First off, some exciting news: I got published! Yep, my brownies got published (complete with a photograph) in the CCNM monthly newsletter, The Vine.
Red blood cells live for about 120 days. When they are broken down, their hemoglobin components are recycled. For instance, their amino acids are used to make new proteins, their iron (from the heme groups in red blood cells) are reused to make new heme groups, and their heme groups are converted to bilirubin. Bilrubin is then excreted. Bilirubin (i.e. a component left over from the recycling of red blood cells) is what gives our feces a dark color and our urine a yellowish color. If our urine turns are brownish color, then we know too much bilirubin is being excreted. Also, if our skins turns yellowish (jaundice), it is the result of elevated levels of bilirubin meaning the bilirubin excretion pathway is not functioning properly.