June 18, 2024

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Will Lower Body Temperature Cause Weaker Immunity?

Will Lower Body Temperature Cause Weaker Immunity?

Will Lower Body Temperature Cause Weaker Immunity?

Human Body Temperature of 37°C(98.6°F) Becomes History: Lower Body Temperature, Weaker Immunity?

What Does Decreasing Body Temperature Mean?

In our collective memory, 37°C(98.6°F) has always been considered the standard body temperature for humans.

However, have you noticed that when we measure our body temperature in our daily lives, it often falls short of 37°C(98.6°F)?

And when it does reach 37°C(98.6°F), our bodies may exhibit various discomforts. Don’t worry; this isn’t an individual issue.

In reality, human body temperatures tend to be lower than 37°C(98.6°F). But why is this the case?



Will Lower Body Temperature Cause Weaker Immunity?



01. Why is the Human Body Temperature Set at 37°C(98.6°F)?

In 1851, German physician Carl Wunderlich measured the armpit temperatures of 25,000 residents of Leipzig, Germany. After collecting the data, he found that the participants’ temperatures ranged from 36.2°C (97.16°F) to 37.5°C(99.5°F).

Wunderlich selected an intermediate value, approximately 37°C(98.6°F), as the standard body temperature. Since then, 37°C(98.6°F) has become widely accepted as the norm for human body temperature and a benchmark for assessing fever, spanning nearly two centuries.


However, why is body temperature consistently around 37°C(98.6°F)? Scientists don’t have a unified answer to this question.

Still, they generally believe it’s essential to understand the advantages of being a warm-blooded (endothermic) animal. When organisms are in a state of thermal stability (homeothermy), biochemical reactions proceed at the ideal rate, and the nervous system functions most effectively, avoiding the dangers of overheating and excessive cold.

Throughout the lengthy process of evolution, endothermic animals were naturally selected, which explains this adaptation.


The choice of a 37°C(98.6°F) body temperature may be related to our adaptation to living in lower environmental temperatures. During early human evolution, our species emerged in Africa, where average daytime temperatures were relatively low.

This made a body temperature of 37°C(98.6°F) helpful in controlling the heat generated during metabolic processes, maintaining internal thermal stability, and providing a survival and reproductive advantage. Therefore, a body temperature of 37°C(98.6°F) resulted from natural selection to suit our environment and way of life.



02. Is Human Body Temperature Decreasing?

Recent research suggests that human body temperatures might be gradually decreasing over time.

In December 2017, researchers from Harvard Brigham and Women’s Hospital published a study titled “Individual differences in normal body temperature: longitudinal big data analysis of patient records” in BMJ. They conducted 243,506 oral temperature measurements on 35,488 adult individuals in the UK. The results showed that their average oral temperature was approximately 36.6°C(97.88°F), and none of them had infections or received antibiotic treatment, suggesting that human body temperature might be declining.

Similarly, in January 2020, a team from Stanford University School of Medicine published a study in eLife titled “Decreasing human body temperature in the United States since the Industrial Revolution.” They analyzed data from the United States and found that the average body temperature had been consistently decreasing since the Industrial Revolution, declining by 0.4°C over less than two centuries, from 37°C(98.6°F) to 36.6°C(97.88°F).

In the same year, a study published in Science Advances by researchers from the University of California, Santa Barbara, and other institutions found that the body temperature of residents of the isolated Tsimane indigenous tribe in the Bolivian Amazon was also decreasing. Over a 16-year period from 2002 to 2018, their average body temperature decreased from 37°C(98.6°F) to 36.5°C(97.7°F).

This indicates the widespread phenomenon of declining human body temperatures and suggests that human physiology might be undergoing some changes.

As for hypotheses regarding this phenomenon, researchers have put forward two viewpoints:

1) Metabolism-Related Hypothesis:

Metabolism encompasses the sum of chemical reactions necessary for maintaining life. If a person’s metabolic rate decreases, the heat produced will also decrease, leading to a drop in body temperature.

This might be related to changes in modern lifestyles, including diet, exercise, and environmental conditions, potentially causing a decrease in metabolic rate. If the metabolic rate of the human body decreases, maintaining a temperature of 37°C(98.6°F) might no longer be necessary, resulting in a gradual decrease in body temperature.

2) Immune System-Related Hypothesis:

Inflammation and immune responses usually accompany an increase in body temperature, which is a natural physiological response that helps combat infections and pathogens.

If improvements in modern healthcare and hygiene conditions reduce the burden on the immune system, body temperature might not need to be maintained at a higher level.

In this case, decreasing body temperature might reflect the more efficient functioning of the human immune system in responding to infections and diseases, reducing the need for elevated body temperature.




03. Does Decreasing Body Temperature Imply Weaker Immunity?

As mentioned earlier, the decrease in body temperature is related to the body’s immunity. Does this mean that human immunity is weakening?

Japanese medical doctor Shizuka Ishikawa mentioned in her book “36.5 Degrees Determines Health” that medical research has found that for every 1°C decrease in body temperature, immunity decreases by more than 30%. Conversely, when the body maintains its temperature within the normal range (i.e., 36.46–37.14°C), every 1°C increase in temperature can enhance immunity by 5-6 times. However, it’s important to note that this conclusion doesn’t apply when body temperature falls outside the normal range.

Professor Zhao Jianguo, from the Department of Integrated Traditional Chinese and Western Medicine Neurology at the First Affiliated Hospital of Tianjin University of Traditional Chinese Medicine, also believes that a lower body temperature may lead to reduced immunity. Low body temperature typically reflects a lower basal metabolic rate, slowed blood flow, and a corresponding decrease in the efficiency of white blood cells. Therefore, even when facing external threats such as viruses or bacteria, the immune response may become sluggish.


In conclusion, it’s beneficial for our overall health to raise our body temperature appropriately. Here are three suggestions to consider:

1. Increase Body Temperature Through Exercise: Engage in basic training, such as squats, to boost metabolism and body temperature. Maintain a regular exercise routine, particularly exercising in the morning, to sustain a higher metabolic rate throughout the day.

2. Maintain Body Heat: Wear appropriate clothing, especially in cold environments, to effectively retain body heat. Additionally, keeping the body dry is crucial because evaporating moisture quickly removes body heat. After washing your hair, it’s advisable to dry it promptly, as this helps raise the temperature of both the head and the entire body.

3. Allow the Body to Naturally Warm Up: Increasing body weight can help the body maintain a relatively higher temperature because extra fat retains heat. Furthermore, don’t intentionally suppress shivering and shuddering, as these instinctive actions are among the ways the body spontaneously regulates temperature and can help raise body temperature.

With this knowledge in mind, it’s essential to pay closer attention to our body temperature in our daily lives. If your body temperature fluctuates inexplicably between highs and lows, remain vigilant and seek medical advice promptly.




Will Lower Body Temperature Cause Weaker Immunity?


[1] “Science Sub-Journal: Human Body Temperature of 37°C(98.6°F) Becomes History, Humans Are Rapidly Cooling Down.” Biological World. October 31, 2020.

[2] “’37°C(98.6°F)’ Becomes History: Why Is Human Body Temperature Lower Than It Was a Century Ago?” Life Times

(source:internet, reference only)

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