Health. The “normal” human body temperature is no longer 37°C (but we don’t know why)

“We are cooling down”: the study conducted by Julie Parsonnet, a doctor specializing in infectious diseases at Stanford University, is formal.

An interval of 1.5 ° C

Today, 36.5 ° C should be considered “normal” for a healthy human body, he said – and that any temperature between 35.7 and 37.3 ° C should be considered normal, remember the researchers.

To function properly, the body must remain within a temperature difference of approximately 1.5°C. Outside, neurons, organs, muscles do not work much. So the body spends a lot of energy to stay at this temperature level.

All this is done by signals released by the hypothalamus, which warns us that our blood is not at the right temperature.

Julie Parsonnet, researcher at Stanford

Many factors have an influence: age, morphology, activity, diet, time and method of measurement, etc. An infection, of course, can also cause a change in temperature, to help the immune system fight pathogens.

At first, Julie Parsonnet worked on weight gain for Americans. By studying 200,000 measurements spread over 160 years, he found that the body temperature of an “average” American dropped 0.5°C (or 1° Fahrenheit) during that time. The data that most justify, according to him, the need to evaluate the level that is considered “normal” in this temperature:

We grew taller, fatter, and cold [nous vivons] Longer. These four elements come together, in a way

Julie Parsonnet

A thermometer error in question?

Confronted with Julie Parsonnet’s results, Philip Mackowiak defended this hypothesis. Professor emeritus of the University of Medicine of Maryland, he thinks that it is … the beginning reference that is not accurate: the famous “37 ° C” dates back to an 1871 book, published by the German doctor Carl Rinhold August Wunderlich. That would have averaged a million temperatures accumulated in his years of practice in a clinic.

Mackowiak pointed out two pitfalls: the fact that he was able to achieve an average, at the time, of a large ensemble, without a computer. And the weakness of the mercury thermometer in time. Pr Mackowiak examines the instrument in use, shown in Philadelphia:

[Il] calibrated 1.5 degrees [centigrade] more than modern or contemporary thermometers

Philip Mackowiak

What is not valid about Julie Parsonnet’s theory? Refusing to decide, he said that he was “not convinced” of his work, but did not close the door – and also disputed 37 ° C as a reference:

I have no way of being sure, one way or the other. But my intuition is not. [la température corporelle humaine] has not decreased over time

Philip Mackowiak

Other researchers, who were not necessarily convinced at first, joined the Stanford scientist. Like anthropologist Michael Gurven from the University of California, who re-examined all the data. And got the same result:

We don’t understand why exactly, but there seems to be a decrease

Michael Gurven

He wanted to examine whether the evolution of lifestyles might have played a role. In the work of the people of Chimanes, a population of Bolivia somewhat isolated from the outside world, he also noticed a decrease from 37 to 36.5 … but only in 20 years! If there is nothing to explain it so far – whether these people or in general.

Among the possible causes, air conditioning, food, chronic diseases, parasites, sleeping habits, medicine… The simple fact of better access to the health system or some basic things , like blankets, can play.

Should we be worried about 37°C?

Researchers insist on the need to change in relation to the unchanging reference of 37 ° C, at least in the field of medicine. However, they remind us: at 36.5°C or 37°C, there is no fever.

37°C is a normal temperature, but it is not “the” normal temperature

Philip Mackowiak

Now, in the hospital, we usually qualify as a fever above 38.3°C (101°F). But this is not the only symptom observed by the nursing staff:

Fever is only one of the symptoms of the disease. But the truth is, if you feel sick, then you are sick, regardless of your temperature.

Julie Parsonnet

Leave a Reply

Your email address will not be published.