Body temperature and life expectancy

Man is a warm-blooded animal. Thermoregulation enables human to live in regions with different climates, all year round to maintain a high level of activity. This evolutionary bonus costs us a lot, for instance, for the huge energy expenses and the ability to live long. As a consequence mammals consume dozens of times more food than cold-blooded creatures of the same weight. So how does body temperature affect life expectancy?

Experiments on lower of the body temperature

"Cool down by only half a degree and extend life by 20%" - concluded the scientists from the Scripps Research Institute (California) during the experiment. Rodents with artificial genetic mutations in the hypothalamus participated in the study. The thermoregulation center located in this part of the brain reacts to the slightest temperature fluctuations and gives an order to switch on the internal "stove" or "conditioner". Therefore, American scientists have led the mice with activated gene responsible for "local heating" of the zone near the hypothalamus. The increase of local temperature of hypothalamus was taken as signals about excessive heat formation in the organism and included "cooling systems".

As a result, the temperature of the body of such mice was 0.2 - 0.5 degrees lower than that of their usual brethren, and life was longer (male rodents, on average, by 12%, and females - by 20%). Both groups of mice had the same lifestyle and diet.

According to biogerontologist Brian Kennedy, there is evidence of a link between low body temperature and the potential for long life in humans. Scientists explain this by the slowdown in metabolic processes, but further research is needed.

With a drop in body temperature, scientists are likely to attribute an increase in life expectancy to a low calorie diet. Since the 30s of the last century, researchers have experimented by putting insects, amphibians, fish, rodents on a diet and adding 20-50% to their average life expectancy. At the end of the 90s, it was found that a low caloric diet in primates has a consistently low concentration of insulin and glucose in the blood, a decrease in body temperature and a decrease in energy consumption.

Long-lived animals: the cooler the longer

Almost all mammals are capable of maintaining a stable body temperature. However, there are exceptions. Unfortunately, one of the most interesting specimens from the point of view of thermoregulation disappeared from the face of the earth about five thousand years ago. These are Balearic goats whose remains were found on the islands of Mallorca and Menorca. Having studied the skeleton and the internal structure of the bones, biologists have come to the conclusion that this strange island animal combined the features of mammals and reptiles. From the latter they got the ability to reduce the rate of metabolic processes and, accordingly, the body temperature, based on the availability of food and weather conditions. Scientists believe that the Balearic goat was a sedentary animal, but lived almost twice as long as its jumping relatives: 28-30 years against the "standard" for such individuals 10-15 years. Biologists believe that it is the ability to lower the temperature of the body and, accordingly, to slow down the metabolism in many ways and determined the long life of this creature.

Among the living animals, the only known mammals whose body temperature depends on the environment is a naked mole rat. This creature, living in savannahs and semi-deserts in some regions of the African continent - a close relative of mice and rats, but lives at the same time ten times longer than his closest relative: about 30 years against 1.5-3 years, typical for ordinary rodents.

Naked mole rat huddle in underground tunnels: when it gets cooler, they move closer to the surface and gather in groups, minimizing heat loss. Animals are resistant to oxygen starvation and high concentrations of carbon dioxide, fatal for other rodents. Researchers believe that the reason for this resistance is the slow metabolism, which is half the speed of similar animals. Thus, low body temperature, slow metabolism, along with some other features of mole rats (for example, the ability to "get stuck" in childhood), are considered by scientists as key factors unprecedented for rodents life expectancy.

Animals capable of reducing body temperature and metabolic rate at certain moments of life are also the object of study. For example, the body temperature of hummingbirds and some other birds, bats, some species of rodents decreases when they fall into the night numbness (torpor) or hibernation. During the day, the hummingbird's organism "warms up" to 43°C, and during night numbness it cools down to 35°C (and, according to some data, below 30°C), in dwarf lemurus during the ten-hour torpor the temperature drops below 7°C, and in Berengia gopher during winter hibernation can fall to -2°C.

Almost all animals with the ability to temporarily "cool down" and slow down substances (be it torpor, winter or summer hibernation) live longer than the species that are evolutionarily close to them and sustainably maintain high body temperature. Thus, hummingbird lives to 10-12 years, despite the highest rate of metabolism, mice, awake all year round, rarely "reach" up to four years, while the life expectancy of their relatives, falling into hibernation, is about eight years, and in bats - about 18 years. According to biologists, the ability to reduce body temperature by 2-3 degrees helps to increase life expectancy by 1.5-2 times.

Is it possible to "freeze" a person?

In the middle of the 20th century, Canadian surgeon Wilfred Bigelow proved that cooling the body to 30°C halves the need for oxygen and slows down the metabolic processes in the heart muscle. As a result, the method has been successfully used in long-term operations on the heart. Later, an anesthesiologist from the University of Pittsburgh, Peter Safar, found that the cooling of the body when the heart stops significantly slows down the process of destruction in the brain. Today in medicine the methods of long-term hypothermia (cooling) of patients with severe injuries, heart attacks, cirrhosis of the liver, etc. are used for a period of up to 10 days and more. And after cardiac arrest and breathing as a result of severe injuries and wounds cooled down to 10 ° C - this is often what saves lives.

Hypothermic methods used in medicine allow scientists to study various nuances of the effects of cold on the human body. However, all these techniques are useful only for short-term use in emergency situations, and not as a lever to influence life expectancy. Prolonged exposure to cold is fatal for the human body. So, the experiment in comparison of influence of low temperatures on cells of the person and cells of the American thirteen-strip gopher whose body during hibernation cools down to zero values has been carried out. It turned out that human cells react to hypothermia by gradual destruction of microtubes - the cellular skeleton, and lysosomes - bubbles with enzymes. No damage was observed in the gopher cells: they responded to the cold by slowing down the metabolism and falling into hibernation.

Conclusions

Is it possible to lower the body temperature in order to get an additional chance to prolong life? Although our thermoregulation center stops any attempts to "unduly shake the temperature" (and even if it is damaged, other brain structures take over this function), we have some opportunities to influence this indicator.

Nutrition. The link between body temperature reduction and calorie deficiency was established through research at the University of Washington. A group of middle-aged subjects had consumed a quarter less calories than age-standard for 15 years. During this period, internal body temperature dropped by 0.2 degrees. Scientists believe that even this slight "self-cooling" can have a positive impact on life expectancy.

At the same time, studies show that low-calorie diets are not always healthy. For example, American scientists have been watching a group of 12,000 successful entrepreneurs for 10 years in order to determine how weight fluctuations affect the body. It turned out that the risk of disease and premature death was 36% higher for people who had gained an extra kilogram than for people with stable weight, and for those who had lost five or more kilograms during the experiment, the risk of disease and premature death was 57% higher. Experts attribute these results to the stress experienced by the human body during radical changes: its impact is often more destructive than the impact of bad habits and unhealthy diet.

Gerontologists at the University of Southern California recommend a "fasting diet", a five-day caloric restriction that can be practiced every month: 50% of the daily calories are consumed on the first day, 30% on the following four days, and the rest of the month can be eaten without restriction. According to scientists, this approach allows not to expose the body to constant stress, but to significantly improve physical performance (after only two months the cholesterol level drops and starts to leave extra pounds).

Stress. Excitement and anxiety lead to an increase in body temperature: scientists call this phenomenon psychogenic fever. In people under stress, body temperature can reach 37-38°C, and in some cases it can even rise above 40°C. Scientists from Kyushu University (Japan) conducted a study on mice, - it turned out that rodents under the influence of stress "turn on" the same mechanisms as the invasion of the infection. It is obvious that a stable "heating" of the body in chronic stress has a negative impact on health. Therefore, any methods aimed at relieving stress, including physical activity, swimming, meditation, breathing practices, etc., also help a person to "cool down" a little.

Sleep. Night sleep can be considered as some kind of numbness or winter hibernation in animals: our metabolism slows down by 10-15%, and body temperature drops to a minimum (35.2 - 35.9°C) between two and three o'clock in the morning. During sleep, the brain temperature fluctuates, increasing during the fast phase and decreasing during slow sleep - the temperature difference can reach 3.5 ° C. Thus, a healthy night's sleep is the easiest and healthiest way to "cool" your body, and its disorders are the causes of disease and premature aging. However, correct falling asleep is often prevented by "internal overheating", when for some reason (excessive physical activity before bedtime, over-eating, stuffiness in the bedroom, etc.) there is no natural evening drop in body temperature. That is why it is so important to switch to quiet lessons, avoid dense dinner, ventilate the bedroom well and cover yourself with a light blanket. Bed linen and night clothes should be sewn from natural fabrics, well-conducting heat. However, it is even useful to get warm in a warm bath before going to bed: studies show that this procedure increases the duration of "slow" sleep, which cools the brain as much as possible.

Yoga and meditation. In the early 1980s, Harvard scientists found that Tibetan monks can slow down the rate of metabolism by 64% during meditation, and are able to easily tolerate cold, raising the skin temperature. Magnetic resonance imaging of the brain performed on meditating monks showed an increase in the blood supply to the departments responsible for maintaining pressure, metabolism and concentration. Today, the St. Petersburg State University is working on the study of the impact on the thermal regulation of yoga Tummo. The breathing exercises practiced in the framework of this system (otherwise called internal fire yoga), change the hormonal balance of the body, which makes it possible to warm up in the cold. Perhaps, further study of these mechanisms will allow us to understand how to achieve the opposite effect - internal cooling.

 

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