The smell of your stool results from the fermentation of bacteria contained in the fecal matter composed of 75 to 85% water and about 20% dry matter . But what about its color? That's a good question.
Once expelled from your digestive system, your stool normally displays a brown hue, regardless of what you ate and drank beforehand. Why ? In fact, they contain a chemical made by your body. This chemical is stercobilin . It is a product of the breakdown of hemoglobin, an iron-containing protein in red blood cells that allows oxygen to be transported throughout the body.
When hemoglobin breaks down, a yellow protein called bilirubin is produced. Bilirubin eventually reaches the liver through the circulatory system, before being modified, and then secreted into the small intestine as bile. Part of the bile, a yellow-green liquid, then helps your body digest and absorb fat, while the rest becomes stercobilin, which your body needs to get rid of.
This stercobilin, which is therefore a pigment of bile origin , eventually combines with water from the broken down food scraps, causing your stools to turn brown. Without the sercobilin, they would probably look pale s. This is because most of the chemicals that give foods their colors are completely broken down during the digestive process.
Although unsavory, stool is often used in medicine to detect a number of diseases depending on their shapes, colors or textures (take a look at this infographic).
Also, for several years, researchers have been developing ways to quickly analyze this excrement as soon as it arrives in the toilet. Recently, a team from Duke University notably presented their approach during Digestive Disease Week® (DDW), a tool aimed at taking images of stool samples in pipe systems for analysis. This is only a prototype at this time, but this data could eventually be used to track chronic gastrointestinal health issues.
A team at Stanford University is also preparing a similar approach. In parallel, these toilets could also deploy urine dipsticks to measure certain molecular characteristics. This could potentially reveal warning signs of several diseases, from urinary tract infections to bladder cancer.
