Psoriasis and a gluten-free diet

Over the past decade or so, a gluten-free diet has been promoted by celebrities for weight loss and improved health, as well as by athletes claiming improved performance.

As anyone who uses the internet as a source of information will know, it has also been extensively promoted as a way of improving – or even eliminating – psoriasis. But is there any real evidence for this? Before we try to answer this question, it maybe helpful to say something about gluten sensitivity and why it’s important for psoriasis sufferers.

Gluten, coeliac disease and wheat allergy

Gluten is a general name for the proteins found in wheat, barley and rye. 

Coeliac disease, which affects around 1% of the population, is a well-defined illness, where the body’s immune system attacks itself when gluten is eaten. This causes damage to the lining of the gut and means that the body cannot properly absorb nutrients from food. Coeliac disease is not a food allergy or intolerance; like psoriasis it is an autoimmune disease.

Non-coeliac gluten sensitivity (NCGS) is when symptoms similar to coeliac disease are experienced, but it is not clear how the immune system might be involved because no antibodies are produced, and there does not appear to be damage to the gut lining. Despite claims that up to 6% of the population has NCGS, the true prevalence is unknown.

Wheat allergy, on the other hand, is a reaction to proteins found in wheat, triggered by the immune system and usually occurs within seconds or minutes of eating. Genuine wheat allergy is very uncommon and probably effects less than 1% of the population.

Gluten sensitivity – fashion fad or fact?

Research shows that up to 20% of people think they suffer from food allergy or food intolerance. However, scientific evidence suggests that the real prevalence of food allergy and intolerance is very much lower than this.

To see how many people are genuinely gluten-sensitive, researchers in Italy enrolled 392 patients who believed they had gluten sensitivity into a controlled clinical trial (ref 1).

All the study participants were asked to eat gluten-containing foods for two months before their initial diagnostic tests to establish whether they had coeliac disease, NCGS or a wheat allergy. All patients then followed a gluten-free diet for six months. After the six-month period, those who did not test positive for coeliac or wheat allergies were instructed to re-introduce gluten-containing foods and they were monitored for symptoms associated with gluten sensitivity.

What were the findings? Of the 392 patients, 26 (6.63%) tested positive for coeliac disease, two (0.51%) for wheat allergy and 27 (0.88%) were found to suffer from non-coeliac gluten sensitivity. In other words, 86% percent of those who believed they were sensitive to gluten, could tolerate it perfectly well. This study clearly shows that self-diagnosed symptoms are a very poor guide to the presence of true gluten sensitivity. Why is this important for psoriasis sufferers?

Psoriasis and coeliac disease

Psoriasis is a chronic autoimmune condition and is well known that patients with psoriasis are more likely to have other autoimmune diseases, including diseases of the gut such as Crohn’s disease, ulcerative colitis – and coeliac disease. In fact, patients with psoriasis have around a 3-fold increased risk for coeliac disease (ref 2). The converse is also true; patients with a diagnosis of coeliac disease have a significantly increased (75%) risk of developing psoriasis (ref 3). So, it’s clear that there is a very close link between the two conditions.

Given this association, it follows that if you have psoriasis and develop symptoms such as bloating, cramping, diarrhoea and lethargy - you should discuss this with your doctor. If tests then show you have a gluten sensitivity, there is good evidence that you may benefit from a gluten-free diet.

A 2001 study demonstrated the impact of a gluten-free diet in 33 people with psoriasis who had raised antibodies to gluten and who were therefore likely to have either coeliac disease or NCGS. After 3 months on a gluten-free diet, 73% of study participants saw a significant improvement in their condition, compared with none of the people without gluten antibodies. Whilst this is a small trial, it does suggest significant benefit.

Psoriasis and a gluten-free diet

But if you have psoriasis and you have no bowel symptoms of any kind, should you still consider a gluten-free diet? The short answer is no. There is no good evidence that in the absence of symptoms suggestive of gluten sensitivity, a gluten-free diet will be of any benefit. More importantly, it may well be harmful.

Whole wheat is a great source of fiber, antioxidants, and multiple nutrients, which means a gluten-free diet eliminates an entire category of healthful foods. Moreover, a gluten-free diet is often higher in calories, fat, salt and sugar because of the need to enhance flavour and texture to make up for the absence of gluten. This may lead to weight gain with all the attendant health risks.

Recommendations:

• If you have psoriasis and you develop bowel symptoms such as bloating, diarrhoea, and lethargy, you should discuss these symptoms with your doctor
• If you have psoriasis and have been diagnosed by your doctor (not self-diagnosis) as having gluten sensitivity, then following a gluten-free diet will probably improve your bowel symptoms and may also help your psoriasis
• If you have psoriasis but have no bowel symptoms suggestive of gluten-sensitivity, you should not embark on a gluten-free diet
• A Mediterranean diet is the best choice for the vast majority of those with psoriasis

Author:
Dr David Ashton MD PhD
1 October 2019

 

Scientific References
1. Capannolo A, Viscido A, et al. Non-Celiac Gluten Sensitivity among Patients Perceiving Gluten-Related Symptoms. Digestion. 2015;92(1):8-13

2. Ungprasert P, Wijarnpreecha K and Kittanamongkolchai W. Psoriasis and Risk of Celiac Disease: A Systematic Review and Meta-analysis. Indian J Dermatol. 2017; 62(1): 41–46

3. Ludvigsson JF, Lindelöf B, Zingone F, et al. Psoriasis in a nationwide cohort study of patients with celiac disease. J Invest Dermatol. 2011; 131::2010-6