly, rehydrate!

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This review was written in English by Peter Poortvliet, postdoctoral researcher in neuroscience at the University of Queensland (Australia).


The original article was translated (by Benoît Tonson with help from DeepL)

and published on The Conversation website.

Declaration of interests

Peter Poortvliet does not work, advise, own shares, receive funds from any organization that could benefit from this article, and has not declared any affiliation other than his research organization.

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