Spinach: Rich in Iron?

[cruciverb]

This week’s e-mail list included a Classic from 1992 about spinach.
For anyone interested, here’s more pertinent “mythbusting” from Wikipedia:

“The myth about spinach and its high iron content may have first been propagated by Dr. E. von Wolf in 1870, because a misplaced decimal point in his publication led to an iron-content figure that was ten times too high.”

[bibliophage]

Welcome to the SDMB, cruciverbe.

A link to the column is appreciated. Providing one can be as simple as pasting the URL into your post, making sure to leave a blank space on either side of it. Like so: http://www.straightdope.com/classics/a3_120.html

[Tammi_Terrell]

@cruciverb

This week’s e-mail list included a Classic from 1992 about spinach.
For anyone interested, here’s more pertinent “mythbusting” from Wikipedia:

“The myth about spinach and its high iron content may have first been propagated by Dr. E. von Wolf in 1870, because a misplaced decimal point in his publication led to an iron-content figure that was ten times too high.”

Sorry, but I’ve gotta say something about that Wikipedia page, which notes in full that,

The myth about spinach and its high iron content may have first been propagated by Dr. E. von Wolf in 1870, because a misplaced decimal point in his publication led to an iron-content figure that was ten times too high. In 1937, German chemists reinvestigated this “miracle vegetable” and corrected the mistake. It was described by T.J. Hamblin in British Medical Journal, December 1981.

Frankly, I find it stupefying that T.J. Hamblin is the frequently cited expert on this little factoid because 1) the thrust of his article for BMJ barely mentions spinach (in fact, his piece was on “[f]rauds, hoaxes, fakes, and widely popularized mistakes [that] run through the warp and woof of the history of science and medicine”), and 2) what Hamblin does have to say about spinach isn’t footnoted.

For the record, here’s the relevant passage from T.J. Hamblin’s “Fake!”, The British Medical Journal 283: 1671-1674, 19-26 December 1981:

In the year that Popeye became once again a major movie star it is salutary to recall that his claims for spinach are spurious. Popeye’s superhuman strength for deeds of derring-do comes from consuming a can of the stuff. The discovery that spinach was a valuable source of iron as red meat was made in the 1890s, and it proved a useful propaganda weapon for the meatless days of the second world war. A statue of Popeye in Crystal City, Texas, commemorates the fact that single-handedly he raised the consumption of spinach by 33%. America was “strong to finish 'cos they ate their spinach” and duly defeated the Hun. Unfortunately, the propaganda was fraudulent: German chemists reinvestigating the iron content of spinach had shown in the 1930s that the original workers had put the decimal point in the wrong place and made a tenfold overestimate of its value. Spinach is no better for you than cabbage, Brussels sprouts, or broccoli. For a source of iron Popeye would have been better off chewing the cans (fig 1).

[Figure 1 is a poorly drawn cartoon of Popeye eating you-know-what. – Tammi Terrell]

Hamblin begins his reference section with this unhelpful comment,

Having spent so much of my time talking about people whose work was unoriginal, I should mention that little of my article is based on original work but has been derived from the publications of others. Among these I should particularly like to mention: [and then he mentions about a dozen or so articles and a couple books, none of which seem to have much to do with spinach – Tammi Terrell].

Last summer, precisely because of that Wikipedia page and its mention of Hamblin’s article, I did some preliminary research into the original works of Emil Theodor von Wolff (1818-1896), whose Aschen-analysen von Landwirthschaftlichen Producten, Fabrik-abfällen und Wildwachsenden Pflanzen (2 volumes; Berlin: Wiegandt & Hempel; 1871 and 1880) provides chemical analyses of burnt plant materials (for the determination of, for example, iron content). Gustav von Bunge (1844-1920) is also often fingered as the culprit who misplaced a decimal point in the estimation of iron in spinach; consequently I looked at an English translation (1902) of his Lehrbücher über die Pathologische und Physiologische Chemie.

As for Hamblin’s claim that “the original workers had put the decimal point in the wrong place and made a tenfold overestimate of its value,” I have to say that I’ve yet to find any evidence of this kind of simple mathematical goof in the works of those who are usually given credit for the original work.

It’s important to note that Wolff and Bunge were working with dried weights of plant material and invariably reported these values as milligrams per kilogram (dried weight). Nowadays concentrations of iron (and other nutrients) are commonly given as derived from raw vegetable matter, which – on average – contains about 90% water. It’s easy to see, then, that a kilogram of dried spinach or dried carrots or dried asparagus is going to contain a significantly greater amount of iron (or calcium or magnesium, etc.) than an equivalent mass of the same plant material in its raw, hydrated state. (That being said, I should note that some of the values reported by Wolff and Bunge are at odds with what the USDA, for example, reports for nutrient content, even accounting for differences due to the mass of the sample. Still, it’s a gross oversimplication to hold that we can blame this on misplaced decimal points.)

My guess is that the values presented by Wolff and, separately, by Bunge were misrepresented as the decades wore on. The distinction that these values came from measurements of dry weights was dropped as medical types in the early 20th century wrote about nutrients found in spinach and other vegetables.

As for Hamblin’s claim that (emphasis mine) “German chemists reinvestigating the iron content of spinach had shown in the 1930s the original workers had put the decimal point in the wrong place and made a tenfold overestimate of its value,” where’s this report by German chemists? (In fact, the Wikipedia pages specifically claims that “in 1937, German chemists reinvestigated this ‘miracle vegetable’ and corrected the mistake.”) So, where’s a paper from the 1930s that shows that “the original workers had put the decimal point in the wrong place”? (Note that Hamblin never specifically cites “Dr. E. von Wolf” as a source for this “blunder.”)

In the end, I think there is more to find out about the historical roots of a misconception about spinach as a great source of iron, but we’re not going to find it in Hamblin’s article or in Wikipedia.

– Tammi Terrell

[Agonist]

Is the only data available from 1937? Has no one bothered to check the nutritional content of vegetables in the last 70 years?

It seems like there should be enough money in the federal budget to allow for a new study, say, every ten years or so. One person with a lab and a hundred bucks for groceries should be able to do it.

[Contrapuntal]

Linky.

[RiverRunner]

@Tammi Terrell

Sorry, but I’ve gotta say something about that Wikipedia page, which notes in full that,
. . .
<much wonderful stuff goes here>
. . .
– Tammi Terrell

Tammi Terrell seldom posts, but when she does they’re usually gems.

RR