The air we breathe
The gases that are produced in our digestive tract, especially in the colon, are eliminated by 80% of us through feces and farts. The remaining 20% passes into the blood and then into the lungs, where it is eliminated with the exhaled air. In this sense, gas analysis tests are based on the study of carbohydrate malabsorption.
At certain times and secondary to gastritis, there may be a pylorus spasm by ingested proteins, which are partially catabolized in the stomach in this process hydrogen sulfide is formed. This is eliminated by eruptions that tend to have an odor reminiscent of rotten eggs.
On the other hand, also after administration of C13 urea and dosage of C13O2 in exhaled air, helicobacter pylori infection can be diagnosed. By administering C13 acetate, this can be determined by collecting exhaled air in special bags and dosing the C13, gastric emptying. These tests, with the exception of hydrogen sulfide dosing, are performed in our Via Augusta unit.
With the exception of hydrogen sulfide, which is the proof that there is gastritis with long delay of gastric emptying, the other gases such as hydrogen, methane, CO2, do not have any bad odor. Therefore, a person could digest carbohydrates poorly and not notice any bad odor in the exhaled air.
Gases expelled through the anus
The gases we expel through the anus are the product of the fermentation in the colon of substances from our diet, especially carbohydrates that have not been digested in the small intestine. In this sense, the products that most frequently produce gases are stachyose and raffinose from legumes, as well as cellulose, hemicellulose, pesctins, lignins (phenylpropane) from vegetable walls, in addition to gases produced by the poor digestion in the small intestine of lactose, sucrose, starch, etc. Some of these gases are completely odorless.
Other gases formed in the colon, due to poor digestion of proteins, mostly putrescine, cadaverine, indole and skatole, may have a more or less pleasant odor, but are not always indicators of poor health, but rather the presence of proteins in the colon by affection of the small intestine or hyperperistalsis.
Sometimes it may happen that methane in exhaled air is very high (above 15 ppm or much more), as well as hydrogen (well above 20 ppm), with good digestion of disaccharides or with absence of these in the diet. This indicates that the individual is ingesting an excess of fibers, so he/she should go to a doctor who has a gas chromatograph, in order to focus the diet correctly. In our Via Augusta unit we have such a device.
Recently, I receive many patients with a large abdominal distension, that is, a swollen belly due to an excess of gases, without a pathology that justifies it. It is largely due to an excess of vegetable fibers in their diet because they have followed bad advice from some dieticians who forget that the human being lacks a rumen. It is due to an excess of methane and not so much hydrogen in the exhaled air of their basal conditions. This is known as the ruminant syndrome.
Sorbitol and fructose are monosaccharides so they do not need to be cleaved to monosaccharides because they are already monosaccharides. Malabsorption is sometimes due to excessive ingestion, since we are all intolerant to sorbitol and fructose if we take too much. This does not imply any pathology, simply that we have taken too many passively absorbed monosaccharides.
In the old days, there was a belief that the stool would float if there was an excess of fat elimination. However, it is rarely really due to this. Usually, it is because they carry methane gas, without any associated pathology. Occasionally, our bacteriome produces hydrogen or methane. Also, it is true that if the stool is mustard colored it could be an indicator of celiac disease or another condition causing poor digestion of fats, among other possibilities.