The Scoop on Poop

The questions are:

1. What is the cause of the awful smell of flatus?
2. What causes the smell of stool?
3. Are they the same?
4. Can anything be done about these smells?

The answers are:

1. The foul smell of flatus is almost exclusively due to sulfide gases manufactured within the colon. The bacteria that make these gases, most of which is hydrogen sulfide, are a certain group of bacteria that live in the left side of the colon where there is no acidity. They take hydrogen made by other bacteria in the colon and combine it with sulfate derived from the foods we eat. You end up with hydrogen sulfide that is a gas the jumps out from the bacteria into the otherwise odorless gases in the colon. It is then passed as flatus and the more of these sulfide gases there are, the more awful will be the smell of flatus.
2. The sulfide gases do not cause much smell in stool. This is caused mostly by 2 chemicals called indoles and skatoles. These 2 smelly molecules come from the metabolism within the colon of the amino acid tryptophan. That’s right. Tryptophan is a simple amino acid that is always present in animal protein. It is especially high in meats. The small bowel absorbs most of this amino acid. In the blood it has a sedating effect and is the reason one feels sleepy after a large meal. However, some of the amino acid will escape and end up in the colon where it is acted upon by other bacteria and becomes either an indole or a skatole. The stool will then have a very bad smell.
3. So the sulfide gases and the indoles and skatoles are entirely different.
4. First the sulfide gases. These bacteria in the left side of the colon need a neutral place to grow. No acidity and not too much alkali. When there is acidity within the left colon these bacteria do not grow well and do not produce much sulfide gas. The trick is to increase acidity in the left colon. Prebiotics are special types of plant fiber that are present in many types of vegetables as well as bananas. You can click here to get a lot more information on prebiotics. When these prebiotic type foods are eaten in greater quantities, they reach over to the left colon. They stimulate the best types of bacteria to make lots of acid like substances. These are called short chain fatty acids and they provide many health benefits. A side effect is that they acidify the contents of the colon and these sulfide producing bacteria do not grow and so no sulfide gas is produced. The flatus has no smell. Our dietary supplement product Prebiotin has been shown to do just this. If you take enough Prebiotin, the smell of flatus usually goes away.Now to the smell of stool. If you are a big meat eater, then you will undoubtedly have enough tryptophan reach the colon that the nasty indole and skatole substances will be produced. So, it is pretty simple. Cutting back on animal protein is the best and really the only thing you can do. You do not need to become a vegan. Just cutting back will likely do the trick.

   So, prebiotics and Prebiotin along with a modest reduction in animal protein are the tricks to an odor free GI track.

- By Frank W Jackson MD