A fist-sized organ behind the left ribs that filters old red blood cells, recycles their iron and hosts immune cells.
Iron recycling
Most of the iron you use each day is recycled from old red blood cells, not from food.
Evidence & sources
Most of the iron needed daily to make new red blood cells comes from recycling old red blood cells. Evidence: established. Known: Iron is tightly conserved by the body. Unknown: — Source: NIH Office of Dietary Supplements, Iron — Health Professional Fact Sheet (Current revision).