International. A new study by Stanford University says that in the last 200 years the human body has been decreasing its temperature substantially and continuously.
"Our temperature is not what people believe," Julie Parsonnet, a professor of medicine at the California-based university and co-author of the research, said in a statement. "What everyone believes, that our normal temperature is 37 degrees Celsius, is incorrect."
This new research claims that since 1800 body temperature has been steadily decreasing every decade.
Thus, the researchers found that men born in the 2000s have a temperature 0.59 ºC lower than those born in the nineteenth century.
As for women, the study found that those born in the late twentieth and early twenty-first centuries have a temperature 0.32 ºC lower than those born in the 1800s.
Less hot
The idea that the standard temperature of the human body is 37 °C was established by the German physician Carl Reinhold August Wunderlich in 1851.
More recent studies, however, had already questioned that idea.
One of them, for example, analyzed the body temperature of 25,000 Britons, and found that the average is 36.6 ºC.
In the new research, Parsonnet and his team looked at the temperature records of more than 677,000 people born between 1800 and the late 90s of the 20th century in the United States.
The analysis showed that from decade to decade in that period, the temporary temperature dropped 0.03 °C.
That means that, on average, today's body temperature is 1.6% lower than that of the pre-industrial era.
Why is that?
The researchers claim that the cause of this decrease in temperature is related to the reduction of what they call "metabolic rate"; that is, the amount of energy that the human body uses to function.
And why this reduction?
The authors believe that it is due to the overall decrease in inflammations in people.
"An inflammation produces all sorts of proteins that speed up metabolism and increase temperature," Parsonnet says.
The authors argue that the lower presence of inflammations could be related to the fact that during the last 200 years medical treatments and hygiene habits have improved significantly.
They also point out that living in less variable environments may have decreased metabolic rate.
In the nineteenth century, for example, there were no good heating or air conditioning systems. Today, because we live in more stable environments, the body needs to expend less energy to keep its temperature constant.
"We're just different than we were in the past," Parsonnet says.
The study has the limitation that it only took into account people from a developed country such as the United States.
The authors, however, argue that the finding allows us to better understand the changes in human health and longevity over the past 200 years.
Source: World Economic Forum.
