Why Do We Sleep, Anyway?

Hunger and Eating; Sleepiness and Sleep

While we may not often think about why we sleep, most of us acknowledge at some level that sleep makes us feel better. We feel more alert, more energetic, happier, and better able to function following a good night of sleep. However, the fact that sleep makes us feel better and that going without sleep makes us feel worse only begins to explain why sleep might be necessary.

One way to think about the function of sleep is to compare it to another of our life-sustaining activities: eating. Hunger is a protective mechanism that has evolved to ensure that we consume the nutrients our bodies require to grow, repair tissues, and function properly. And although it is relatively easy to grasp the role that eating serves— given that it involves physically consuming the substances our bodies need—eating and sleeping are not as different as they might seem.

Both eating and sleeping are regulated by powerful internal drives. Going without food produces the uncomfortable sensation of hunger, while going without sleep makes us feel overwhelmingly sleepy. And just as eating relieves hunger and ensures that we obtain the nutrients we need, sleeping relieves sleepiness and ensures that we obtain the sleep we need. Still, the question remains: Why do we need sleep at all? Is there a single primary function of sleep, or does sleep serve many functions?
An Unanswerable Question?

Scientists have explored the question of why we sleep from many different angles. They have examined, for example, what happens when humans or other animals are deprived of sleep. In other studies, they have looked at sleep patterns in a variety of organisms to see if similarities or differences among species might reveal something about sleep’s functions. Yet, despite decades of research and many discoveries about other aspects of sleep, the question of why we sleep has been difficult to answer.

The lack of a clear answer to this challenging question does not mean that this research has been a waste of time. In fact, we now know much more about the function of sleep, and scientists have developed several promising theories to explain why we sleep. In light of the evidence they have gathered, it seems likely that no single theory will ever be proven correct. Instead, we may find that sleep is explained by two or more of these explanations. The hope is that by better understanding why we sleep, we will learn to respect sleep’s functions more and enjoy the health benefits it affords.

This essay outlines several current theories of why we sleep. To learn more about them, be sure to check out the “Bookshelf” feature at the end of this essay. There you’ll find links to articles by researchers who are studying this fascinating question.

Theories of Why We Sleep

Inactivity Theory

One of the earliest theories of sleep, sometimes called the adaptive or evolutionary theory, suggests that inactivity at night is an adaptation that served a survival function by keeping organisms out of harm’s way at times when they would be particularly vulnerable. The theory suggests that animals that were able to stay still and quiet during these periods of vulnerability had an advantage over other animals that remained active. These animals did not have accidents during activities in the dark, for example, and were not killed by predators. Through natural selection, this behavioral strategy presumably evolved to become what we now recognize as sleep.

A simple counter-argument to this theory is that it is always safer to remain conscious in order to be able to react to an emergency (even if lying still in the dark at night). Thus, there does not seem to be any advantage of being unconscious and asleep if safety is paramount.

Energy Conservation Theory

Although it may be less apparent to people living in societies in which food sources are plentiful, one of the strongest factors in natural selection is competition for and effective utilization of energy resources. The energy conservation theory suggests that the primary function of sleep is to reduce an individual’s energy demand and expenditure during part of the day or night, especially at times when it is least efficient to search for food.

Research has shown that energy metabolism is significantly reduced during sleep (by as much as 10 percent in humans and even more in other species). For example, both body temperature and caloric demand decrease during sleep, as compared to wakefulness. Such evidence supports the proposition that one of the primary functions of sleep is to help organisms conserve their energy resources. Many scientists consider this theory to be related to, and part of, the inactivity theory.

Restorative Theories

Another explanation for why we sleep is based on the long-held belief that sleep in some way serves to “restore” what is lost in the body while we are awake. Sleep provides an opportunity for the body to repair and rejuvenate itself. In recent years, these ideas have gained support from empirical evidence collected in human and animal studies. The most striking of these is that animals deprived entirely of sleep lose all immune function and die in just a matter of weeks. This is further supported by findings that many of the major restorative functions in the body like muscle growth, tissue repair, protein synthesis, and growth hormone release occur mostly, or in some cases only, during sleep.

Other rejuvenating aspects of sleep are specific to the brain and cognitive function. For example, while we are awake, neurons in the brain produce adenosine, a by-product of the cells’ activities. The build-up of adenosine in the brain is thought to be one factor that leads to our perception of being tired. (Incidentally, this feeling is counteracted by the use of caffeine, which blocks the actions of adenosine in the brain and keeps us alert.) Scientists think that this build-up of adenosine during wakefulness may promote the “drive to sleep.” As long as we are awake, adenosine accumulates and remains high. During sleep, the body has a chance to clear adenosine from the system, and, as a result, we feel more alert when we wake.

Brain Plasticity Theory

One of the most recent and compelling explanations for why we sleep is based on findings that sleep is correlated to changes in the structure and organization of the brain. This phenomenon, known as brain plasticity, is not entirely understood, but its connection to sleep has several critical implications. It is becoming clear, for example, that sleep plays a critical role in brain development in infants and young children. Infants spend about 13 to 14 hours per day sleeping, and about half of that time is spent in REM sleep, the stage in which most dreams occur. A link between sleep and brain plasticity is becoming clear in adults as well. This is seen in the effect that sleep and sleep deprivation have on people’s ability to learn and perform a variety of tasks.

This theory and the role of sleep in learning are covered in greater detail in Sleep, Learning, and Memory.

Although these theories remain unproven, science has made tremendous strides in discovering what happens during sleep and what mechanisms in the body control the cycles of sleep and wakefulness that help define our lives. While this research does not directly answer the question, “Why do we sleep?” it does set the stage for putting that question in a new context and generating new knowledge about this essential part of life.

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The Best Sugar Substitutes

There are so many alternative sweeteners available now that they seem to be elbowing sugar right off the supermarket shelf. But what’s so wrong with sugar? At just 15 calories per teaspoon, “nothing–in moderation,” says Lona Sandon, R.D., an assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center in Dallas. “The naturally occurring sugar in an apple is fine, but if we can reduce some of the added sugar in our diet, we can remove some of the empty calories.” Less than 25 percent of your daily calories should come from the added sugar in foods like cookies, cereal, and ketchup, she says. To satisfy your sweet tooth–especially if you’re counting calories, limiting carbs, or dealing with diabetes–try these options:

SWEETLEAF AND TRUVIA

What they are: These sugar alternatives are the latest made from stevia, an herb found in Central and South America that is up to 40 times sweeter than sugar but has zero calories and won’t cause a jump in your blood sugar. Stevia was slow to catch on because of its bitter, licorice-like aftertaste, but makers of Truvia and SweetLeaf have solved this problem by using the sweetest parts of the plant in their products.

Where to find them: In grocery stores and natural-food stores throughout the country and online at sweetleaf.com and truvia.com.

How to use them: Both work well in coffee and tea or sprinkled over fruit, cereal, or yogurt. You can’t substitute stevia-based products for sugar in baked goods, though, because these products are sweeter than sugar and don’t offer the same color and texture. Makers of SweetLeaf promise to come out with a baking formulation soon.

Health Rx: “Truvia’s one of the most promising alternatives out there,” says nutritionist Jonny Bowden, Ph.D., author of The Healthiest Meals on Earth . “Right now, it looks safe. It tastes just like sugar and has almost no glycemic index, which means it won’t spike your blood sugar.”

WHEY LOW

What it is: Three naturally occurring sugars–fructose, the sugar in fruit; sucrose, or table sugar; and lactose, the sugar in milk–are blended to create this sweetener. While individually the sugars are fully caloric, when blended in Whey Low they interact in such a way that they aren’t completely absorbed into the body. As a result, at four calories per teaspoon, Whey Low has one quarter of the calories and less than one third of the glycemic index of sugar, so you’re less likely to crash after consuming it. It’s available in varieties similar to granular sugar, brown sugar, maple sugar, and confectioners’ sugar.

Where to find it: At grocery stores, like Whole Foods Market, online at wheylow.com, and in some baked goods at bakeries around the country.

How to use it: “Whey Low’s flavor and texture are very similar to sugar’s and it’s easy to use,” says Yasmine Sandhu, the pastry chef at Rock Creek, a restaurant in Washington, D.C., which uses Whey Low to keep calorie counts down. “I’ve substituted it into all my recipes as if it were sugar. The only product I’ve had trouble with is meringue–it browns a little quicker and doesn’t set quite as well.”

Health Rx: “Whey Low’s creator argues that the way the sugars interfere with each other means that you get all of the sweet but many fewer calories than sugar,” says Thomas Castonguay, Ph.D., a professor of food science at the University of Maryland in College Park. “We’re testing that process here in the lab, and the preliminary results look promising.”

XYLITOL

What it is: This naturally occurring sugar alcohol is found in foods such as beets, berries, and corn. Xylitol tastes almost as sweet as sugar but is only partially absorbed by the body, so it has only about nine calories per teaspoon and a lower glycemic index.

Where to find it: Natural-food stores and online at vitaminshoppe.com.

How to use it: Substitute it for sugar in small amounts in tea or coffee. If you use it for baking, it’s recommended that you substitute it for only half of the sugar called for in a recipe.

Health Rx: Xylitol prevents bacteria from causing plaque to stick to teeth, which is why it’s often used in sugar-free gum and can help prevent tooth decay. It can also cause stomachaches, gas, and diarrhea if you have too much of it. “Sugar alcohols aren’t digested well by the body,” says Bowden. “That’s what keeps xylitol from raising blood sugar, but it’s also what can give you gas.”

AGAVE NECTAR

What it is: Several types of agave, the plant that’s used to make tequila, are blended to create this liquid sweetener.

Where to find it: At natural-food stores, in some grocery stores, like Whole Foods Market, and in various baked goods.

How to use it: “It’s great for teas and coffee, but it’s a little difficult to bake with,” says Sandhu. “I use it at about a third of the capacity of sugar–agave nectar is far sweeter than sugar or honey, so you have to reduce the amount a recipe calls for. I look for recipes that use another liquid sweetener, like honey, as the base. I also tend to lower my oven temperature when I use it because agave nectar browns a bit more. It’s probably not the best option out there for beginner bakers.”

Health Rx: Agave nectar’s benefits are still under debate. “It doesn’t raise the blood sugar as rapidly as sugar,” says Sandon. “And although it has more calories than sugar–about 20 calories per teaspoon–agave nectar is sweeter, so you can use less of it.” There is some concern about agave’s high fructose content, however; some experts wonder if it will have the same metabolic effect as high fructose corn syrup (HFCS), which has been blamed for increasing rates of obesity. But experts still don’t know whether the large quantities of HFCS we’re consuming are partly responsible for America’s obesity problem, or whether HFCS just happened to enter the American diet at the same time as negative lifestyle changes that led to weight gain.

The bottom line, say experts: We all could afford a little less sweet in our lives. “If you’re eating a lot of foods that have these alternative sweeteners in them, that means you’re still probably eating a lot of cookies, cakes, and other processed foods that aren’t good for you,” says Sandon. “We need to get back to eating more whole foods. Sugar substitutes are not a substitute for a healthy diet.”
The Scoop On the Most Popular Sweeteners

Rumors persist about the health hazards of artificial sweeteners such as Sweet’N Low, Splenda, and Equal, but several food-safety groups and regulatory bodies, including the FDA, have consistently deemed them safe for consumption.

Sweet’N Low (saccharin) has fewer than four calories in each 1⁄4-teaspoon packet, which is as sweet as two teaspoons of sugar. It’s best used in tea, coffee, or other drinks as it reacts differently to baking than sugar does, leading to differences in the volume and texture of foods.

Splenda (sucralose) is 600 times as sweet as table sugar; one packet is as sweet as two teaspoons of sugar. Though sucralose is made from a sugar molecule, it’s chemically altered in a lab so it passes through the body unmetabolized. Splenda has no calories and is heat stable, so it’s ideal for use in baking.

Equal (aspartame) has the sweetness of two teaspoons of sugar in each 1⁄4-teaspoon packet. Use it only in recipes designed specifically for Equal.

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Fitness and Health in the office

Health, vitality and fitness!

Work on the computer is not ideal from a health perspective. The lack of exercise, poor diet, or even the wrong attitude can lead to health problems.Obesity and lack of fitness are not only offside work a problem, but can also adversely affect one’s work performance.

Therefore, the topic plays an important role in me. In this blog carnival, I would like to know from you what you think about it. ”

The theme concerns certainly not only internet self-employed, but most office stool and therefore I would like to present my favorite measures for better fitness and health.

The radiation of the computer

I have developed in recent years a good perception of energies that do not like my body and the radiation of my computer is one of them. It weakens my body significantly, especially since the iMac computer and screen form a unit.

Lack of exercise

If I concentrate really am on to something, then it may be that I almost motionless sitting two hours at a stretch and actually scurry only the fingers on the keyboard. This brings a whole lot of health challenges. Movement is life, standing still means death – this is a simplified truth.

Cellular stress

In addition to the radiation of the computer, of course, is the whole issue to bear radiation, whether from smartphones, tablets, etc.

There cellular stress builds up and electrostatic charge puts us in the truest sense of the word tension.
Durable tension and stress burn out of us, especially at the cellular level.

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The health consciousness of the German

The health consciousness of the people in Germany is growing and more and more people realize that you can increase your endurance, strength and power through sports and fitness, and so gets a better life.

Meanwhile train around eight million people in over 6,000 fitness and health clubs in this country alone. The biggest step in the right direction is the jump over his own shadow. If you are in his every day life, it is extremely hard to get back out because most lack the inner drive.

Should be to motivate yourself to set goals. It is important that the target is a serious and you can reach it in small steps. Sport, too, can not perform miracles. Are the first steps in the right direction done, of course, one must reward. Be it with a delicious meal, or a new piece of clothing ( perhaps even one size smaller ).

One should not be too hard on yourself, because in sports there are bad days. So do not be equal to hang the head when times no progress.

After reaching its final destination, it is important not to stop, but to put the same the next target.

Nutrition & Sports

Not only for losing weight but also for muscle building diet plays a major role. Who does not adjust his diet to his training, is significantly less success.

The most important role in strength training take a protein and carbohydrates. The protein daily requirement of a non- exercisers amounts to 0.8 g -1, 0g/kg body weight. This need increases to up to 2.5 g / kg body weight, when operating strength training. Speak with a 70kg person, the daily requirement increases from 56g to 175g. Protein can be obtained from many products : meat, fish, oatmeal, egg, cheese, cottage cheese and much more.

The drawback is that these products often contain cholesterol and fat, so you should also dietary supplements, such as protein shakes / bolt, fall back. The greatest need for protein, the muscles immediately after training while shouting begs. Thus, the protein is also used as a building material and not as energy, is also to ensure adequate carbohydrate and fat intake. In strength training, the body primarily uses carbs for energy supply.

The supply should be chosen increasingly long chain carbohydrates. These can be in pasta, potatoes, rice, whole grain products and more. Find. Short-chain carbohydrates (sugars ) only make sense immediately before training, and then only in small doses. The last meal before exercise should be taken 1-3 hours (depending on quantity ) before.

To advance to come effectively in training, so you should both pay attention to his daily protein requirements as well as enough energy, out in the form of carbohydrates and fats.

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Breathing as a pillar of our health

Breathing is something elemental to our body. Without the supply of oxygen is as good as nothing, neither a long-term energy, nor a thought process in the brain. A good example of this can be the feeling of fatigue that affects us when we work long hours in confined spaces and in which we do to fix it, open the windows or go for a walk. What we want to achieve?

Basically two things are thus addressed:

a) Normalization of the breathing sequence that is under tension during strenuous work and more and more flatten and

b ) A targeted improvement of oxygen supply, so that the ” head clearer again ” (maybe also run remedy headaches) and our thought processes better.

And precisely these processes also aims forest walk or Nordic walking tour. All the more it amazes me when I walk in the forest smoking people see. That’s what I see for me is always with the driver who give the gas the handbrake attracts.

The same can be perceived even when the rest breaks in the cottages. When you see which portions gets expected of so many hikers stomach, then you wonder highest that this stomach even still allows some breathing. So a belly but can not help but say “ouch” when still breathing additional pressure is applied to it.

And the reaction of the body who wants to avoid a disruption of its operations, is simply a shift to the chest breathing – a reduction in the pressure feeling in the stomach. Thank you, one can only say.

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