Mould: mycotoxins in food and damp in the home

What mould toxins can do in the gut, which dangers are well established, and which tests and cures do not deliver what they promise.

How solid is the research? Promising

Well established: damp, mouldy homes promote respiratory symptoms, allergies and asthma, and aflatoxins damage the liver. For the gut, most findings come from animal and cell studies. A distinct "mould poisoning" with many vague symptoms is not proven, and urine mycotoxin tests are not validated for diagnosis.

Cause or consequence? Often a cause

Damp and mould in the home are a starting point: they hit the gut barrier and the defence cells, without the gut itself being diseased.

Healthy state

Moulds are everywhere, and we breathe in their spores every day. Some are even wanted, for example in blue cheese or on salami. A healthy body copes well with everyday amounts: the cilia of the airways, the stomach with its acid, the immune system of the mucous membranes and the Microbiome, gut microbiota The community of all microbes in the gut, mainly bacteria, plus viruses, fungi and archaea. Most live in the colon. More in the chapter “Building microbial diversity” keep them small.

Mycotoxins Toxins from moulds, such as aflatoxins or deoxynivalenol, taken in mainly through mouldy or contaminated food. are the problem: poisons that some moulds produce on food, in the field or in damp storage, above all in warm, humid climates. According to the WHO, several hundred are known, and about a dozen are considered important. Aflatoxins occur in grain, peanuts and other nuts, dried figs and spices, deoxynivalenol (DON) mainly in wheat, fumonisins in maize, ochratoxin A in storage (also in coffee and wine), patulin in apples and apple juice, and zearalenone, with hormone-like action, in grain. Most are chemically very stable and survive boiling, baking and processing. They can also be taken in via animals: aflatoxin M1 gets from contaminated feed into milk.

That this usually has no consequences is down to controls. For aflatoxins in nuts, grain, dried figs and milk, the Codex Alimentarius sets maximum levels in the range of 0.5 to 15 micrograms per kilogram, and for patulin in apple juice 50 micrograms per litre. The liver matters too: it usually makes absorbed poisons excretable in two steps (conversion, then attaching a water-soluble substance). Aflatoxin B1 is the exception, where the first step first produces the actual cell poison that binds to the genetic material. That is why it is dangerous for the liver in large amounts, and together with hepatitis B the risk of liver cancer rises markedly.

The gut flora plays a part too. Some gut bacteria convert mycotoxins into less toxic substances or bind them; this partly explains why animal species differ so much in sensitivity. It can also work the other way: some plants contain “masked” mycotoxins, bound to a sugar and therefore unremarkable in tests, and gut bacteria can release these again. For humans, how strongly this matters at normal amounts is open. It may differ between people and depending on gut flora.

Cut hard foods generously, throw soft ones away. That keeps mycotoxins out and leaves the gut barrier undisturbed.

Disrupted state: causes and effects

Larger amounts harm the gut. According to the WHO, trichothecenes such as DON irritate the gut lining and cause diarrhoea, and patulin can cause nausea, stomach and bowel upset and vomiting. In animal and cell experiments, aflatoxin B1 and DON weaken the gut barrier: less mucus, looser cell junctions, an altered gut flora. Conversely, mycotoxins change the make-up of the gut flora, because some act against microbes and damage gut and immune cells. How important this is at the usual amounts in food is open, since almost all findings come from animals and cell cultures.

Aflatoxins mainly damage the liver, are life-threatening in large amounts, and over time can cause liver cancer. Fumonisins are linked with oesophageal cancer, and ochratoxin A damages the kidneys in animal experiments. In regions with damp-stored peanuts and maize, aflatoxins are also linked with gut damage and stunted growth in children. Whether aflatoxin really causes stunting is not settled, though: studies show mixed results, exposure fluctuates strongly over time, and trials in which children are deliberately given a poison cannot be justified. Children are nevertheless particularly at risk because they eat more in proportion to body weight.

Damp, mouldy homes: the WHO reviewed the evidence in 2009, and later reviews confirm it. Dampness and visible mould consistently go with more asthma, breathlessness, wheeze, cough, respiratory infections, hay fever and eczema, in allergic and non-allergic people alike. In children the evidence strongly suggests that they trigger asthma attacks. A Meta-analysis An analysis that combines the results of several studies. It is only as good as the studies it includes. of 16 studies found a risk of new-onset asthma raised by roughly a quarter to nearly a half. Measured spore counts in the air, on the other hand, predict little. With weakened defences or lung damage, moulds such as Aspergillus can also cause infections.

What is not supported is the picture of a “mould poisoning” with fatigue, digestive symptoms, concentration problems and much more, to be confirmed by a urine test. Mycotoxins are also found in the urine of healthy people because they come from food, and there are no values above which they make you ill. The US Centers for Disease Control (CDC) therefore warns against such tests. The mechanism remains unclear: through the air you only breathe in tiny amounts of poison compared with what comes in via food. Anyone suffering from such symptoms does have them all the same, and many other causes (iron deficiency, thyroid, Coeliac disease An autoimmune disease in which gluten damages the lining of the small intestine. It is diagnosed with a blood test and usually a biopsy while you are still eating gluten. More in the chapter “Lactose, fructose, gluten: making sense of intolerances”, lack of sleep, depression, irritable bowel) are well treatable. They should be looked for first.

Mouldy nuts or grains deliver mycotoxins. They strain the liver, and in animal studies they weaken the gut barrier.

Where it comes from and where it leads

The same symptoms can have different roots. This map shows what may be involved in this problem and what may follow from it.

Possible causes
This problem
Possible consequences

The preview fits the screen width. In the large map you see everything at once.

Move the mouse over a box: its connections are highlighted and everything else steps back.

Tap a box to highlight its connections. Tap it again to open the chapter.

Connections, not certainty: a link means “can”, not “must”. What applies to you is best clarified in a talk with your doctor.

What often helps

Lifestyle

Diet, exercise, sleep, social contact and dealing with stress.

Remove the damp, not just the stain Find the cause (leak, cold wall, too little airing), dry out and remove affected material. Air regularly with short bursts of open windows and dry water damage promptly. For larger areas, call in professionals. According to the evidence this reduces respiratory symptoms, even without measuring spores. Well supported How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [1][2]
Handle mouldy food correctly Throw away soft and moist foods entirely: bread, yoghurt, jam, cooked dishes, soft fruit, nuts. For hard cheese and firm vegetables, cut off generously, about 2.5 cm around the spot. Promising How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [3]
Check nuts, grain and spices and store them dry Throw away discoloured, shrivelled or mouldy nuts, figs and grains. Store dry, not too warm and not for too long, and buy fresh. Eating a varied diet spreads the risk. Well supported How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [4]
Do not use rotten fruit for juice and purée Patulin forms mainly in apples with rotten spots. For juice, purée or compote take only sound fruit and cut rotten spots away generously. That keeps exposure low. Promising How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [4]
Do not expect too much from indoor air measurements Visible mould, damp damage and a musty smell are enough to act. Measured spore counts or toxins in the air have proved to say little. The money is better spent on remediation. Promising How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [2]

Natural supplements

Supplements do not replace a medical check-up. Discuss dosage and interactions with your doctor or pharmacist.

No "mycotoxin detox" on suspicion Binders, antifungal courses and detox protocols against "mould poisoning" have not been tested in controlled studies and can cause harm themselves. Plausible How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [5]
Activated charcoal and clay are not a long-term solution In the gut, binders also hold back medicines and some nutrients. Studies showing they help with mould symptoms are lacking. More in the chapter on the Herxheimer reaction and detox cures. Plausible How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open.

Medical treatments

Information, not a treatment recommendation. Decide together with a doctor. Approval and availability differ from country to country.

Get respiratory symptoms checked Cough, wheezing, asthma or a constant runny nose in a damp home should be checked by a doctor, often with an allergy test and lung function test. Children in particular should be examined early. Well supported How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [6][1][7]
No urine mycotoxin tests for diagnosis These tests are not approved or validated for diagnosis. A "positive" result usually only shows what you have eaten. Well supported How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [8]
Keep an eye on the liver if you are at risk Anyone with chronic hepatitis B or C, or who often eats heavily contaminated foods (for example in regions with damp-stored maize and peanuts), should have liver values checked regularly. The role of aflatoxins in liver cancer risk is well established. Promising How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [4]
Work up unclear symptoms broadly Fatigue, concentration problems and digestive symptoms in a damp home can also have other, treatable causes. A basic medical work-up (blood count, iron, thyroid, coeliac test, sleep, mood) helps more than a special test. Promising How we rate the evidence Established Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies. Well supported Several randomised studies in humans with largely consistent results. Promising Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies. Plausible Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms. Experimental Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open. [5]

From the community: what people report

Experiences and tips from people with the same problems that come up again and again, but for which there are no meaningful studies yet. They are explicitly not evidence.

“Mould illness” and genetic susceptibility

A widespread model is that mould toxins lead to a chronic inflammatory illness and that only some people are genetically unable to excrete the toxins; those affected describe years of going from doctor to doctor and not being believed. Within the same community the model is also sharply doubted, for instance because of how common the gene variants are and the thin evidence. In parents' forums, by contrast, the talk is plainly about mould in the home and symptoms in children.

Evidence: first hints widespread Reported in: r/ToxicMoldExposure (Reddit community),Phoenix Rising (ME/CFS forum),Mumsnet (parents' forum)
Binders over months to years

Central is treatment with binders, above all cholestyramine, alongside activated charcoal, bentonite and zeolite – often over months to years and with the advice to separate them in time from other products. Many report improvement, others constipation and intolerance. Medically the approach rests essentially on a single research group; self-treatment without medical supervision is risky, because binders also bind medicines and fat-soluble vitamins.

Evidence: conflicting widespread Reported in: r/ToxicMoldExposure (Reddit community),Phoenix Rising (ME/CFS forum)
Moving out, home measurement, sweating

Moving out of the affected home or having it remediated is considered the most important step; many report that without leaving the environment nothing improves. Home measurements to determine an “active” exposure, dealing with contaminated furniture and textiles, and sauna and sweating as “elimination” are widespread. Critical voices point to commercial interests in the measurements and in “toxin-free” furnishings.

Evidence: first hints widespread Reported in: r/ToxicMoldExposure (Reddit community),Phoenix Rising (ME/CFS forum),Mumsnet (parents' forum)

Personal reports can mislead: what helps many people may be a placebo, and what helps one may harm another. Treat them as ideas to raise with your doctor or pharmacist – not as instructions.

In the mood for something completely different? Another one, at random

How we rate the evidence

Trust score 5 of 5:Established: Recommended in medical guidelines or supported by several consistent meta-analyses of randomised human studies.
Trust score 4 of 5:Well supported: Several randomised studies in humans with largely consistent results.
Trust score 3 of 5:Promising: Single randomised or controlled studies in humans, not yet independently confirmed — or many consistent observational studies.
Trust score 2 of 5:Plausible: Two cases: first observational or pilot studies with small samples — or a settled basis that is not in dispute, such as movement, sleep or meal pauses. But not tested in humans for symptoms.
Trust score 1 of 5:Experimental: Barely studied in humans. Mainly lab and animal studies or theoretical reasoning; whether it helps is open.

Sources

Your progress

Ratings by readers

No averages yet. They appear once 3 readers have answered a question.

Is something wrong here?

If you think something is wrong, outdated or misleading, report it for review. Every report is read and answered.