Do Human Bodies And Brains Hibernate During Winter?
Hibernation may bring to mind visions of a bear lazily sleeping away a cold winter, but there’s much more to it than meets the eye. What has for centuries been a survival tactic for several species is now being studied by hibernation biologists for application to humans. So can we, as humans, really hibernate? And should we?
Hibernation – something we might associate with a bear, a bat, or even a squirrel, but certainly not other humans. Scientists, however, are also studying hibernation with a keen eye to see if it can apply to humans for treating health problems like strokes and even metabolic disorders. But is it in fact possible to actually hibernate or slow down when external conditions get too extreme? And is there really a need for this survival tactic in our lives?
Nature’s Way Of Slowing You Down
Hibernation is the slowing down of your metabolism, not unlike what some other species do during winter. Hypometabolism or hibernation in human beings, however, is a much-contested notion. Researchers question whether there is a real need for this slowdown for any biological reason. Yet, there are seasonal disorders like Seasonal Affective Disorder (SAD) that crop up during the long dark months each winter, resulting in some symptoms or behaviors that could be explained as the body going into a form of hibernation. For instance, sexual abstinence, a feature of hibernation, is reflected in the loss of libido of someone with SAD. Oversleeping and lethargy, as you might see in the lead-up to hibernation, are also common as metabolic rate drops.1
Hibernation: Walking The Fine Line Between Life And Death
Metabolic activity slows down 5–7 percent with every degree of dip in body temperature. Blood pressure and heart rate drop. But as a BBC report explains, when your body temperature falls by a mere 4 degrees celsius below its normal level, you will experience a flutter in the heartbeat. Dropping the temperature further puts you at risk of cardiac arrest.2 In this state of hypometabolism, your body begins to use lipids as an energy source instead of carbohydrates. Outwardly, this causes a hibernating animal to shed as much as 40 percent of its total body weight during hibernation, most of which is lost as it comes out of hibernation to a wakeful state.3 The body teeters between slowing down enough to stay alive and return from hibernation, and not going too far and risking death. In a true state of hibernation, the animal or organism does everything it can to conserve energy, and that includes abstinence from any kind of sexual activity. Studies also find that associated reproductive functions including spermatogenesis, lactation, and fetal development slow down or stop during hibernation.4
Hypothermia lowers cellular metabolism needs and is one step in the direction of hibernation. However, if this goes too far and you experience severe hypothermia it could even cause cardiac arrest. That’s because, unlike species that hibernate, the human body is not built for this extent of lowered metabolism.5
The circadian system of mammals that hibernate is described by researchers as “damped” or sometimes completely absent. However, this very system can sometimes also be a regulator of the timing of phases of torpor or deep sleep.6
Some researchers have suggested that certain other human pursuits of today can replicate some of the physiological changes associated with hibernation. For instance, when you meditate, your metabolic rate drops. This state of hypometabolism is also achieved when you undergo hypnosis or are asleep. But there are some differences. Significantly, when an animal is in hibernation, it is not in a conscious wakeful state. Humans in meditation-induced hypometabolism, however, are both alert and conscious.7
Should You Hibernate In Winter?
Winter and natural weather phenomena still affect us, much as they always have. However, with a little help from your friendly neighborhood consumer goods store, you can pick up all the gadgets you need to simulate summer indoors. Heaters keep us warm, electric lights bathe our rooms with warm yellow light, and light thermal fabrics and gloves and boots help ward off any frozen fingers and toes. In other words, you don’t really have any reason to hibernate anymore. You are neither deprived of nutrition sources (starvation being another trigger for hypometabolism), nor is the climate so extreme as to warrant deep sleep or hibernation. However, there are specific things like diet, exercise, and sleep which you can modify to slow down if you need to.
Sleep: Do You Need More In Winter?
Have you noticed how you are always sleepier in winter? The absence of sunlight for long stretches and the limited exposure you have to the rays of the sun make the body produce less of the hormone melatonin. Melatonin is a vital piece of the sleep puzzle and is responsible for making you drowsy. Its release is also closely tied to exposure to light and dark. Which is why, when the sun dips down the horizon early, you get sleepy earlier too. Often, our lifestyle prevent us from turning in at this new early hour, and the result is drowsiness and what some call “winter tiredness.” Not giving in to this need for sleep can be hard and you might feel eternally drowsy, but sleeping in a hibernation like manner could make it worse. According to the NHS in the UK, you need the same amount of sleep in winter as you do in summer. Which is about eight hours for the average adult.8
Slow Down Or Not
Unlike animals in harsh environments, you do not need to “slow down” in winter. On the contrary, you should try and stay active to boost your mood. Symptoms of winter depression or SAD can actually be alleviated with the release of feel-good endorphins when you work out. In fact, the link to circadian rhythms is being studied to see how exercise helps stabilize sleep patterns and consequently enhance mood.9
Tank Up Or Eat Light
Hibernating animals are known to consume highly calorific foods in anticipation of their period of hibernation when they will lose nearly half their body weight. Interestingly, they seem to be able to do this without clogging up their arteries. For humans to hibernate following a similar period of binge eating may not be worth the cardiovascular risk from elevated cholesterol levels. However, simply being out in the cold can activate brown fat in your body. This kind of fat burns calories much faster with a view to warming you up.10 That might seem like license to gorge through winter, but remember there is further study needed to see if this will hold up to further tests. Until then, you can indulge just now and then without feeling too guilty!
References [ + ]
|1.||↑||Seasonal affective disorder, Mental Health America.|
|2.||↑||Human Hibernation: Secrets Behind The Big Sleep, BBC.|
|3.||↑||Brown Bear Facts, Born Free Foundation.|
|4.||↑||Morrow, Gemma, and Stewart C. Nicol. “Cool sex? Hibernation and reproduction overlap in the echidna.” PLoS One 4, no. 6 (2009): e6070.|
|5.||↑||Lee, Cheng Chi. “Is human hibernation possible?.” Annu. Rev. Med. 59 (2008): 177-186.|
|6.||↑||Heller, H. Craig, and Norman F. Ruby. “Sleep and circadian rhythms in mammalian torpor.” Annu. Rev. Physiol. 66 (2004): 275-289.|
|7.||↑||Young, John Ding-E., and Eugene Taylor. “Meditation as a voluntary hypometabolic state of biological estivation.” Physiology 13, no. 3 (1998): 149-153.|
|8.||↑||5 ways to wipe out winter tiredness, NHS UK.|
|9.||↑||Peiser, Benny. “Seasonal affective disorder and exercise treatment: a review.” Biological Rhythm Research 40, no. 1 (2009): 85-97.|
|10.||↑||Lee, Paul, Joyce D. Linderman, Sheila Smith, Robert J. Brychta, Juan Wang, Christopher Idelson, Rachel M. Perron et al. “Irisin and FGF21 are cold-induced endocrine activators of brown fat function in humans.” Cell metabolism 19, no. 2 (2014): 302-309.|
Disclaimer: The content is purely informative and educational in nature and should not be construed as medical advice. Please use the content only in consultation with an appropriate certified medical or healthcare professional.