What Causes Bloating?

Bloating is the feeling that the abdomen is full, tight, under pressure or swollen. Some people have only the sensation of bloating; in others there is also a visible increase in girth.

Bloating is a very common complaint and most of the time it is not due to a serious disease. Bloating that recurs continually, that is steadily increasing, or that is accompanied by other important symptoms should nevertheless have its cause investigated.

Are wind and bloating the same thing?

No.

Not everyone who is bloated has an excessive amount of gas in the bowel.

Bloating can arise through many mechanisms, such as:

• The formation of gas in the bowel,
• The movement of gas within the bowel,
• Increased sensitivity of the bowel to its contents,
• Constipation,
• Changes in bowel movement,
• The way the abdominal wall and the diaphragm behave.

For this reason, the complaint described as “I have a lot of wind” does not always have genuinely excessive gas production behind it.

What are the commonest causes of bloating?

Eating habits

Eating quickly, swallowing a lot of air while eating, consuming large portions and certain foods can all increase bloating.

In some people in particular:

• Pulses
• Onion and garlic
• Cabbage, broccoli and cauliflower
• Certain fruits
• Fizzy drinks
• Certain sweeteners

can increase the symptoms.

The same foods do not, however, cause bloating in every patient. Cutting a large number of foods out of the diet unnecessarily is therefore not the right approach.

Can lactose cause bloating?

Yes.

When lactose is not sufficiently digested and absorbed, it reaches the large bowel and is fermented by the bowel bacteria.

This can result in:

• Wind,
• Bloating,
• Abdominal pain,
• Rumbling,
• Diarrhoea.

It cannot be said, however, that everyone who is bloated after drinking milk has lactose malabsorption. Where necessary, an assessment can be made with suitable tests.

Does constipation cause bloating?

Yes. Constipation is one of the important causes of bloating.

Stool remaining in the bowel for a long time, the slowing of the passage of bowel contents, and changes in the movement of gas within the bowel can all increase the sensation of bloating.

Correcting the constipation can, in some patients, produce a marked reduction in the bloating as well.

Does bloating occur in irritable bowel syndrome?

It is very common.

In people with irritable bowel syndrome (IBS), bloating may be seen together with abdominal pain and changes in bowel habit.

In these patients the problem is not simply that there is too much gas in the bowel. The bowel being more sensitive to normal amounts of gas and content also contributes to the sensation of bloating.

Why does bloating occur after eating?

It is normal for the stomach and bowel to expand naturally after a meal.

In some people, however:

• Eating very quickly,
• Large portions,
• Functional dyspepsia,
• Gastroparesis,
• Food intolerances,
• IBS,
• Constipation

can make bloating after meals pronounced.

Where the bloating is accompanied by early satiety on very little food, prolonged fullness in the stomach, nausea or vomiting in particular, the emptying of the stomach may need to be assessed.

Why is bloating slight in the morning and marked in the evening?

Some people notice that their abdomen is normal when they wake in the morning and becomes progressively more swollen through the day.

Eating over the course of the day, fermentation and gas formation in the bowel, bowel movement and the response of the abdominal wall can all contribute to this change.

This is seen particularly in functional bowel disorders.

Can there be another disease behind bloating?

Sometimes there can be.

Long-standing bloating may be associated with different diseases such as:

• Coeliac disease
• Constipation
• Inflammatory bowel diseases
• Certain malabsorption states
• Delayed emptying of the stomach
• Diseases of the bile ducts and pancreas
• Fluid collecting within the abdomen (ascites)

In women, certain gynaecological diseases can also present as bloating or an increase in abdominal girth.

For this reason, newly started and steadily increasing bloating in particular should not simply be put down to “wind”.

What helps bloating?

Treatment varies according to the cause of the bloating.

In general the following may help:

• Eating slowly and chewing food well,
• Avoiding very large portions,
• Cutting down fizzy drinks,
• Taking regular physical activity,
• Treating constipation where it is present,
• Identifying the foods that markedly increase that person’s own symptoms.

In some patients a low-FODMAP diet, in which certain carbohydrates are reduced, may help. As this diet can be quite restrictive, however, rather than following it long-term without supervision, a planned and temporary approach of elimination and reintroduction should be preferred in suitable patients.

Do probiotics help bloating?

They do not have the same effect in every patient.

The gut microbiota may play a part in bloating and the formation of gas. It cannot be said, however, that all the probiotics on the market have the same effect, or that every patient with bloating should be given a probiotic.

Rather than using probiotics indiscriminately and continuously, it is therefore more appropriate to make an assessment according to the individual’s symptoms.

When does bloating matter?

Although bloating is a very common and mostly benign complaint, assessment is required if certain symptoms accompany it.

A doctor should be consulted where there is:

• Unexplained weight loss
• Loss of appetite
• Blood in the stool
• Black stools
• Anaemia
• Persistent or severe abdominal pain
• Recurrent vomiting
• Fever
• Long-standing diarrhoea
• Newly started, marked constipation
• A steadily increasing abdominal girth
• Symptoms that wake the person from sleep at night

Where marked abdominal swelling develops suddenly together with severe pain, vomiting and an inability to pass wind or stool, urgent assessment may be required.

How is bloating investigated?

Gastroscopy or colonoscopy is not needed in every patient with bloating.

First of all, when the complaint began, its relationship to meals, the bowel habit, the medicines being taken and the accompanying symptoms are assessed.

Depending on the patient’s circumstances, investigations such as:

• Blood tests
• Coeliac tests
• Stool examinations
• Ultrasound
• Gastroscopy
• Colonoscopy
• Tests for malabsorption
• Gastric emptying studies

may be required.

Which tests are carried out is determined by the patient’s symptoms and examination findings.

Remember

Bloating does not always mean “too much gas”.

It can arise from many different causes, from eating habits to constipation, and from food intolerances to functional bowel disorders.

Short-lived bloating mostly does not point to a serious problem. It is important, however, to investigate the cause of bloating that is newly started, long-standing or steadily increasing, or that is accompanied by alarm symptoms.