Test phases

Choose a test phase

Take the gut check, and we will suggest matching test phases. Start the check

• Two weeks without lactose

  Shows whether lactose is behind bloating, abdominal pain or diarrhoea.

  14 days of testing Promising

  Lactose, fructose, gluten: making sense of intolerances

  How it works

  1. Eat as usual for one week and keep the diary every day.
  2. For two weeks, leave out milk, yoghurt, cream, ice cream and cream cheese. Hard cheese and lactose-free products are fine.
  3. Then eat dairy again for one week, for example a glass of milk a day.

  What to watch: Bloating, diarrhoea and abdominal pain, especially in the hours after eating.

  Afterwards: If things clearly improve without lactose and get worse again with milk, lactose intolerance is likely. Reducing the amount is usually enough. You rarely need to cut it out completely.

• Two weeks low in fructose and sorbitol

  Shows whether fructose or sugar alcohols trigger bloating or diarrhoea.

  14 days of testing Promising

  Lactose, fructose, gluten: making sense of intolerances

  How it works

  1. Eat as usual for one week and keep the diary every day.
  2. For two weeks, leave out fruit juice, honey, agave syrup, apples, pears, mango, dried fruit and sugar-free sweets with sorbitol or xylitol. Berries, citrus fruit and bananas in small amounts are usually well tolerated.
  3. Then eat as before for one week.

  What to watch: Bloating, wind and soft stools.

  Afterwards: If leaving them out helps, you can test how much you tolerate. Fructose is often absorbed better together with glucose.

• Four weeks low-FODMAP

  The best-studied diet for IBS and bloating. This covers only the first phase: leaving things out.

  28 days of testing Well supported

  Doing low-FODMAP right

  How it works

  1. Eat as usual for one week and keep the diary every day.
  2. Eat low-FODMAP for four weeks: avoid wheat and rye, onion and garlic, legumes, many fruits, lactose and sugar alcohols. The low-FODMAP chapter explains what is allowed.
  3. If you improve, reintroduce food groups one at a time, each over three days. The check phase here does not replace that; it only shows whether it makes a difference overall.

  What to watch: Bloating, pain, stool form. If it does not help after four weeks, you can stop.

  Afterwards: Low-FODMAP is not meant to be permanent. Less fibre over the long term harms the gut microbiota. Ideally, broaden your diet again with a dietitian.

• Two weeks low in histamine

  Shows whether headaches, flushing, a runny nose or diarrhoea after certain foods are related to histamine.

  14 days of testing Plausible

  Histamine intolerance: much searched, little proven

  How it works

  1. Eat as usual for one week and keep the diary every day.
  2. For two weeks, leave out aged cheese, red wine, sparkling wine, beer, salami, cured ham, canned tuna, sauerkraut and reheated leftovers. Cook fresh and freeze leftovers quickly.
  3. Then eat as before for one week.

  What to watch: Also note symptoms outside the gut: headache, flushing, nose, palpitations.

  Afterwards: If it helps, broaden your diet step by step. A permanently strict low-histamine diet is rarely necessary and limits variety.

• Three weeks of psyllium husk

  Psyllium husk is the best-supported fibre for IBS and constipation. It ferments slowly and causes little gas.

  21 days of testing Established

  Prebiotics that build up gently

  How it works

  1. Eat as usual for one week and keep the diary every day.
  2. Start with one teaspoon a day in a large glass of water and increase every few days to about one to two tablespoons. Drink plenty. Tick “Psyllium husk” in the diary.
  3. Then take a one-week break.

  What to watch: Stool form, frequency, bloating. In the first week there may be more gas.

  Afterwards: If it helps, you can keep taking it. Keep at least half an hour between it and medication.

• Two weeks of set meals without snacks

  Gives the cleansing wave in the small intestine time. A physiological idea you can test on yourself.

  14 days of testing Plausible

  Intermittent fasting and meal timing: 16:8, 5:2 and Ramadan

  How it works

  1. Eat as usual for one week and keep the diary every day.
  2. For two weeks, eat three meals at least four hours apart, with only water or unsweetened tea in between. Nothing after 8 pm.
  3. Then eat as before for one week.

  What to watch: Bloating after meals, fullness, belching.

  Afterwards: If it helps, you can keep regular meal times. If you take diabetes medication, talk to your doctor first.

• Two weeks without coffee

  Coffee stimulates the bowel and can make heartburn or diarrhoea worse in some people.

  14 days of testing Plausible

  Heartburn and reflux

  How it works

  1. Carry on as usual for one week and keep the diary every day.
  2. No coffee for two weeks, not even decaf. Cut down gradually, or you may get headaches in the first days.
  3. Then drink as before for one week.

  What to watch: Heartburn, urge to go in the morning, sleep.

  Afterwards: If it makes no difference, you can enjoy your coffee with a clear conscience.

• Three weeks without alcohol

  Alcohol irritates the gut lining, changes the gut microbiota and is rich in histamine and sugar.

  21 days of testing Promising

  The gut barrier

  How it works

  1. Carry on as usual for one week and keep the diary every day.
  2. No alcohol for three weeks.
  3. Then return to how it was for one week.

  What to watch: Stool form, bloating, sleep, heartburn.

  Afterwards: If it helps, it is worth limiting alcohol to a few occasions for good. If you drink a lot every day, do not stop abruptly; get medical support.

• Three weeks without ultra-processed food

  Tests whether emulsifiers, sweeteners and other additives affect your symptoms.

  21 days of testing Plausible

  The mucus layer and additives

  How it works

  1. Eat as usual for one week and keep the diary every day.
  2. For three weeks, cook yourself from simple ingredients. Leave out ready meals, fast food, sugary drinks, diet products and packaged snacks.
  3. Then eat as before for one week.

  What to watch: Bloating, stool form, hunger and energy.

  Afterwards: Even if your belly does not change: more home-cooked food is well supported for the gut microbiota.

• Three weeks of 30 minutes of exercise a day

  Exercise speeds up the bowel, eases IBS symptoms in studies and is good for your mood.

  21 days of testing Promising

  A gut-friendly everyday life

  How it works

  1. Carry on as usual for one week and keep the diary every day.
  2. For three weeks, walk briskly, cycle or exercise for at least 30 minutes every day. Tick “30 minutes of exercise” in the diary.
  3. Then return to how it was for one week.

  What to watch: Stool frequency, bloating, stress and sleep.

  Afterwards: Exercise works best long term. Even shorter sessions spread over the day count.

• Two weeks without supplements

  Finds out whether one of your products is behind diarrhoea, constipation, nausea or bloating.

  14 days of testing Plausible

  When the supplement itself is the problem: iron, magnesium, excipients and more

  How it works

  1. Take all products as usual for one week, tick “Supplement” in the diary and note your symptoms.
  2. Leave out all supplements for two weeks, including powders, chewable tablets and bars. Keep taking prescribed products such as iron for anaemia, vitamin B12 or vitamin D for a proven deficiency.
  3. Then take the products again for a week, ideally one after the other a few days apart.

  What to watch: Stool form, bloating, nausea and abdominal pain, especially in the hours after taking them.

  Afterwards: If things get clearly better without and worse again with a particular product, you have found the trigger. Often a different form, a smaller dose or taking it with food is then enough.

• Four weeks of a probiotic

  Probiotics work strain by strain and not for everyone. A structured test shows whether yours helps you, instead of spending money for months.

  28 days of testing Plausible

  Spore-forming bacteria: Bacillus and co. as probiotics

  How it works

  1. Carry on as usual for one week and keep the diary every day.
  2. Take a probiotic with a studied strain at the dose used in the study for four weeks. Tick “Probiotic” in the diary.
  3. Then one week without.

  What to watch: Bloating, stool form, pain. There may be a little more gas in the first days.

  Afterwards: Without a clear difference after four weeks, it is not worth continuing. With severe immune deficiency or a central line, no probiotics without medical advice.

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