Although it may not be apparent to a layperson, the human body is largely run by “biological rhythms.” All organs, systems and cells are controlled by exact, cyclic patterns of rest and activity, which we can aptly call the “universal laws of life.” The following are a few examples of the biological rhythms that follow these laws:

• Normal menstrual cycles repeat themselves every 27 ½ days.

• The stress hormones adrenaline and cortisol are naturally released into the bloodstream during the early morning hours to promote physical activity.

• Immunity and iron concentrations in the blood reach low levels in women during menstruation and high levels during ovulation.

• The liver is more active during the night than it is during the day.

• Red bone marrow produces more blood cells during the night.

• Most digestive enzymes are secreted during the day.

• Bile secretions peak at midday.

• The large bowel is most active and efficient during the early morning hours.

• Different types of cells have different life spans and are turned over at specific intervals.

• The happiness-producing brain hormone serotonin is produced in response to natural daylight.

• The sleep-inducing hormone melatonin is secreted in response to the darkness of night.

It is estimated that over 1,000 of these biological rhythms operate in and control the human body.

The Human Body Clock

Each biological timer dictates a specific rhythm or cyclic behavior to a group of cells, an organ or an endocrine gland. The various individual timers or body clocks are intrinsically linked to a common master clock. The master clock coordinates the individual clocks with one another and makes certain that every activity in the body is carried out according to its master plan. This master plan consists of nothing but the body’s constant effort to maintain perfect equilibrium or balance.

The body’s master clock is controlled by nature’s most influential cycle, known as the circadian rhythm. The circadian rhythm prompts us to become active in the morning and to wind down in the evening. The sun is the main giver of life on the planet. Both organic and inorganic life forms require sunlight or sun energy for their existence, and so do all human beings. The movements of the Earth on its axis and around the sun create the precise cycles of day and night, as well as the seasonal changes. These rhythmic, repetitive patterns of the forces in nature, in turn, program our DNA to conduct all physical activities with perfect precision and ideal, accurate timing.

All external events occurring in the natural world are linked with similar events inside the body. A sunrise in nature, for example, triggers a “sunrise” in your body. It wakes you up and gets you going. The morning light enters your eyes as soon as you open them. First, the light is broken down into its full color spectrum (seven colors) by the lenses of your eyes. Immediately, the individual light rays travel to the body’s master gland, the hypothalamus. The hypothalamus, which controls the body’s biological clock, then dispatches light-encoded messages to the pineal gland, which is often referred to as the “third eye.” These messages contain specific instructions for the pineal gland to secrete hormones.

One of the pineal gland's most powerful hormones is the neurotransmitter melatonin. The secretion of melatonin follows a regular 24-hour rhythm. Melatonin production reaches peak levels between 1 and 3 a.m. and drops to its lowest levels at midday. The pineal gland secretes this hormone directly into the bloodstream, which makes it instantly available to all the cells in the body and tells them “what time it is” in nature, meaning, what position the Earth is in related to the sun. It also tells a specific gene in the DNA of every single cell when it is time for it to die and be replaced by a new cell. Without the timely secretion of melatonin, the timelines of normal cell-division become extended and cancer cells develop, according to the latest cancer research (Nurses' Study 2006).

The brain synthesizes another important neurotransmitter, serotonin, which relates to our state of well-being. It has a powerful influence on day and night rhythms, sexual behavior, memory, appetite, impulsiveness, fear and even suicidal tendencies. Unlike melatonin, serotonin increases with the light of day—with peak secretions at midday—and also through physical exercise and the intake of sugar. It is very interesting to note that over 95 percent of this extremely important neurotransmitter is actually made in your gut, not in your brain. This gut/brain connection shows how crucial eating good food and healthy digestive functions are for the overall wellbeing of both the mind and the body, and vice versa.

The increasing and decreasing levels of melatonin and serotonin indicate to the cells whether it is dark or light outside and whether they should be more active or slow down their activities. This intricate mechanism ensures that all physical functions are synchronized with the rhythmic changes that occur in the natural environment. This is known as “entrainment.” The health of each cell in the body depends, therefore, on the degree to which we allow the body to be in synchrony and harmony with the cycles of day and night.

Any deviation from the circadian rhythm causes abnormal secretions of the hormones melatonin and serotonin. This hormonal imbalance, in turn, leads to erratic biological rhythms, which can subsequently disrupt the harmonious functioning of the entire organism, including the digestion of food, cell metabo-lism and overall hormonal balance. Suddenly, we may feel “out of sync” or shaky and become susceptible to developing an illness, which could include a simple head cold, headache, depression or even a cancerous tumor. The pineal gland controls reproduction, sleep and motor activity, blood pressure, the immune system, the pituitary and thyroid glands, cellular growth, body temperature, and many other vital functions. All of these depend on the regular melatonin cycle which, yet again, is controlled by our body’s ability to be in synchrony with nature’s rhythms. The amount of melatonin made available to the body in response to the darkness of the night depends on the concentration of serotonin secreted in response to the amount of natural light we are exposed to during the day. As daylight diminishes, serotonin is automatically broken down into melatonin.

If your body makes a good amount of serotonin from natural light, it will also produce sufficient amounts of melatonin during the nighttime, provided your eyes are closed. (When exposed to light, the pineal gland does not secrete melatonin in sufficient amounts.) The pineal gland starts secreting mela-tonin between 9.30 and 10.30 p.m. (depending on your age). Unless you use stimulants such as caffeine or food at that time, melatonin naturally induces sleepiness or drowsiness.

With sufficiently high levels of melatonin in the blood, the body is able to regenerate and rejuvenate itself. This sustains good health, vitality and longevity. [Note: Melatonin in pill form is a popular sleep aid, but it interferes with the body's own melatonin production, which dosage and timing is perfectly synchronized with the circadian rhythm.] The cycles of melatonin and serotonin totally depend on each other and are precisely controlled by our changing environment. By disregarding these rhythmic changes in nature and living against these unspoken laws, the body and mind surely move out of sync with one another. This is a leading cause of physical and mental illness.

One of the greatest secrets of good health lies in the discovery of our intimate relationship with the universe. Any sense of separateness between nature and us can only exist in the mind, not in the body. The body has formed an essential link with the external world. All its efforts are directed toward staying synchronized with our immediate and distant environment.

More on biological rhythms and how to live a balanced diet and lifestyle in Timeless Secrets of Health and Rejuvenation (490 pages), Amazon.com or Ener-chi.com.