How Sleep Heals the Body

Can sleep build strong bones? Experts say yes. Find out the benefits of healthy sleep on every part of your body.

Being asleep may seem like the ultimate form of inactivity, but those unconscious hours are actually a time of hard work for your body. Sleeping is one way that your body recovers from damage and protects itself against illness, says Michael Twery, PhD, director of the National Center on Sleep Disorders Research for the National Heart Lung and Blood Institute. “Sleep is one part of the whole rhythm of life,” Twery says. “Whenever researchers go in and disrupt that rhythm, the biology becomes less efficient. And that inefficiency basically leads to disease.” Here’s a head-to-toe look at how sleep revives the various parts of your body.

Brain Health

Surprisingly, most people need only three to four hours of sleep a night to maintain minimal cognitive brain function, the processes responsible for carrying out everyday things like driving a car or getting dressed. But “if you have to solve a problem that requires attention and focused thinking, that will be difficult” on such little sleep, Twery says. To properly execute a difficult project at work, for example, your brain needs seven to eight hours of sleep. Your brain also needs that much rest to most efficiently carry out “automatic” tasks like hormone secretion.

Skeletal System Health

Eating calcium-rich foods is not all you need to do to strengthen your bones. Adequate amounts of sleep are necessary for healthy bone marrow, the spongy tissue inside the bones that contains stem cells, which eventually form blood cells in the body. “We get stem cells and immune cells from bone marrow,” Twery says. “Healthy sleep is part of that.”

Face and Skin Health

Ever feel ugly after a night with little rest? It might not just be your imagination. Several years ago, a small Swedish study found that people who were photographed after 31 hours of sleep deprivation were perceived as less healthy and attractive than when they were photographed after a full night of sleep. “If you’re sleep-deprived, that’s correlated with appearing unwell and tired, which can make you seem less attractive,” says Carl Bazil, MD, PhD, director of the neurology division of the Columbia Sleep Disorders Center at the Neurological Institute of New York City. This effect may have something to do with the correlation between sleep deprivation and elevated levels of the stress hormones adrenaline and cortisol. “Those stress factors do compromise the health of skin,” Twery says.

Heart Health

Consistently skimping on needed rest can have detrimental effects on the old ticker. Sleep deprivation can send the body’s sympathetic nervous system into overdrive, causing the release of greater amounts of the hormone adrenaline. “This tells the body’s tissues to be prepared to take immediate action,” Twery says. “It makes the heart work harder.” People who are sleep-deprived are at greater risk for developing hyperlipidemia, or high cholesterol, which can lead to heart attack or stroke. So do your heart a favor and get to bed early tonight.

Immune System Health

If you don’t get adequate sleep, you could find yourself sick a lot more often. Research has found that people are more likely to catch the common cold when they are behind on their rest. “Obviously we worry about [colds] more from a convenience standpoint, but there’s a concern that for more serious types of infections, the same thing may be going on,” Dr. Bazil says. Researchers have also discovered that rest can help you get more benefits from preventive vaccines — a study published in the journal Sleep found that people produced more antibodies in response to the hepatitis B vaccine when they had adequate sleep.

Healthy Weight

People often consume too many calories when they are sleep-deprived, which can lead to weight gain. Why? Being behind on sleep can disrupt the body’s balance between ghrelin and leptin, two hormones that stimulate and suppress appetite, respectively. “Sleep deprivation contributes to moving that ratio in the direction of increasing appetite,” Twery says. “It’s like you’re attempting to compensate for the stress [of being tired].” The lesson? Aim for a full night’s sleep every night and be mindful of your food intake on those occasions when you don’t get enough shut-eye.

Liver Health

Like the rest of your body, your liver — your largest internal organ — is attuned to a certain rhythm that varies with the time of day. For example, the liver produces the most cholesterol in the evening hours. Being behind on sleep can throw off this rhythm, making it less able to efficiently carry out functions like detoxifying, breaking down adrenaline, and managing blood sugar levels. “It doesn’t respond well when the liver clock is desynchronized,” Twery says. Yet another reason to get your rest tonight.

Sexual Health and Fertility

If you’re chronically shorting yourself on sleep, you could find that your sex life suffers. “People who don’t sleep enough are going to have less interest in sex and decreased performance,” Bazil says. This could be because of sleep’s ability to keep the body’s hormones in balance — a lack of sleep can throw hormones, including those related to sexual function, out of whack. For example, a study published in the Journal of the American Medical Association found that a week of restricted sleep (five hours a night) led to a reduction in testosterone levels.

By Jennifer Acosta Scott