Is Our Restriction of Food Groups Actually Causing Us to Have More Food Intolerances?
The short answer: yes.
Every day you hear about people restricting certain foods or food groups. Many times it is because of a new fad diet such as paleo, keto, or the raw food diet, but sometimes people legitimately talk about having foods that their body “doesn’t digest”. I’ve heard clients as well as friends and family say their body does not tolerate certain foods, or some people straight up avoid foods because they heard they were “bad” for them. The lists of food people avoid ranges from sugar, wheat, dairy, meat, “processed” food, even certain fruits and vegetables; the list goes on and on. When I was growing up there weren’t droves of people that couldn’t eat certain foods, or who chose to avoid entire food groups on their own volition. This leads me to wonder… are we actually causing ourselves to have more food intolerances by restricting ourselves of certain foods?
Allergies vs. Intolerances
The Centers for Disease Control and Prevention reports that the prevalence of food allergy in children increased by 50 percent between 1997 and 2011. Additionally, between 1997 and 2008 the prevalence of peanut or tree nut allergy appears to have more than tripled in US children. But these are food allergies, not intolerances. A food allergy is something that is considered a medical condition that produces a harmful immune response. A food intolerance, or functional gastrointestinal disorder (FGIDs) is something that isn’t necessarily (but can be) harmful for your body, but produces unfavorable digestive issues. And because FGIDs are often self-diagnosed and not often monitored by a medical doctor, the research and statistics on them are sparse.
What helps us digest food
What we DO know about food and metabolism is that it is a complicated system with many moving parts; specifically hormones and gut microbiome (the microbiome in our guts is comprised primarily of bacteria but also includes fungi, yeasts, and parasites). Insulin, glucagon, leptin, ghrelin and hundreds of bacteria found in our gut are all responsible for how our body digests food, how quickly it moves food through our system, and how our tummy feels after a meal. When we remove foods from our diet (by diet I mean the foods in general that we eat) our hormones and bacteria are altered. In general it looks like this:
You restrict foods/ food groups
Change in hormones/ decrease in gut microbiome
Temporary improvement in symptoms
Change in metabolism/ rate of digestion
Get off new diet
Old foods cause issues
Confirmation bias (our bias that we are intolerant to these foods is confirmed).
In looking at several different studies on the influence of diet on our gut microbiome, it is clear that the evidence shows that partaking in most restrictive diets leads to a decrease in the number of bacteria in our guts. The research looked at many different diets; high protein/low carb, gluten free, vegan, and Mediterranean diet to name a few. It was shown that the only one of these diets that did not cause a decrease in gut microbiome was the Mediterranean diet. This diet includes a variety of foods and does not eliminate any food groups.
Our gut microbiome (bacteria) is incredibly important. The higher amount of bacteria in our stomach, the greater number of foods we can digest, thus causing less FGID’s. Think of each bacterium in your stomach as a little enzyme that is there to help digest all the various foods you eat in a day. It makes logical sense that the more diverse this bacterium is in your body, the easier it is to digest all the various food you eat. If you stop eating all types of food, your body will stop having as many different types of bacteria.
Additionally, it has been shown that greater numbers of bacteria in our gut contribute to better overall physical health. In other words…. bacteria is the shit. The more you have the better.
What should you eat?
What do we do with this information? If you want to improve your digestion, my recommendation is to only eliminate foods that you absolutely suspect might be causing you digestive issues. And if you do not have problems with digesting food, absolutely do NOT eliminate foods or food groups. You run the risk of reducing your gut bacteria and actually causing food intolerances.
Do not believe all the hype you read about foods being “bad” for you and definitely do not go on any fad diets! The best advice, as always, is to eat ALL foods in moderation, except of course, if you have a legitimate food allergy.
Boyd, C., Abraham, S., & Kellow, J. (2010). Appearance and disappearance of functional gastrointestinal disorders in patients with eating disorders. Neurogastroenterology and Motility, 22(12), 1279–1283.
Janssen, P. (2010). Can eating disorders cause functional gastrointestinal disorders? P. Janssen Eating and functional gastrointestinal disorders. Neurogastroenterology & Motility, 22(12), 1267–1269.
Talley, N.J. (2008). Functional gastrointestinal disorders as a public health problem. Neurogastroenterology & Motility, 20(1), 121-129.
Bird, A., Conlon, M. (2015). The Impact of Diet and Lifestyle on Gut Microbiota and Human Health. Nutrients 17(1), 17-44.
Singh, R. Chang, H., et al. (2017).Influence of diet on the gut microbiome and implications for human health. Journal of Translational Medicine. 15(73),