December 24, 2014 | Posted in Concepts, Concepts in Anthroposophic Medicine, Mind / Mood, Nutrition

Rudolf Steiner extends what we know of light metabolism in plant photosynthesis and in the role of Vitamin D and health.


To discuss light metabolism in nature and in the human being we may begin in the furthest reaches of space.
“According to science, light streams from the stars as planes of energy.” (Sacred Agriculture: The Alchemy of Biodynamics, page 107)

There is both an externally visible light streaming onto earth, and an invisible light which carries cosmic forces to support life activity. In addition to external light streaming onto the earth, human beings create inner light. (“Problems of Nutrition,” page 5)


Plants capture external light in their chlorophyll molecule. In photosynthesis, sunlight combines with air (carbon dioxide) and water to make starch. From light, living physical matter is built. Carbohydrates are stored light which is released when carbon (for example, wood) is burned.
“It (the plant) can take in light and combine it with terrestrial materials in such a way that living substance arises. This substance contains the etheric formative forces that originate in the life processes and that are the mark of all real foodstuffs.” (The Anthroposophical Approach to Medicine, volume 1, page 210)


When external light reaches the human being’s skin, it activates an inner light process. “…thus in letting light pour upon us from outside we activate ourselves to produce inner light.” (Spiritual Science and Medicine, page 149)

Plants can only respond to external light. But humans, and to some extent animals, create inner light which is similar in character to the invisible light from the far reaches of space which carries cosmic forces to support life activity. It is the astral make-up in humans and animals that makes this inner light possible (see Astral body).

The astral body generates inner warmth and inner light in the process of annihilating foodstuffs in digestion. The destructive chemical actions in digestion result in the creation of warmth and light. The warmth created permeates the blood, and the light created supports the actions of the nerves and …”makes possible imagination and calls forth thinking.” (“Problems of Nutrition,” page 5)

“Man exhales carbon dioxide; but, due to the process of exhalation, ether is left behind everywhere in the organism;….The ether left behind by carbon attracts the cosmic impulses which in turn impose form principles on man. They prepare the nervous system, for example, so that it can be the bearer of thoughts.” (Man as symphony of creative word, page 151) (See Thinking: Inner light)


Plants and humans are in contrast to one another in a number of ways in relation to light metabolism.  A polarity often reflects a common origin.  During evolution, humans have left behind the mineral, plant, and animal kingdoms.  Human metabolism including light metabolism reflects the independence achieved by humans.

  • Plants build substance using external light; these substances are the basis of life.
  • Humans create inner light by destroying substance, and consciousness becomes possible in the fleeting states of substances going through changes from one state to another.
  • Chlorophyll and hemoglobin form a polarity. Chlorophyll is green – hemoglobin is red. Chlorophyll contains magnesium – hemoglobin contains iron. Chlorophyll takes up carbon dioxide, and hemoglobin takes up oxygen.
  • Both substances, magnesium and iron, give off a white light when ignited. They have great capacity to store light. However, iron shoots its light out into the surrounding darkness in sparks, like no other metal does. “A particle of iron bears light actively into the darkness”  showing us its active nature.  (The Anthroposophical Approach to Medicine, Volume 1, pages 37, 290-295.)

The human being obtains its highest capacities by being independent from the environment. The spiritual make-up of the human being uses the biochemical and physical workings of the physical body as a vehicle for expression of the individuality.

In speaking to teachers, Rudolf Steiner elaborated:

 “Early alchemists called carbon the “stone of the wise,” which is nothing other than carbon fully understood. Upward it has the tendency to form oxygen compounds, acids, or oxides. These stimulate the thoughts, and whenever we vitally occupy a child we stimulate the formation of carbon compounds and therewith the activity of thinking. Whenever we guide children into some form of action while they are thinking, we call forth a state of balance between the formation of carbonic and cyanic acids. In human life everything actually depends upon producing symmetry between these two things.” (“Comprehensive Knowledge of the Human Being,” page 97)

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Understanding light metabolism is in an early stage.

Whenever we take chlorophyll or magnesium in our foods or as a supplement, or feel sunlight on our skin, we involve our light metabolism. Magnesium is better absorbed through the skin, than orally. Our skin is a broad external surface area, reminiscent of the planar surfaces of leaves which absorb sunlight.

“Frequent overfeeding and excessive protein impede the utilization of light.” (The Anthroposophical Approach to Medicine, Volume 1, pages 37, 290-295.) The widespread vitamin D deficiency in the western world may be related in part to the malnourishment-obesity epidemic.

Anthroposophic doctors use a variety of potentized remedies (see Homeopathy and anthroposophic remedies) to address light metabolism issues, for example, phosphorous, carbo (carbon),  aurum (gold), hypericum (St. John’s wort), quartz, magnesium and meteoric iron.

Light root was pointed out by Rudolf Steiner as the plant which concentrates the light ether.  (See The Light Root (Dioscorea Batatas aka Chinese yam): Human consciousness and health.)

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Diagnosing problems in light metabolism is a new concept entering conventional medicine (studying vitamin D) (see Vitamins) and being developed in holistic / anthroposophic medicine.  The jury is still out, even in regard to vitamin D.  Practitioners may have no or very little understanding to use as a basis for diagnosing and treating.

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Dennis Klocek, Sacred Agriculture:  The Alchemy of Biodynamics, Lindisfarne Books, 2013.

Rudolf Steiner, “Problems of Nutrition,”

Rudolf Steiner, Man as Symphony of the Creative Word, Rudolf Steiner Press, Sussex, 1991

Husemann and Wolff,  The Anthroposophical Approach to Medicine, volume 1, Anthroposophic Press, 1982

Rudolf Steiner,  Spiritual Science and Medicine, Rudolf Steiner Press, 1975.  Recently republished as Introducing Anthroposophical Medicine

Rudolf Steiner, “Comprehensive Knowledge of the Human Being,”  in Deeper Insights into Education, Anthroposophic Press

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