Average Human Body Temperature Lowering, No Single Cause Known

living in high-income societies no longer believed to be cause of lower body temperatures

By Jonny Lupsha, Wondrium Staff Writer

Human bodies are increasingly falling short of 98.6 degrees Fahrenheit, Science Alert reported. While previously believed to be confined to the US and UK, the phenomenon was recently found in a remote Bolivian tribe as well. In animals, homeostasis regulates body temperature.

Dog panting in hot weather
Animals experience homeostasis due to physiological processes that allow for a consistent internal body temperature. Photo By Shevs / Shutterstock

According to Science Alert, if you’ve been feeling chillier the last couple of years, you aren’t alone. “Over the years, it seems as though people in the United States and the United Kingdom have grown steadily colder, with body temperatures coming up short of the usual 98.6 degrees Fahrenheit, or 37 degrees Celsius, a generally accepted average,” the article said.

“New research on the Tsimane, a relatively remote indigenous tribe in Bolivia, suggests this trend is not a fluke, nor is it simply a product of high-income living. Instead, it appears to exist even in rural and tropical areas, where healthcare is minimal and infections are widespread.”

Animals regulate their body temperatures as part of the process known as homeostasis, which helps an organism’s cells stay buffered from changes to the external world.

Where’s the Thermostat?

The first question about homeostasis to answer is why body temperature matters so much to animals.

“All of the biochemical reactions needed for a cell to stay alive and function well are dependent on the particular physical conditions in which they occur,” said Dr. Stephen Nowicki, Bass Fellow and Professor of Biology at Duke University. “The reason for this is that all of these activities are mediated by proteins. The structure and functions of proteins can be affected by a number of physical and chemical conditions—things like pH, or salt concentration, or oxygen concentration, or carbon dioxide levels.”

Dr. Nowicki said that temperature is critical to protein function because biochemical reactions occur at different rates. Usually, higher temperatures mean higher rates. Temperatures that are far too high or too low can either cause an enzyme to unfold and cease functioning or freeze the entire cell, respectively.

The Body’s Thermometer

“In addition to a mechanism for modifying the internal environment, homeostasis also requires mechanisms for obtaining information about the internal environment and for using this information to determine how much control to exert,” Dr. Nowicki said.

“We call any mechanism that modifies some parameter of the internal environment an ‘effector.’ We call any mechanism that obtains information about the present state of the internal environment a ‘receptor.’ An organism finally also needs some mechanism that compares the current value of the parameter to the desired value of the parameter, calculates the difference, and then directs an effector to change the value of the parameter in the appropriate direction.”

Dr. Nowicki said that mammals are what are called “endothermic organisms,” meaning we get our body heat from within. We generate heat by metabolism, or cellular processes that break down sugars and other biomolecules in the name of producing cellular energy.

The lower an external temperature is below an animal’s preferred temperature, the higher the metabolic rate of an endothermic organism, like needing to use more energy to pedal a bike uphill. Metabolic rates are lowest when an external temperature matches an animal’s preferred environment. Very high temperatures also raise the metabolic rate because the animal must use energy to lose heat, in processes like panting.

For now, the reason so many people aren’t reaching 98.6 degrees Fahrenheit internally remains a mystery.

Edited by Angela Shoemaker, Wondrium Daily

Dr. Stephen Nowicki contributed to this article. Dr. Nowicki is Bass Fellow and Professor of Biology at Duke University. He is also Dean and Vice Provost of Undergraduate Education at Duke, and holds appointments in the Department of Psychological and Brain Sciences and in the Neurobiology Department at Duke University Medical Center. Prior to taking his position at Duke, he was a post-doctoral fellow and assistant professor at The Rockefeller University. Professor Nowicki earned his undergraduate degree and a master’s degree at Tufts University, and his PhD from Cornell University.