Porridge with apple in the morning, a bowl with chickpeas and raw vegetables at lunch, wholegrain bread and fruit in between. You are eating more healthily than ever – and yet by the afternoon your belly is bloated, it pinches and rumbles. Sound familiar?
That is not a contradiction. The very foods that are considered especially healthy contain types of sugar and fibre that not every gut tolerates equally well. This article explains what may be behind it and how you can find out, instead of cutting out more and more foods at random.
At a glance
- What it's about: You eat healthily, with fruit, wholegrains and pulses – and yet your stomach is often bloated. How does that fit together?
- Possible causes: Fructose or lactose malabsorption, poorly absorbed carbohydrates (FODMAPs), histamine or too many bacteria in the small intestine (SIBO).
- What you can do: Keep a food diary for two weeks instead of cutting out more foods. Have warning signs such as blood in your stool checked by a doctor.
- What can be measured: Hydrogen and methane in your breath for fructose, lactose and SIBO, plus histamine in your stool and DAO activity in your blood.
Bloating despite a healthy diet: what happens in your gut
Whatever the small intestine does not absorb moves on into the large intestine. Trillions of bacteria live there and ferment undigested carbohydrates. This produces gases such as hydrogen and methane. In addition, some types of sugar draw water into the gut. The result can be wind, a tight belly, rumbling and soft stools.
A certain amount of gas is completely normal. But bloating and a distended belly are also among the most common digestive complaints of all (PubMed 32246999). What matters is whether they bother you regularly and whether there is a pattern behind them.
Which “healthy” foods can cause bloating
Experts group carbohydrates that are poorly absorbed and easily fermented under the term FODMAP. Many of them are found in exactly the foods people eat more often on a healthy diet:
- Fruit sugar (fructose): apples, pears, mango, honey, dried fruit, fruit juices, smoothies
- Milk sugar (lactose): milk, yoghurt, quark, cream cheese
- Fructans and galactans: wheat and rye (including wholegrain), onions, garlic, chickpeas, lentils, beans
- Sugar alcohols: sorbitol and xylitol, for example in stone fruit, sugar-free chewing gum and “light” products
In a controlled study, people with irritable bowel syndrome had clearly fewer symptoms, including bloating, on a low-FODMAP diet than on a typical diet (PubMed 24076059). That does not mean these foods are unhealthy – they are simply not tolerated equally well by everyone.
Fructose, lactose, histamine: causes many people do not think of
Fructose malabsorption: The small intestine can only absorb a limited amount of fruit sugar at a time. In some people this capacity is lower, and the rest reaches the large intestine (PubMed 17217453). This is not the same as the rare, inherited fructose intolerance, which is investigated differently by doctors.
Lactose malabsorption: Many adults produce less of the enzyme lactase, which breaks down milk sugar. How strongly you react also depends on the amount – small amounts are often tolerated (PubMed 31427404).
Histamine: Histamine is found mainly in matured and fermented foods such as aged cheese, red wine, sauerkraut, smoked fish and tomatoes. In some people it is not broken down sufficiently. Besides abdominal complaints, headaches, skin flushing or a blocked nose are then also described (PubMed 17490952). Diagnosing histamine intolerance is difficult, however, and individual lab values alone are not enough.
Bacteria in the wrong place: small intestinal bacterial overgrowth (SIBO)
Normally, relatively few bacteria live in the small intestine. If too many settle there, this is called small intestinal bacterial overgrowth, or SIBO for short. The bacteria then ferment food early on in the digestive tract. Typically described symptoms are wind, a bloated belly, abdominal pain and diarrhoea (PubMed 32023228).
People are affected more often after abdominal surgery, with slowed gut movement or with certain medications such as long-term acid blockers (PubMed 32023228). Do not stop a prescribed medication without talking to your doctor first.
When bloating should be checked by a doctor
Please have abdominal complaints examined by a doctor promptly if any of the following applies: blood in your stool, unintended weight loss, fever, symptoms at night that wake you up, persistent diarrhoea, anaemia, new symptoms from around the age of 50, or bowel disease in your family. Coeliac disease (gluten intolerance) also needs to be clarified by a doctor – and before you cut out gluten, because otherwise the tests are no longer meaningful.
Test instead of cutting out: how to narrow down the cause
Many people start by cutting out one food after another. The risk: your diet becomes more and more one-sided without it being clear what is really causing the problem. A structured approach is better.
1. Food diary: For two weeks, write down what you eat, when symptoms occur and how strong they are. Often a pattern already shows up, for example after fruit, dairy products or onions.
2. Breath tests: For fructose, lactose and small intestinal bacterial overgrowth, hydrogen and methane are measured in your breath after you have drunk a test solution. If the gases rise, this can be a sign that the sugar was not fully absorbed or is being fermented early. Professional societies have set uniform rules for carrying out and evaluating these tests (PubMed 28323273). ORY offers these breath tests for use at home:
3. Histamine: The histamine and DAO analysis measures histamine in the stool and the activity of the enzyme that breaks it down in the blood. Both values are building blocks for the assessment, not proof on their own.
It is best to discuss the results with professionals – with your doctor or the ORY expert team. If you try a low-FODMAP diet, you should only do so for a limited time and ideally with support from a nutrition professional, so that your diet stays balanced.
In brief
- Healthy foods in particular, such as fruit, whole grains, pulses and dairy products, contain types of sugar that not everyone tolerates well.
- Common reasons are fructose or lactose malabsorption, less often histamine or bacterial overgrowth in the small intestine.
- A food diary helps you spot a pattern.
- Breath tests can clarify whether fructose, lactose or bacteria in the small intestine play a role.
- Warning signs such as blood in your stool or weight loss need to be checked by a doctor straight away.
Frequently asked questions
Why do I get bloated even though I eat healthy?
Many healthy foods contain poorly absorbed carbohydrates such as fructose, lactose or fructans, which are fermented in the large intestine (PubMed 24076059). If you are sensitive to them, a healthy diet in particular can bring more symptoms.
Which foods cause bloating?
Commonly mentioned are pulses, onions, garlic, cabbage, wheat, apples, pears, honey, dairy products and sugar alcohols such as sorbitol. Which of them affect you varies from person to person.
How do I know if I have fructose intolerance?
Typical signs are bloating, abdominal pain or diarrhoea after foods rich in fruit sugar such as fruit, juice or honey (PubMed 17217453). A fructose breath test is more reliable than observation alone.
Can histamine cause bloating?
In some people, yes. Besides abdominal complaints, headaches, skin flushing or a blocked nose can also occur, especially after matured foods or red wine (PubMed 17490952). The assessment is difficult and belongs with professionals.
What is SIBO and how is it diagnosed?
SIBO means too many bacteria in the small intestine. In practice, a breath test measuring hydrogen and methane is often used for this (PubMed 32023228) (PubMed 28323273).
Bloated stomach after eating – what can I do?
Keep a food diary, eat slowly, watch out for large portions of fruit, pulses and dairy products, and if symptoms persist, have the cause investigated instead of cutting out more and more foods. If you notice warning signs, please see a doctor promptly.
Important note: This article does not replace medical advice, diagnosis or treatment. It is for general information only. If your symptoms are persistent or severe, please contact your doctor.
Sources
- Lacy BE et al. Management of Chronic Abdominal Distension and Bloating. Clin Gastroenterol Hepatol. 2021. PubMed 32246999
- Halmos EP et al. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology. 2014. PubMed 24076059
- Gibson PR et al. Review article: fructose malabsorption and the bigger picture. Aliment Pharmacol Ther. 2007. PubMed 17217453
- Misselwitz B et al. Update on lactose malabsorption and intolerance. Gut. 2019. PubMed 31427404
- Maintz L, Novak N. Histamine and histamine intolerance. Am J Clin Nutr. 2007. PubMed 17490952
- Pimentel M et al. ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. Am J Gastroenterol. 2020. PubMed 32023228
- Rezaie A et al. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. Am J Gastroenterol. 2017. PubMed 28323273
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