What is poop made of? About 3/4 of your average turd is made of water. Of course, this value is highly variable - the water content of diarrhea is much higher, and the amount of water in poop that has been retained (voluntarily or otherwise) is lower. Water is absorbed out of fecal material as it passes through the intestine, so the longer a turd resides inside before emerging, the drier it will be. Of the remaining portion of the turd, about 1/3 is composed of dead bacteria. These microcorpses come from the intestinal garden of microorganisms that assist us in the digestion of our food. Another 1/3 of the turd mass is made of stuff that we find indigestible, like cellulose, for instance. This indigestible material is called "fiber," and is useful in getting the turd to move along through the intestine, perhaps because it provides traction. The remaining portion of the turd is a mixture of fats such as cholesterol, inorganic salts like phosphates, live bacteria, dead cells and mucus from the lining of the intestine, and protein. Why is poop brown? The color comes mainly from bilirubin, a pigment that arises from the breakdown of red blood cells in the liver and bone marrow. The actual metabolic pathway of bilirubin and its byproducts in the body is very complicated, so we will simply say that a lot of it ends up in the intestine, where it is further modified by bacterial action. But the color itself comes from iron. Iron in hemoglobin in red blood cells gives blood its red color, and iron in the waste product bilirubin gives rise to its brown color. To SmellyPoop.com Hi, A friend of mine just sent me the link to your website for fun. I really enjoyed the ‘Survival Guide for Taking a Dump at Work’. However, I believe that there is an error among your explanation for the color of feces. The brown color is a result of broken down red blood cells, but I don’t think that it’s a result of iron. Most of the iron that is released from the breakdown of heme is reabsorbed by cells in the bone marrow for incorporation into new red blood cells. That’s why we don’t have a large daily requirement for iron in our diets. Anyhow, what remains of the hemoglobin is then called biliverdin, which is converted into bilirubin and is excreted. This compound can build up in some people and cause jaundice. The colors of these molecules are due to their complex structures, which contain rings of carbon and nitrogen atoms. Intestinal bacteria further modify bilirubin to produce urobilinogen and stercobilinogen. If I remember correctly, the red color of blood is also due to the porphyrin ring of heme and not iron. So, you’re absolutely correct to say that it’s a complicated explanation and it has to do with the breakdown of red blood cells, but I don’t think that iron has anything to do with the brown color of poop or the red color of blood. -Dustin What other colors of poop are possible? Poop is mostly shades of brown or yellow, but other colors can arise under certain circumstances. For example, someone with a bleeding ulcer might have tarry black poop from the presence of partially digested blood. Bleeding in the intestine, from an anal fissure or split, for example, can stain the poop red. Some illnesses in babies gives them green or even blue-green poop. But another source of blue poop in children is more innocent: it can come from eating a concentrated source of blue food coloring such as ice cream. Intense red food coloring can produce bright red poop. Sometimes brightly colored foods pass through the gut almost unchanged, and the turd may be speckled with bright red fragments such as pimentos, or bright yellow kernels of corn. One can experience white poop after consuming a barium milkshake for the purposes of getting an x-ray of the upper gastrointestinal tract. What is the cause of yellow poop? According to Michael F., one cause of this is Gilbert's Syndrome. "I have a benign condition known as Gilbert's Syndrome. It affects quite a few people, males mostly, in their teens+. It is a deficiency in the liver where red blood cells are broken down. I was informed when this was diagnosed that the broken down blood cells is what gives poop a lot of its color. People with Gilbert's Syndrome don't process as many blood cells - or not as fast - and their poop tends to be pale brown or yellow from the lower quantity of discarded red blood cell matter. This is especially true if there is less matter in your intestines (i.e., on a diet - as I have noticed) to remove the excess blood cells. Very frightening until you determine what is causing it. Gilbert's is a totally benign thing that doesn't harm anyone, although when a person is sick they can turn yellowish as if jaundiced, but it is not jaundice." Another cause of yellow poop is a giardia infection. Giardia are tiny Protozoan parasites that can invade the intestines and result in severe yellow diarrhea. It is a dangerous and contagious affliction that doctors are obligated to report to the Center for Disease Control. What is the cause of green poop? (Question submitted by ap, CrAzYMiC98 and several others) I have consulted with a doctor, a physiologist and a microbiologist on this question, and the following summarizes their answers: Healthy people can have green poop if they eat a diet rich in leafy green vegetables, or if they consume large quantities of food coloring (in ice cream, cake frosting etc.). Green poop can also be caused by excess iron in the diet, from dietary supplements, for example. If the body does not absorb all the iron consumed, the iron may stain the poop green, the color of iron (II) salts. Ordinarily, the green color may be masked by the normal brown poop color, but if digestion is thrown off by illness so that bilirubin is less concentrated in the intestine, the green color may become apparent. This can happen when a person is afflicted with diarrhea. Green poop in sick babies may come from iron in baby formula not being properly absorbed, or by green pigments in bile salts (again, green from iron).