Our Body Temperatures Have Grown Colder Since the 19th Century

Today's standard temperature of 98.6 degrees Fahrenheit may not be correct.

Today's standard body temperature of 98.6 degrees Fahrenheit was established by German physician Carl Reinhold August Wunderlich in 1851. It's a standard that for the most part has served us well, however, more recent studies have indicated that our body temperatures may actually be colder.


Not what people think

"Our temperature's not what people think it is," said Julie Parsonnet, MD, professor of medicine and of health research and policy. "What everybody grew up learning, which is that our normal temperature is 98.6, is wrong."

For their study, Parsonnet and her team compiled temperatures from three distinct historical periods. The three periods covered people born in the early 1800s all the way to today.

The researchers then used 677,423 temperature measurements to develop a linear model that interpolated temperature over time. What their calculations found was a decrease in body temperature of 0.05 F for every decade.

For those stipulating that these differences can be simply attributed to better thermometry, it should be noted that the researchers took this into account in their study.

Reduction in metabolic rate

So, what could be causing this decrease in temperature? The researchers stipulate it could be attributed to a reduction in metabolic rate. 

"Inflammation produces all sorts of proteins and cytokines that rev up your metabolism and raise your temperature," Parsonnet said. 

There is no doubt that today we have much better public health than 200 years ago. We also live more comfortable lives at constant ambient temperature reducing inflammation and other health problems. 

"Physiologically, we're just different from what we were in the past," Parsonnet said.

"The environment that we're living in has changed, including the temperature in our homes, our contact with microorganisms and the food that we have access to. All these things mean that although we think of human beings as if we're monomorphic and have been the same for all of human evolution, we're not the same. We're actually changing physiologically."

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