It is generally accepted that spinach is the champion among plants in terms of iron content. We checked if this is true.
“Spinach is a real storehouse of nutrients, but most of all it is valued for its high iron content,” it says on the website of the influential Louis Bonduelle Foundation. In an article from the American journal Progressive Medicine for 1924 approvedthat 100 g of spinach contains 35 mg of iron. IN dissertations “Nutritional value and culinary-technological properties of main leafy vegetables”, protected in 1983, you can read: “The high content of chlorophyll, folic acid and iron determines the use of spinach as a therapeutic and dietary remedy for certain blood diseases.” Biochemist Hidaya Aliush from the University of Manchester in a 2021 paper leads range of 4–35 mg iron per 100 g spinach, which is much higher averages for other plant products.
In the body of an adult healthy person contained approximately 3–5 g of iron, but 1–2 mg of this microelement is excreted from the body daily - with sweat, urine, and sometimes with blood. Daily allowance need In an adult, the average amount of iron in an adult does not exceed 15 mg, and if it is not replenished, then one may encounter a disease such as anemia. With the latter, the formation of the skeleton, the functions of the central nervous and vascular systems are disrupted, and hypoxia is observed in the tissues.
The main source of iron in the body is food. The average daily human diet contains enough of this trace element to satisfy all the body's needs. However, during periods of intensive growth, pregnancy or lactation, this amount may not be enough. Typically, a list of foods with high iron content can be seen in all sorts of reference books and thematic articles.
But the numbers we see in reference books are usually deceptive. The amount of iron supplied from food is one thing, the absorbable portion is another. This is where other components of the food product come into play. For example, the presence of oxalic acid in it can play a negative role. The proteins contained in legumes inhibit the absorption of iron especially strongly: here the absorption is only 0.8–1.9%. From meat products digestible about 30% of the iron contained therein, while from cereals - only 5-10%. At the same time, initially there is less iron in meat than, for example, in beans. Also known happening, when patients with iron deficiency anemia were fed raw beef treated with the gastric juice of a healthy person, and they recovered, despite the fact that individually these components did not give such an effect. There are many other influencing factors - for example, the valence of iron.
What about spinach? If we look into modern tables, we will see that the leaves of this plant generally contain a considerable, but far from fantastic amount of iron - about 2–3.5 mg, that is, at the level of many vegetables and much less than in legumes or a number of cereals. Let's add high content here oxalic acid, which makes consuming raw spinach relatively ineffective in terms of replenishing iron deficiency. Where did the information about 35 mg come from then?
Very often write, that an error about the iron content in spinach appeared many years ago, when, when publishing an article with chemical analysis data, the comma was accidentally moved one position to the right. Accordingly, the analysis result was overestimated exactly ten times. The version about the typo became widely known. She is even cited as an example of how important it is to take a critical approach to published data.
Criminologist Mike Sutton from the University of Nottingham became interested in the history of this myth. The interim result of his work was a 34-page study, published in 2010, to which the author added an addition seven years later. Sutton tried to find the original article with the error, but he was unsuccessful - the specified works had their own logic for obtaining this number. The only thing he was lucky enough to find was a few publications 1934 in American magazines, which claimed that 100 g of spinach contains 53 mg of iron - almost 20 times more than it actually is. However, the decimal point (in the USA - a period) had nothing to do with it. The error was quickly discovered, corrected, and had no consequences. In any case, none of those who claimed that spinach has a lot of iron referred to this article.
Then Sutton took up the story of the “mistake about a mistake.” As it turned out, the British expert on nutrition and food toxicology, Arnold Bender (1972), and Professor of Immunohematology at the University of Southampton, Terence Hamblin (1981), were among the first to misinform people about the “semicolon error.”
Then Sutton followed a different trail. In pre-war America, Popeye the sailor, a comic book and cartoon character who ate huge amounts of spinach, was extremely popular. Popeye creator, artist Elsie Segar chose spinach to promote healthy eating among children. As a result, the consumption of this product in the United States has increased markedly, and agronomists, as a sign of gratitude, erected monuments to Popeye in several states.
However, in none of the numerous comics and cartoons did Sutton find direct hints that the character’s extraordinary strength is associated specifically with the iron in spinach - only some visual metaphors. Here and there Popeye directly explains that he eats spinach because it contains vitamin A (useful, rather, for vision). Additionally, Popeye first appeared with spinach in 1932, two years before the 1934 paper with erroneous data was published.
And yet, a plausible hypothesis for the occurrence of an error can be put forward here, as some do researchers. In particular, in table, which was cited by one of the founders of agrochemistry, Jean-Baptiste Bussingault in 1872, in the column “Spinach leaves” there is 0.0045 g, that is, 4.5 mg of iron per 100 g of product. For this work in 1897 in his article Emil Hausermann referred, but he already gives a range of 32.7–39.1 mg:
The fact is that Hausermann gives the iron content in 100 g of dry matter, and not in fresh leaves. He calculated the upper value from Bussingault’s article, and the lower value from articles Gustav von Bunge (1892). It can be assumed that the average value of 35.9 mg, attributed to dehydrated spinach, was interpreted by someone as the iron content of fresh spinach.
As for examples of less radical deviations of centuries-old data from today’s indicators (1.5–1.7 times), then, as shown by modern calculations, scientists at the turn of the 19th and 20th centuries simply did not take oxygen into account - the classical tables contained data on the proportion of iron oxide in spinach, and not pure iron at all. Such an error could be enough for someone to incorrectly declare spinach a “champion in iron content.”
As you can see, in our case we were faced with two myths at once: about the iron content in spinach and about the history of the appearance of this error.
Not true
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