Explaining Leaky Gas

You’ll come across this term a fair bit on IBS forums. Put simply, Leaky Gas (LG) refers to gas that leaks out. For some people, the gas leaks out without their knowledge. They only know about this by comments people make. For the rest of us, we’re quite aware of the build-up of gas and its eventual leaking out. Holding it in is too painful.

There is nothing mystical about the gas. Leaky Gas doesn’t seem to be considered a form of IBS by the researchers, which goes to show you really need to have IBS to fully understand it.

Leaky Gas is a symptom of constipation. For most of us with LG, the problem isn’t necessarily “traditional” constipation where you’re blocked up for days. It’s more of an incomplete evacuation type of constipation. For me, this just grew progressively worse as I got older.

People with Leaky Gas might have a genetic predisposition to not being able to digest certain foods efficiently. These foods typically include grains (wheat, rice etc), all nuts and legumes (baked beans etc). These foods are all considered acellular and are typically difficult to digest for a lot of people. What these foods have in common is a concentrated, dry form of energy – carbohydrate or protein – that can resist breaking down by natural digestive enzymes or stomach acid.

The following is an excellent explanation of why acellular foods like flour from grains, nuts etc are difficult to digest. It isn’t written from an IBS viewpoint, but the important points relate to the differences between acellular, dry foods and cellular vegetables and fruits, the bulk of which is made up of water, and which are much easily digested.


Grains, nuts and legumes also contain anti-nutrients that resist digestion, such as lectins, phytates and opioid peptides. Some people are more sensitive to these chemicals than others.

So Leaky Gas is a form of constipation, from not being able to digest certain foods properly. Carbohydrate is mostly digested in the small intestine and protein in the stomach, but if you lack enough stomach acid or Amylase enzymes you won’t be able to digest either protein or carbohydrate very well.

Any food that escapes digestion tends to putrify in the colon. Because it is still undigested to a certain degree, it feeds bacteria and so is fermentable. This is where the gas comes from. It makes sense too, that if bacteria are constantly feeding on undigested food in the small intestine or colon, then those populations of bacteria will grow, either as Small Intestinal Bacterial Overgrowth (SIBO) or as general bacterial dysbiosis in the colon (large intestine).

Another complication is that gas itself can cause constipation. Dr Mark Pimentel pioneered a famous study which proved the link between methane gas and slow transit constipation.



The foods which are easy to digest tend to be low FODMAP vegetables. These don’t have the complex sugars of FODMAPs that can also be difficult to break down in the small intestine. Soluble vegetables, apart from being mostly made up of water, also act to swell and bulk up in the colon, helping peristalsis – the contractions that move faeces along in the colon.

Anything that causes excess gas in the colon can cause Leaky Gas, because LG is just gas.

The reason why non-IBS people can eat FODMAPs, nuts, wheat etc and not get IBS symptoms is due to their ability to process the food more efficiently than we do. FODMAPs are mildly fermentable, even for normal people, but don’t produce the volume of gas that it does for us.

If we continue to eat foods that we can’t digest, we can get Leaky Gas in 2 forms. One is from the stool itself, the other is from foods being digested.

The cure for Leaky Gas is fairly simple. Remove completely all antinutrient foods that damage the colon and restrict all highly fermentable foods, which will in turn reduce the gas.

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