Vital Substances: Qi, Blood, Fluids, Essence and Spirit

In traditional Chinese medicine, the body is not described in terms of cells or molecules, but through a small group of vital substances that keep it alive and active: Qi, Blood, Body Fluids, Essence and Spirit. Understanding what each one means is key to understanding how a Chinese medicine practitioner reasons, from diagnosis to treatment. On this page we explain each substance, its function and how they relate to one another.

What are the vital substances?

The vital substances are the components that, according to traditional theory, sustain all the functions of the body. Some are more "material," such as Blood or Fluids, and others more subtle, such as Qi or Spirit. All of them are related to Yin and Yang: Qi is considered Yang because of its active character, and Blood, Fluids and Essence are considered Yin because of their nourishing character.

These substances are produced and regulated by the zang-fu organs, and, in the case of Qi and Blood, they circulate through the network of meridians.

Qi: the activity that animates the body

Qi (气, qì) is probably the best-known concept in Chinese medicine. It is often translated as "vital energy," but the character also means air, breath or vapor. In the body, tradition attributes five functions to it:

• Propelling: it moves Blood and Fluids and activates the organs.
• Warming: it maintains body temperature.
• Protecting: the so-called defensive Qi (wei qi) defends against external factors.
• Holding: it keeps Blood inside the vessels and the organs in their place.
• Transforming: it converts food and air into other substances.

According to the theory, Qi comes from three sources: inherited Essence, food, digested by the Spleen and Stomach, and the air we breathe, through the Lung. Its typical disturbances are Qi deficiency, associated with tiredness and weakness, and Qi stagnation, associated with a feeling of oppression, distension or irritability.

Blood (Xue): nourishment and support for the mind

Blood (血, xuè) in Chinese medicine includes the blood we know, but its meaning is broader: it is the substance that nourishes and moistens all the tissues and that "anchors" the mind, so its deficiency is related to insomnia or anxiety.

Tradition says that "Qi is the commander of Blood and Blood is the mother of Qi": Qi produces and moves it, and Blood nourishes Qi. It is associated above all with the Heart, which governs it, the Liver, which stores it, and the Spleen, which produces it and keeps it in the vessels. The most common patterns are Blood deficiency, Blood stagnation and Blood heat.

Body Fluids (Jin Ye): moistening and lubricating

Body Fluids (津液, jīn yè) are all the fluids of the body other than Blood: saliva, sweat, tears, digestive juices, joint fluid and others. They are divided into two types:

• Jin (津): lighter and more fluid, they circulate at the surface and moisten skin and mucous membranes.
• Ye (液): denser, they lubricate the joints and nourish the brain and the orifices.

Their traditional imbalances are a lack of fluids, with dryness, and their accumulation, which Chinese medicine describes as dampness, phlegm or edema.

Essence (Jing): the constitutional foundation

Essence (精, jīng) is the deepest substance and is stored in the Kidney. According to the theory, it has two components:

• Prenatal or innate Essence: inherited from the parents, it determines the basic constitution.
• Postnatal or acquired Essence: obtained from food, it complements and protects the former.

Essence governs growth, sexual maturation, fertility and aging. The Huangdi Neijing describes human development in cycles of seven years in women and eight in men, linked to Essence. That is why tradition insists on not depleting it through overwork, lack of sleep or a disorderly life.

Spirit (Shen): consciousness and vitality

Spirit (神, shén) refers to the mind, consciousness and the vitality perceived in a person, above all in the brightness of the eyes. It is said to reside in the Heart and to depend on Blood and Essence. A person with a "clear" Shen shows lively eyes, orderly thinking and restful sleep; a disturbed Shen is associated with restlessness, insomnia or poor concentration.

The three treasures and the relationship among substances

Jing, Qi and Shen make up the so-called three treasures (精气神, jīng qì shén). Tradition describes them as a continuum: Essence is the material foundation, Qi is its active expression and Shen is its most subtle manifestation. Caring for these three treasures is the classical goal of practices such as qigong and tai chi.

All the substances influence one another: Essence helps form Blood, Qi moves the Fluids, and Blood and Fluids share their origin in digestion.

Traditional concept and scientific evidence

The vital substances are concepts of traditional theory, not measurable entities. The existence of Qi as a form of energy has not been demonstrated, and "Blood deficiency" is not the same as a lab result. These concepts make it possible to understand the language of Chinese medicine and its view of the body, but they should not replace a medical evaluation for symptoms such as persistent tiredness, pallor or insomnia.