The Link Between Gluten and Psoriasis

Might a gluten-free diet reduce psoriasis flares?

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Credit: Getty Images / Jodi Jacobson

Dermatitis herpetiformis is not the only skin condition closely linked with celiac disease. Several studies have suggested that psoriasis also shares links with the disease. This is not an altogether uncommon occurrence given that autoimmune disorders can often co-exist.

In fact, a 2012 study in the journal Autoimmune Disorders suggested that as many as 34 percent of people with one autoimmune disease will have another (a condition referred to as polyautoimmunity). Some people may even have two or more co-occurring diseases.

What makes the association between celiac disease and psoriasis unique is that they may be both be linked to the dietary protein gluten. Gluten, found in cereal grains, is considered the fundamental trigger of celiac disease. There is also evidence that gluten may incite symptoms in certain people with psoriasis.

Polyautoimmunity

Celiac disease and psoriasis are both autoimmune disorders, meaning that the immune system mistakenly attacks normal cells and tissues. With celiac disease, the immune system will attack the lining of the intestine, known as the villi. With psoriasis, the immune system attacks cells known as keratinocytes in the outer layer of skin (epidermis).

One of the common denominators in all autoimmune disorders is inflammation. With celiac disease, inflammation flattens and damages the finger-like villi, interfering with their ability to absorb nutrients. With psoriasis, inflammation triggers the hyperproduction of keratinocytes, leading to the formation of dry, scaly plaques.

Inflammation also contributes to joint damage with rheumatoid arthritis and nerve cell damage in people with multiple sclerosis.

Role of Genetics

Genetics also plays a central role. According to a 2016 review in the Journal of Immunology Research, genetic mutations are commonly shared between different autoimmune disorders, increasing the risk of polyautoimmunity.

One such example is a signaling protein called human leukocyte antigen (HLA). Among its functions, HLA presents disease-causing microorganisms to the immune system for destruction. If the protein is flawed, it may direct the immune system to attack normal cells instead of abnormal ones.

Mutations of the HLA gene—specifically HLA-DRB13—are linked to several autoimmune diseases, including psoriasis, psoriatic arthritis, rheumatoid arthritis, multiple sclerosis, and myasthenia gravis.

Psoriasis and celiac disease also share HLA mutations, specifically HLA-DR3, HLA-DQ2, and HLA-DQ8. With that being said, it remains unclear how these mutations influence either disease and what, if any, role they play in gluten sensitivity.

Current Evidence

The evidence supporting the link between gluten and psoriasis flare is both compelling and conflicted. The proof is based largely on the presence of gluten antibodies in many (but not all) people with psoriasis.

Antibodies are immune proteins that the body produces in response to any microorganism it considers harmful. Their role is to alert the immune system whenever the microorganism is present so that a defensive attack can be launched.

Each microorganism has its own unique antibody which the body produces when the organism is first detected. Thereafter, it remains to sentinel for re-infection.

The very fact that a person has gluten antibodies means that the immune system considers gluten harmful. If it didn't, there wouldn't any antibodies.

As such, the antibodies are the "fingerprint" that pathologists use to positively identify celiac disease. The presence of these antibodies in people with psoriasis can mean one of several things:

  • It could mean that a person has two independent autoimmune disorders with no genetic link. Even if there are no overt signs of celiac disease, the disease could be latent and only manifest with symptoms in later years.
  • It could mean that there are shared genetic links between the autoimmune disorders, but they are only activated when exposed to specific environmental triggers.

Conflicting Research

It is important to note that the presence of gluten antibodies in people with psoriasis does not mean that gluten is a trigger for psoriasis. To date, the evidence supporting this link is uncertain at best.

On the one hand, a 2008 study from Poland found significantly higher levels of gluten antibodies in people with psoriasis than in a matched set of people without psoriasis. This raises the possibility that the affected people may, in fact, have latent celiac disease.

On the other, a 2010 study from India reported that people with severe psoriasis had significantly higher concentrations of two types of antibodies used to diagnose celiac disease. However, none of the study participant had IgA anti-endomysial antibodies, considered the most sensitive and specific to celiac disease.

In the end, the researchers concluded that the results "seem to imply an association between psoriasis and asymptomatic celiac disease/gluten intolerance."

Despite such assertions, the very fact that not everyone with psoriasis has gluten antibodies leaves plenty of room for doubt.

Currently, no medical association in the United States or abroad has issued recommendations for celiac disease antibody testing in people with psoriasis.

Benefits of a Gluten-Free Diet

If you have been diagnosed with both psoriasis and celiac disease, you will need to follow a gluten-free diet to treat your celiac disease. As a bonus, it may help your psoriasis.

A 2014 study in the Journal of the American Academy of Dermatology reported that, among 33 people with psoriasis who had high gluten antibodies, nearly three out of four (73 percent) experienced an improvement in their skin symptoms after going gluten-free.

The conclusions were limited by the small size of the study. Moreover, there was no indication that the same would occur in people with low levels of gluten antibodies. (It is highly doubtful that it would benefit people with no gluten antibodies.)

For its part, the National Psoriasis Foundation believes that the jury is still out as to whether a gluten-free diet is a viable treatment option for psoriasis. With that being said, obesity is a major trigger for psoriasis and, as such, any effort made to reduce weight should be considered beneficial.

In the end, the positive results may be attributed to weight loss rather than the alleviation of gluten sensitivity. Further research is needed before any conclusions can be made.

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