Is gluten bad for you?

A lot of people are avoiding gluten, a protein found in wheat, barley and rye, because of supposed health benefits. How true are these claims, and would you be better off without gluten?

What Does Gluten Do to Your Gut?

Unlike most other dietary proteins, gluten doesn’t break down completely during digestion. Fragments of the long chains of amino acids that make up proteins, called peptides, remain intact. Individuals have different amounts and types of the enzymes and gut microbes that break down gluten, which partly explains why some people react worse than others to gluten exposure. Gluten peptides accumulate in the intestines, and can do several things. 

Gluten can change your microbiota

The large intestine houses the largest share of gut microbes in the GI tract, with different species and higher concentrations than the small intestine. But microbes that can feed on undigested gluten peptides, mainly Lactobacillus, Streptococcus, Staphylococcus and Clostridium genera bacteria, can be lured to the rich food source in the small intestine and may be a cause of small-intestinal bacterial overgrowth (SIBO) (Davila et al., 2013). Some research suggests that there is a higher prevalence of SIBO in those with celiac disease, an autoimmune reaction to gluten (Shah et al. 2022). SIBO is also increased with slowed gut motility – movement of intestinal contents through the intestinal tract (Avelar Rodriguez et al., 2019). Gluten exorphins, gluten peptides that attach to opioid receptors in the gut, can slow motility (Pruimboom & de Punder, 2015). 

Proliferation of gluten-feeding species can crowd out other species, causing imbalance. Studies show that in gluten-sensitive participants, gluten in the diet causes a reduction in gut microbial diversity, especially in the Firmicutes phylum, compared to non-gluten-sensitive controls. However, in some studies there was an increase in Streptococcaceae and Lactobacillaceae families, coinciding with species that feed on gluten peptides. Although Lactobacillus species are associated with positive effects on gut health, some evidence shows that overabundance can have negative results (Mohan et al., 2016). This indicates that something about gluten-intolerant individuals causes a change in microbial balance when exposed to gluten peptides. 

It’s likely that gluten intolerance is triggered by dysbiosis in genetically-susceptible people, and also that immune and microbial reactions to gluten further contribute to dysbiosis (Bernardo et al., 2009). So factors like the amount of antibiotics you’ve taken, type of diet you’ve had or how reactive your immune system is influence how you react to gluten.

Gluten can increase gut permeability

The spaces between intestinal cells, called tight junctions, are held together by proteins that open and close to let certain nutrients enter the body. Gluten peptides and pathogenic gut microbes can attach to receptors on intestinal cells and trigger tight junctions to open, or trigger release of a substance called zonulin, which then triggers tight junctions to open when they shouldn’t, and stay open for too long (Fasano, 2011). One study showed that intestinal cells from celiac, gluten-sensitive and non-gluten-intolerant control participants all had increased tight-junction permeability when exposed to gluten, with celiac and gluten-sensitive tight junctions being equally more permeable than controls (Hollon et al., 2015). Some people produce a type of zonulin, prehaptoglobin-2 (Veres-Székely et al., 2023), but others don’t have the gene for it, so those with the gene may have more zonulin.

Some researchers speculate that, because gluten peptides have amino acid sequences similar to those on the surfaces of pathogenic bacteria, the body opens tight junctions to flush out the bacteria (Fasano, 2020). However, this also allows food particles, including gluten, gut microbes and other substances to travel through the barrier and into the tissues beneath intestinal cells, and possibly into the bloodstream (Fasano, 2011).

Gluten causes inflammation

Accumulation of undigested gluten peptides in the intestinal tract allows them to have more contact with the intestinal lining, and loosened tight junctions allow them and other substances to enter the tissues beneath and make contact with immune cells. Certain receptors on intestinal and immune cells have just the right shapes to fit with amino acid or carbohydrate chains sticking out of or emanating from pathogens like bacteria or fungi, and also some gluten peptides (Fasano, 2020). When they attach, it causes a reaction that leads to release of pro-inflammatory chemicals into the area. 

Pro-inflammatory chemicals can disrupt or poke holes in the membranes of pathogens, weakening or killing them (Alberts et al., 2002). The chemicals don’t differentiate between good gut microbes and bad, and may cause dysbiosis if chronically released into the gut. Other inflammatory chemicals attract immune cells that swallow up pathogens and assault them with free radicals and other chemicals. These free radicals, or reactive oxygen species, can escape the target and damage other cells and DNA, leading to further inflammation (Leiberman & Peet, 2018). Finally, immune cells release protein-degrading enzymes into the area to break down damaged tissues, but they also damage healthy tissues, exacerbating inflammation. The damaged proteins are replaced with collagen, forming scar tissue (Braun & Anderson, 2017).

The same study that found that gluten loosens tight junctions, even in non-gluten-sensitive controls, also found that it caused inflammation in all participants (Hollon et al., 2015). Continued exposure to gluten can cause chronic inflammation that may lead to reduced nutrient absorption and the spread of pro-inflammatory chemicals throughout the body, causing systemic, low-grade inflammation.

Should Everyone Avoid Gluten?

There are so many variables that can contribute to an individual’s reaction to gluten. If you have a healthy, strong microbiome, genetic and environmental factors that keep your tight junctions functioning as they should and a robust anti-inflammatory response, the benefits of eating gluten-containing foods may outweigh the costs. 

Gluten-containing whole grains can be high in fiber, B vitamins and minerals, and most refined wheat flour is enriched with certain B vitamins and iron while gluten-free flour is not, so replacing refined-wheat products with their gluten-free counterparts can actually be a step down in nutritional quality. Gluten-free products are usually denser and higher in calories, and rely heavily on rice flour, which can spike blood sugar and contain high levels of arsenic and heavy metals. 

But here’s the thing: many of us are not so lucky to have strong defenses against the undesirable effects of gluten, and suffer from dysbiosis, decreased nutrient absorption, digestive disturbances and inflammation as a result. Plus, eating a diet high in refined carbohydrates, the majority of which comes from refined wheat flour in the Western Diet, is the main cause of obesity, type 2 diabetes and cardiovascular disease. 

The combined benefits of eliminating the negative health effects of gluten along with reducing refined carbohydrates in the diet is a win-win when replacing gluten-containing foods with fiber and nutrient-rich whole foods. Alimental Nutrition’s Gut Restoration Program includes healing, low-carbohydrate, gluten-free weekly meal planners and recipes to get you on the right track. Check it out here. 

References

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