Most of us realize that a body temperature of 98.6 degrees Fahrenheit or 37 degrees Celsius is considered normal. Surely there is a reason for 98.6 to be an optimal temperature for us humans.
In 2011, Bjorn Carey reported that humans and other advanced mammals are less susceptible to invasion or infection by many fungal species because we maintain a high body temperature, higher than some other animals that are more cold blooded. Many reptiles are susceptible to thousands of fungal species, but humans are invaded by only a few hundred species of fungi. There are fungal-fighting benefits in keeping the temperature between 80 degrees and 104 degrees F. The number of fungal species that can invade declines by 1.6 percent for every 1.8 degree F rise in body temperature.
Mammals need to spend more time eating in order to help maintain a higher normal body temperature however. The body produces heat through metabolic processes by taking in food or fuel in the form of glucose and from glucose produces carbon dioxide, water and energy. Some of this energy is stored in a chemical called ATP or adenosine triphosphate. ATP is used for cellular functions and about 85 percent of heat needed to maintain body temperature is produced by our skeletal muscles.
Different parts of the body have different temperatures. There is also a fairly wide range in body temperatures in normal healthy people. Morning temperatures tend to be lower than afternoon temperatures. There may be as much as 0.9 degree F variation throughout the day. The lowest temperatures are usually recorded during the second half of the sleep cycle and about two hours before awakening. In other words body temperature is not the same for each time of day and may normally vary by between 97.7 and 99.1 F.
The elderly may have problems generating adequate body heat and maintaining normal temperatures. During an illness, they may have a decreased ability to generate body heat therefore a somewhat elevated temperature could suggest a serious underlying problem usually of infectious origin.
Most fevers are caused by infections. Fever makes the body a less than favorable host to many microbes. The hypothalamus, which is located at the base of the brain, acts as the body’s thermostat. However, temperatures greater than 105 degrees F may interfere with the “integrity and function of proteins accustomed to the body’s usual temperature variations.”
Fever is part of the immune response to infections, but sometimes antipyretics are helpful in reducing symptoms, as well as fever. Aspirin and nonsteroidal anti-inflammatory drugs, or NSAIDS, cause the hypothalamus to override the fever stimulus.
In general aspirin should not be given to children and younger teens because of the association with a medical condition known as Reye’s syndrome.
The core body temperature refers to the temperature of internal organs such as the liver, kidneys or heart. In these organs essential enzymatic reactions occur within the normal variations of temperature. Oral temperatures are usually about 0.7 degrees F lower than rectal or internal body temperatures.
Ear thermometers use infrared sensors to determine temperature emitted from the eardrums and could give a different reading for each ear. Forehead infrared thermometers are popular but not more accurate than digital stick thermometers.
A well read colleague has recently shown me a very interesting article in the Dec. 12, 2015, issue of Economist magazine. In this article a study by Mirko Trajoviski reports that our body temperatures are somewhat related to our intestinal microflora.
Mice kept in a cold environment were more efficient at extracting nutrients from their diets compared to mice maintained under exactly similar conditions but housed at normal room temperature conditions. Therefore the article concludes that at least in some part our body’s thermostat may be partially influenced by our intestinal microflora.
Keep your microbes happy, and they can help to keep you warm during the colder days yet to come.
David Keisler is a gastroenterologist and internist in Aiken.