In the developed world, most anemia is the result of a nutritional deficiency—an inadequate amount of easily absorbed iron in the diet—and it is corrected relatively easily, if slowly, by adding iron to the diet. The best sources of easily absorbed dietary iron are meat and leafy green vegetables—though not spinach (forgive me, Popeye). This vegetable contains plenty of iron, but in a form that's hard to absorb.

In my practice, the vegetarian patients oddly tend to have remarkably high levels of iron in their blood. This isn't because their food is especially rich in iron but because their families often avoid aluminum and stainless cookware in favor of cast iron. It doesn't take much acidic spaghetti sauce to leach a healthy amount of iron out of the skillet.

"Greensickness"—the severe anemia of adolescent girls in frontier America—resulted from chronic iron loss through menstruation, with inadequate dietary replenishment. It was sometimes treated by placing metallic iron in a glass of wine for a period of time, then offering the liquid to the patient.