I’m sure you’ve heard it over and over “Get more sleep!” or “You’ll get sick if you don’t get more sleep!”. While those things certainly can be true, I’d rather focus on the benefits of sleep in this article instead of the dire warnings that are aimed at those that don’t get enough. It is true enough that lack of sleep can contribute to a number of conditions and ailments, from high blood pressure, diabetes, depression, and an increased risk of a heart attack. Getting enough sleep can certainly help decrease the risk of these things, but why? How does sleep make the body stronger? What role does sleep play in overall health?
While your body sleeps, it repairs its muscles and cells
A note in the British Medical Journal in 1984 mentioned that: “Bodily tissues are continuously degraded and continuously renewed. Wounds heal through the same processes as make possible the normal renewal, by cell division and protein synthesis, and these do appear to be aided by rest and sleep. Across the 24 hours, there is normally a balance between catabolism (degradation) and anabolism (renewal): the activities of wakefulness enhance catabolism, while sleep shifts the balance in favour of anabolism”. In other words, your body’s cells are breaking down during the day and being repaired every night. Cortisol, glucagon, and catecholamines are increased in the body by infections and trauma, while hormones like testosterone and insulin are inhibited by those same factors. Both cortisol and catecholamines are inhibited by sleep. In layman’s terms, cellular toxins increase during the day, muscles break down, and both are actively repaired at night. Deep sleep is when most of our growth hormones are released, which does things like build new bone cells and red blood cells. Growth hormone increases our synthesis of protein and motivates fatty acids to provide energy to the body, and in fact, cell division and protein synthesis is active at night and almost absent during the day, as the surge of adrenaline during the day minimizes these processes. ( Bullough WS, Laurence EB. Accelerating and decelerating actions of adrenaline in epidermal mitotic activity. Nature 1966;210:715-6.). The rate of healing from injury is greater in sleep than while awake (Adam K, Oswald I. Protein synthesis, bodily renewal and the sleep-wake cycle. Clin Sci 1983;65:561-7.). Basically, the body is degrading itself over the course of the day, and the body replenishes itself during sleep- particularly at night.
Exercise and Sleep
Many studies have shown that exercise improves a night’s sleep, as long as it is not within the three hours prior to sleeping. Exercise during the day seems to bring on the sleep impulse, relaxes the body, and sets the stage for better deep sleep. (Youngstedt SD, Kline CE. Epidemiology of exercise and sleep. Sleep Biol Rhythms. 2006;4:215–221) Other research has found that this is somewhat of a two-way street. Not only does the body repair itself at night, but the lack of sleep not only led to decreases in performance in long-distance runners and weight trainers, but it can decrease the motivation to exercise since psychologically, the exercise seems more difficult and therefore you are demotivated.
Sleep and the Brain
Obviously, if the body’s cells and muscles are repaired during sleep, it would stand to reason that sleep would help the brain as well. This indeed seems true. The American Psychological Association noted in 2006, “Recent studies have suggested that the brain, so active during the day, may use the downtime of sleep to repair damage caused by our busy metabolism, replenish dwindling energy stores and even grow new neurons.” One way that sleep can repair the brain at night is to focus on damage from oxidative stress. For those of you that have followed our blog, you know that oxidative stress is a topic that we’ve stressed the importance of. Free radicals that are generated throughout the day and can damage brain cells seem to be repaired by sleep, as demonstrated by the higher level of oxidative damage found in night workers (https://www.nature.com/articles/s41598-019-40989-6). Sleep also seems to be a time to recharge all of the energy expended in thought and in controlling our body during the day. Glycogen seems to be increased during sleep, as does ATP. Both are possible candidates for sleep allowing the brain to replenish its energy at night. Aside from new neurons being created, cells being repaired, and energy replenished, much work has been done on the importance of dreaming, and there is a growing sense that REM sleep and dreaming have their own role in brain health. Psychologist Rubin Naiman, a sleep and dream specialist at the University of Arizona Center for Integrative Medicine was quoted in Time Magazine in 2017. “Naiman describes the brain during REM sleep as a sort of “second gut” that digests all of the information gathered that day. “Everything we see, every conversation we have, is chewed on and swallowed and filtered through while we dream, and either excreted or assimilated,”. This might be important to prepare our brains for the next day. In addition, there is some speculation that sleep helps regulate norepinephrine, which builds up during the day. The theory is that sleep decreases norepinephrine levels and that lower levels of norepinephrine result in less fear and anxiety. It is known that lack of sleep interferes greatly with concentration and affects memory and clarity of thought.
The importance of circadian rhythms
We’ve written recently about circadian rhythms and their surprising role in the rise of colorectal cancer rates among younger people. The reason we’ve mentioned why nighttime sleep is so particularly important is that aside from sleep alone providing health benefits, preserving one’s circadian rhythms is also linked to a number of health benefits. Circadian rhythms are the 24-hours of sleep and wake cycles. Almost all research seems to show that these rhythms are tied to night/day cycles, and in healthy sleepers are triggered by darkness. Interrupting these cycles has been demonstrated to cause a variety of ills in night workers, including increasing the risk for cancer development, suppression of the immune system, and fatigue. Throw off your cycle and you may suffer insomnia and have trouble ever getting enough sleep.
Sleep is restorative in many ways. If you are healthy, it helps keep you that way by clearing out toxins, repairing cells and muscles, and regulating insulin, and the rest of your metabolic system. It recharges your immune system and helps your brain feel refreshed and alert, reorganizes your thoughts, and prepares you to deal with the stresses of the World. If you are ill, wounded, or have recently had a medical procedure, sleep may help your body heal itself. Make getting a healthy night’s sleep a priority for your health- not an afterthought. In the next part, we’ll discuss strategies for getting the most out of your night of sleep.