What Causes Bloating and Gas?




The number one digestive complaint I hear about from people I work with is bloating. For most people who suffer from bloating, gas comes along with it, and this makes sense because most bloating is caused by gas production so the two come as a package deal.


The million dollar question is always WHY am I so bloated and gassy, and what causes it?


If you are struggling with bloating and gas, keep reading, because this post is going to cover what actually causes that bloating and gas, and understanding the root cause of it is the key to overcoming it.


What is bloating?


Bloating is the sensation of feeling full, and can range from normal bloating you may feel after eating a large meal, to abnormal bloating that comes frequently, with distention and can be painful or just very uncomfortable.

The definition of bloated is “swollen with fluid or gas”. Which makes sense as bloating is usually caused by gas production, which is then expelled through burps or farts.


What’s normal and what’s not?


Some bloating is considered normal, and usually comes after eating a large meal, often heavy in carbohydrates. We’ve all experienced that feeling of overeating and then having to lay down afterwards. This type of bloating is more associated with large amounts of food in the intestine, which results in more gas production, as there is more food to be fermented. This type of bloating is considered normal. Similarly with gas production, we all fart and burp from time to time.

Abnormal bloating happens frequently, and often feels like it doesn’t matter what you eat, the bloating comes. I’ve even had clients tell me that they get bloated after drinking a glass of water. Some people wake up bloated, for others it builds throughout the day. Abnormal bloating often comes with distention and is described as looking six months pregnant (or nine, depending on how bad it gets). For others, the bloating may not be that noticeable, but the gas is. Abnormal gas production is usually very frequent, often smelly, and sometimes painful to pass.


What causes it?


There are many reasons and contributing factors for constantly feeling bloated and gassy. Some can be more serious and need to be ruled out by a doctor, such as Celiac Disease, ovarian cancer, liver disease, IBD, diverticulitis and bowel obstructions.

However, the majority of people have less sinister reasons for bloating and gas, which will be covered in this blog.

Food triggers for bloating


Certain foods can trigger bloating, usually because of over fermentation, or because your body is having difficulty breaking them down.


Fermentable foods: Foods that we cannot fully break down ourselves, and instead broken down/fermented by our gut bacteria can lead to bloating, because gas production is a byproduct of this. This is a normal process, but it can cause abnormal bloating and gas if you have a bacterial overgrowth, have slow motility (constipation), or bacterial imbalances. The most common food triggers for bloating and gas are high FODMAP foods and some carbohydrates and sugars.


Raw vegetables can be harder to digest for those with gut dysfunction as they contain a high amount of insoluble fiber and are just more difficult to break down. This can lead to bloating, gas, cramping, and changes to your bowel movements. If you’re having difficulty with raw vegetables, you may not be producing enough digestive enzymes, or have imbalances in your gut bacteria that need to be addressed.


Red meat can be difficult to digest in some cases. Usually if it is in large chunks, contains a lot of fat, or is not chewed properly. It sits in the stomach longer, slowing down the transit of other foods. This leads to gas building up, resulting in wind and bloating. Again, this is usually linked to your body’s digestive fire, or you have overgrowth of bacteria in your gut impacting things like stomach acidity.


Meal time practices:


Overeating is something most people have experienced bloating from, and it’s usually pretty obvious when this is the cause, but always worth keeping in mind when trying to work out the cause of your bloating.


Not chewing properly is often overlooked when it comes to bloating. Chewing food is an important step in digestion, helping to break down foods and mix with saliva, which contains enzymes that help to break down carbohydrates.


Eating too fast is another common cause for bloating and gas, and like not chewing properly, it’s often overlooked. If you’re a fast eater, you probably don’t chew your food properly either. Eating fast can also mean taking in more air, which can increase bloating. The medical term for this is aerophagia. If you experience regular bloating and gas after meal times, it’s worth assessing how you eat and try to slow down and chew your food thoroughly to help support your digestion.


Eating while stressed/anxious/distracted - this can impact your digestion via the nervous system. If your body is under stress while eating, your nervous system is more likely to be in a state of ‘fight or flight’, which doesn’t prioritise digestion. This can result in lack of digestive enzymes and stomach acid output, leading to poor digestion of food. That food will then sit in your gut and ferment, causing gas production and bloating.

It’s important to note that distraction can also be perceived as stress. Eating while multitasking can have the same impact on digestion where it’s not prioritised. Although it’s difficult in the modern world today to focus solely on eating during meal time, with busy family and work lives, do your best to make adjustments to prioritise distraction-free meal time like putting your phone or laptop down, and turning off the TV.



Functional reasons for bloating:


Your digestive system is complex, and a lot of processes are carried out for it to work smoothly. Any disruption to these processes can lead to discomfort. Low levels of digestive enzymes, stomach acid or bile, or low levels of beneficial bacteria and high levels of problematic bacteria in your gut are some of the common causes of disruption to digestion. Let's break these down into some more detail:

Insufficient enzymes, stomach acid and bile - the main digestive enzymes include Amylase, Protease and Lipase, and there can be a number of reasons why these may be low. Digestive enzymes are mostly produced in the pancreas and small intestine. As we age, levels naturally drop. However, conditions like Exocrine Pancreatic Insufficiency (EPI) can reduce enzyme production, and therefore impair the breakdown of your food, leading to gas production from undigested foods. Other conditions such as SIBO and intestinal permeability (“leaky gut”) can also lead to damage and inflammation of the gut lining, impacting brush border enzyme production.

Your stomach acid - hydrochloric acid (HCl) plays an important role in digestion and needs to be at the correct pH level to properly digest food. If your levels are too high or low, your digestion can be impacted. Low levels of stomach acid can result in undigested food particles in your stools, burping and bloating, as well as overgrowths of opportunistic bacteria and yeast species. Some of the reasons your stomach acids may be too low include your age, chronic stress/anxiety, overuse of antacids and PPI’s, or harmful bacteria like H. Pylori, which shuts down production of HCL in the stomach. I wrote a full blog post on this topic here.

Bile is another important part of digestion and has a similar impact as HCl and enzymes. It is needed to break down fat in particular, and if the gallbladder becomes blocked, this can result in painful bloating, among other gut symptoms.

Chronic stress can contribute to all of the above, by triggering the ‘fight or flight’ nervous system, which reduces the output of digestive juices as your body focuses on dealing with the stressor/s.

Imbalanced gut microbiome - our gut microbiome is made up of various species of bacteria, fungi and viruses, many of which play important roles in immune function, protection against pathogens, maintenance of structural integrity of the gut mucosal barrier and metabolism. They are also fundamental for our digestion, helping to break down food and absorb nutrients.

Many things throughout life impact the gut microbiome and change it over time. These include medications (antibiotics, the oral contraceptive pill, SSRIs, PPIs), smoking, chronic stress, eating a highly processed western diet, lack of plant foods in diet and even the way you were born (c-section vs vaginal birth).

When beneficial populations in the microbiome are diminished, this can allow for opportunistic species to overgrow and lead to problems by impacting digestion, causing inflammation, and impairing nutrient absorption, which can all lead to symptoms like gas and bloating.

SIBO - Bacterial overgrowth in the small intestine - small intestinal bacterial overgrowth (SIBO) is a common cause for chronic bloating. Most of our gut bacteria lives in the large intestine, and only a small population resides in the small intestine in comparison. SIBO is a condition where the population in the small intestine has overgrown, or some of the bacteria from the large intestine has migrated up to the small intestine. This bacteria feeds on certain foods that we eat and produce gas as a byproduct. This normally happens in the large intestine, which is better designed to accommodate gas production, vs the small intestine which is narrower and has lots of turns. You can read more about SIBO here.

There can be a few causes for SIBO including: lack of stomach acid, motility abnormalities, antibiotics, PPI’s and opioid medications, impaired immune function and abdominal adhesions from endometriosis or surgery. The most common symptoms of SIBO include burping or reflux, and bloating within an hour after meals, as well as chronic diarrhea or chronic constipation or an alternating of both, a lot of gas (which usually smells bad), and stomach gurgling and discomfort or cramping.

Altered motility - The Migrating Motor Complex (MMC), plays an important role in intestinal motility, which is the process by which food travels through the digestive tract via a series of muscular contractions. These contractions occur roughly every 90-120 minutes, in between meals, and stop when we’re eating. It is a wave like motion that sweeps away the bacteria, waste and undigested food particles for excretion.

When the MMC is impaired, it can result in a build-up of bacteria and food (specifically high-FODMAP foods) for the existing bacteria to feed on in the small intestine. Resulting effects are the development of SIBO and its associated symptoms, among which is bloating and gas. Slow transit of high-FODMAP food particles can cause them to over-ferment, leading to gas production, and more wind and bloating. You can also stop your MMC yourself inadvertently by constantly snacking and grazing throughout the day. If you don’t allow a break from food for at least 90 minutes, then your MMC won’t be regularly doing it’s job,

What to do next?

As you can see, the underlying causes of bloating and gas range from simple to complex, so there is no one-size-fits-all plan to fix this issue.

I can, however, point you in the right direction.

Always begin by ruling out the more simple causes. Assess your meal time practices and ask yourself if you’re regularly overeating, eating too fast, not chewing your food, or eating distracted. If you know that you’re guilty of doing these things, put in a conscious effort to start improving where you can to help support your digestion.

If meal time practices are not an issue for you, or if you make changes and things don’t improve, the next step is to begin testing for root causes. There are plenty of diet strategies which can help reduce your symptoms, like the low FODMAP diet, but this shouldn’t be your long-term strategy, as fermentable fibers (FODMAPs) are important food for your beneficial bacteria.

The two tests that are helpful in identifying root causes for those with chronic bloating and gas are a SIBO breath test and a Comprehensive Stool Analysis. These tests will help to gain more understanding around specific imbalances in the gut, and allow an accurate treatment plan to be put in place, rather than just guessing, or only focusing on food triggers to manage symptoms.

If you’re sick of being bloated and gassy, and don’t know what steps to take next, let me take the guesswork out for you. Start by scheduling a free 20 minute introductory consultation here.


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