Huangdi Neijing (Yellow Emperor's Internal Classic)

The ancient Chinese described the physiological stages of women 2,000 years ago. The Huangdi Neijing (Yellow Emperor's Internal Classic), the Bible of traditional Chinese medicine (TCM) states: "When a girl is 7 years old, she has abundant kidney qi for the growth of permanent teeth as well as body hair. At 14, tian-gui begins to be produced which ensures active functioning of the Conception Vessel and the Thoroughfare Vessel; thus she starts to menstruate and is able to conceive. At 21, the level of kidney qi attains its peak and her body's development stops and her wisdom teeth grow. When she is 28, her body is at its peak and she has strong muscles and bones, and thick, luxurious hair. Her body starts to decline at the age of 35; initial aging signs such as a sallow face, wrinkles or hair loss are usually due to the degeneration of the Yang Ming Meridian. At 42, the three yang meridians in the upper body begin to decline, which leads to facial sagging, and graying hair which eventually turns white. At 49 due to declining tian-gui production, the Conception Vessel and Thoroughfare Vessel become empty and collapse, her body will then deteriorate generally, and her ability to menstruate and give birth will cease."

For men, the following occurs: "When a boy is 8 years old, his kidney qi has consolidated properly and he grows permanent teeth as well as body hair. At 16, his kidney qi is abundant and tian-gui starts to be produced; as a result, kidney essence will transform into sperm, and if he has sex, he can make a girl pregnant. At 24, the level of kidney qi attains its peak, his body development stops, the wisdom teeth grow and his limbs are strong. At 32, his body reaches its peak and it will be sturdy with powerful bones and tendons. The kidney starts to decline at 40 that usually shows signs like hair loss or loose teeth. When he is 48, the body's yang-qi starts depleting from the upper body, and there will be facial sagging and gray hair. At 56, the liver degenerates leading to joint problems; kidney degeneration gives rise to declining tian-gui production and less essence storage, so both of his vitality and body wane greatly. At 64, he will lose his hair and teeth."

The book further specifies: "The kidney forms the foundation for the body's reproduction and development; it receives and stores essence from the other organs. Only if all five organs are in good condition, can the body develop and reproduce. As the organs decline with age, essence stored in the kidney is depleted and no more tian-gui is produced; the bones and tendons weaken, and the hair will turn gray; there will be clumsiness and loss of fertility."

In TCM understanding, aging is mainly due to congenital essence being used up while the ability to supply acquired essence declines. The two essences are what make up human vitality. We inherit a fixed amount of congenital essence from our parents and obtain acquired essence constantly from ingested foods and fluids. They are stored in the kidneys and form the material basis for all kinds of functional activities. When kidney essence is exhausted, our physiological activities will stop and one's natural life span soon ends.

Click here to find out the physiological functions of kidney essence (jing)