If you’re dealing with daily bloating that leaves you uncomfortable or looking six months pregnant, SIBO might be the cause. 

As a nutritional therapist working with people who have SIBO, bloating is one of the main issues I hear about from my clients. In this blog, I’ll explain how SIBO causes bloating, how it’s different from other gut issues, and what you can do to feel better.

Bloating is a common symptom in SIBO

Apart from bloating, other common symptoms of SIBO include abdominal pain, nutrient insufficiency (e.g. B12 or iron), aching joints, excessive gas, belching, diarrhoea or constipation.

Our small intestine is where nutrients from our diet are absorbed, and this is often where bloating in SIBO can begin if food is not properly broken down and absorbed.

Non SIBO bloating

Issues with your breakdown of food in the small intestine aren’t always caused by SIBO. They may be triggered by:

• Damage to the villi – villi are small finger like protrusions in the intestines which help you absorb nutrients. These villi can be damaged which reduces the breakdown of food. Damage may be caused by untreated coeliac disease, inflammatory bowel disease, alcohol misuse, scarring such as an operation, or other causes of damage to the gut.
• Not chewing properly – large chunks of food take more work for your digestive juices to break the food down. This phase of chemical processing inside the gut needs a wide surface area on each mouthful of food you swallow. This is the reason I wrote about why chewing is so important.
• Digestive enzyme insufficiency  – we have digestive enzymes which break down fats, protein and carbohydrates. An overgrowth of small intestine microbes can damage the brush border enzymes in the small intestine. This could mean you don’t break down your food effectively. High chronic stress or anxiety can also reduce levels of digestive enzymes. 

How does SIBO cause bloating?

When carbohydrates are left in the small intestine it can be food for bacteria living there. The small intestine shouldn’t normally have a large amount of microbes, but they can start to overgrow if you have issues such as slow gut motility, poor diet, surgery, adhesions or medication.

So when these bacteria start to eat the carbohydrates they produce gas. This gas can be hydrogen, methane or hydrogen sulphide.

Gas in your small intestine may take a long time to come out, and can really add to bloating. You may also get abdominal pain from the stretching of the intestines.

How bacteria in your small intestine cause gas and bloating

Bacteria in our gut love to eat carbohydrates. They ferment the food we eat and a by product of this is gas.

However, this doesn’t mean you shouldn’t eat carbohydrates. Here are three important reasons why carbohydrates are still important:

• Firstly, we need to feed the bacteria in our large intestine with fibre and starches in carbs. Fibre also helps regulate bowel movements, reduces the risk of heart disease, maintains a healthy weight and so much more!
• And secondly reducing carbohydrates won’t get rid of the SIBO, so cutting out carbs on its own won’t improve your digestion long term. You need to look at the causes of SIBO, and reduce the bacteria (more on that below).
• Lastly, carbohydrates are a fantastic source of energy, and removing them from your diet long term may leave you feeling tired, hungry and miserable.

As a quick reminder here is a list of foods containing carbohydrates:

• Grains – bread, pasta, crackers, rice, oats
• Vegetables
• Nuts and seeds
• Fruits
• Sugars and sweeteners – honey, sugars.
• Lactose in milk

Difference between SIBO and carbohydrate malabsorption

Although both things cause bloating they are different! 

SIBO bloating

• SIBO causes bloating through bacterial fermentation of foods in the small intestine.
• Normally occurs 1-8 hours after eating. 

Carbohydrate malabsorption

• Undigested molecules of larger sugars (e.g. fructose or lactose)
• Can occur 1-24 hours after eating.
• May also occur in the large intestine. 

Large intestine bloating

We need to break our food into smaller molecules to be absorbed into our intestinal cells. For example, you may feel more bloated with dairy in your diet, which could be lactose malabsorption.

Lactose is found in milk, cheese or yoghurt. When we eat lactose containing foods an enzyme called lactase breaksit down into glucose and galactose. These small molecules can be taken into the cells.

If you don’t have enough lactase enzyme some of the lactose stays whole. A larger molecule of lactose then travels to the large intestine.

This can cause bloating and gas as the large intestine bacteria ferment the lactose. This process can also draw more water in the large intestine which may trigger diarrhoea or more bloating.

Can improving SIBO reduce bloating?

Yes! Getting rid of SIBO helps bloating in two ways.

Firstly, reducing SIBO may improve the levels of digestive enzymes in your small intestine. Which means you could reduce the symptoms of carbohydrate malabsorption. Some clients I’ve worked with have been able to start eating a much wider diet after they get their SIBO levels under control. 

Secondly, if there are fewer microbes creating gas in the small intestine you may see some improvement in the daily bloating. The key is reducing the amount of microbes causing the excessive gas.

SIBO isn’t one size fits all

Unfortunately there is no standard set of symptoms, or treatment plan with SIBO. Everyone reacts to different foods, and may respond differently to medication or supplements. 

This is because:

• Not all SIBO microbes are the same – some prefer different types of sugars, so not everyone reacts to the same foods

• The location of the overgrowth matters – if it’s higher up, symptoms may appear sooner after eating

• Enzyme levels vary between people – some have more damage to enzyme production, while others may have genetic differences

• Other health issues can play a role – medication, stress, or nutrient deficiencies may influence digestion too

Should you go low carb during SIBO treatment?

There’s no one-size-fits-all diet for SIBO – and going low carb might not be right for everyone.

The way to treat an overgrowth of bacteria in the small intestine depends on your symptoms, your budget, your lifestyle, your current diet and more!

Most approaches to treating SIBO include some kind of agent to reduce bacterial overgrowth, whether that is through antibiotics or herbal antimicrobial supplements. You need advice from a nutritionist or doctor on the best approach for you and your situation.

There are two dietary approaches for managing SIBO either

• Feeding the bacteria and taking antibiotics to kill them whilst they replicate
• Reducing the food for bacteria so they are starving whilst also attacking them with antibiotics or antimicrobials.

You’ll see specialists recommend either of these options, so it’s not always clear in what order to follow all these recommendations. Especially if you’re trying to figure this out on your own.

It depends on how significant the bloating is, and how much it’s affecting your life.

When can low carb help SIBO?

Reducing bloating can sometimes be done by limiting your carbohydrate intake. This reduction takes away the food for the bacteria so they produce less gas.

But a diet change alone doesn’t get rid of the overgrowth.

You’ll need a treatment protocol for reducing the SIBO microbes. This isn’t just about taking supplements!

It would also include looking at elements of your lifestyle such as sleep, eating patterns, stress management and timing of food.

Read more about SIBO diets and what to eat with SIBO.

Need help with bloating?

If bloating is affecting your daily life and you think SIBO might be the cause, let’s chat.

You can book a free discovery call or Book a free discovery call or explore my resources on managing SIBO here.