The Body Temperature Revisited

Friday, July 06, 2012

"The 'fire' present in our body helps in keeping us alive. Therefore, to maintain the required body-temperature, it is important that we nourish our body with nutritious food."

It's time to go back and upgrade the body temperature talk beyond just low thyroid and metabolism so as to further understand said mechanism's function and relativity to overall health and wellness. The reason I find this aspect of health so intriguing is mainly because it gets overlooked so often. Someone goes to a doctors appointment and their temperature is 97.5. This doesn't cause concern for the nurse because the temperature is not elevated and it has become so common to see these readings among those who frequently visit the doctor. (not in all cases, but could be statically high in most). The hypothalamus has a set point for the human body temperature: 98.6. Now the set point is not an exact temperature as you will see that depending on what your eating, time of day, how your exercising or managing stress in what ever form we will see the body temperature oscillate within a certain range. (What is interesting is that the set point of temperature is much like the set point of weight and eating. When you don't eat for awhile the hypothalamus send out signals to the organs to demand food. When the body temperature drops the hypothalamus will send out signals in the organs to warm up.) Lets say between 98.1 and 99.0 would what be considered optimal for the normal human in their late teens and early to late twenties. Sometimes it's lower and sometimes its slightly elevated given the context that brought about those events. Now obviously you can still function even at a lower body temperature but As I have stated before, the optimal temperature for chemical reactions should be as close to a normal body's temperature set point as possible. Recently there has been some contradictions over what is actually considered normal...

"The 98.6° F “normal” benchmark for body temperature comes to us from Dr. Carl Wunderlich, a 19th-century German physician who collected and analyzed over a million armpit temperatures for 25,000 patients. Some of Wunderlich’s observations have stood up over time, but his definition of normal has been debunked, says the April issue of the Harvard Health Letter. A study published years ago in the Journal of the American Medical Association found the average normal temperature for adults to be 98.2°, not 98.6°, and replaced the 100.4° fever mark with fever thresholds based on the time of day."
"Now, researchers at Winthrop University Hospital in Mineola, N.Y., have found support for another temperature truism doctors have long recognized: Older people have lower temperatures. In a study of 150 older people with an average age of about 81, they found that the average temperature never reached 98.6°. These findings suggest that even when older people are ill, their body temperature may not reach levels that people recognize as fever. On the other hand, body temperatures that are too low (about 95°) can also be a sign of illness."

Dr. Carl did his armpit temperature back in the day when it is possible that his measurements may not have been as accurate but it can also be said that the amount of obese hypothyroid people in the world had increased dramatically in the last 150 years when JAMA did their study. There were also no cars, processed food or Jersey Shore. A lot of variables to mix in there as having an impact on the human organism.

Further investigation into why this temperature reading is important is to demonstrate that it can be used for a bio-marker of health and not just some quack theory. Many endocrinologists and others practicing in other fields use the body temperature along with other symptoms to diagnose many common ailments or to give clues as to what state the body is in.

Ways to get Heat

1. Cellular Respiration:

ADP + Pi + Energy= ATP (ATP transports chemical energy within cells for metabolism.)

C6H12O6(glucose) + 6O2(oxygen) = 6CO2(Carbon-dioxide) + H2O(Water) + Energy

"Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions, which break large molecules into smaller ones, releasing energy in the process as they break high-energy bonds. Respiration is one of the key ways a cell gains useful energy to fuel cellular activity."-(3)

"Resting (or “basal”) metabolic rate (RMR) accounts for approximately 80% of energy output. About two thirds of RMR is for maintenance of homeothermy (warm-bloodedness); about one third is to maintain cellular integrity, ionic gradients, protein turnover, and the like [6-8] Resting metabolic rate is largely regulated by thyroid hormones, with a minor contribution from the sympathetic nervous system. Resting metabolic rate differs by as much as 600 kcal/d for a 70-kg man" -(1)

2. Muscular activity/ Friction: Cellular respiration in the muscle along with exercise itself. When surfaces in contact move relative to each other, the friction between the two surfaces converts kinetic energy into heat.

"Physical activity (exercise) accounts for about 10% in truly sedentary humans; in addition to intentional activity, this category includes non-purposeful motion such as fidgeting, which may differ among lean and obese individuals [9], as well as upright posture." -(1)

3. Digestion: Enzymatic reactions, storage of nutrients, breakdown of substances etc all generate heat.

"The remaining 10% is frequently referred to as thermo- genesis, which means heat production unrelated to physical activity. This component is regulated by the sympathetic nervous system and includes “nonshivering thermogenesis” in response to cold exposure and “diet-induced thermogen- esis” in response to dietary intake. These are “adaptive” or “facultative” forms of thermogenesis in that they mediate specific physiologic functions [11]. Although disputed in the past, evidence for adaptive thermogenesis in humans has now been convincingly established [12-14]. "-(1)

Body temperature affects on enzyme and metabolic efficiency:

The body temperature is a homeostatic mechanism, all homeostatic mechanisms use negative feedback to maintain a constant value (i.e the set point). Negative feedback means that whenever a change occurs in a system, this automatically causes a corrective response, which reverses the change and brings the system back to the set point. The bigger the change the bigger the correction (i.e the harder the diet, the bigger the binge)

Now as I stated before, the set point is not just 98.6 (or 98.2 if your JAMA) it will oscillate from this point. The point then being that an efficient homeostatic system minimizes the size of the oscillations. However there must be some variation in between change and correction otherwise both mechanism would try to operate at once. With hormonal systems, like the hypothalamus, there is significant time lag before the mechanism can be corrected. This because it takes time for protein synthesis to commence, the hormone to diffuse into the bloodstream, and for it to circulate around the body and take effect.

I just recently came across this paper as well which discusses energy metabolism, dissipation of heat, and obesity. Now we are not sure exactly how the body utilizes energy in every circumstance but this study is interesting to note. Please be aware that in this study they use the word efficiency in a different manner then myself. For instance they say that those who store fat instead of dissipation of heat have a more efficient metabolism. My definition of efficient metabolism is the act of burning fat (not storage) and allowing NEFA to be metabolized properly. A constant balance of burning and storing, instead of one process dominating over another. See the following quotations:

"The energetic requirements of homeothermy, the maintenance of a constant core temperature in the face of widely divergent external temperatures, accounts for a major portion of daily energy expenditure. Changes in body temperature are associated with significant changes in metabolic rate. These facts raise the interesting possibility that differences in core temperature may play a role in the pathophysiology of obesity."- (1)

"Inspection of the energy balance equation shows that increases in energy output broaden the range of energy intakes over which balance can be achieved. The overfeeding
experiment [3] described above demonstrates that some individuals can achieve energy balance at a greater caloric intake, thereby making them resistant to weight gain. On the other hand, those individuals with more efficient metabolic traits have a diminished capacity to dissipate energy, are prone to obesity, and may be said to have a “thermogenic handicap.” - (1)

"Since the initial formulation of the “thrifty gene” hypothesis by James Neel in 1962 [16], the nature of thrifty traits has been the subject of considerable research and speculation. A recent formulation [17] highlights 2 distinct components: (1) decreased metabolic rate and/or a diminished capacity for “thermogenesis” and (2) decreased insulin sensitivity. These 2 components address the 2 main physiologic imperatives of starvation: energy conservation and protein preservation. A decrease in metabolic rate would lead to more efficient storage of calories as fat, thereby prolonging survival during famine; during periods of abundance and in the face of dietary excess, this trait would predispose to obesity." -(1)

"Raising core temperature by 1°C is associated with a 10% to 13% increase in metabolic rate [41]. During starvation, a fall in body temperature occurs, contributing to the decrease in metabolic rate noted in this state" -(1)

" 1°C increase in core temperature increases expenditure of 100 to 130 kcal/d. Such an individual could achieve energy balance eating 100 to 130 kcal more per day than one with a 1.0°C lower body temperature. Individuals with the 1°C lower core temperature, thus, would have a thermogenic handicap of about 100 to 130 kcal/d or about 3000 to 4000 kcal/mo." -(1)

"In 1 month, this would account for 1 lb of fat, 12 lb in 1 year, and about 120 lb in a decade, all else being equal. In the normally active example described above where RMR constitutes 37% of total energy expenditure, the impact is less but still impressive. Under these circumstances, the thermogenic handicap of a 1°C lower core temperature might approximate 74 to 96 kcal/d or about 2200 to 2900 kcal/mo. Greater falls in temperature, perhaps during sleep or in response to low-energy diets, would have correspondingly greater effects. " -(1)

Body temperature regulation is of the utmost importance because this works in sync with enzyme reaction rates, glucose control, hormonal shifts and so many more aspects that are important to the body. Now there are some people out there who claim that a lower body temperature is optimal for "longevity" or anti aging. This comes from a number of animal studies "proving" that calorie restriction and low body temperature is preferred for superior health and longevity in humans as well. I generally don't see it that way and suggest that superfluous calorie restriction has the opposite effect in humans who don't live in cages.

“In some animal forms, at least, chronic under nutrition prolongs the natural life span. It has been suggested that the natural life span is fixed, not in time, but in terms of total metabolism or some function of the rate of living. But in man severe under-nutrition makes him look, feel, and act prematurely old. There are also changes in basal metabolism and in sexual function which resemble those produced by age.” -Ancel Keys The Biology of Human Starvation.

"Our findings suggest that 2 biomarkers of longevity(fasting insulin level and body temperature) are decreased by prolonged calorie restriction in humans and support the theory that metabolic rate is reduced beyond the level expected from reduced metabolic body mass. Studies of longer duration are required to determine if calorie restriction attenuates the aging process in humans."-(2)

After seeing some of the pictures of people with some of the lowest body temperatures in the health community I can confidently say they couldn't be farther from truth or reality for that matter. I would much rather live a full life to the age of 80 and die rock climbing then practicing calorie restriction my whole life, having no energy or rational thought. A low body temperature is a sign of failure to thrive not vitality. I think we all want to be metabolically Invincible in some respects:

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