The small intestine is where a lot of the body’s action is—especially regarding the immune system. It absorbs nutrients, releases chemicals, sends messages to the brain, and moves food through the digestive system. It’s a strong, dynamic organ, that is surprisingly delicate at the same time.

When food enters the small intestine, the body begins to collect the micronutrients through the villi (and their microvilli) and send the nutrients to the bloodstream. All of the body is made up of tight junctions. Tight junctions are protein-based structures that bind cells together making up bodily tissues. As incredibly complex as these tissues are, they must be impressionable as well in order to collect nutrients, chemicals, information, etc. to keep the body running.

The Small Intestinal Wall—The Foundation for the Immune System

The barrier the tight junctions create in the small intestine is known as the epithelial wall. Some foods are mild irritants that disturb the epithelial wall causing the tight junctions to damage and separate. This happens on a microscopic level. The invisible-to-the-naked-eye pores allow food molecules to incorrectly pass through to the bloodstream in which the body marks it as a dangerous foreign substance, causing a response from the immune system.

Which Foods Irritate the Epithelial Wall

There are certain foods that contain chemical compounds that irritate the lining of the intestinal wall. Compromising the intestinal wall and its tight junctions, these foods can also damage the gut flora or microbiota.

Nightshade Vegetables

Nightshade vegetables are part of the Solanaceae family. Fruits and vegetables that are nightshades are:

    Tomatoes.
    Tomatillos.
    Eggplant.
    Potatoes.
    Goji Berries.
    Tobacco.
    Peppers (bell peppers, chili peppers, paprika, tamales, tomatillos, pimentos, cayenne, etc)

They contain various compounds, but the notable ones are glycoalkaloids. Glycoalkaloids are derived from sugar and alkaloids (alkaloids are an acid). Solanine is a glycoalkaloid that acts as a natural pesticide for these plants. It is most concentrated in the stems and skin of the nightshade vegetables. Think about the pungent odor of a tomato stem. That strong smell is the plant’s natural defense mechanism to the protect the fruit—especially the fleshy part of the fruit.
Solanine acts as a pro-inflammatory to other organisms keeping them away from the fruit.

In low levels, the glycoalkaloid could still do some damage to the small intestine. Individuals that already have inflammation of the small intestine might experience even more after ingesting nightshades.

Countless anecdotes from individuals with autoimmune disorders suggest a strong correlation between flares and nightshades. People with overactive immune systems might find the pro-inflammatory effects of nightshades trigger intense flares because of the powerful inflammatory response these plants provoke.

Gluten

There are countless studies as well as supporters that caution the consumption of gluten. Gluten is the main culprit for damaging the intestinal wall because of a protein it contains. This protein stimulates the production of a molecule known as zonulin that controls the opening and closing of the intestinal wall.

The body uses zonulin as a defense mechanism against harmful bacteria. When someone contracts salmonella, for instance, zonulin will trigger the gut flushing out the bacteria through diarrhea as well as opening up the tight junctions in the intestinal wall to begin the immune system’s response.

No one can really fully digest gluten. It’s speculated that everyone is gluten intolerant to some degree. Thus, when gluten is not fully digested, the body activates zonulin production and the tight junctions open. This creates the opportunity for food molecules to seep through the microscopic pores into the bloodstream. The body will then begin to mark the food molecules as antigens (or harmful foreign matter) and begin to the immune system’s attack involving inflammation.

Gluten is found in wheat, rye, barley, and all the typical bread products. It’s surprisingly a common filler as well in different processed foods. It hides in condiments, sauces and most packaged and boxed foods. It’s no wonder bodies are becoming increasingly more gluten sensitive or gluten intolerant—we’re exposed to gluten on a larger scale than ever before.

Dairy

Dairy is also a common trigger food or cause for gut problems. Just like gluten, there are individuals with very apparent and acute reactions to dairy. These individuals who are considered lactose intolerant cannot tolerate the sugar lactose. The body needs to produce the enzyme lactase to properly break down this sugar. People who are lactose intolerant do not make enough of (or even at all) this enzyme.

The other component of dairy that tends to cause issues for people is the protein casein (whey is also a protein some individuals have difficulties processing as well.) Casein is a protein with a very similar molecular structure to gluten and 50% of people who are gluten intolerant are casein intolerant as well.

Casein causes the body to have a similar experience as it does with gluten. It triggers the enzyme zonulin, and the tight junctions of the intestinal wall will open up. Food particles—(from any food)—can seep through creating all kinds of food sensitivities.

Autoimmunity, Gluten, & Dairy

Individuals with thyroid problems and autoimmune conditions need to be extremely careful around gluten and dairy. Gluten and casein (the protein found in dairy) have a molecular makeup that is very similar to the body’s tissues. When zonulin initiates leaky gut because of these two foods, their molecules will pass through to the bloodstream and the body memorizes the molecule to develop the perfect defense.

Unfortunately, the immune system isn’t perfect and might mistake its own tissues as the gluten and casein, because of the similarities in structures. Therefore, the body will truly attack its own tissues leaving the individual in a very uncomfortable and often painful flare.

Putting It All Together

Hopefully after reading this series, it will be easy to understand the body is incredibly complex. And each person is different. There are environmental factors that play a role in weakening the immune system, perhaps throwing things off balance and incorrectly marking a substance such as a benign food as harmful to the body.

Autoimmunity is on the rise these days. Women, in particular, are developing autoimmune conditions at a faster rate than men. The time is now to be very present and mindful of one’s health. Understanding the small intestine’s role in the immune system can help individuals take some control over their health and find a dietary regimen that not only keeps the body at a healthy weight but aiding the immune system to function properly—which is fundamentally important.