Sunlight Food: Bircher-Benner’s Theory of Food as Stored Sunlight

Table of Contents

1. A Physician Looks at Energy
2. The 1903 Book on the “Energy Tension” of Food
3. Beyond the Calorie
4. The Physics He Drew On
5. Plants as Collectors of Sunlight
6. Light-Charged Molecules: His 1933 Evidence
7. The Three Classes of Light Accumulators
8. Why Cooking and the Animal Lower the Value
9. From Theory to Table: Raw Food and Muesli
10. Echoes in Later Whole-Food Writing
11. Later Research on Raw and Cooked Food
12. Key Research Papers
13. Connections
14. Featured Videos

1. A Physician Looks at Energy

Bircher-Benner did not arrive at his theory in a laboratory. He arrived at it at the bedside. By his own and his family’s account, a run of experiences in the mid-1890s — his own recovery from jaundice on finely cut raw apple, and a stomach patient who improved only when she was given uncooked fruit and vegetables — convinced him that raw plant food had a healing power that the medicine of his day could not explain. The Swiss historical lexicon calls the 1895 episode the “decisive experience” of his career.

The question he then set himself was why. The textbooks of the 1890s judged food by chemistry: how much protein, fat and carbohydrate it contained and how many calories it yielded when burned. By that measure a cooked meal of meat and bread was richer than a plate of raw apple and lettuce. Yet his patients were telling him the opposite. Bircher-Benner concluded that the textbooks were measuring the wrong thing, and he went looking for a different yardstick in physics.

• The 1900 lecture. He presented his new theory of nutrition to the medical society in Zurich in 1900. It was printed that year as “Erste Mitteilung über eine neue Ernährungslehre” (“First Report on a New Theory of Nutrition”) in the Correspondenz-Blatt für Schweizer Ärzte.
• The reception. Historians Elisabeth Meyer-Renschhausen and Albert Wirz write that the medical establishment “reacted with horror” and that his ideas were treated “as heresy and quackery,” but that “he stood firm, claiming that his ideas were based on the latest discoveries in natural science.”
• Its place in his life’s work. Thirty-three years later, in London, he described the sunlight idea as “the quintessence of the theory of nutrition which I discovered at the beginning of the century.”

Back to Table of Contents

2. The 1903 Book on the “Energy Tension” of Food

The theory got its first book-length statement in 1903, published in Berlin: Kurze Grundzüge der Ernährungs-Therapie auf Grund der Energie-Spannung der Nahrung — in English, “Brief Fundamentals of Nutritional Therapy on the Basis of the Energy Tension of Food.” The key word is Energie-Spannung, “energy tension”: the idea that a food holds energy in a more or less highly charged, ordered state, and that this charge, not the bare number of calories, decides what the food does in the body.

The book went through several editions (the Neue Deutsche Biographie lists a fourth edition of the Grundzüge der Ernährungstherapie in 1925). Its ideas, Meyer-Renschhausen and Wirz note, “were translated into delicious menus by his sisters Alice Bircher and Berta Brupbacher-Bircher who were in charge of the kitchen at the clinic.” Bircher-Benner returned to the theme for the rest of his life:

• Die Grundlagen unserer Ernährung (“The Foundations of Our Nutrition”), Berlin, 1921.
• Eine neue Ernährungslehre (“A New Theory of Nutrition”), 1924, with a fourth edition in 1928.
• Food Science for All and a New Sunlight Theory of Nutrition, an English translation published in London in 1928 — the title itself names the “sunlight theory.”
• Vom Wesen und der Organisation der Nahrungsenergie und über die Anwendung des zweiten Hauptsatzes der Energielehre auf den Nährwert und die Nahrungswirkung (“On the Nature and Organisation of Food Energy, and on the Application of the Second Law of Energetics to Nutritive Value and the Action of Food”), Stuttgart, 1936; in English as The Essential Nature and Organisation of Food Energy, London, 1939.

The 1936 title is the clearest summary of the whole project: he was trying to apply the second law of thermodynamics to the question of what makes food nourishing.

Back to Table of Contents

3. Beyond the Calorie

Bircher-Benner’s theory began as a criticism of the nutrition science he had been taught. In his 1933 address to the Food Education Society at University College London he set out the argument in a few sentences. He started from the German physiologist Max Rubner, the great authority on food calories:

“According to Rubner, 96 per cent. of the calories introduced through nutrition serve to maintain the consumption of energy in the static formation of the body and only 4 per cent. serve the building up. Research into the energies of the processes of nutrition may, therefore, claim a prominent and predominating interest of highest value. But the caloric values do not tell us anything about the type, constitution and quality of the energy contained in the foodstuff.”

Then came the step on which the whole theory rests:

“Yet, I said to myself, it is impossible that type, constitution and quality of this energy should be of no significance; on the contrary, they must be the decisive element in the effect of food.”

He made the same point later in the address in sharper form: “Light is a superior and more finely differentiated energy than heat, and light quants are something quite different from calories.”

The calorie was not his only target. In the same lecture he blamed the medical world for having been “misled by chemical theories of nutrition,” and he pointed to the Wisconsin feeding experiment begun in 1906 as the moment research learned “that the chemical theory of nutrition ignored the dietetic qualities of the several foodstuffs, which after all is the chief point.” Meyer-Renschhausen and Wirz place this in context: since Justus von Liebig, Carl Voit and Max Pettenkofer, meat had been prized as the most efficient source of energy for the working man, and Bircher-Benner’s plant-first diet “contradicted the medical thinking of the day, which stressed the value of animal protein above all else.”

Back to Table of Contents

4. The Physics He Drew On

Bircher-Benner presented his theory as physics, not philosophy. The two laws of thermodynamics — the science of heat and energy that had matured during the nineteenth century — were the backbone of it:

• The first law says energy is never created or destroyed, only converted. A calorie count is a first-law measurement: it tells you how much energy a food releases when it is burned.
• The second law says that every conversion of energy loses some of its quality — ordered, concentrated energy runs down into disordered heat. This running-down is called entropy (in German, the Entropiegesetz, “law of entropy”).

The Swiss historical lexicon summarises his project this way: from about 1900 he sought to work the law of entropy from thermodynamics into a new, holistic theory of nutrition, and divided foods by their content of “living” solar energy into foods of the first to third order. Meyer-Renschhausen and Wirz describe the same reasoning: his ideas were based “particularly [on] the second law of thermodynamics, which stipulates an energy loss with each transformation,” and so “anything eaten raw had a higher energy and therefore nutritive value than anything cooked, and that with each further process, the value decreased even more.”

He used this to turn the tables on his critics. As the same historians put it, he “tried to fight the scientists on their own ground, claiming that their view of meat as a source of concentrated energy focused exclusively on the first law of thermodynamics, while his recognition of the vegetable basis of the food chain took the second law into account as well.” In other words: the physiologists counted how much energy a food held; Bircher-Benner asked how many times that energy had already been converted — and degraded — before it reached the plate.

In his 1933 address he stated the principle directly: “The problem of energy governs nutrition and assimilation. All material occurrences in the organism are subordinated to it. Chemical research leads us into a boundless dismemberment of isolated details, in which we lose ourselves. On the other hand, research into energetics gives us the supreme line of direction showing the way through the labyrinth.”

Back to Table of Contents

5. Plants as Collectors of Sunlight

If every transformation loses energy, the best food is the one closest to the original source. For Bircher-Benner that source was the sun, and the first and most important collectors of it were green plants. Meyer-Renschhausen and Wirz write that “essential for his argument was the fact that plants can transform energy (sunlight) directly into carbohydrates” — the process we now call photosynthesis. In his 1933 address he put it in the phrase that gave the theory its name:

“By intensive study of the theory of energy, I gradually came to realise that nourishing energy must partake of the character of accumulated sunshine stored up in the vegetable kingdom.”

• Green leaves. He singled out green leaves as the “key to the whole mystery of nutrition and nutritive value” (in a 1930 paper quoted by Meyer-Renschhausen and Wirz). This is why, in his own diet plan, a raw dish was “always accompanied by salad of some green leaves.”
• Fruit. He called fruit “sunlight food,” and to both leaves and fruit he attributed, in the historians’ words, “the power to stimulate and strengthen the body’s inherent healing power.”
• Sonnenlichtspeisen. In the family cookbook Früchtespeisen und Rohgemüse (“Fruit Dishes and Raw Vegetables”), written with his son Dr. Max Edwin Bircher, he gave raw foods a name of their own: “Sonnenlichtspeisen möchte ich diese reinen, weder durch Hitze noch durch Auslaugung denaturierten Speisen … nennen” — “I would like to call these pure foods, denatured neither by heat nor by leaching, sunlight foods.”

The same passage goes on to praise these foods as a true source of strength for the weak, healers for the sick, and “protective angels” for the healthy, keepers of sound teeth, good digestion, clear skin and resistance to infection. Their value, it says, rests on two things: the fullness and wholeness of the nutritive forces nature put into them, and their power to repair what dietary mistakes have done to health. (Translation ours.)

Back to Table of Contents

6. Light-Charged Molecules: His 1933 Evidence

By the time he spoke in London in January 1933, Bircher-Benner believed that the science of the 1920s had caught up with him. He gathered several findings of the period that he read as support for the idea that living food carries a “charge” of light. As he presented them:

• Vitamin D. He opened with the work of Adolf Windaus on ergosterol, which “when exposed to ultra-violet rays of a certain wavelength acquires the action of vitamin D. Therefore, vitamin D is an organic molecule charged with light. If the charging of light be withdrawn the vitamin effect ceases.” The difference in heat of combustion between charged and uncharged ergosterol, he noted, “may be so small as to be practically undiscernible,” but “the difference in the biological effect is magical.” To him this was the calorie’s blind spot in a single molecule.
• The new atomic physics. He drew on the quantum picture of the atom: when molecules absorb light, electrons move into a higher, “stimulated” state and later fall back, releasing the light again. “According to this theory,” he said, “a ‘living’ molecule is an organic molecule that is rich in atoms and which has received such a high charge of light that it ‘pulsates’ inwardly and is outwardly fluorescent.”
• Gurwitsch’s radiation. He cited the Russian biologist Alexander Gurwitsch as having shown “that the living substance does actually fluoresce. Thus, ultra-violet rays are emitted from a raw onion, whilst in one that is cooked they are extinguished.”
• Lakhovsky and Hackh. He quoted the Paris physicist Georges Lakhovsky’s view that living cells contain highly charged molecules which “can only be replaced through raw food, especially out of the vegetable kingdom,” and the San Francisco chemist Ingo Hackh’s diagrams of a light-charged living molecule, which he showed on a lantern slide. The slide caption states the conclusion: the energy that living protoplasm loses is made good “through living food, such as fresh or raw vegetables and fruit, through vitamins and finally through absorption of the energy of light.”

From these he drew his question to the audience: “Is it not to be expected that the charging with light of all living food molecules should be significant for the biological effect of food?”

Back to Table of Contents

7. The Three Classes of Light Accumulators

The practical heart of the theory was a ranking. If foods differ in how much stored sunlight they carry, they can be sorted. The Swiss historical lexicon describes his division of foods into those “of the first to third order” by their content of “living” solar energy. In the 1933 London address he gave the ranking in his own words: “I arranged the materials of human nutrition into three classes according to their values as light accumulators.”

“Class I.—Raw plant organs and products, e.g., nuts, oil, honey, milk from healthy and rightly-nourished mothers and cows. Possibly also raw eggs from healthy and rightly-fed hens.”

“Class II.—Wholemeal bread, rightly-prepared and cooked vegetable food, cooked milk and dairy produce, cooked eggs.”

“Class III.—All kinds of meat dishes, canned and preserved food, white flour and white flour products, refined sugar, mushrooms, and so forth.”

A few points stand out when the list is read closely:

• Raw is the dividing line. Milk and eggs appear twice: raw in Class I, cooked in Class II. The same food drops a class when it is heated.
• Whole beats refined. Wholemeal bread sits in Class II; white flour and refined sugar sit in Class III, alongside canned and preserved foods.
• Meat is at the bottom. “All kinds of meat dishes” are in the lowest class, for reasons explained in the next section.
• Mushrooms in Class III. Mushrooms, which do not photosynthesise, are listed in the lowest class with no further comment in the address.

The ranking was also a rule for treatment. He stated it directly: “The dietetic therapeutic principle was, therefore, simply as follows: the more severe, the more obstinate, the more constitutional the illness, the more must nutrition belonging to the first class of light accumulators preponderate.” For prevention in healthy people he asked for “a carefully adjusted and sufficient increase in the daily diet of light accumulators of the first class, and a considerable reduction of third class accumulators.”

Back to Table of Contents

8. Why Cooking and the Animal Lower the Value

In Bircher-Benner’s scheme, every step between the sun and the mouth costs something. He named three main steps.

Heat and processing

Cooking, to him, was a transformation like any other, and by the second law it degraded the energy in food. His “sunlight foods” were defined as those “denatured neither by heat nor by leaching” — leaching being what happens when vegetables are boiled and the water poured away. In London he said he had reached the same conclusion as the British nutrition researcher Robert McCarrison did twenty years later, and he quoted McCarrison’s list of what lowers a food’s value: “this value may be reduced by boiling, cooking and pasteurisation; by storage, oxidation and decomposition; by subjecting to heat or to the action of alkalis; by drying, canning or other methods of preservation; and by various manufacturing and refining processes.”

Passage through an animal

An animal that eats plants converts their energy into its own flesh, and by the second law that conversion loses energy again. So meat, in his reckoning, was sunlight at second hand. In 1933 he said: “I also perceived, although I was then a regular meat-eater, that the charging with light must be greatest in the organs of raw edible plants, and least in boiled or roast animal food.” Meyer-Renschhausen and Wirz record that, “a talented polemicist, he attacked meat as being like soot-caked coal in a furnace belching fumes — a dirty and inefficient energy source.”

It is worth noting how he framed this. He did not begin from a moral objection to meat. For most of his career, his historians write, he “refrained from any kind of normative statement regarding meat consumption” and argued on grounds of energy alone; only in 1927, when he was almost sixty, did he make public his personal abstention from meat, for ethical reasons. In the 1933 address he described his own path: meat daily until his thirtieth year, then twice a week for twenty-six years, and none at all for the last nine.

The bacteriological era

He also blamed the hygiene movement of the late nineteenth century for pushing raw food off the table. “Bacteriology has banned raw food and created canning,” he told his London audience, and the sick-room diet of the day made things worse “by rigorously excluding everything raw, by prescribing overcooked food for diseases of the intestines and stomach.”

Back to Table of Contents

9. From Theory to Table: Raw Food and Muesli

The sunlight theory was the reason behind everything Bircher-Benner served. In 1933 he said the theory “enabled me to understand the relations of nutrition and health, and thence to deduce the constitution and composition of the curative diet.” That curative diet was his Rohkost (“raw food”) therapy, described on its own page: Bircher-Benner’s Raw Food (Rohkost) Therapy.

In practice, he told his London audience, it meant:

• Fruit first. “I employ the plan of giving fruit at the beginning of every meal. The empty stomach likes and digests the fruit better than when full and — what is most important — the appetite for cooked food is gradually reduced.”
• A raw course every day. “Once daily, at the principal meal, a dish of various raw vegetables, prepared as hors d’oeuvres and always accompanied by salad of some green leaves, is served.”
• Class II foods to follow. Wholemeal bread, and “rightly-prepared, conservatively-cooked vegetables and potatoes, with as little meat as possible.”
• Class III kept to a minimum. Tinned and preserved food used “rarely and only in the absence of fresh”; sugar, sweet cakes and pastry curtailed; little salt.
• Thorough chewing. Raw food “demands thorough mastication and thorough mastication accomplishes wonders,” he said, invoking Horace Fletcher.

His menus inverted the order of the well-to-do meal of his day, which began with hot soup and ended with fruit. Meyer-Renschhausen and Wirz describe the Bircher-Benner order: a bowl of fresh fruit or muesli first, then raw vegetables as the main course, then a cooked dish, then dessert. The muesli itself — mostly grated raw apple, with a little soaked oats, nuts and lemon — was the most concentrated “Class I” dish he devised, and the one that outlived him: see The Original Bircher Muesli (“d’Spys”) Recipe and History.

He claimed wide results for this diet in his sanatorium. In the same address he stated that in 95 per cent of cases the most obstinate chronic constipation disappeared “within from five days to four weeks,” and that eczema, high blood pressure, gout, obesity, diabetes, migraine and other conditions were favourably affected or cured. He read these results as proof of the theory: they verified, he said, “that the cause of disease is alimentary, lack of light-charged food, the preponderance of light accumulators of the third and second class.” He added one sentence on a contemporary: “A similar basis underlies the Gerson-Herrmannsdorfer-Sauerbruch diet.”

The sunlight theory was one part of a larger outlook. Late in life he gathered his rules for living under the name Ordnungstherapie (“order therapy”), in which nutrition stood beside light, air, water, movement, rhythm of life and the psyche; Melzer and colleagues trace that concept back to him.

Back to Table of Contents

10. Echoes in Later Whole-Food Writing

Bircher-Benner’s idea that foods can be ranked by how far they have been changed from their living, natural state outlived its physics. The clearest echo is in the work of the German hygienist Werner Kollath (1892–1970), whose 1942 book Die Ordnung unserer Nahrung (“The Order of Our Food”) gave German the word Vollwertkost (“full-value food,” usually rendered “whole food”).

• The debt. Drawing on Jörg Melzer’s history of the whole-food movement (Vollwerternährung, 2003), the English Wikipedia article on Kollath states that for the food concept itself “he resorted mainly to Maximilian Bircher-Benner’s publications.”
• The value levels. The same source says Kollath “classified all foods into six value levels. The lower the degree (of processing), the higher was the food’s value. Plants were always rated higher than animals, and raw food higher than cooked food.” Those are the same two rules that order Bircher-Benner’s three classes — plant above animal, raw above cooked — spread over six steps instead of three.
• Living and dead food. Kollath also distinguished unprocessed or lightly processed “living” food from highly processed “dead” food (tote Nahrung), a language close to Bircher-Benner’s “living” molecules.
• In the journals. Kollath set out his whole-food idea in a 1947 paper on whole food and its determination by growth and cell replacement, and by 1950 a Spanish-language article on radiology in preventive medicine could name a “Bircher-Benner syndrome” beside a “Kollath syndrome” — the two names already paired.

The theme was also carried on inside his own family. A. Kunz-Bircher and his niece Dr. Dagmar Liechti-von Brasch, who later served for decades as the clinic’s chief physician, published on the “clinical significance of fresh food” in 1956. In 1948 a Dutch vegetarian journal reprinted his short text “Why natural food?” alongside an article on “Dr. Bircher-Benner’s diet.” Nutrition scientist Claus Leitzmann, surveying the history of vegetarian nutrition in 2014, lists him with Sylvester Graham and John Harvey Kellogg among its prominent figures.

Back to Table of Contents

11. Later Research on Raw and Cooked Food

Modern nutrition science does not use the language of stored sunlight or light charges, but it has studied the question Bircher-Benner cared about most — what happens to people who eat mostly raw plant food, and how cooking changes particular nutrients. Two cross-sectional studies from the University of Giessen in Germany, where Leitzmann worked, examined long-term raw food eaters directly:

• Blood fats and B12 (2005). In 201 people eating 70–100% raw food, mainly vegetables and fruit, the researchers found favourable LDL cholesterol and triglycerides; 46% had low HDL cholesterol, and 38% were vitamin B12 deficient, which raised homocysteine.
• Carotenoids (2008). In 198 strict raw food eaters (about 95% of intake raw, mainly fruit), vitamin A status was normal in 82% and 63% had beta-carotene levels associated with chronic disease prevention, while 77% had lycopene below average reference values. Fat from fruit, vegetables, nuts and oil was the main predictor of blood carotenoids.

The lycopene finding fits a broader observation of later food science: some nutrients survive best raw, while others become easier to absorb after cooking. The site’s pages on cooked versus raw tomatoes and cooking versus raw spinach look at that question food by food.

Back to Table of Contents

Key Research Papers

1. Meyer-Renschhausen E, Wirz A. Dietetics, health reform and social order: vegetarianism as a moral physiology. The example of Maximilian Bircher-Benner (1867-1939). Med Hist. 1999;43(3):323-41. — PubMed PMID: 10885127
2. Melzer J, Melchart D, Saller R. [Development of ‘Ordnungstherapie’ by Bircher-Benner in naturopathy of the 20th century]. Forsch Komplementarmed Klass Naturheilkd. 2004;11(5):293-303. — PubMed PMID: 15572870
3. Bircher-Benner MO. [Why natural food?]. Veg Bode. 1948;51(9):132-4. — PubMed PMID: 18099596
4. Koning MW. [Dr. Bircher-Benner’s diet]. Veg Bode. 1948;51(9):137-40. — PubMed PMID: 18099597
5. Kollath W. [The whole food and its determination by growth and cell replacement]. Z Gesamte Inn Med. 1947;2(1-2):31-6. — PubMed PMID: 20254358
6. Ingber E. [Radiology applied to preventive medicine; the radiological equivalents of the clinical Bircher-Benner syndrome, the bradytrophic Bouchardat-Grote-Gaethgens syndrome and the mesotrophic Kollath syndrome; the concept of capillary pathology]. Dia Med. 1950;22(15):549-52. — PubMed PMID: 15414739
7. Kunz-Bircher A, Liechti-von Brasch D. [Clinical significance of fresh food]. Hippokrates. 1956;27(22):705-13. — PubMed PMID: 13384929
8. Leitzmann C. Vegetarian nutrition: past, present, future. Am J Clin Nutr. 2014;100 Suppl 1:496S-502S. — PubMed PMID: 24898226
9. Koebnick C, Garcia AL, Dagnelie PC, Strassner C, Lindemans J, Katz N, Leitzmann C, Hoffmann I. Long-term consumption of a raw food diet is associated with favorable serum LDL cholesterol and triglycerides but also with elevated plasma homocysteine and low serum HDL cholesterol in humans. J Nutr. 2005;135(10):2372-8. — PubMed PMID: 16177198
10. Garcia AL, Koebnick C, Dagnelie PC, Strassner C, Elmadfa I, Katz N, Leitzmann C, Hoffmann I. Long-term strict raw food diet is associated with favourable plasma beta-carotene and low plasma lycopene concentrations in Germans. Br J Nutr. 2008;99(6):1293-300. — PubMed PMID: 18028575

PubMed Topic Searches

1. https://pubmed.ncbi.nlm.nih.gov/?term=Bircher-Benner
2. https://pubmed.ncbi.nlm.nih.gov/?term=raw+food+diet
3. https://pubmed.ncbi.nlm.nih.gov/?term=cooking+nutrient+retention+vegetables
4. https://pubmed.ncbi.nlm.nih.gov/?term=whole+food+nutrition+history

Further Reading

• Bircher-Benner MO. The Prevention of Disease by Correct Feeding. Address delivered to the Food Education Society, University College, London, 6 January 1933. London: Food Education Society; 1933. Wellcome Collection scan at the Internet Archive
• Bircher-Benner M. Erste Mitteilung über eine neue Ernährungslehre. Correspondenz-Blatt für Schweizer Ärzte. 1900;30(12):382.
• Jagella-Danoth C. Bircher-Benner, Maximilian Oskar. Historisches Lexikon der Schweiz, version 1999, edited 3 November 2010. hls-dhs-dss.ch
• Friedli P. Bircher-Benner, Maximilian. Neue Deutsche Biographie 2 (1955). deutsche-biographie.de
• Bircher-Benner M, Bircher ME. Früchtespeisen und Rohgemüse. Zurich: Wendepunkt-Verlag. Passage on “Sonnenlichtspeisen” reproduced in a Wienbibliothek digital leaflet.
• “Werner Kollath.” English Wikipedia, citing Melzer J, Vollwerternährung, Stuttgart 2003. en.wikipedia.org

Back to Table of Contents

Connections

• Dr. Max Bircher-Benner and the Raw Food Cure
• Max Bircher-Benner: Life and Career
• The Raw Apple Cure
• Raw Food (Rohkost) Therapy
• The Original Bircher Muesli
• Ordnungstherapie: Laws of Order for Health
• Dr. Max Gerson and the Gerson Therapy
• Dr. Weston A. Price
• Chlorophyll and Chlorophyllin
• Apples
• Whole-Food Superfoods
• Nutrition and Orthomolecular Pioneers

Back to Table of Contents

Featured Videos