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No one knows exactly why we sleep, but we do know that during the deepest phases of sleep, appetite-regulating hormones are released, energy is restored, the immune system is strengthened, repairs are completed, and healing hormones are released. During REM (rapid-eye-movement) sleep, we have vivid dreams and our brains may be working on consolidating memories. Moreover, a study published in Nature found that our brain restructures new memories during sleep, helping us solve problems and become more insightful.

What Is a Good Night's Sleep?

A good night's sleep doesn't simply involve lying on your fluffy pillow for seven to nine hours. The time spent snoozing should also be restful and restorative. Restorative sleep involves sleeping through the night without awakening, or with few awakenings, and also experiencing all the stages of sleep the body was meant to enjoy.

Many people find that not only are they sleeping less these days, but the sleep they do get is not deep and restorative. Nonrestorative sleep (NRS) appears to be the result of modern industrialized society. Because of NRS, more and more people are waking up tired, and they are irritable, lack concentration, are less productive throughout the day, and are hungrier, even when they've slept eight hours.

Sleep is meant to heal and rejuvenate the body physically, mentally, and emotionally. But for a growing number of people, it doesn't. After a night of tossing and turning, waking up frequently, and dreaming fitful dreams, most people are exhausted. Then their day begins, stressors impact their waking hours, and appetite-stimulating hormones pump into their system. Compounding the problem, NRS contributes not only to weight gain but also to such conditions as chronic pain (such as fibromyalgia), muscle aches, heart disease, cancer, chronic fatigue syndrome, immune system dysfunction, and many illnesses, as well as various sleep disorders. Lack of sleep or NRS is also related to safety issues such as car accidents and medical errors, plus impaired job performance and loss of productivity in numerous other activities.

The Stages of Sleep

Sleep is divided into two states known as non-rapid-eye-movement sleep (NREM) and rapid-eye-movement sleep (REM). These two states occur in a ninety-minute cycle, which is repeated five to six times a night and includes at least four stages of NREM and REM. NREM sleep is the state from which REM sleep emerges. There are altogether five stages of sleep.

Stage 1 sleep. This first sleep stage is experienced as falling to sleep and is a transition stage between being awake and asleep. It usually lasts between one and five minutes and occupies approximately 2 to 5 percent of a normal night of sleep. This stage is dramatically prolonged in some people with insomnia who suffer from restless legs syndrome or disorders that produce frequent arousals such as sleep apnea.

Stage 2 sleep or theta sleep. Theta sleep follows Stage 1 and is the baseline of sleep. This stage is part of the ninety-minute cycle and occupies approximately 45 to 60 percent of the sleep cycle.

Stages 3 and 4 or delta sleep. Stage 2 sleep evolves into delta sleep or slow-wave sleep (SWS) in approximately ten to twenty minutes and may last fifteen to thirty minutes. It's called slow-wave sleep because brain activity slows dramatically from the theta rhythm of Stage 2 to a much slower rhythm of one to two cycles per second called delta; the height or amplitude of the waves increases dramatically as well. In most adults, these two stages are completed within the first two ninety-minute sleep cycles or within the first three hours of sleep. Contrary to popular belief, it is delta sleep (not REM) that is the deepest and most restorative stage of sleep. Delta sleep is what a sleep-deprived person's brain craves most. In children, delta sleep can occupy up to 40 percent of sleep time. This is what makes children difficult to awaken during most of the night.

Stage 5: REM (rapid-eye-movement) sleep. This is a very active stage of sleep. It composes 20 to 25 percent of a normal night's sleep. Breathing, heart rate, and brain wave activity quicken. Vivid dreams often occur. Sleep specialists call this fifth stage of sleep REM because a person's eyes are moving rapidly. After the REM stage, the body usually returns to Stage 2, theta sleep.

How Much Sleep Do We Need?

Everyone is different. There is no one-size-fits-all when it comes to sleep needs. Though most people need seven to nine hours, some people need as little as four hours while others need ten. The important thing to note is how you function during the day. Are you tired, sleepy, hungry, lacking in concentration, or irritable? If so, perhaps you are not getting enough sleep or you are not sleeping well.

You can determine the amount of sleep your body needs by following these recommendations. Go to bed at the same time each night and see when you naturally wake up without an alarm. Or, if you've been sleep-deprived, the next time you have two consecutive days when you can sleep in - perhaps a weekend or a vacation - sleep as much as you can the first couple of days. That way you can pay your sleep debt. Then, once your sleep has stabilized, record how much you sleep naturally without an alarm, plus or minus fifteen minutes. (You may have to go to bed extra early the third night if you have to get up early for work just to see when you naturally wake up.) That's your sleep need or capacity.

Copyright © 2007 by Cherie Calbom and John Calbom

Tags: Diets and Weight Loss, Sleep

About the Author

Cherie Calbom is known to millions of fans as "The Juice Lady," and her infomercials are world-renowned. A registered nutritionist, Cherie Calbom has become one of America's foremost celebrity experts on "drinking your vitamins." Her previous books, Juicing for High Level Wellness and Vibrant Good Looks (Crown, 1999), and Juice Lady's Guide to Juicing for Life (Avery, 1992).

About the Author

John Calbom, MA, is director of Trinity Retreat House and vice president of Trinity Wellness Institute. He is a behavioral medicine specialist, organizational development consultant, Eastern Orthodox priest, and coauthor of The Complete Cancer Cleanse.