Yesterday I was reminded of the occasion on which I first learned about spinach having not as much iron as commonly believed, and that the idea came down to a transcription error. I wasn’t really confident in my recollection so I went and looked it up and fell into reading about “Academic urban legends”.

It’s a wild ride. So many twists and turns. Read the whole thing before continuing here because spoilers follow. Read the whole thing even though I’m about to say how unsatisfying the conclusion is.

Now the original article is written on the topic of the quality of academic citations, as promised in the abstract, but I’m here to talk about spinach.

For me the story left too many questions unanswered. Some easy to resolve (spinach’s iron content is high-middling in its class, and the science has been broadly stable on this for well over a century), but where did spinach’s special status in popular understanding really come from if not the origins we now take to be “debunked”?

After finding the original story’s main reference for declaring closure on the matter I was even more dissatisfied. I tried plugging the names of the scientists mentioned into Google, and I found discussion on the matter by a JL Dagg offering suggestions as to where pieces of the misplaced decimal story might have come from.

I can’t help but imagine all this as a long chain of pedantic one-upmanship.

[Content Warning: gross oversimplification]

Spinach is good for you because it contains a lot of iron.

Well actually, that belief was caused by a decimal place error in the 1930s, causing the iron content to appear ten times greater than it actually was.

Well actually, that’s a popular misquote of what Terence Hamblin wrote. The actual decimal error occurred in the 1890s and was discovered in the 1930s.

Well actually, Hamblin gave no references and it looks like they must have just imagined the whole thing. Also, Popeye ate spinach for its vitamin A content, not iron.

Well actually, Arnold Bender had published the same assertion several times prior to Hamblin, giving specific names and an example of a textbook perpetuating grossly exaggerated iron content.

Well actually, those references don’t join up and the book in question doesn’t contain any decimal place error. Also, nobody in the UK or US would have been influenced by the findings of these German scientists anyway.

Well actually, it was a conflation of dry and fresh samples which merely looked like a decimal place error because fresh spinach is roughly 90% water.

well actually, one of the scientists left a footnote about needing to correct for the fact that the produce they bought from their local grocer was old and wilted.

Well actually, it was the confusion between iron and iron oxide in the measurements.

Well actually, it was the result of faulty scientific methods.

Well actually, faulty recollections may well have synthesised this narrative from a series of actual events, including a decimal place error exaggerating iron content in 1939. Also, the same flawed methodology was applied to several vegetables and consequently spinach was seen to be unexceptional in that context.

But of course none of this really matters, because iron in spinach is in the wrong form for effective absorption, and because spinach contains oxalates.

Well actually…

Dagg’s tone and approach appeals to me. Rather than asking “is this true?”, which is a question I see as ultimately unhelpful and misleading given the fractal nature of nuance and context, they ask “why do they believe this?”.

Is Dagg’s hypothesis right? There’s no knowing that, but maybe I’ll just assume or pretend it’s right because I can’t do any better. All knowledge is provisional, after all (with apologies to Karl Popper).

But this still doesn’t answer my original question.

What was the question again?

Why do people believe that spinach is a good source of iron?

Dagg suggests a conflation of symptoms and remedies relating to tuberculosis and anaemia.

But a much deeper dive into the matter is ‘Spinach in Blunderland’, wherein we learn … a lot! Everything that went before is, comparatively, a very narrow and distorted view on a much broader picture.

I can’t possibly summarise it all, but one thing that stands out to me in this narrative is the reappearance of Gustav von Bunge. In this context Bunge’s research appears to debunk earlier, unreasonably high figures but, importantly, the matter goes viral with the effect of drawing public attention to the still-relatively-high iron content in Bunge’s results. The values aren’t exceptionally high by modern estimates, but high enough to cause a wave of misplaced enthusiasm around the world.

It seems that the resulting public over-enthusiasm had been called out a few times subsequently, but virality had not been attained until Hamblin got the matter into BMJ in 1981 and people started digging in to the origin of the resulting citations.

Unfortunately the subsequent focus has been on falsifying a specific error at a specific point in a specific line of communication in order to produce a debunked myth, without due regard to the greater network of errors and miscommunications which produced the outcome; and in order to achieve that great debunk a lot of truths were overlooked.

Despite all that there’s still a final possibility: that the popular belief about spinach having high iron content exists simply because it’s basically true. It isn’t the best, but among commonly recognised and available plant sources it seems to still rate fairly highly (with caveats and exceptions). Maybe people don’t mean anything more than that when they repeat “the myth” that spinach is “high in iron”.