Why am I bloated? Here are some possibilities to consider

Written by Saman Khalesi, Postdoctoral Fellow of the National Heart Foundation & Senior Lecturer and Discipline Lead in Nutrition, School of Health, Medical and Applied Sciences, CQUniversity Australia

If your tummy seems to feel full or stretched and is rumbling all the time, you’re not alone. Up to 30% of people of all ages experience bloating, with symptoms such as gassiness, a sense of fullness and pressure.

This can be with or without distention (a visible increase in abdominal girth).

So what might be behind your bloating?

The role of gas

Bloating is in fact a complex condition that can be caused by several direct and indirect factors. Gas often plays a role.

Gas production in the digestive system is part of the normal digestion process, and is released through the mouth (burps) or anus (farts).

On average, our gas expulsion is around 600–700 millilitres per day, resulting in around 14 farts a day. That said, there isn’t a set number for the normal amount of gas or expulsions; each body is different.

Bloating can occur as a result of retained gas, excess gas production, altered gas transit (changes in the speed and movement of gas), or intestinal hypersensitivity.

An imbalanced gut microbiome can lead to the overproduction of gas.

What is the human microbiome?

We have more than 40 trillion microbes living in and on our body. They can be helpful or harmful. The balance between these helpful and harmful microbes plays an important role in our immune response, metabolism and health.

These bacteria need food to survive. Their food comes from fermenting carbohydrates such as dietary fibre from the plants we eat.

One of the byproducts of this fermentation process is hydrogen gas.

Most of these microbes live in the lower parts of our intestine (colon). The upper parts of the intestine (small intestine) have far fewer microbes.

But if an excessive number of microbes colonise the small intestine (a condition known as small intestine bacterial overgrowth), more gas is produced in the small intestine.

This can lead to bloating, abdominal discomfort, diarrhoea and nausea.

Could it be IBS, lactose issues or FODMAPs?

Some disorders of the intestine and colon can affect the amount of gas and severity of bloating symptoms.

For example, in constipation, movement of stools is reduced, allowing more time for the bacteria to ferment the stool content, increasing gas production.

Bloating is also very common in people with irritable bowel syndrom (IBS).

Changes in gut muscle tone and greater sensitivity to gas contribute to bloating in IBS sufferers.

Bloating may also occur because of poor digestion and malabsorption of some carbohydrates.

Lactose malabsorption (in those with lactose intolerance) is a common issue.

Lactose malabsorption (in those with lactose intolerance) can cause gut problems for some people. Image by Bogdan Sanfira from Pixabay, CC BY

Symptoms may also occur with other digestive resistant short-chain carbohydrates known as FODMAPs (fermentable oligo-, di-, monosaccharides and polyols).

FODMAPs are found in a wide variety of foods, including certain fruit and vegetables, grains and cereals, nuts, legumes, lentils and dairy foods.

While these are good foods for our gut bacteria, they can add to gas production and trigger bloating symptoms, especially in people with digestive disorders (like IBS). They can also cause water to be drawn into the intestines, causing distension. This can contribute to bloating.

Other factors: salt, hormones or swallowing air

There are of course other factors that could be behind bloating.

For example, consuming too much sodium or salt in your diet causes water retention, resulting in abdominal distention. But this may also alter the gut microbiome and influence gas production.

For many women, bloating can be linked to the menstrual cycle phase. This is most common at the onset of bleeding, when peak fluid retention occurs, but is also related to underlying hormonal changes.

Swallowing too much air, especially when eating, can also increase the amount of gas entering the gastrointestinal tract and lead to bloating.

Talking while eating, eating in a rush, and carbonated beverages can also increase the amount of air swallowed.

Talking while eating and eating in a rush can increase the amount of air swallowed. Photo by MART PRODUCTION/Pexels, CC BY

How can I reduce bloating?

Dietary strategies can be effective ways of managing bloating. While foods that trigger symptoms can be different for everyone, you could try to:

eat fewer gas-producing FODMAP foods such as onion, cabbage, brussels sprouts, cauliflower, dried beans and lentils
eat fewer foods containing lactose, like milk, ice-cream and some yoghurts (there are lactose-free alternatives for people with intolerance)
replace carbonated drinks such as soft-drinks with water, and drink less alcohol
consume more probiotics (such as yoghurt or certain fermented foods)
do more exercise, as mild physical activity enhances intestinal gas clearance and can reduce symptoms of abdominal bloating
eat and drink more slowly; taking your time means you can enjoy your food, but will also help you swallow less air.

See an accredited practising dietitian for personalised advice on managing symptoms using dietary strategies.

When to see a GP

Most of the time, bloating goes away soon enough and is no cause for concern. But consider seeing a doctor if:

your gas is persistent and severe and it’s impacting your quality of life
your gas is associated with other symptoms such as vomiting, diarrhoea, constipation, unintentional weight loss or blood in the stool.

Authors: Saman Khalesi, Postdoctoral Fellow of the National Heart Foundation & Senior Lecturer and Discipline Lead in Nutrition, School of Health, Medical and Applied Sciences, CQUniversity Australia