Food sensitivities are increasingly common in our modern society, and our gut bacteria might be to blame. Infections early in life and an out-of-balance microbiome play a role in developing a food sensitivity — but, a healthy lifestyle with lots of dietary fiber could help you out of it.

By Maria Arvaniti Lactose-free milk. Gluten-free bread. Coconut yogurt: free of dairy, soy, gluten, egg, preservatives, and artificial colourings! A few years back, these products were hard to find, but lately, food sensitivity is on the rise – and the market seems to be following suit. Our modern lifestyle has definitely taken its toll on our gut’s well-being, and scientists have turned  their focus on the role of out-of-balance gut microbiota, as way to determine the underlying cause of food sensitivities. A recent review, published in the journal Nature Reviews Gastroenterology & Hepatology, sums up the most relevant experimental and clinical data for the involvement of gut microbiota in food sensitivity1. So, what’s the hardcore evidence?

Your childhood is important

Importantly, when talking about food sensitivity, we should keep in mind that not all cases share a common biological mechanism. Food sensitivities can be divided into two main categories: food allergies and food intolerances. When a generalized immune reaction starts after we consume a certain type of food, then we’re talking about food allergy. Contrarily, food intolerance occurs when our body cannot digest a compound – as when we lack lactase, an enzyme that degrades lactose from dairy products. So in general, food allergies could lead to life-threatening conditions, while in food intolerance, symptoms are milder and commonly centered on our digestive system. To date, researchers have often focused on childhood, when investigating the primary cause of immune reactions. That’s because in this early life stage (neonatal and infant period), the still-developing immune system is much more vulnerable to changes, which might be engraved and reflected later in life.

Viral and bacterial infections early in childhood – combined with certain genetic markers – may increase the risk for developing food sensitivities.

There are different ways that microbes can influence this critical process. For example, viral and bacterial infections early in childhood – combined with certain genetic markers – may increase the risk for developing food sensitivities. Interestingly, scientists have found an association of rotavirus infections with the development of celiac disease and food allergies. Apart from infections, dysbiotic gut microbiota in infancy has been linked to food sensitivities in adulthood. Interestingly, reduced levels of Bacteroidetes, Proteobacteria and Actinobacteria, together with increased Firmicutes and abundance of the bacterium Clostridium sensu stricto in infancy, have been linked to the development of food allergies2. Also, scientists have found increased Proteobacteria and opportunistic pathogens in the small intestine of people with celiac disease3.   These results point out how a balanced gut microbiota community during the vulnerable period of infancy can protect our guts from food sensitivities later in life.

Your gut has protective effects 

One way our gut microbiota can protect us from food sensitivities is by metabolizing compounds that would otherwise initiate an immune response. In the case of gluten for example, bacteria such as Rothia or Lactobacillus are able to degrade it into smaller compounds that are less likely to cause an immune response.

So, by degrading possible allergens and through activating protective molecular pathways, gut microbes have a key role in preventing the development of food sensitivity. 

Another important product of our gut microbiota that affects food sensitivity is the family of short-chain fatty acids (SCFAs). These compounds are produced by our gut bacteria when we eat dietary fibers. Studies have shown that SCFAs can affect our immune system through interactions with the mucus layer of the intestines. In that way, they can influence whether we will be predisposed to food sensitivities. Also, an interesting mouse study has shown that a high-fiber diet activates many protective pathways in the gut of mice4. In the same study, fiber and SCFAs were found to be necessary for preventing allergic reactions to peanuts! So, by degrading possible allergens and through activating protective molecular pathways, gut microbes have a key role in preventing the development of food sensitivity.  Lastly, our genes of course come into play in this intricate topic of food sensitivities. Nevertheless, the interactions with our environment – even in our first hours of existence – seem to decisively shape our future well-being .

References

  1. Caminero, A., Meisel, M., Jabri, B. & Verdu, E. F. Mechanisms by which gut microorganisms influence food sensitivities. Nat. Rev. Gastroenterol. Hepatol. 1 (2018). 
  2. Ling, Z. et al. Altered fecal microbiota composition associated with food allergy in infants. Appl. Environ. Microbiol. 80, 2546–54 (2014).
  3. Nistal, E. et al. Differences in faecal bacteria populations and faecal bacteria metabolism in healthy adults and celiac disease patients. Biochimie 94, 1724–1729 (2012).
  4. Tan, J. et al. Dietary Fiber and Bacterial SCFA Enhance Oral Tolerance and Protect against Food Allergy through Diverse Cellular Pathways. Cell Rep. 15, 2809–24 (2016).