• All
• False (10)
• Not proven (13)
• Partly true (5)
• True (1)

• False

  “A urine mycotoxin test shows whether I have mould poisoning.”

  Mycotoxins are also found in the urine of healthy people because they come from food. There are no levels above which they make you ill. The US CDC warns against these tests.

  Evidence in the chapter: Mould: mycotoxins in food and damp in the home Copy link

• False

  “A probiotic is a probiotic; what matters is lots of bacteria.”

  The effect depends on the strain. In IBS, individual strains helped in meta-analyses, other strains of the same species did not. Many products only name the species.

  Evidence in the chapter: Spore-forming bacteria: Bacillus and co. as probiotics Copy link

• False

  “A low DAO value in the blood proves histamine intolerance.”

  In studies the blood test does not reliably separate affected people from healthy ones. A food diary, a low-histamine trial phase and ruling out other causes tell you more.

  Evidence in the chapter: Histamine intolerance: much searched, little proven Copy link

• False

  “Candida in the stool means a fungal infection of the gut.”

  In many people Candida is part of the normal gut flora in small numbers. Finding it in stool alone is not a result that needs treatment.

  Evidence in the chapter: Fungi in the gut: what is true about Candida Copy link

• False

  “Spore probiotics settle permanently in the gut.”

  Spores germinate in the gut, become briefly active and then move on. After stopping, they disappear within days.

  Evidence in the chapter: Spore-forming bacteria: Bacillus and co. as probiotics Copy link

• False

  “Fasting detoxes the gut, and symptoms during fasting show that toxins are being eliminated.”

  False. Fasting markedly changes the gut microbiota and metabolism, but there is no evidence of “detoxification”. Headache, dizziness or nausea during fasting usually have simple causes such as lack of fluid and salt, caffeine withdrawal or low blood sugar.

  Evidence in the chapter: Longer fasting: water fasting, therapeutic fasting and fasting-mimicking Copy link

• False

  “Certain plants or fibres work like “natural Ozempic”.”

  False. Fibre stimulates the body's own GLP-1 via gut bacteria, but only briefly and weakly. For berberine, weight loss in studies averaged less than one kilogram; for the drug semaglutide it was around 15 per cent of body weight.

  Evidence in the chapter: GLP-1 from the gut: what bacteria do and what “natural Ozempic” cannot do Copy link

• False

  “A liver and gallbladder flush with olive oil washes out gallstones.”

  False. The greenish “stones” afterwards consist of fatty acids, a kind of soap made from the oil itself. Real gallstones are not flushed out this way, and if stones are present, the cleanse can trigger a colic.

  Evidence in the chapter: Pressure under the right ribs: bile, liver and gallstones Copy link

• False

  “If an all-meat diet ends the bloating, the gut is healed.”

  False. Without carbohydrates and fibre, gut bacteria have less to ferment, so less gas is produced. At the same time, butyrate producers decline. This is symptom control by starving the bacteria, not healing, and long-term data are missing.

  Evidence in the chapter: Carnivore and keto: less gas, but at what cost? Copy link

• False

  “If you have diverticula, you must avoid nuts, seeds and popcorn.”

  False. In a study of more than 47,000 men, those who often ate nuts or popcorn tended to have diverticulitis less often. That seeds get stuck in diverticula and trigger inflammation is not supported by evidence.

  Evidence in the chapter: Diverticula, haemorrhoids and fissures: what can go wrong at the end of the gut Copy link

• Not proven

  “If I feel worse on the protocol, it is working: that is die-off.”

  A genuine Herxheimer reaction occurs almost only with antibiotics against spirochaetes and lasts hours. It is not proven for Candida, gut or parasite protocols. Reading worsening as healing overlooks side effects.

  Evidence in the chapter: Herxheimer reaction, die-off and toxins Copy link

• Not proven

  “Lots of Firmicutes in the gut make you fat.”

  In mice there was a link; in humans large studies show no clear pattern. Both groups contain hundreds of species with very different properties.

  Evidence in the chapter: Firmicutes, Bacteroidetes and body weight Copy link

• Not proven

  “Vitamin C helps with histamine intolerance.”

  Evidence in humans is lacking. In the lab, vitamin C is even on the list of substances that inhibit the histamine-degrading enzyme DAO. That lab value, however, may be a measurement artefact: vitamin C consumes the hydrogen peroxide through which DAO activity is measured. In humans, neither benefit nor harm is established.

  Evidence in the chapter: DAO: the enzyme that intercepts histamine from food Copy link

• Not proven

  “A microbiome stool test tells me what to eat.”

  The same sample can give different results at different providers, and there are no reference ranges for most values. Targeted tests for pathogens or inflammation, on the other hand, are useful.

  Evidence in the chapter: Gut tests: what they show and what they do not Copy link

• Not proven

  “Clay, zeolite and activated charcoal detox the gut.”

  There is no evidence for this. Products can be contaminated with lead, and activated charcoal also binds medicines.

  Evidence in the chapter: Herxheimer reaction, die-off and toxins Copy link

• Not proven

  “Many unexplained symptoms are explained by mast cell activation syndrome.”

  Unproven. Genuine MCAS is rare and needs lab evidence during an attack. Professional societies warn that the diagnosis is often made without this evidence, so other, treatable causes are overlooked.

  Evidence in the chapter: Mast cells: alarm cells in the gut, histamine and the disputed MCAS Copy link

• Not proven

  “A three-gas breath test reliably shows whether I have hydrogen sulfide SIBO.”

  Unproven. The test has been studied almost only by the group that co-developed it, there is no uniform cut-off, and it does not show where in the gut the gas is produced. An abnormal result is a clue, not a diagnosis.

  Evidence in the chapter: Hydrogen sulfide and methane: the other gases in the gut Copy link

• Not proven

  “Herbs work just as well as antibiotics for SIBO and are harmless.”

  Unproven. The most cited study was retrospective and not randomised. For single substances such as allicin or oregano oil there are no studies in SIBO. Herbal remedies can also have side effects and interactions.

  Evidence in the chapter: SIBO treatments compared: rifaximin, herbs, elemental diet and faecal transplant Copy link

• Not proven

  “If you cut out oxalate, you experience "oxalate dumping": stored oxalate is flushed out and causes symptoms.”

  Unproven. There is not a single study on this term. Real oxalate problems are calcium oxalate stones and oxalate excess with poor fat digestion. They are detected with urine tests, not by symptoms after a change of diet.

  Evidence in the chapter: Oxalate, salicylate, lectins: hidden culprits or internet myth? Copy link

• Not proven

  “Lectins in pulses, whole grains and tomatoes make the gut leaky and should be avoided.”

  Unproven. Raw or undercooked kidney beans can indeed cause poisoning. But soaking and thorough cooking inactivate lectins, and according to EFSA properly prepared food poses no risk. Pulses are linked to better health.

  Evidence in the chapter: Oxalate, salicylate, lectins: hidden culprits or internet myth? Copy link

• Not proven

  “A mix of colostrum, zinc, aloe and collagen repairs a leaky gut wall.”

  Unproven. Colostrum and zinc carnosine curbed permeability caused by painkillers or hard training in healthy people. For none of the ingredients is it shown that they help people with gut symptoms by tightening the gut wall. Long-term zinc can cause copper deficiency.

  Evidence in the chapter: The “leaky gut stack”: colostrum, zinc carnosine, aloe and co. Copy link

• Not proven

  “Stubborn SIBO or Candida hides in biofilms, and only “biofilm busters” make a protocol work.”

  Unproven. Biofilms on the gut lining exist, and in some people with IBS they are even common. No controlled study shows that NAC, enzymes or EDTA dissolve them in the gut and make protocols more effective. Enzymes such as nattokinase, on the other hand, can promote bleeding.

  Evidence in the chapter: Biofilms in the gut and “biofilm busters” Copy link

• Not proven

  “Without a gallbladder you have to eat low-fat for life.”

  Unproven. The liver still makes enough bile. In one study, quality of life after surgery improved regardless of how much fat people ate. If large, fatty meals give you diarrhoea, spread the fat out rather than cutting it.

  Evidence in the chapter: Life without a gallbladder: diarrhoea, fat and symptoms after surgery Copy link

• Partly true

  “Sauerkraut and yoghurt from the supermarket always contain live cultures.”

  Many products are pasteurised after fermentation, such as sauerkraut in cans or jars. Then the cultures are dead. Fresh products from the chiller are more likely to contain live cultures.

  Evidence in the chapter: Using fermented foods well Copy link

• Partly true

  “Probiotics must always be taken with a gap from the antibiotic.”

  For bacterial probiotics it is barely studied whether a gap helps. Saccharomyces boulardii is a yeast and is not attacked by antibiotics, so no gap is needed.

  Evidence in the chapter: Saccharomyces boulardii: the probiotic yeast Copy link

• Partly true

  “The more fibre, the better for the gut.”

  Basically yes, but fast-fermenting fibres such as inulin cause strong bloating in sensitive people. Slow fibres and building up gradually are often better tolerated.

  Evidence in the chapter: Prebiotics that build up gently Copy link

• Partly true

  “Intermittent fasting reliably improves the gut microbiota.”

  Partly. Individual studies show more diversity, especially with an early eating window and during Ramadan. But a 2026 systematic review considers the evidence very uncertain, and the changes are largely lost after fasting.

  Evidence in the chapter: Intermittent fasting and meal timing: 16:8, 5:2 and Ramadan Copy link

• Partly true

  “If heartburn comes back after stopping an acid blocker, you need it permanently.”

  Partly. After a few weeks of use, acid often temporarily overshoots on stopping, even in people who had no symptoms before. This is usually not a relapse. Stopping step by step is one option; according to the American gastroenterology association, stopping at once is another. With clear reasons such as Barrett's oesophagus, however, the acid blocker remains important.

  Evidence in the chapter: Acid blockers (PPIs): what they change in the gut and how to stop them properly Copy link

• True

  “With lactose intolerance, kefir is often tolerated better than milk.”

  True. Kefir contains less lactose, and its cultures help break it down. In one study kefir produced clearly less hydrogen in the breath than milk.

  Evidence in the chapter: Fermenting at home: milk kefir, water kefir and S. boulardii soda Copy link

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