The deep roots of urban legends about the health benefits of spinach

The wrong old narrative
A decimal separator misplaced in the 1870s caused the false reputation of spinach for being the vegetable that was richest in iron. Though still highly popular, this narrative is wrong (see here and here). Ignoring wrinkles in the narrative, such as that spinach is still rather rich in iron but that it cannot be assimilated because of its high content of oxalic acid, the new narrative can be stated most simply as follows.

The wrong new narrative
The decimal error is a myth, it never occurred. The false reputation of spinach was due to unreliable methods or poor experimentation. That is, errors were inherent in experimental methods, not data handling (see here). This new narrative is combined with stuff about Popeye and peddled as a supermyth busting hero story. But it is also not completely right, because a real decimal error did occur and this is probably the source of one eminent nutritionist, getting things wrong in his memory and unvolutarily creating the spinach-iron-decimal-error myth.

Deep history
The narrative coming closest to the true history of this myth about a myth is given in an earlier post (here). The current post explores the deeper roots of the folklore about the health benefits of spinach going back way beyond the time long before any research implicated in the myth about the decimal point error. And this folklore tenaciously maintains itself, despite repeated refutations by researchers.

The ancient lore
Once upon a time, when the Linnean system of identifying species was not even standard, Johann Ernst Zeiher (1756, vol. 2, pp. 374-375) wrote about the medical uses of spinach. The title of the book already indicates that Zeiher translated a work from French into German, but I found no indication of the original. "Vollständiger Unterricht von Küchengewächsen: oder ausführliche Beschreibung aller Küchengewächse [...] Ferner, ihrer Nutzbarkeit für das menschliche Leben, und ihrer Tugenden, zur Erhaltung der Gesundheit, [...] u.s.w. [...] aus dem Französischen übersetzt von D. Johann Ernst Zeiher, ernenneten Professor bey der Kaiserl. Akademie der Wissenschaften zu St. Petersburg [...]". Some online search, however, shows that it must be a translation of: M. de Combles (1752) L'école du jardin potagere, [...] Paris: Chez Boudet ou Le Prieur.

For the French original see: de Combles (1752, vol. 2, pp. 24-25), for a German translation see:  Zeiher (1756, p. 374f). My own translation of it into English follows:

"The qualities of spinach in the medical arts are, to open the body/belly [whatever that means], to relieve the cough and the acerbity/acuteness of the chest: the water distilled from its leaves also has the power to attenuate the heat of the gut/bowel [sic, he uses it in singular], and the burning of a stomach irritated by an inflamed bile. One also uses the leafs for decoctions and emollient compresses. The short-winded [literal translation: tight chested] get great relief therefrom, and sometimes they were completely cured through repeated use of spinach boiled with veal: and this was the only remedy used by Mr. [Guy-Crescent] Fagon, first personal physician of Ludwig XIV, who was heavily burdened by this disease. When applied externally to the belly and the liver, it takes their inflammation and pain away. According to the opinion of a recent writer, the overuse of this plant leads to melancholy bloods: from my point of view, Mr Fagon's experience alone suffices to overthrow this opinion." 

The 18th century seems to have known a lot of lore about the medical powers of spinach, even connected to the Sun King. However, Combles (1752) also accounted for the health effects of shalotte coming before spinach and tarragon coming after. He probably discussed the health effects of each plant he treated.

Robert Hooper (1811. "Quincy's Lexicon Medicum. A new medical dictionary") corroborates that Combles's account of health effects of spinach was widespread:

"This plant Spinacea oleracea of Linnaeus is sometimes directed for medical purposes in the cure of phthisical complaints; made into a poultice, by boiling the leaves and adding some oil, it forms an excellent emollient. As an article of food it may be considered as similar to cabbage and other oleraceous plants." (Hooper 1811, p. 759) 

Phthisis is a dated term for suffering from consumption (tuberculosis) or other emaciating diseases. 12 years later, Achille Richard (1823, "Botanique médicale ou histoire naturelle et médicale [...]", p. 171) wrote:

"L'épinard est cultivé dans tous les jardins.Il fleurit en mai et juin. Il est peu usité comme médicament, si ce n'est à L'extérieur; on L'emploie en cataplames, et il est très émollient. Mais, comme aliment, son usage est trés-repandu. Il parait être légèrement laxatif; il est peu nourrissant et presque insipide." (For a German translation see p. 266 here)

"Spinach is grown in any garden. It blooms in May and June. It is rarely used as a drug, and if so then only externally; it is used in poultices, and it is very emollient. But as food its use is widespread. It appears to be slightly laxative; it is not nourishing and almost tasteless." (My translation)

The trend, however, seems to downgrade the medical utility of spinach from the account of Combles (1752), giving it as the only remedy for Luis XIV, to Hooper (before 1822), saying it was sometimes used, and Richard (1823), stating it was little used and if so, then only externally.

These accounts are from a time before Robert Koch described the pathogen causing tuberculosis in 1882. Phthisis and Combles' account on cough and short-windedness reminds me of the much later research of Kobert (1914) on the health effects of saponins in spinach against tuberculosis and other lung diseases (see here). That is, early research applying "modern" methods of science (e.g., chemical analyses) naturally derived its hypotheses from earlier experiences described by physicians. One such research endeavour formulated hypotheses associating spinach components (saponins) with effects against tuberculosis.

But how did the ancient lore transmogrify into a myth about the iron richness of spinach? One symptom of tuberculosis is anaemia, a lack of red blood cells or hemoglobin. Tuberculosis, however, is not the only possible cause of anaemia. Another cause is iron deficiency. Hence, other researchers could have taken the same lore documented by Combles (1752) and derived another hypothesis from it associating spinach with iron richness.

An early documentation of this spinach-iron connection can be found in a German encyclopaedia published by F. A. Brockhaus in 1852 (see P.P.S. to this blog entry). As Brockhaus only collected then-current knowledge, the idea must be older still.

The recalcitrant lore
In parallel to this tenacious folklore, there's a narrative about research being error prone but also self-correcting. For example, Bunge (1892) did not correct the iron contents of ash analyses for oxygen gained during combustion (see here), but he nevertheless concluded that spinach (and strawberries for that matter) do not have the high values given by Wolff (1871). That is, he drew a basically correct conclusion despite erroneous data treatment. Again, Haensel's (1909) iron contents were an order of magnitude too high for all the vegetables he analysed, but the relation between the data showed that spinach was not exceptional in comparison with the other vegetables. Consequently, Haensel drew a correct conclusion based on poor data (see here). And so on in the 1930s etc.

Most of this research was not centrally or exclusively concerned with the iron content or spinach. The ash analyses of Wolff, for example, were basic/applied research in biochemistry, while Bunge was interested in finding out how baby mammals got over the suckling period depending on milk that is devoid of iron. The answer to this research question is, they get born with a store of iron that carries them through till weaning.

The myth about spinach's iron richness has been refuted along the way in the late 1800s, the early 1900s, and the 1930s, long before the legend about the misplaced decimal error has ever been aired. But the lore did not go away. Finally, Arnold Bender threw up his hands in despair and suggested that the belief may even be due to a misplaced decimal point. Now we have three legends piled upon each other: the iron richness of spinach, the misplaced decimal separator leading to this reputation of spinach, plus the claim that no decimal error ever occurred (see here).

Conclusion
Combles's account of the beneficial effects of spinach on the Sun King is probably the ultimate source of all urban legends about the health benefits of spinach. It never went away, no matter what researchers found. Finally, despairing of the tenacity of the lore, Arnold e. Bender (1972, 1977) threw up his hands in despair and suggested that something like the decimal point error may also have been its origin (see here). However, this trial at killing the initial lore only made everything worse it seems.

Spinach-iron data transformations: Boussingault (1872) to Berg (1913)

For an introduction see any other entry under the spinach-iron label of this blog

In 1872, Jean-Baptiste Boussingault ("Du fer contenu dans le sang et dans les aliments." Comptes Rendus de l'Académie des Sciences, Tome 74: 1353-1359) published his results on the iron contents in the blood of various animals and in food products. This publication contains a table at pp. 1355-56 listing the contents of "Fer exprimé à l'état métallique. Dans 100 grammes de matiére." This means that the values are not for iron oxide (Fe₂O₃), which was the usual state in which iron contents were measured but elemental. The second statement ("Dans 100 grammes de matiére.") was specified in the text above the table: "En ce qui concerne les aliments, les dosages ont éte exécutés à l'état où ils sont consommés, c'est-à-dire avec leur eau constitutionnelle." (In the case of food, the dosages were carried out in the state in which they were consumed, that is to say with their constitutional water.) Hence, Boussingault's table gives the iron content for spinach leaves ("Feuilles d'épinards") as 0.0045g per 100 gram fresh matter.

In 1897, Emil Häusermann ("Die Assimilation des Eisens. Zeitschrift für Physiologische Chemie 23: 555-592) published a table (pages 586-588) listing the iron contents of food products per 100g dry matter. He cited Boussingault for various items, but the values vary.

Boussingault (g per 100g fresh matter)	Häusermann (mg per 100g dry matter)
Riz: 0.0015	Reis: 1.7
Haricots blancs: 0.0074	Weisse Bohnen: 8.3
Lentilles: 0.0083	Linsen: 9.5
Pommes de terre: 0.0016	Kartoffeln: 6.4
Feuilles d'epinards: 0.0045	Spinat: 39.1

Obviously, Häusermann took values for the water contents of the food stuffs from elsewhere, in order to calculate the iron contents in the dry matter from Boussingault's values for fresh matter. Apparently, these values of the water contents of the fresh matter were 11.7% in rice, 10.8% in white beans, 12.6% in lentil, 75.0% in potatoes and 88.5% in spinach leaves. Bunge (1892. "Weitere Untersuchungen über die Aufnahme des Eisens in den Organismus des Säuglings." Zeitschrift für Physiologische Chemie 16:173-186) has done the same with Boussingault's data before and given König (1889. "Chemie der menschlichen Nahrungsmittel.") as his source for water contents (see footnote ****, here). As Bunge took the water content for spinach to be 88.49%, we can conclude that König has also been Häusermann's source.

In a later edition, Josef König (1904. Chemie der menschlichen Nahrungs- und Genussmittel, Band 2, p. 353) cited the value of Häusermann properly, that is, he gave the range of values as 32.7-39.1mg per 100gr dry matter (the first value being from Bunge 1892 and the second from Häusermann 1897).

Ragnar Berg (1913. Die Nahrungs- und Genussmittel. p. 34-35) gave the contents of iron-oxide (Fe₂O₃) in 100g fresh matter as he explained in the introduction at page 6: "Damit nun jeder leicht umrechnen kann [...], habe ich in den folgenden Tabellen [...] den Gehalt von 100 g frischen Nahrungsmitteln an einzelnen Mineralbestandteilen in Grammen [...] aufgeführt."
     Berg (1913, p. 34-35) cited König (1904) with a value of 0.0596g Fe₂O₃ in 100g fresh spinach. (Berg indicated the sources by superscripts given above the values in the table. As he explained at page 11 of the introduction, the roman numeral I stands for König 1904.) If we assume that Berg took the average value (35.9mg/100g dry matter) of König's range (32.7-39.1mg/100g dry matter), then König's average iron (Fe) content in dry matter amounts to 60% of the iron-oxide (Fe₂O₃) content that Berg imputed to König for fresh matter.
    Berg can hardly have assumed that 60% of fresh spinach leaves were dry matter, when Häusermann had earlier taken its water content to amount to 88.5% (see above). Berg's transformation factor lies much closer to the 70% that is suggested as the correction factor needed to calculate the portion of the mass of Fe₂O₃ that is due to the iron in it according to the atomic weights (Fe: 55.8; O: 16). Nevertheless, a discrepancy of 10% remains. That is still not satisfying to see how Berg got from König's range of iron contents for dry matter to his imputation to König of iron-oxide content for fresh matter.

Anyway, Berg also performed his own analysis and that yielded 0.0437g Fe₂O₃ per 100g fresh matter. As it happens, this value was just about ten times higher than what Boussingault had started with (0.0045g Fe per 100g fresh matter) despite the fact that no decimal separator had been misplaced in any of the various data transformations.

Carl von Noorden & Hugo Salomon (1920. Handbuch der Ernährungslehre. Erster Band, p. 476) gave a range of 44-60mg Fe₂O₃ per 100g spinach and cited Berg (1913) as well as Hermann Schall & August Heisler (1917. Nahrungsmitteltabelle. 5. Auflage. Curt Kabitzsch Verlag, Würzburg) as sources.

The publication of Schall & Heisler (1917, not online) in turn has two values for spinach at page 41: 60mg and 44mg per 100g fresh matter. The latter value bears a footnote referring that value to "R. Berg" (sic), who had given 0.0437g/100g fresh mater as the result of his own analysis. As Berg also gave 0.0596g/100g fresh weight and referred that to König (1904), I presme that Schall & Heisler have simply taken that value from Berg as well, rounded it, but did not specifically cite König, because they have gotten it from a secondary source. The introduction of Schall & Heisler 81917) states that they collected data from "König, Rubner, Atwater und Byrant, Schwenkenbecher, Sautier, Strauss, Tischler, Leva, v. Noorden, Nauny, Magnus-Levy, Janney, Walker Hall, Brugsch, Bessau und Schmidt, Hesse, Offer und Rosenquist, Vogel, Berg, Albu-Neuberg, das "Deutsche Bäderbuch", die Angaben der Nahrungsmittelindustrie u. a. mehr." Sic! No sources, journals, publishers, years or anything else to ease retrival. The publication contains no reference list either to look up citations.

The real decimal error that transmogrified into the spinach-iron-decimal-error myth

[Click here to get all posts in this series.]

The wrong old narrative
A decimal separator misplaced in the 1870s caused the false reputation of spinach for being the vegetable that was richest in iron. Though still highly popular, this narrative is wrong (see here and here). The new narrative can be stated most simply as follows.

The wrong new narrative
The decimal error is a myth, it never occurred. The false reputation of spinach was due to unreliable methods or poor experimentation. That is, errors were inherent in experimental methods, not data handling or a typo (see here). Moreover, Arnold E. Bender and Terence Hamblin were, according to this judgmental new narrative, promulgating pure and utter nonsense based on no true decimal error whatsoever, when they popularized the old narrative. This new narrative is combined with stuff about Popeye and peddled as a hero story about busting a myth about a myth (or "supermyth"). It seems to be highly popular for this reason, but it is also wrong, because a real decimal error did occur and it can explain why the eminent researchers, Arnold E. Bender and Terence J. Hamblin, mixed things up and, inadvertently, created the spinach-iron-decimal-error myth.The important difference between the new narrative and the one to follow is that the latter can explain Bender's and Hamblin's blunder, where the above only returns a verdict verging on insult.

The narrative that explains instead of returning verdicts
Throughout this series of reconstructing the data handling of the primary research literature, I found that the relevant research was full of data handling and data transformation errors, but none of these errors was as simple as misplacing a decimal separator (see here). Neither Mike Sutton's original sleuthing, nor my in depth analysis and reconstructions of the historic data handling and transformations ever found a displaced decimal separator that could explain why an eminent researcher such as Arnold E. Bender should have come up with that myth.

Surprisingly, I now found a real decimal error that can, indeed, explain how Bender's memory fused it with other peculiarities in the research record and, inadvertently, caused the myth in the 1970s. A simple decimal-point error did occur in an article published in—wait for it—Science 90, no. 2347, pp. 596-597 (1939). But the research reported there was about the iron content of dried peas and beans instead of spinach.* So how can it be the mythical error recurring in the urban legend about spinach & iron?
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* The full reference is: Aschman, Leah, Mary Speirs & Dorothy Maddox (1939) The availability of iron in dried peas and beans. Science 90, 596-597.
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The original decimal error
Let's first take a look at the error itself. Aschman et al. (1939) report the results of an experiment that was pretty similar to the much older experiments by Bunge (1892), for example. They rendered baby rats anaemic by feeding them on milk only (mammalian milk is poor in iron). Then they fed the anaemic rats dried peas and beans, did the proper controls and measured the recovery of the rats. Along the way, they also measured the iron content of the dried products and gave the values as follows:

Anybody with a sharp eye will spot the decimal-point error in the value given for butter beans at the end. And that is what the staff of the Nutrient Section of the Bureau of Home Economics did, when they published abstracts in the Journal of Home Economics 32, no. 7, p. 481:

As you can see, however, this correction of a decimal point error concerning the iron content of butter beans follows directly on an abstract concerning the contents of oxalic acid in vegetables including spinach. Now, one big topic in the debate about the usefulness or uselessness of spinach as a dietary source of iron was oxalic acid, because it binds the iron and thus inhibits the absorption of it by the consumer.

The first and second claim of a misplaced decimal separator
In his inaugural lecture, Arnold E. Bender (1972, The wider Knowledge of Nutrition, Queen Elisabeth College) attributes the discovery of the decimal error explanation for the exaggerated iron content of spinach to the work of a professor Schupan (see here for an account of the sleuthing up of this first claim that a decimal error occurred in relation to the iron-content of spinach).

"One common belief, that spinach is good for you, appears to be due to experimental error since the belief predates Hollywood nutrition films based on the muscular development of the film star Popeye. I am indebted to Professor den Hartog of Holland for tracing the possible origin of this belief. It appears to date soon after 1870 when Dr. E. von Wolff published food analyses showing spinach to be exceptionally rich in iron, a figure that was repeated in many generations of textbooks; it was in the Handbook of Food Sciences (Handbuch der Ernährungslehre) by von Noorden and Saloman [sic] in 1920. In 1937 Professor Schupan analysed spinach for its iron content with α-α'-dipyridyl and found the figure to be one tenth of that reported by von Wolff – the fame of spinach may well have grown from a misplaced decimal point." (Bender 1972, p. 11)

C. den Hartog (1971)

A lot of this passage is enigmatic or wrong. First, that Professor den Hartog never seems to have published anything himself on the issue. Some C. den Hartog (1971. Nutrition of infants and children. Royal Society of Health Journal 91(3): 111-114) from the Agricultural University in Wageningen, The Netherlands, however, was much into the issue of nutrition, iron deficiency and all that writing: "Neither breast milk nor cow's milk can obviate the need, early in life, for supplements to meet vitamin C, vitamin D and iron requirements" (den Hartog 1971, p. 111, see also p. 114). He has probably been the correspondent of Bender.
     Second, Dr. Emil Wolff had no title of nobility, when he published his research in 1871 or 1880; the "Von" in "Von Dr. Emil Wolff" on the title-page must be translated as: "By Dr. Emil Wolff." The fact that Emil Wolff did get knighted towards the end of his life does not change his publishing as a regular guy (same with Justus Liebig, Johann Wolfgang Goethe and many other Germans who are often falsely cited as if knighted).
     Third, Wolff's publications contained no misplaced decimal point relating to spinach and iron content (see here and here). In fact, spinach does not even feature as exceptionally rich in iron content in his publications (lettuce and asparagus should have become famous instead of spinach, if it was up to Wolff's data). The one thing that could be called a decimal error occurred in Wolff's later Aschen-Analysen of 1880 and concerned all chemical compounds in all analyzed vegetables (see here). That is, in transferring data from his 1871 Aschen-Analysen, a heading of a whole table said "in 100 parts" instead of "in 1000 parts." Fourth, the guy studying the iron content of vegetables with the α-α'-dipyridyl method was W.C. Sherman not Schupan. Fifth, the discrepancy of the findings of Sherman and colleagues was indeed down to the difference in methods and not to misplaced decimal point (see here).

Later, Bender (1977) released the decimal-point-error legend upon a wider public through a letter to The Spectator.

"Sir: In a recent article (18 June) spinach is given undeserved nutritional eminence, although, since the facts have never been widely publicised, the author can be excused.

     For a hundred years or more spinach has been (and clearly still is) renowned for its high content of iron compared with that of other vegetables, but to the joy of those who dislike the stuff this is quite untrue. In 1870 Dr E. von Wolff published the analyses of a number of foods, including spinach which was shown to be exceptionally rich in iron. The figures were repeated in succeeding generations of textbooks—after all one does not always verify the findings of others including the 'Handbook of Food Sciences' (Handbuch der Ernährungslehre) by von Noorden and Saloman in 1920.

      In 1937 Professor Schupan eventually repeated the analysis of spinach and found that it contained no more iron than did any other leafy vegetable, only one-tenth of the amount previously reported. The fame of spinach appears to have been based on a misplaced decimal point."

     Professor Arnold Bender, The Spectator (18 July 1977, p. 18)

The fusion of the real decimal error with the spinach-iron issue
Looking, again, at the above image of the Journal of Home Economics (1940, vol. 32, no. 7, p. 481), we can reconstruct Bender's or den Hartog's faulty and mixed up memory as follows (as den Hartog remains an elusive figure in this legend, I will treat Bender's and Hartog's memory as one). He probably remembered the occurrence of a real decimal error concerning the iron-content of some vegetable, but did not remember correctly that it was made by Ashman et al. (1939. Science 90, 596-597) in relation to butter beans.

Why did Bender's/Hartog's memory fuse this real decimal error from 1939 to spinach, the name of Schupan and the year 1937? The link to spinach is obvious, if we remember that oxalic acid was a big issue in relation to the iron content of spinach (and other vegetables), because it binds iron and that way renders it unavailable to animals consuming spinach. As the abstract preceding the one with the decimal error was exactly about this issue and mentioned spinach as being high in oxalic acid, the fusing of the decimal error concerning iron content in butter beans to oxalic acid in spinach becomes intelligible. This leaves two remaining questions concerning Bender's faulty memory:
1. Who was Schupan?
2. Why the year 1937? 

Who was Schupan?
I was able to trace "Werner Schuphan" (mind the h after the p) instead of Schupan. While he did publish on all sorts of vegetables including spinach, the following publication from 1940 shows that he can hardly have debunked the myth of spinach's exceptional iron richness in 1937:

Spinat zeichnet sich – wie wir sehen – besonders durch hohe Gehalte an Carotin, Chlorophyll, Eisen und Reineiweiß und Vitamin C aus." (Schuphan, W. 1940. Über den Einfluss der Chlorid- und Sulfatdüngung auf Ertrag, Marktgängigkeit und biologischen Wert verschiedener Gemüse unter Berücksichtigung edaphischer und klimatischer Faktoren. Bodenkunde und Pflanzenernährung 19(5-6): 265-315)
"Spinach distinguishes itself – as we see – especially through high contents of carotin, chlorophyll, iron and pure protein and vitamin c." [my translation]

As the above quote reiterates the idea that spinach is richer in iron than other vegetables, it is unlikely that he had some years before claimed the opposite.

Why the year 1937?
One article published by Schuphan in 1937 (Untersuchungen über wichtige Qualitätsfehler des Knollenseleries bei gleichzeitiger Berücksichtigung der Veränderung wertgebender Stoffgruppen durch die Düngung. Bodenkunde und Pflanzenernährung 2, issue 5-6, pp. 255-304) dealt with quality issues in celeriac including the so-called Eisenfleckigkeit (iron blotchiness) of tubers. He therein debunked the belief that celery tubers turn brown at the cut surface, because of the oxidation of iron and claimed that the colouring is due to resins and essential oils instead. That is, he debunked the idea that the oxidation of iron at the air is the cause of the celeriac getting brown, where it is cut.

The last question remaining is: Why did Bender think (misremember) that the decimal error occurred in the 1870s?

Why place the decimal error in the 1870s?
Schuphan (1937, p. 258) does cite H.W. Dahlen (1874. Beiträge zur chemischen Kenntnis der Gemüsepflanzen. Landwirtschaftliche Jahrbücher 3: 723-751) as follows: "Dahlen (5) findet z. B. in der Asche von knollensellerie einen Gehalt von 1,41% Fe₂O₃." ["Dahlen (citation no. 5), for example, finds the a content of 1.41% Fe₂O₃ in celeriac."]**
     As a matter of fact, Dahlen's publication consisted of two parts, part A being published at pp. 320-336 of the journal, Landwirtschaftliche Jahrbücher 3, and part B at pp. 723-751. In neither of the parts does Dahlen drop a single word on iron content. He only measured the contents of water, ash, nitrogen, fat, sugar, starch, raw fiber, sulfur, phosphor, ammonia.
     That is, Schuphan's citation of Dahlen (1874) as authority on the iron content of celeriac is false. Moreever, the erratum at the very end of Dahlen's two-part publication mentions an error of a decimal dimension:

"Druckfehlerberichtigung. In Heft III. Seite 336 letzte Zeile der Tabelle muß es heißen statt 3.244 Stickstoff 0.244 pCt. Stickstoff." ["Erratum. In issue no. III, page 336, last row of the table it must read, instead of 3.244 nitrogen, 0.244 percent nitrogen."]

Hence, there is at least an erroneous citation by Schuphan (1937) to Dahlen (1874), as well as a typo by Dahlen involving a decimal order of magnitude.
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** Another article from Schuphan in 1937 (Der gegenwärtige Qualitätsbegriff bei Gemüsen und die Notwendigkeit seiner Erweiterung auf chemisch erfaßbare Wertmerkmale. Der Forschungsdienst 3: 290-303) discussed the general discrepancy between criteria for the marketability of vegetables (e.g., size, form, colour, solidity) and nutrient quality (e.g., contents in essential oils, proteins, sugar, vitamin c). Most of his examples are taken from his own and others' research on celery. He mentions aside, the effect of P-manure on contents of vitamin c, phosphoric acid and lezithin in spinach, but iron is no issue at all.
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Conclusion
This is probably the explanation for Bender's/Hartog's faulty memory and his inadvertent causing of a mythical debunking of a decimal error that did occur, but not in the 1870s, not in relation to spinach and not by Werner Schuphan. Arnold Bender fused the real decimal error concerning iron centent in butter beans with the oxalic acid content and hence low availability of iron in spinach; he further fused the debunking of an allegedly high iron content in celeriac as the cause of brown blotches at its cutting edges with a faulty citation by Schuphan of Dahlen (1874) and Dahlen's typo of a decimal order of magnitude with all this. And he thus came up with a false story about a decimal separator concerning the iron content of spinach having been displaced in the 1870s, and this having been debunked by Schuphan in 1937.
     While this is the profane solution to a myth about a myth about the iron content of spinach, everybody is now fascinated about the further myth peddled by Mike Sutton, that no decimal error ever occurred, that no researcher ever existed that would fit to Bender's wrongly spelled "Schupan," and that Bender's memory is anyway pure fantasy and has no roots in anything that really ever happened.

The first chemical analysis concerning the legend of spinach's iron-richness

[Update: While the chemical analyses of Richardson (1848) may well be the first scientific research touching the iron-content of spinach, the folklore of the medical use of spinach is much older (see here).]

[For an introduction to the whole problem of the spinach-iron myth and its many ramifications read the last 7 posts of this blog (chronology: oldest post deals with oldest literature) and follow the links given in them. Beware, this myth is a mess concocted in over 160 years. What has never been discovered is the first source for spreading the opinion, during the second half of the 19th century, that spinach was a good source for dietary iron.]

As you can see from my comments under this earlier blog entry, the data of Thomas Richardson (1848. Beiträge zur chemischen Kenntnis der Vegetabilien. Annalen der Chemie und Pharmacie LXVII Bd. 3.)* may well be this first chemical research that has fed into the widespread opinion that spinach is a good source of iron.

*[This publication hangs in a digital limbo, because it has been concatenated to the end of the preceding article by C. List (1848. Ueber das sogenannte Terpentinölhydrat. Justus Liebigs Annalen der Chemie 67(3): 362-376. That is, you currently must download List (1848) in order to get Richardson (1848) at the end of that download. I've informed Wiley Online about the glitch, so you better check whether a separate publication by Richardson (1848) occurs after List (1848) before downloading List (1848).]

Educational publications from shortly after 1848 spread the belief that spinach was rich in iron and good for anemic people. For example, an encyclopaedia published by Brockhaus (1852. Die Gegenwart. Eine encyklopädische Darstellung der neuesten Zeitgeschichte für alle Stände. Siebenter Band. Leipzig: F. A. Brockhaus) stated at page 172: "Weiße Rüben enthalten nur eine geringe Menge von Eisen, Spinat dagegen viel." [White turnips contain only a little iron, spinach however a lot.] One year later, Aaron Bernstein published a popularisation of scientific findings in a work called "Aus dem Reiche der Naturwissenschaft: ein Buch für Jedermann aus dem Volke" (Berlin: Franz Duncker, 1853). At pages 157-158, Bernstein praised spinach as an iron rich and organic alternative to medicine for pale children. The patriarchic Hermann Klencke (1867. Chemisches Koch- und Wirtschaftsbuch oder die Naturwissenschaft im weiblichen Berufe. Leipzig: Eduard Kummer. p. 49) lists spinach among the food that is good for the breath and hematosis.

Richardson gave the values of various chemical compounds of various vegetables as percent values in relation to the raw ash and as percent values in relation to the pure ash (raw ash minus carbonic acid, charcoal and sand). The iron content, in particular, was given as the percent values of "Phosphorsaures Eisenoxyd," which literally translates as phosphor-acidic iron oxide but chemically means iron(III) phosphate (FePO₄). Richardson's data sheet also provides the percent values of the ashes in relation to the fresh matter.

As I have argued elsewhere, it is false to calculate the portion of, say, the iron compound in the fresh matter by simply multiplying the portion of the iron compound in relation to the ash with the portion of ash in relation to the fresh matter. This leads to false values, because the ashes gain mass during combustion. Gaseous oxygen binds to the burning matter, and some products of combustion end up gaseous themselves (e.g. carbon dioxide), while others end up as solid ash (e.g. magnesium oxide). That is, the ashes gain matter through combustion that is not part of the fresh matter.

It is not anachronistic to call the above mentioned calculation a mistake in relation to Richardson's time, because Phlogiston theory had been questioned in the second half of the 18th century already, and experiments had  shown that metals gain mass during combustion. Hence Richardson's contemporaries and followers should have known that simply multiplying the portion of iron compound in ash times the portion of ash in fresh matter would yield false values for the portion of iron compound in the fresh matter.

Nevertheless, Bunge (1892) failed to correct the ash values accordingly in manipulating data from Wolff (1871) as shown here. Therefore, it seems likely that others have also simply multiplied the percent values of Richardson's data and drawn false conclusions. Or, anyway, it is interesting to reconstruct what conclusions might have been drawn from such a data manipulation.

As you can see from the table below, spinach comes out second after radish herbage. Assuming that the herbage of radish was usually not eaten, however, spinach would be the edible item with the highest iron content in Richardson's data set. Hence Richardson (1848) may well be the first source from which the widespread opinion sprang that spinach was a good source for dietary iron in turn.

Item	portion of iron phosphate in raw ash times portion of ash in fresh matter	portion of iron phosphate in pure ash times portion of ash in fresh mater
Ananas, ganze Frucht
ditto Schopf
Spargel	1,25E-04	1,60E-05
Lauch, Zwiebel	5,52E-04	6,11E-04
ditto Stengel	6,76E-04	8,91E-04
Feige, ganze Frucht
Walnuts, Kern
ditto Schale
Gurke	1,19E-04	1,30E-04
Brocoli (Kohl), Herz	2,02E-04	2,14E-04
ditto Blätter	9,86E-04	1,06E-03
Blumenkohl, Herz	2,80E-04	2,61E-04
Rettig, Wurzel	1,20E-03	1,41E-03
ditto Kraut	3,20E-03	4,54E-03
Kastanie, ganze Frucht	1,77E-04	1,93E-04
Erdbeere, ganze Frucht	3,69E-04	4,56E-04
Orange ditto
Rhabarber, Stengel	1,66E-04	1,91E-04
ditto Blätter	2,62E-04	2,87E-04
Spinat	1,28E-03	1,76E-03
(Kidney Beans) Bohnen	3,09E-04	3,56E-04
Erbsen, Hülsen	6,90E-05	8,00E-05
Pflaumen (greengages), ganze Frucht	1,80E-04	2,42E-04
Orleans-Pflaumen, Haut der Frucht	5,39E-04	6,63E-04
Orleans-Pflaumen, Fleisch derselben	9,50E-05	1,49E-04
Orleans-Pflaumen, Kern	5,76E-04	6,28E-04
ditto Samenschale	9,40E-05	1,05E-04
Kirschen, ganze Frucht	1,47E-04	1,61E-04
ditto Stiel derselben	4,74E-04	5,57E-04
Birne, ganze Frucht	6,60E-05	8,00E-05
Apfel, ditto	5,90E-05	7,20E-05
Artischoke	4,86E-04	5,55E-04
Lattich	Spur	Spur
Endivie	6,72E-04	8,71E-04
Stachelbeere	2,94E-04	3,37E-04
Sellerie	2,56E-04	2,85E-04
Möhre	2,46E-04	2,39E-04
Pastinak	4,63E-04	5,53E-04

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Values in scientific notation: 1,76E-03 means 1.76*10^-3 or 0.00176. This portion would be equal to 176 milligram in 100 gram fresh matter.

P.S: The Genealogical World of Phylogenetic Networks has a new post with a phylonetwork illustrating the whole dataset of Richardson (1848).

Sources of the spinach-iron myth: Schup(h)an's true name

[Click here to get all posts in this series.]

The old narrative:
A misplaced decimal point caused the false reputation of spinach for being the vegetable that was richest in iron. Though still highly popular, this narrative is most likely wrong (see here). The decimal error probably never occurred in that stupidly simple way. Ignoring wrinkles in the narrative, such as that spinach is still rather rich in iron but that it cannot be assimilated well for other reasons, the new narrative can be stated most simply as follows.

The new narrative:
The decimal error is a myth, it never occurred. The false reputation of spinach was due to unreliable methods or poor experimentation. That is, errors were inherent in experiments not data treatments (see here). 

The complex history
Still, not everything about the spinach-iron legend is clear yet. In particular, nobody has yet thoroughly reconstructed where the original data came from, how they have been treated (mathematically) by the various researchers who wanted to reach comparability with their own data, and whether any mistakes were made in these data treatments. At the end of this series of reconstructing data handling, you will see that the whole research endeavour was full of data handling errors, though none as simple as a misplaced decimal point.

Bender's false lead
One of the unsolved riddles in the thicket of myths around spinach is the source of the decimal-point-error myth. While the urban legend is very widespread, the source of this legend remains elusive. A.E. Bender has said as much in his inaugural lecture in 1972 (see here). He later released the decimal-point-error legend upon a wider public through a letter to The Spectator.

"Sir: In a recent article (18 June) spinach is given undeserved nutritional eminence, although, since the facts have never been widely publicised, the author can be excused.

     For a hundred years or more spinach has been (and clearly still is) renowned for its high content of iron compared with that of other vegetables, but to the joy of those who dislike the stuff this is quite untrue. In 1870 Dr E. von Wolff published the analyses of a number of foods, including spinach which was shown to be exceptionally rich in iron. The figures were repeated in succeeding generations of textbooks—after all one does not always verify the findings of others including the 'Handbook of Food Sciences' (Handbuch der Ernährungslehre) by von Noorden and Saloman in 1920.

      In 1937 Professor Schupan eventually repeated the analysis of spinach and found that it contained no more iron than did any other leafy vegetable, only one-tenth of the amount previously reported. The fame of spinach appears to have been based on a misplaced decimal point."

     Professor Arnold Bender, The Spectator (18 July 1977, p. 18)

Who was Schupan?
However, neither the decimal-point error could ever be verified (see here) nor some researcher with the name Schupan be found, who published on spinach and iron during that time.

I was able to trace "Werner Schuphan" instead (mind the h after the p). While he did publish on all sorts of vegetables including spinach, the following publication from 1940 shows that he can hardly have debunked the myth of spinach's exceptional iron richness in 1937: 

"Spinat zeichnet sich – wie wir sehen – besonders durch hohe Gehalte an Carotin, Chlorophyll, Eisen und Reineiweiß und Vitamin C aus." [Schuphan, W. 1940. Über den Einfluss der Chlorid- und Sulfatdüngung auf Ertrag, Marktgängigkeit und biologischen Wert verschiedener Gemüse unter Berücksichtigung edaphischer und klimatischer Faktoren. Bodenkunde und Pflanzenernährung 19(5-6): 265-315]

"Spinach distinguishes itself – as we see – especially through high contents of carotin, chlorophyll, iron and pure protein and vitamin c." [my translation]

As the above quote reiterates the idea that spinach is richer in iron than other vegetables, it is unlikely that he had some years before claimed the opposite.

Schuphan 1937
One article published by Schuphan in 1937 [Untersuchungen über wichtige Qualitätsfehler des Knollenseleries bei gleichzeitiger Berücksichtigung der Veränderung wertgebender Stoffgruppen durch die Düngung. Bodenkunde und Pflanzenernährung 2, issue 5-6, pp. 255-304] dealt with quality issues in celeriac including the so-called Eisenfleckigkeit (iron blotchiness) of tubers. He therein debunked the belief that celery tubers turn brown at the cut surface, because of the oxidation of iron and claims that the colouring is due to resins and essential oils instead.

Another article from Schuphan in 1937 [Der gegenwärtige Qualitätsbegriff bei Gemüsen und die Notwendigkeit seiner Erweiterung auf chemisch erfaßbare Wertmerkmale. Der Forschungsdienst 3: 290-303] discussed the general discrepancy between criteria for the marketability of vegetables (e.g., size, form, colour, solidity) and nutrient quality (e.g., contents in essential oils, proteins, sugar, vitamin c). Most of his examples are taken from his own and others' research on celery. He mentions aside, the effect of P-manure on contents of vitamin c, phosphoric acid and lezithin in spinach, but iron is no issue at all.

That is, Bender's citation of a publication by Schupan in 1937 is probably wrong.

Schuphan and spinach
However, Schuphan is an interesting figure in the spinach legend for other reasons. Firstly, several of his publications suggest that spinach is rich in provitamin A, which makes him a potential source for Popeye's eating spinach for vitamin A (see here). Secondly, he published a study intended to show that the content of oxalic acid in spinach is unproblematic in 1958 (Schuphan and Weinmann: "Der Oxalsäuregehalt des Spinats." Qualitas Plantarum 5(1): 1-22). Thirdly, in 1965 he discovered that high incidences of methemoglobinaemia in babies around Hamburg, Kiel and Berlin was probably due to over-manuring spinach with nitrogen-fertilizer. A subsequent accumulation of nitrite from nitrate due either to false storage, processing or re-heating the prepared food lead to the poisoning, he suggested.*

These publications can at least suggest how the name Schup(h)an, research on spinach compounds, and the debunking of a legend about iron (though in celery) got associated in the mind of Arnold E. Bender.

* Now, I remember vividly how my parents and grandparents would always claim that the spinach mush must be eaten all up, for it cannot be re-heated. Parents always find creative ways to turn scientific findings into the claim that the greens must be eaten, it seems.

Sources of the spinach-iron myth: König (1926) woozily

[Click here to get all posts in this series.]

The old narrative
A misplaced decimal point caused the false reputation of spinach for being the vegetable that was richest in iron. Though still highly popular, this narrative is most likely wrong (see here). The decimal error probably never occurred in that stupidly simple way. Ignoring wrinkles in the narrative, such as that spinach is still rather rich in iron but that it cannot be assimilated well for other reasons, the new narrative can be stated most simply as follows.

The new narrative
The decimal error is a myth, it never occurred. The false reputation of spinach was due to unreliable methods or poor experimentation. That is, errors were inherent in experiments not data treatments (see here). 

The complex history
Still, not everything about the spinach-iron legend is clear yet. In particular, nobody has yet thoroughly reconstructed where the original data came from, how they have been treated (mathematically) by the various researchers who wanted to reach comparability with their own data, and whether any mistakes were made in these data treatments. At the end of this series of reconstructing data handling, you will see that the whole research endeavour was full of data handling errors, though none as simple as a misplaced decimal point.

König 1904
J. König (1904. "Chemie der menschlichen Nahrungs- und Genussmittel." Vol 2, p. 353) gives the range of iron contents in spinach as 32.7 to 39.1mg per 100g dry mass (see table below). The text above the table says that these values are from Bunge and Häusermann.

And indeed, Bunge found 0.0327g in 100g dry mass (see here), which is the same as 32.7mg in 100g. The other value of 39.1mg/100g is from Emil Häusermann (1897. "Die Assimilation des Eisens." Zeitschrift für Physiologische Chemie 23: 555-592). Like Bunge, Häusermann's main aim was to induce and study the anemia in animals, but he lists the iron contents of vegetables at the end of his publication. The value for spinach can be found at page 588 and it is taken, in turn, from Boussingault (1872. "Du fer contenu dans le sang et dans les alimants." Comptes Rendus de l'Académie des Sciences 74: 1353-9), or rather from Bunge (1892), who had taken Boussingault's data and transformed it according to König (1889, see footnote: **** here). 

Later, J. König (1926 "Nahrung und Ernährung des Menschen. Kurzes Lehrbuch. Berlin: Julius Springer, p. 31) tried to combine these values with those of a later publication by Haensel (1909. "Über den Eisen- und Phosphorgehalt unserer Vegetabilien." Biochem. Zeitschrift 16: 9-19) it seems. Haensel compared his data for various vegetables and concluded correctly, that spinach was not the richest in iron, despite the fact that his particular value for iron in spinach was roughly ten times higher than Bunge's (see here). König seems to have grappled with this inconsistency in the research record as follows:

"Eine besondere Bedeutung wird auch dem Eisen in der Nahrung zur Bildung des Hamoglobins zugeschrieben. Von dem durchschnittlichen Eisengehalt des erwachsenen Körpers von 3g sollen etwa 1/6 auf Hamoglobin entfallen. Hiervon werden täglich 80-100 mg in Freiheit gesetzt. Diese werden von Leber, Milz und sonstigen Drüsen größtenteils gespeichert, so daß der tägliche Bedarf in der Nahrung nur 20-30mg betragen solI. Solche Mengen Eisen sind auch wohl in einer gemischten Nahrung vorhanden. Die größten Mengen Eisen finden sich in grünen Gemüsen, nämlich in 100g 30-60mg Fe₂0₃ (die Höchstmenge im Spinat); andere Nahrungsmittel enthalten nur den 10. Teil und noch weniger." König (1926, p. 31)

"Special significance for forming the hemoglobin is attributed to the iron in the diet. About 1/6 of the average 3g iron in an adult body if in the hemoglobin. Of these, 80-100mg are liberated daily. These are mostly stored in the liver, spleen and other glands so that the daily requirement in dietary iron amounts to 20-30 mg. Such amounts of iron are also well available in a mixed diet. The largest amounts of iron can be found in green vegetables, namely in 100g 30-60mg Fe₂0₃ (the maximum quantity in spinach); other foods contain only the 10th part of this and even fewer." (my translation)

At page 82 König cites Haensel (1909) and another, but not on spinach. My translation below is not garbled, the original is:

"Unter den Mineralstoffen wird auch dem Eisen der grünen Gemüse wegen der blutbildenden Eigenschaft eine besondere Bedeutung zugeschrieben. R. Berg fand in 100g frischem Gemüse Spuren (Wirsing) bis 150 mg Eisen (Bleichsellerie); E. Haensel 3,9 mg (Zwiebel) bis 68,9 mg Eisen (Kohlrabiblätter) oder 31-37,9 mg Eisen in 100 g Trockensubstanz."

"Among the minerals a special importance is also attributed to iron of the green vegetable because of the blood-forming capacity. R. Berg found in 100g fresh vegetables tracks (Savoy) up to 150mg iron (celery); E. Haensel 3.9mg (onion) to 68.9mg iron (Kohlrabi leaves) or from 31 to 37.9mg of iron in 100 g of dry matter."

Coming full circle, page 86 correctly states that spinach contains no more iron than other green vegetables and refers back to page 82, where, as we have seen, nothing is said about spinach.