Coeliac disease

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Introduction

Most of us include grain-based foods such as bread, cake, cereal, pasta and beer as part of our diet. These foods are good sources of carbohydrates, minerals and vitamins. Healthier choices such as rye, wheat, barley and oats have even been linked with lower risk of heart disease and diabetes [7] Jump to reference section: [7] . However, for some of us, consuming grain-based foods may cause gut irritation due to an inability to digest gluten, a protein naturally found in grains. This condition is called gluten intolerance, and has been linked to symptoms like abdominal pain, diarrhoea and bloating within a few hours of eating foods containing gluten. 

Gluten intolerance occurs in 5% of the general population. The condition occurs due to wheat sensitivity or an in-born chronic condition known as coeliac disease [8] Jump to reference section: [8] . Coeliac disease (CD) is quite common, affecting about 1% of people. In addition to intolerance symptoms, CD may cause damage to the small intestines. In the long-term, this condition can cause improper functioning of other body systems. People with CD may lose weight and or experience problems with bone development because their body cannot acquire enough nutrients needed for healthy bones [1] Jump to reference section: [1] . 

Heritability of coeliac disease

Does gluten intolerance run in families? Research shows that you can inherit genes that increase your susceptibility to gluten intolerance from your parents. Having genes linked to wheat sensitivity and coeliac disease may increase your risk of gluten intolerance. However, only the contribution of genes linked to coeliac disease are currently known. Accordingly, if either of your parents have coeliac disease, there is up to a 15% chance that you and your siblings may suffer from the condition too [2] Jump to reference section: [2] .

Overall, the genes responsible for causing gluten intolerance are linked to the immune system. While the immune system’s role is to protect you from invasive molecules, sometimes it may attack healthy cells. Common invasive molecules include bacteria, viruses and allergen particles. In the case of gluten intolerance, genetic changes cause the immune system to attack and destroy healthy cells in the small intestines that contain gluten molecules. 

Genetics of gluten intolerance and coeliac disease

Variations in genes that control the immune system may increase your susceptibility to gluten intolerance. For instance, the human leukocyte antigen (HLA) genes tell the immune system whether or not to attack molecules that enter your body.

In coeliac disease, undigested gluten molecules are presented to the immune system as harmful. The immune system then mistakenly attacks and damages parts of the small intestines where these molecules are found. In general you are more likely to suffer from coeliac disease if one or both of your parents have the condition. Specific genetic variants have been linked to risk of gluten intolerance due to CD, and are highlighted below.

HLA-DQA1 gene

The HLA-DQA1 gene provides instructions that help prevent the immune system from attacking healthy cells. Having variant rs2187668 increases the possibility that your immune system will react inappropriately to protein fragments like those in gluten.

This variant is mostly found among European populations and up to 82% of coeliac patients in the UK carry this particular variant [3] Jump to reference section: [3] . Genetic testing for coeliac disease looks for the rs2187668 variant specifically, confirming its involvement in the condition. 

CCR3 gene

The CCR3 gene helps the immune system to identify and respond correctly to each invasive molecule. Variant rs6441961 may cause your immune system to fail to correctly differentiate between healthy cells and invasive molecules from gluten [5] Jump to reference section: [5] . 

IL2 gene

The IL2 gene is linked to how your immune system responds to invasive molecules. Variant rs13151961 may help reduce the effect of immune responses that attack and damage the small intestine tissues due to exposure to gluten molecules [4,3] Jump to reference section: [4,3] . 

Other Causes of gluten intolerance

There are no known causes of gluten intolerance apart from genetic changes affecting the immune system. However, ongoing research suggests that early childhood infections affecting the digestive tract may cause gluten intolerance. The condition has also been linked with changes in the contents of the intestines, such as the amount of acids available [6] Jump to reference section: [6] . 

What can I do about it?

If you have been diagnosed with coeliac disease or are concerned that you may have wheat sensitivity, it’s best to speak to your doctor or other healthcare professional. For many people, dietary changes like replacing bread, cakes, beer and cereals with gluten-free alternatives can help.  According to the National Institute of Health [9] Jump to reference section: [9] , these alternatives may help your intestines to recover while preventing any further damage due to the condition. You can learn about the source of gluten in your diet by checking food labels for natural and added gluten. You can also keep a diet diary to help you note which foods cause symptoms after eating.