Three generations of children have been told to eat their spinach so they get enough iron and grow up to be a strong as Popeye. Leaving aside the fact that muscle strength has got more to do with training and eating well, more than a focus on a single nutrient, we face those funny things called facts.
Spinach and iron
Spinach does contain iron. Half a cup of cooked spinach provides around 4 mg of iron. That’s pretty impressive considering the average bloke needs 8 mg a day and young ladies need 18 mg a day. Most other vegetables barely give you 1 mg of iron per half cup served. So, spinach has quite a bit of iron. And that’s about as far as some people look.
Although spinach is high in iron it is a lousy source of iron. How’s that? Well, it all revolves around the word “bio-availability”, that is, the ability of the body to absorb a nutrient from the intestines and use it within the body. Most of the iron in spinach is bound to oxalate (in the form of ferrous oxalate) and you do not have a digestive enzyme to split that binding to release the iron. That means that most, estimated at 95%, of the iron goes in one end and out the other about a day later. Spinach is iron’s way of taking a 10 metre (11 yd) voyage through your guts.
The decimal point fallacy
Now, Popeye is unlikely to have known that because he was created around 1929, featuring in his own cartoon in December 1930. A British Medical Journal paper from 1981 claimed that the fallacy of spinach being high in iron came about because the decimal point was placed in the wrong spot in the original analysis back in the 19th century, giving spinach an iron content ten times more than it was in reality.
Earlier this year, Dr Mike Sutton from Nottingham Trent University in the UK, refutes the whole argument stating that there is no evidence that a decimal point was ever placed in the wrong spot. He has even written to author of the BMJ article and says the response from the author provided no proof for the claim.
The really, really interesting bit
Well, to me at least. OK, so spinach is not a great source of iron and it never appeared to be. When Popeye was created in 1930 we knew about the minerals like iron and calcium and only the vitamins A, B1, C, D and E. Vitamins like folate, B12 and niacin were yet to be isolated.
Did Popeye himself say he ate spinach for iron? No. Not once, according to Mike Sutton. He did, on 3rd July 1932, mention that he ate spinach for one particular nutrient. Vitamin A (see cartoon). You and I know that there isn’t pure vitamin A in spinach; it’s in the pre-vitamin A form of beta-carotene. All the same, Popeye ate spinach for a vitamin, not a mineral.
What does it all mean?
It is wonderful when someone goes that extra distance to get information. So, hat’s off to Mike Sutton. I didn’t take Mike’s word for it. I went and bought the first two years of Popeye cartoons (because I yam what I yam), and I agree with Mike: Popeye only mentions vitamin A. Popeye is right, spinach is a great source of beta-carotene (and folate). Eat your spinach for the vitamins, not for the minerals.
If you would like to read the complete report by Mike Sutton then just got to: http://www5.in.tum.de/~huckle/Sutton_Spinach_Iron_and_Popeye_March_2010.pdf. Warning: it is a 35 page in-depth study as you might expect from a criminologist, which is just what Mike is.
Reference: British Medical Journal 1981; 283: 1671-1674