In the previous blogs we have discussed the role of the “exposome” which are the environmental factors we are exposed to that may contribute to autoimmunity.  One of the more common and important factors is diet/food.  This process involves an immune reaction against a food particle such as a peptide that then spreads to attacking our own tissue.

Normally, peptides in food are not absorbed through the healthy gut barrier into the immune layer of the wall.  They must be digested into the individual amino acids which can be absorbed but do not trigger antibody production.  This normal physiology however is changed if the gut barrier is “leaky” which allows larger, foreign looking food molecules into the immune layer.  If food reactions are suspected, it is important to examine the integrity of the gut barrier.

The gut epithelial cells that separate the gut food contents from the underlying immune layer are held together by tight junction proteins.  When these junctions are disrupted as shown on the right side of this diagram, poorly digested and “foreign looking” food molecules can enter the immune layer triggering antibody reactions.

The integrity of the tight junctions can be looked at with an antibody panel against the tight junction proteins.  When they separate they enter the system and the immune system reacts to them.  Healing the tight junctions must be done at the same time triggering foods are avoided to quiet autoimmunity.

The most well known food triggered autoimmune disease is celiac disease where antibodies are made against peptides in gluten and these antibodies then confuse tissue in the small intestine with the gluten peptides destroying the intestinal lining.  In addition to being triggered by food, celiac disease is resolved by strict avoidance of the food which quiets the antibody reaction.

Research over the past decade has found that gluten antibodies cross-react with other tissues in the body including the brain, skin and joints.  Foods causing cross-reactivity with self-tissue is not limited to gluten and is equally common with other foods such as dairy peptides.

Cross reactivity is caused by similarity of the structure of a food peptide and a peptide in our own tissue.  The phenomenon is called sequence homology or molecular mimicry.  Peptides are long chains of amino acids.  Segments within these chains may have a string of amino acids called an epitope which is similar to another peptide. The diagram shows the sequency homology or similarity between a peptide in dairy, milk butyrophilin peptide (BTN) and a peptide in myelin producing cells in the nervous system, myelin oligodendrocyte glycoprotein or MOG.  All of the areas of amino acids in red overlap creating potential for antibodies made against the milk peptide to react to MOG and potentially setting off multiple sclerosis.

Another example of this molecular mimicry is between aquaporins in food and one in nerve cells called aquaporin 4.  Immune attack against human aquaporin 4 is associated with two demyelinating autoimmune diseases neuromyelitis optica and multiple sclerosis.  Food aquaporins are rich in soy, corn, spinach, and tomato.

These are just some of the potential cross reactions between foods and human tissue that is involved in autoimmune disease.  Virtually every autoimmune disease has the potential to be activated by some food molecule that the immune system reacts to.  The essence of using food avoidance to quiet autoimmunity is dependent on identifying these food reactivities.  This is done by avoiding the activating foods and healing the gut barrier.

Ironically, one of the more common causes of damage to the gut barrier is food, (or collective group of food additives termed “industrial food additives”.)  These include many artificial sweeteners and emulsifiers such as soy lecithin, algin, carrageenan, and agar.  These components are used to alter taste and texture in food but are unhealthy for the gut barrier.  Processed foods should be eliminated to allow the gut barrier to heal.  This can be facilitated by supplementation with factors that help repair the barrier such as glutamine, glucosamine, zinc and MSM.

There is an old saying, “let food be thy medicine”.  At times, certain foods can be the enemy.  Solving that mystery is important in autoimmune disease.

Lerner A, Matthias T.  CHANGES IN INTESTINAL TIGHT JUNCTION PERMEABILITY ASSOCIATED WITH INDUSTRIAL FOOD ADDITIVES EXPLAIN THE RISING INCIDENCE OF AUOIMMUNE DISEASE.  Autoimmune Rev, 2015 Jun; 14(6):479-89.