Mushroom intolerance

I love mushrooms and can eat them in abundance. But I know a lot of people dislike mushrooms – perhaps for a genetic reason? For some people with intestinal problems and a specific genetic variant, mushrooms can exacerbate these problems.

Mushroom Intolerance and Crohn’s

Crohn’s disease is a serious inflammatory disorder affecting the lining of the intestines. It can cause abdominal pain, fatigue, diarrhea, and weight loss. For some people, it is a chronic condition, and for others, it may just flare up periodically.

An interesting study published in the British Journal of Nutrition looked at some of the foods that trigger intestinal issues for people with inflammatory bowel diseases (mainly Crohn’s).

The study participants were a group of New Zealand Crohn’s patients and a control group without Crohn’s. The researchers were looking at the interaction between foods, disease symptoms, and genetics.[ref]

The top foods found to aggravate intestinal symptoms were corn and mushrooms. Corn is a known allergen and general trigger for a lot of people. The mushroom connection, though, was linked to a specific compound in mushrooms and a specific gene.

The researchers linked the ‘intolerant of mushrooms’ group to a genetic variant of the OCTN1 gene, which in previous studies had links to an increased risk of Crohn’s disease (without a reason why).

The OCTN1 / SLC22A4 gene:

The OCTN1 gene (now known as SLC22A4) codes for a transporter of organic cations, which means it moves solutes with a positive charge across the plasma membrane.

Specifically, SLC22A4 moves ergothioneine, a compound available abundantly in mushrooms, across the plasma membrane.

Additionally, the SLC22A4 transports gabapentin, and the variant below impacts the clearance of gabapentin.[ref]

Related article: GABA levels: Genetic variants that impact this inhibitory neurotransmitter

What is ergothioneine?

Ergothioneine has been the subject of many research studies lately due to its antioxidant properties and potential role in helping cardiovascular disease. Researchers are looking at it as a positive factor with potential for use as a supplement. Which may be great – for some people…

Ergothioneine is a compound naturally synthesized by bacteria and fungi. We naturally consume ergothioneine in our diet in small quantities. Specific soil fungi and bacteria produce ergothioneine, and then it is taken up by the roots of some plants.

Our main food source for ergothioneine is mushrooms (white button, shiitake, portobello, and oyster). Other food sources that contain some ergothioneine include liver, black and red beans, and oat bran.[study] It is interesting to note that in the Crohn’s study referenced above, other foods on the top offenders’ list included baked beans, chickpeas, and dried beans.

The variant of SLC22A4 linked to Crohn’s disease and, in the study referenced above, to mushroom intolerance for those with Crohn’s disease, causes a gain of function with a 50% increased transport of ergothioneine (ET).

Even though we often think of antioxidants as something to consume in abundance, the study explains: “high levels of ET might lead to an antioxidant overload in red blood cells or epithelium, leading to pro-oxidant effects and/or imbalance in immune reaction. An alternative possibility might involve effects on pro-inflammatory cytokines or heat shock protein 70”.[ref]

Ergothioneine, mushrooms, and adaptation of an agricultural diet?

Researchers who look at evolutionary genetic traits find that certain genetic variants are linked to humans switching from hunter/gatherers to a more agriculture-based society.  Some researchers theorize that this genetic variant in the SLC22A4 gene is an adaptation in European populations to protect against ergothioneine deficiency in agriculture-based diets.[ref]

Related article: Inflammatory Bowel, Crohn’s Disease, and Gut Microbes

Genetic variant linked to mushroom intolerance:

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The SLC22A4 variant (rs1050152) is also referred to as the OCTN1 L503F variant.

Check your genetic data for rs1050152 (23andMe v4, v5; AncestryDNA):

  • T/T: increased OCTN1 transport[ref], more likely to be intolerant of ergothioneine foods (mushrooms) with IBD; increased risk of inflammatory bowel disease[ref]
  • C/T: increased OCTN1 transport, more likely to be intolerant of ergothioneine foods (mushrooms) with IBD
  • C/C: typical

Members: Your genotype for rs1050152 is .

Note that mushroom intolerance only correlates between the SLC22A4 variant and in those with IBD. If you don’t have any intestinal problems, you may feel perfectly fine when eating mushrooms.

I find it interesting that this SLC22A4 variant is associated with the risk of Crohn’s disease and ulcerative colitis in some populations, but not all. It makes me wonder if the risk could be driven by the amount of ergothioneine in the diet either due to the popularity of mushrooms or due to local soil microbial content.



Carrier of the rs1050152  T-allele? If you have intestinal issues, and especially if you have an inflammatory bowel disease, you may want to try cutting out foods high in ergothioneine.

What foods contain ergothioneine?

Foods high in ergothioneine include:[ref]

  • Many commonly eaten mushrooms including oyster, shiitake, and portobello.
  • Tempeh
  • Soy products
  • Garlic, in larger amounts
  • Asparagus
  • Brazil nuts
  • Kidney beans

Curcumin, in a cell study, reduced OCTN1 transport in cells. The research shows that when curcumin is added to the OCTN1 upregulated variant (e.g. T-allele above), the curcumin reduces OCTN1 to the levels of a normal cell. The researchers believe this is one mechanism by which curcumin is helpful in IBD.[ref]  Curcumin is available as a supplement and also in the spice turmeric.

Related Genes and Topics:

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Originally published 06/2017. Updated 11/2019.

Author Information:   Debbie Moon
Debbie Moon is the founder of Genetic Lifehacks. She holds a Master of Science in Biological Sciences from Clemson University and an undergraduate degree in engineering from Colorado School of Mines. Debbie is a science communicator who is passionate about explaining evidence-based health information. Her goal with Genetic Lifehacks is to bridge the gap between the research hidden in scientific journals and everyone's ability to use that information. To contact Debbie, visit the contact page.