Iron, Anemia, and Spinach

Spinach contains large amounts of oxalic acid. This binds to iron and calcium to form oxalates.  Iron is abundant in spinach because of the great affinity of iron and oxalic acid for each other, resulting in iron oxalate.  If you burn spinach and analyze the ash you find iron.  Eighty years ago a laboratory analysis of spinach revealed a surprisingly high iron content.  Eager spinach farmers hired a promoter to sell their product.  So POPEYE was born.  He ate spinach (iron) and became a strong man.  Only, here's the rest of the story.  Oxalates do not dissolve in water.  They make stones in urine. THEY ARE POORLY ABSORBED FROM FOOD.  Furthermore since the oxalic acid is not saturated, it can grab the iron from other foods eaten at the same time.  Although spinach is otherwise an excellent food, the iron and calcium in it are poor sources of these nutrients. Eating more spinach is not a remedy for iron deficiency.  The iron is passed out, not absorbed.  Calcium in spinach is 8% absorbed, compared, for example to 50% absorption from broccoli.