SPINACH

Spinach is the source of Popeye's muscular prowess- upon eating it, his biceps immediately swell to three times their normal size. E.C. Segar (1894-1938) chose this vegetable, instead of Brussels sprouts or broccoli, due to an 1870 German study which claimed it contained the same amount of iron as red meat (the perception that the original comic strips promoted the consumption of spinach for its iron content is an incorrect one, even though it did encourage more people to pick up spinach). This is why you can see him stepping on a broccoli flower. In reality, this was nothing more than an accounting error; the scientists put the decimal point in the wrong place. The mistake was corrected in 1937; it was too late for Popeye, though. He'd already been getting strong on spinach for almost 10 years.

Error or not, spinach does indeed contain more iron than red meat but only a fraction of the iron contained in spinach is available as a dietary source. In meat, iron is commonly found in the form of heam iron, which is easily absorbed in the body. In vegetables, the iron content in non-heam iron, which isn't absorbed as easily by our bodies and other factors can impact on its absorption. Part of the reason so little of the iron in spinach is absorbed when we eat it is the other compounds present. For a time, it was thought that the high oxalic acid content of spinach played a part. Most recent studies show that this is not the case. Instead, it's thought that the polyphenolic compounds found in spinach are responsible; they reduce the amount of iron available for absorption by binding to it and forming insoluble compounds.

There are still good reasons to eat spinach, even if it's not for the iron content. It's particularly high in vitamin A precursor compounds called carotenoids. Vitamin A is important for our eyesight and immune system, amongst other things. Beta-carotene is an example of carotenoid, well known as the chemical that gives carrots their orange colour. It doesn't give spinach the same colouration as the green of chlorophyll masks it; I still drew the beta-carotene in orange on the green spinach though.

Oxalic acid might not have much to do with the absorption of spinach iron content, but it does play in one of the consequences of eating spinach. You might have experienced the so-called 'spinach teeth' effect. This is a kind of 'chalky' feeling on the surface of your teeth after eating spinach. The effect is due to the oxalic acid in spinach forming calcium oxalate by reacting with calcium ions in saliva. The calcium oxalate is insoluble and coats your teeth to give the 'chalky' effect. To show all of this, I drew oxalic acid in front of the spinach about to go in Popeye's mouth. There's a calcium ion in his mouth to show where it can be found and the calcium oxalate is the compound a little on the side; it was hard to draw it all in his mouth, so I just made sure it was touching his teeth through one of his oxygens.

Reference for the website used for research: https://www.compoundchem.com/2018/07/17/spinach/