Date: December 17th, 2015
Guest Skeptics: Bob Edmonds is a 3rd year emergency medicine resident at the University of Missouri at Kansas City. Prior to medical school, he graduated from the US Air Force Academy, and when he completes his training will rejoin the Air Force for nine years as an Emergency Medicine physician. In his spare time he enjoys reading, finding random facts online, and hanging out with his wife and son.
This is a SGEM Xtra Holiday Edition. Last year we looked at paper by Chan et al (New Pun-land Journal of Medicine 2014) on Early Goal Directed Dating (SGEM#100). This was a review of an early goal directed dating protocol in the treatment of singledom and severe loneliness for physicians. The episode was in the spirit of the BMJ Holiday Edition that is put out every year at this time. One of the most famous papers in this series was the classic Parachute study (Smith and Pell BMJ 2003).
The SGEM has critically reviewed a couple of BMJ Holiday Edition articles over the years. The first one was SGEM#6 that reviewed the study called Orthopedic Surgeons: As Strong as an Ox and almost Twice as Clever? Multi-Centre Prospective Comparative Study (Subramanian et al. BMJ 2011). The other one we covered was SGEM#23 called Pain over Speed Bumps in Diagnosis of Acute Appendicitis: A Diagnostic Accuracy Study (Ashdown et al. BMJ 2012).
We hope you enjoy this SGEM Xtra Holiday edition on Spinach, Popeye, Iron and the Decimal Error Story (SPIDES).
Case: A 34-year-old former sailor presents to his primary care provider for a routine employment screening. He asks if he should consider eating lots of spinach to make him strong and healthy. He is noted to enjoy pipe smoking and to have disproportionately developed forearms.
Background: For many decades spinach has been promoted as a food with a super high iron content. It is also part of pop culture that Popeye the Sailor ate spinach for the iron to make him strong.
There has been a story about spinach, iron and Popeye that has been circulating for decades. It is referred to as the Spinach, Popeye, Iron and the Decimal Error Story (SPIDES). The story has been told by many academics and reproduced in many books. However, it turns out the story is complicated and not accurate.
I first heard of the story reading a book called the Half-life of Facts: Why Everything We Know Has an Expiration Date while on a cruise for my 20th wedding anniversary. Complexity scientist Samuel Arbesman wrote the book. He has been a fellow at Harvard and at the University of Colorado. He also writes for the New York Times and a few other magazines and newspapers.
In the Half-Life of Facts he tells the story about Popeye and the decimal error made in the calculation of the iron content of spinach. Apparently back in the 1870’s a German scientist named von Wolff was measuring the iron content of vegetables including spinach.This is where the infamous decimal point error was allegedly made changing the magnitude of iron in spinach to be ten fold greater.
This incorrect amount of iron per 100g serving would be comparable to eating a small piece of a paperclip. Arbesman goes on to say that when Popeye was created in the early 20th century he was shown to eat spinach for his strength due to its health properties.
This transcription error was supposedly corrected way back in the 1930’s. But the story goes that this error wasn’t corrected until after Popeye was already in the press, and that this in turn led to decades of mistaken public belief about spinach’s iron content.
I have used that story to illustrate how long it takes for knowledge translation. The talk is called Popeye and the Paperclip. The story was used to demonstrate my point about knowledge translation at the SMACC conference in Chicago, on The Reality Podcast earlier this year and at other meetings.
You heard me tell this story on The Reality Check podcast and having a major in Biochemistry found it odd that a German chemist would make such a gross error. You were skeptical and did a google search to find out SPIDES was not true and that the good Dr. von Wolff was innocent.
Bob contacted me and I invited him on the SGEM to clarify the story. So in the spirit of the holidays, correcting previous errors and encouraging skepticism, I wanted to do a SGEM Xtra on the Popeye and the paperclip story.
Clinical Question: Is spinach high in iron and is that where Popeye gets his strength?
Reference: Dr. Mike Sutton. SPINACH, IRON and POPEYE: Ironic lessons from biochemistry and history on the importance of healthy eating, healthy scepticism and adequate citation. International Journal of Criminology 2010
- Who is Dr. Mike Sutton? He is a lawyer with a PhD in criminology who has a special interest in myth busting. He runs the Internet Journal of Criminology, a free open access journal.
- How did he become involved in the Spinach/Popeye story? Dr. Sutton was preparing some citations regarding the introduction to a talk on the impact of bad data on policy making he had given at Manchester University. He used the SPIDES story as an example, but when he tried to get citations for the origins of SPIDES he noticed a disturbing lack of primary sources. After a few weeks he found that all roads led to a 1981 BMJ article by Dr. TJ Hamblin, this article in turn had some very sketchy sources on the origins of this myth. He emailed Hamblin, who stated he couldn’t remember who had told him about the myth in the first place, but was pretty sure he didn’t make it up. Sutton then took an obsessive turn and reread all the original Popeye comics from 1928-1935.
Spinach, Iron and Popeye
- Was there a German scientist named Erich von Wolf mentioned in the book the Half-Life of Facts? Yes and No. There appears to have been a typo from the book you had read, the real name of the German scientist was Emil Theodor von Wolff spelt with two “f”s.
- Did he calculate the iron content in spinach? Yes, he calculated the iron content from burnt spinach residue.
- Is there evidence that von Wolff made a transcription error? There is no any primary evidence of this error. Also, there is no secondary or tertiary evidence of von Wolff making this error prior to the BMJ article.
- So how did this error get into the literature at the end of the 19th and beginning of the 20th century? According to Sutton’s investigation, it appears this was actually based on a confusing table in a 1934 paper from the University of Wisconsin by Sherman et al (J Biol Chem 1934). They reported iron contents for dry and fresh spinach.
- What about the dry vs. fresh measurements? As spinach’s iron content is measured based on 100 g of spinach, the dry measurements of spinach’s iron content are much higher since the water content is gone. The paper by Sherman et al is very confusing as to whether it is referring to dried or fresh spinach, but does report a value of iron in spinach that is more consistent with the current values seen in dried spinach.
- Do we know who corrected the error in the 1930s? Kohler et al (J Biol Chem 1936) issued a paper two years later. They modified the chemical method of extracting the iron and also used fresh spinach. Their results are consistent with our current fresh spinach values.
- Tell us about the 1981 BMJ article by Dr. TJ Hamblin called “Fake”. The BMJ puts out a holiday article every year that is light hearted and less meticulously researched like the Parachute Trial. They approached Hamblin asking for a humorous piece and didn’t ask him to provide references. He did in fact give 13 references to the article, but none specifically referenced the SPIDES story.
- Who was Dr. Hamblin? He was a well-published immunohematologist who specialized in his work on chronic lymphocytic leukaemia.
- Where did he get his information for the story? This is very unclear. When Sutton emailed Hamblin in 2010, he was unclear, stated he couldn’t recall his source, but was sure he had heard it once or read it in the Reader’s Digest.
- Apparently the story may have come form a Professor Arnold E. Bender? Yes, it appears that in 1972 during an inaugural lecture and an article in The Spectator in 1977. Professor Bender reiterated the SPIDES story but stated the error was fixed in 1937 by professor Schupan. There is no record of who this professor Schupan was or where his correction came from. Bender incorrectly cites a paper that measures the iron oxide, not iron content, of spinach.
- “For a hundred years or more spinach has been (and clearly still is) renowned for its high iron content 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 Ernahrungslehre) by von Noorden and Saloman  1920. In 1937 Professor Schupan eventually repeated the analyses 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.”
- Does spinach even contain iron? Yes. Here is the quote from Dr. Sutton’s paper:
- “Iron levels for fresh spinach contains around 2.75mg per 100gm (USDA 2009). Once dried, however, spinach contains substantially more mg of iron per 100gm, just as dried herbs contain far more concentrated flavour by weight and volume than when fresh.”
- Who Popeye and when was he created? Popeye started as a character in a comic strip in 1929 by Segar. He was added into an already existing comic strip that had been around since 1919 called Thimble Theatre. Perhaps this is why Sutton’s analysis of the cartoons started one year prior to Popeye’s debut in 1929. He is a strong sailor man who is well known for having a gruff way of talking and a deep love of spinach-although this love of spinach was not added to the comics until 1932.
- So where does Popeye get his strength? Segar actually goes out of his way in the first comic panel to point out that Popeye eats spinach. “Spinach is full of vitamin “A” an’ tha’s what makes hooman’s strong an hefty”. Spinach does contain a large amount of beta-carotene, which in turn becomes vitamin A.
- Where does the idea come from of Popeye being “iron man”? In another panel, Popeye’s doctor says he has a “cast iron interior” and Popeye later states he is an “iron man” in the sense of being a tough guy.
Summarize Key Parts of the Story:
- It is a myth that spinach is SUPER high in iron as suggested by SPIDES
- There does not seem to be any evidence of a decimal point or transcription error by von Wolff
- Popeye does eats spinach for his strength
- Vitamin A (beta carotene) not iron in spinach is credited for making Popeye strong
SGEM Bottom Line: Popeye is strong to the finish because he eats spinach that contains beta carotene. Spinach is not SUPER high in iron content as suggested by SPIDES but can be part of a healthy diet.
Case Resolution: You support this sailor presenting for an employment physical to eat spinach, as a healthy complement to a balanced diet but it is not an independent factor for increased strength or health. You also encourage him to stop pipe smoking and work on his other muscle groups besides just his forearms.
Keener Kontest: Last weeks’ winner was Nathan Finnerty, PGY3 from The Ohio State University Emergency Medicine program. He knew Heinrich Quincke was the German physician credited for introducing the lumbar puncture for diagnostic and therapeutic purposes?
Listen to the podcast to hear this weeks’ question. Send your answer to TheSGEM@gmail.com with “keener” in the subject line. The first correct answer will win the cool skeptical prize.
More Information on SPIDES:
- Half-Life of Facts Errata
- Wired Magazine: Paradox of Hoaxes: How Errors Persist, Even When Corrected
- Super Myths: Spinach Iron Decimal Point Error Myth Busted
- Best Thinking: The Spinach, Popeye, Iron, Decimal Error Myth is Finally Busted
- Academic Urban Legends. OB Rekdal. Social Studies of Science 2014
I hope everyone has a wonderful holiday and gets to spend some time with friends and family. The SGEM will be back in early 2016 with another Hot Off the Press episode. This time it will be on asthma.
Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.