“spinach is rich in iron.” this is a rumor from a decimal point.

Myth: in 1870, German chemist Wolf published a paper pointing out for the first time that spinach is high in iron, which is worth as much as red meat. The conclusion that spinach is rich in iron is written in the most authoritative encyclopedia. Segar, the cartoonist, created Popeye in 1929, a fearless, powerful image of a recessionary, meat-hungry American. It became an effective weapon of public opinion in the United States during World War II, and even boosted spinach sales by 33% in the 1930s. In 1937, a German scientist found that his test for iron in spinach was much lower than in any previous textbook. Tracing back to source found that Wolf had misplaced the decimal point, which was ten times larger. So far, this fallacy, which has influenced people for 70 years, has been corrected in academia. However, because of the enduring image of Popeye, the wrong decimal point 140 years ago still affects people today. Generation after generation of small pot friends of spinach is the number one impression is “rich in iron.” 

Truth: this story is different from the average online grapevine and has considerable “international clout.” If you look up the words “spinach” and “Popeye” on Wikipedia, they all tell you about it. BBC published an article in 2006 explaining the “spinach truth.” the company launched a feature on the 115th anniversary of Popeye’s founder, Segar, in 2009. 


However, this is not the most direct evidence. Rumor-shredding investigators then found a 1981 article in the British medical journal, the earliest information so far on the “wrong decimal point”. Unfortunately, the article does not give references. Fortunately, a man named Sutton had the same doubts and did a lot of work. Sutton sent an email directly asking the author of the article. In his reply, Professor Hamblin said he could not remember the details because the editor asked him to write for the Christmas edition without asking for a source of reference, but he assured himself that he was not making it up. Well, this tells you: when you write an article, be sure to indicate the source of the reference material. )

Is “the wrong decimal point” really true? 

Can we still find the earliest spinach iron test report? Who is the scientist who corrected the error after that? What happened in the 100 years from the first iron test in spinach in 1870 to 1981? To answer these questions, shell rumors shredded investigators on a quest spanning more than a century. 

At first, the rumor shattered the investigator a little dismayed. The original literature and data, which were first measured 140 years ago, are simply not available. Who was the mysterious German scientist who corrected the “decimal error”, and which article was published, did not come up with anything. However, some of the subsequent findings are encouraging, and the story of the “decimal error” is likely to be another rumor: 


As can be seen from a list of foods considered to be rich in iron in 1916, scientists at that time had basically figured out the iron content of the food, although spinach was listed first. But spinach is not thought to contain much more iron than other green vegetables. Considering that the scientific community at that time did not know that some of the iron in food was not absorbed (it was not until 1936 that the relationship between inorganic iron and anemia, let alone factors affecting iron absorption, such as oxalic acid, was known), the table was reasonable, There is no indication that iron levels in spinach were misled to nearly 10 times at the time. 

With regard to the iron content of spinach, it is true that mistakes have been made. This led to an “error correction” in the 1930s. In 1934, a scientist published his measurements of iron content in spinach, indicating that there was 53 milligrams of iron per 100 g of spinach [8]. The real spinach contains only 2.7mg iron per 100g spinach, so this value is 20 times greater than the actual situation.Fortunately, this amazing achievement was corrected by the American Academy of Science the following year. They say only 1/4 of the iron in spinach can be used, not necessarily better than the average vegetable. [9] another year later, another group of scholars published their data, pointing out that 100g of dried spinach had only the iron of 35.2mg [10], which completely corrected the situation. It is worth mentioning that there is no mention in the relevant reports of the “wrong article” of 1870, much less of the “wrong decimal point”.

The Truth about Iron in spinach

In terms of 100g, the average iron content of spinach in our country is 2.7 mg, so long as it is not compared with pig liver, which perversely reaches the highest level of 22.6mg, this value is definitely the best in vegetable family. You know, even pork and eggs are just 1.6mg and 2mg. [11] it is therefore wrong to say that “spinach contains almost as much iron as other vegetables”. However, to rely on spinach to meet the human body’s need for iron is not reliable. 

About 20% of the world’s people have iron deficiency anemia. The daily iron intake recommended by the Chinese Nutrition Society is: 15mg for adult men, 20mg for adult women, and 25mg for pregnant women. According to this is not a person to eat a catty of spinach can meet the needs? Unfortunately, in addition to the content, we also have to consider the absorption rate and utilization rate. Iron from food sources can be divided into hemoglobin iron and non-hemoglobin iron, vegetables, beans, cereals, seaweed, eggs, cheese, shellfish iron is not easy to absorb non-hemoglobin iron. For example, is also rich in iron food, beef hemoglobin iron can absorb more than 20%, soybean, egg non-hemoglobin iron absorption rate is less than 10%. In addition, spinach also contains a large amount of oxalic acid, oxalic acid can combine with a variety of minerals to affect the absorption, so the spinach iron absorption rate is only 1%. In other words, more than ten catties of spinach is worth 50 grams of pig liver, it is estimated that before you finish eating the face should be green.In short, if you really want to get iron, you have to rely on animal livers, whole blood, fish, and poultry meat. 

Although iron supplement is not reliable, spinach also has its merits. As a dark green vegetable is rich in β-carotene spinach is still quite high nutritional value. Spinach is also rich in vitamin C, which can increase the absorption rate of iron in other foods. However, because spinach leaves have a lot of dehiscent bubble hairs, the tiny fragments they form tend to absorb radioactive particles, which have been mentioned in recent reports of nuclear contamination. Plus spinach nitrite more, purine high, “food is mutually exclusive” rumors also can not escape it. In fact, just remove the roots of the spinach (although this part contains 12mg / 100g iron) [12]; rinse the leaves down a little longer; blanch and drain before cooking, and you can greatly reduce the unhealthy ingredients of the spinach. 

Conclusion: myth cracking. Claims such as “spinach is rich in iron”, “the scientists who first tested iron in spinach had the wrong decimal point”, and that “spinach is no different from other vegetables in iron content” are rumours. Communicators may want to warn us to do things seriously, perhaps to remind us that spinach can not be iron.That is a good conclusion, but it would also be shameful if such good intentions were based on false rhetoric.

Source: shell net


  • [1] The Source of spinach ‘ s power
  • [2] spinach-the Truth
  • [3] e.c Segar, Popeye ‘ s creator, celebrated with a Google doodle [4] Hamblin, T.J. (1981) fake! British Medical Journal vol. 283.19–26 December.
  • pp.1671-1674 [5] Sutton, M. Spinach Iron and popeye:ironic lessons from biochemistry and history on the importance of healthy E ating, healthy scepticism and adequate citation.
  • Internet Journal of criminology [6] Hamblin, J.T. Personal email communication to the author by email following email request for references for T He spides that is reported in Hamblin, T.J. (1981) fake! British Medical Journal. Vol. 283.19-26 Decemeber.
  • pp.1671-1674 [7] McKillop, M. (1916) Food Values:what They are, and how to calculate them.
  • London.routledge. [8] Sherman, w.c Elvehjem, C.A. and hart.e.b. (1934). Further studies on the availability of Iron in biological materials. The Journal of biological chemistry. Vol. 107. N0.
  • 3. pp383-394. [9] The science news-letter. (1935) Spinach over-rated as Source of Iron vol., no.749.
  • Aug, p. 110 [d] Kohler, G. Elvehjem, C. and Hart, E. (1936) Modifications of the Bibyridine method for Available Iron. Journal of biological Chemistry. Vol. 113.
  • PP 49-53.
  • [11] “China Food Ingredient List” 2002 edition [12] Li Licheng etc. Study on the content and distribution of iron in vegetables [J] modern agricultural science and Technology, 2007, (05)

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