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That’s right, spinach. Since data quality blogging can be dry and technical I thought I would talk about one of my favourite data quality mistakes to spice things up. The myth that spinach is high in iron. It comes from a simple data quality mistake – the recording of a number with the decimal point in the wrong place. It gave spinach the reputation of having 10 times more iron then any other green leafy vegetable. Timeline 1870 – Dr. E von Wolf publishes a work that claims that spinach has ten times more iron then other green leafy vegatables. 1929 – the character Popeye the sailor appears in the daily comic strip Thimble Theatre throwing down spinach and getting big musles to save his goyl. 1933 – Popeye gets his own spinoff cartoon – Popeye the Sailor. Popeye was the “Joey” of his time only the spinoff turned out to be good. 1937 – a group of party pooping German scientists discover that spinach has just 1/10th the level of iron previously claimed. 1938 – Popeye goes into hiding amid claims that he was on steroids all along. So for over sixty years spinach was considered a food that was extraordinarily high in iron with Popeye as the poster boy of the iron muscle advertising. It took a long time for news of the mistake to filter through to people as it had to travel through medical journals and there was a little distraction of World War II. Spinach took another hit in the early 90s when research into nutrition refined what we know about iron absorbtion. To quote the Innvista website:

Although much lauded as a nutritional vegetable, spinach has a drawback in that, while containing high levels of iron and calcium, the rate of absorption is almost nil. The oxalic acid binds calcium into an insoluble salt (calcium oxalate), which cannot be absorbed by the body. The same applies to the iron, as it is bound, leaving only 2-5% of the seemingly plentiful supply actually available for absorption.

The spinach iron myth suffered two big falls. Cut to 1/10th and then further cut to 2-5% of that 1/10th. A pretty big data drop. I did a blog search of the spinach / iron combination and found a lot of entries from people taking spinach for the iron content who had never heard the correction to the myth. It is better to try and get iron from a range of foods rather then spinach along. Spinach has a lot of positive things going for it but iron is not one them. Simple business intelligence derived from data will travel further and be remembered more easily than complex intelligence. The simple rule that spinach is high in iron has stayed with the majority of people. The more complex rules about spinach and oxalic acids and absorbtion is harder to spread and harder to remember. It shows the difficulty of fixing data quality problems, that fixing it in the source is relatively easy, that fixing all the people who have derived incorrect intelligence from the original data is bloody hard. If you know of good data quality stories send me a note at websphereblog@gmail.com. You might also enjoy my overview of the Mizuho Securities 40 billion Yen data entry error blog. 47572-060627-392861-18 Rate content:



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