“Early to bed, early to rise” has been well-regarded health advice since ancient times. An ancient Chinese saying says, “Work since sunrise and rest at sunset.” But why is sleep so important? The idea of activity beginning at sunrise and ending at sunset aligns with the laws of nature and the human body’s internal processes.
Three American scientists discovered a biological clock inside the human body, also known as the circadian rhythm. They also identified the key genes that control the biological clock, earning them the 2017 Nobel Prize in Physiology or Medicine. However, as early as 2,500 years ago, the Chinese medicine classic “The Yellow Emperor’s Canon of Internal Medicine” discussed the existence of this law, calling it “Zi Wu Liu Zhu (Midnight-noon and ebb-flow doctrine).”
Traditional Chinese medicine (TCM) discovered that the human body has a meridian system responsible for transporting “qi” and “blood” around the body. These basic substances constitute human life and maintain all its physiological activities. Twelve primary meridians follow specific timing and pathways. The 12 hours of a day (one hour is equivalent to two hours in our 24-hour clock) correspond to the 12 main meridians of the human body. In each of these 12 hours, the qi and blood on the corresponding meridian will be particularly active, and the viscera governed by that meridian is in its prime too.
For example, between 11:00 p.m. and 3:00 a.m., the gallbladder and liver meridians are in full swing, and this is the best time to sleep. During this period, activities such as often staying up late, eating late-night snacks, or drinking alcohol are more likely to damage the liver and prevent it from performing its normal detoxification functionality, which may cause liver and gallbladder complications. In addition, the abnormal bile secretion that follows can also cause digestive tract problems.
The optimal amount of sleep for the human body is six to eight hours. A good quality sleep lasts until dawn, without waking up before that time. In addition to giving you more energy, getting a good night’s sleep provides six other benefits.
Quality sleep can lead to weight loss, partially determined by the time you fall asleep. It is also closely related to the hormones produced during sleep.
What hormones are produced during sleep?
The first is growth hormone, produced between 10:00 p.m. and 2 a.m. This hormone helps children grow. In adults, it helps break down fat and promotes anti-aging. Going to bed at 10 p.m. will aid growth hormone production.
The second hormone is cortisol, secreted between 3 a.m. and 5 a.m. Cortisol can break down fat and sugar. Don’t stay up late; avoid interrupting your sleep at night to achieve the best weight loss effects.
A paper published in JAMA Internal Medicine pointed out that developing the habit of sleeping more would also lead to reduced calorie intake.
The research team collected data on the sleeping habits of 80 randomly selected participants and tracked their weight changes over six years. Previous data show that the average sleep time for this group was usually less than six and a half hours.
For a two-week experiment, participants were divided into two groups. Then, one group’s sleep duration was adjusted to eight and a half hours. The results showed that the group that slept eight and a half hours consumed an average of 270 fewer calories daily. Researchers then predicted that continuing this behavior would result in a loss of 26 pounds over three years. Studies like this show that good sleep quality can help balance appetite-regulating hormones and have an auxiliary effect on weight loss.
Most people who live long lives value sleep. A good night’s sleep can allow organs to get enough rest, maintain normal operation, and avoid illness. Sleep also relieves stress, which can help you keep a better mood and thus extend your life.
A research report released at the 2023 American Heart Association’s annual meeting pointed out that sleep quality impacts both total and cardiovascular-induced mortality and is related to life expectancy. Therefore, starting a healthy sleep habit early can reduce the risk of premature death.
According to TCM theory, the liver oversees emotions. During insomnia, one has a lot of liver heat, leading to a bad temper. For instance, women often have insufficient liver blood during menstruation, leading to poor mood. Therefore, it is best to go to bed before 11 p.m. to nourish the liver and improve spirit and mood.
Studies in Italy published in the Journal of Sleep Research have also confirmed that lack of sleep may cause people to have a negative emotional bias. This means that people who get less sleep are likelier to feel and think negatively.
In the study, researchers asked 42 participants to alter their sleep patterns over a two-week experimental period. The participants started off sleeping normally for five consecutive nights, but after a two-day buffer, they were asked to sleep less than five hours for five straight days. During the sleep-restricted phase, participants fell asleep at about 2 a.m. and woke up at 7 a.m.
After five nights of sleep restriction, the participants had negative thoughts even while viewing pleasant and neutral pictures, compared to when they had normal sleep schedules.
After the brain is fully rested, thinking will become sharper, improving work or study efficiency.
A 2019 study published in Science pointed out that during the “slow wave sleep (SWS)” period, the brain will stabilize memory and cognitive functions. In addition, the cerebrospinal fluid in the brain will remove metabolic waste from the brain, including beta-amyloid. This is important because beta-amyloid aggregation is a hallmark of Alzheimer’s disease.
The lymphatic system secretes T cells that can engulf bacteria and viruses. Sleep can strengthen the lymphatic system, thereby strengthening the immune system. This is why doctors often say that when you have a cold, you should rest more and don’t stay up late to keep your immune system functioning properly. The endocrine system also balances while you sleep to help the body prevent diseases.
Quality sleep can promote skin metabolism and has beautifying and anti-aging benefits. Studies have also shown that there is such a thing as beauty sleep, and people who don’t get enough tend to be less attractive to others.
This study published in the journal Royal Society Open Science involved 25 people, including 11 men and 14 women. Participants first got a good night’s sleep two nights in a row. After a week, they could only sleep four hours a night for two consecutive days.
Afterward, researchers took photos of them without makeup. The researchers then asked 122 men and women living in Stockholm to look at the photos and evaluate the attractiveness, health, sleepiness, and trustworthiness of these people, asking, “How much would you like to socialize with this person (in the photo)?”
The raters could tell when someone looked tired; if the person looked sleepy, their attractiveness score would drop. Raters also said they were less willing to socialize with people who looked tired and less healthy.
“Panda eyes” and puffy eyelids are enough to make other people less likely to socialize with you, according to the researchers. When you look tired, strangers see you as less healthy and less approachable.
So how do you get good sleep and stay healthy?
- Don’t touch your phone before bed: Playing with your phone before bed will stimulate you, and you won’t feel sleepy. If you play with your phone in a place with insufficient light, the blue light from the screen will also hurt your eyes. Going to bed late inhibits the brain from secreting melatonin, an antioxidant that increases immunity. You don’t need to take melatonin supplements because the chemical will be secreted naturally if you sleep well. It’s best to naturally boost melatonin production by consuming milk, eggs, bananas, and other foods containing tryptophan. Tryptophan is the raw material that helps the body produce melatonin and serotonin.
- Go to sleep at the same time every night: Go to bed and wake up regularly every day, even on holidays and weekends. When you get used to it, you will naturally go to sleep or wake up at the same time. This is thanks to your biological clock.
- Don’t eat greasy food before going to bed: It is best not to eat supper or drink alcohol before going to bed, and do not eat fried food or sweets. Instead, if you are hungry, drink a small cup of warm milk without sugar to satisfy your hunger and help you sleep.
Sleeping more than nine hours is sleeping too much. TCM has a saying: “Prolonged lying hurts qi.” Lying down for too long will cause blood circulation to lose its natural rhythm, slow the heartbeat and blood flow, affect gastrointestinal peristalsis, and cause indigestion. In addition, if a person has no appetite, he will have no energy. In TCM, this is called qi deficiency, leading to physical fatigue, lack of vitality, inactivity, and drowsiness.
Therefore, sleeping too much will disrupt both your waking and sleep schedules. To stay in good health, you must maintain a proper work-rest balance. As the saying goes: “If you want to live, you have to move.” I have found that many Japanese people are still working 70 or 80 years old. They use work to move their joints, promote blood circulation, and make their lives healthier and more meaningful.