I know, in order to make the nutrition available from spinach, you have to pair it off with a vegetable that has vitamin C, like a tomato.
The problem isn’t solved by adding a tomato. The amino acids found in spinach means our body won’t use more than 55-60% of the protein in it. I’m not sure what the problem is with iron, but it is common for plants to have stuff that looks good on paper but simply isn’t very useful for our body.