Our bodies make different kinds of gasses. When our cells break down food to release energy, they make carbon dioxide. This is absorbed into the blood and released into the air in our lungs. We can then breathe it out. The carbon dioxide moves from the place where there’s a lot of it to the place where there’s less of it due to a process called diffusion. Diffusion is a passive process that happens because molecules are always moving around randomly.

There’s also the kind of gas produced in our digestive system. That’s mostly hydrogen, methane, and some sulfur. When we eat something that our bodies can’t break down easily, the bacteria that live in our large intestines break down that food and produce methane and other gases. I don’t actually know if methane is small enough to move into the cells that line our gut, then into the blood, but if any does, it’s not much. That’s why the gas has to be released.

The foods that cause flatulence (gas) tend to be things we don’t break down either because they are made of big molecules (example: beans), or they need a specific enzyme that some people don’t produce (example: milk sugar, which is also called lactose). Unfamiliar foods may lead to gas because our bodies don’t produce the enzymes for dealing with them.

The air we swallow every time we eat, drink (especially using straws), or chew gum also ends up in our digestive systems and must be released. Carbonated (fizzy) beverages also contain carbon dioxide bubbles that add CO₂ to our gut. We usually burp this air and CO₂ out.

What else do you think our bodies need to absorb?

Thanks for your interesting question. Here is an answer. It says gas comes from swallowing air and from gases formed by microbes in our intestines.

"some of the swallowed oxygen is absorbed by the blood capillaries in the stomach. ... Nitrogen is not absorbed as a gas and is usually passed on.

Most of the gas I believe is a waste product, so yes, it must be released.

The gas inside our bodies can be either absorbed or released. Gas in the body usually comes from two sources: gas swallowed into the stomach and gas byproducts from digestion.

Gas in the stomach usually comes from swallowing air. Things like chugging drinks or chewing gum can increase the amount of gas we swallow. Gas in the stomach is usually released by burping, but some of it may be digested with the rest of our food. The gas that does get digested can be absorbed on its way through the intestines, but some of it will remain and leave as flatulence.

Gas can also be produced inside the body by bacteria as we digest food. This gas cannot be burped out but instead collects in our large intestine and is expelled by flatulence.

Flatulence is actually a good sign and means that our digestive system is doing its job to break down foods into the vitamins and minerals our body needs to function!

This is an interesting question! Gas is formed in our bodies from food, drink, and ingested air. Gas can be released from the body in a couple of ways: either through the mouth through burping, or out the rectum via flatulence.

With regard to burping: our stomachs will sometimes contain excess gas (from air that has been swallowed or from digesting food which contributes to excess gas -- e.g. carbonated beverages). The excess gas in our stomach builds pressure against the lower esophageal sphincter (located at the base of our diaphragm and at the top of the stomach). Eventually, as the pressure builds up enough, air will be released into the esophagus, and when enough pressure builds up against the upper esophageal sphincter (at the back of the throat), air is released there as well.

The gas formed in our intestines which is eventually destined to be expelled as flatulence is a very low density mixture of various chemical compounds, ranging from nitrogen and carbon dioxide to various molecular compounds that are byproducts of the bacterial fermentation that our food and drink undergo during digestion. There are a couple of things we need to think about when trying to determine if this gas can be absorbed by the body. The first surrounds molecular considerations: how soluble a certain gaseous compound is in solution. When we talk about solubility, we talk about the ability of a solute to dissolve in a solvent (solute + solvent = solution).

Various factors affect solubility, such as temperature, how similar the polarities of solvent and solute molecules are, pH, pressure, and molecular size. How much solute actually exists in a solution can also be affected by equilibrium balances and extent of reaction (you can read more about this by looking up Le Chatlier's principle ). And even then, sometimes, especially in living organisms, chemicals can move up their concentration gradient with the help of enzymes or other auxiliary molecules.

While the compounds comprising intestinal gas could theoretically be absorbed into the body to some extent (they might be somewhat soluble in our bodily fluids), they do end up being expelled. To a large extent, this is driven by the fact that these byproducts are considered waste and not really usable by the body.

However, that is not to say that there is not a large amount of gas that is actually held by the body. For instance, carbon dioxide we breathe in (air we breathe has a mixture of gases!) forms bicarbonate in the body and also can combine with hemoglobin. These processes contribute to the solubilization of carbon dioxide relative to how much could normally be held in a simple solution.