Understanding Food Intolerances




One of the main complaints I hear from people I work with is that they are becoming more and more intolerant to foods, but they are having trouble pinpointing which foods are causing the problem.

So this post is all about how you can begin to understand your food intolerances, and how to identify them.


Firstly, I think it’s important to point out that there is a huge difference between food intolerances and allergies, as the terms are often used interchangeably, when they are in fact very different.


Food allergies are classified by an exaggerated immune system response to a food protein and the body triggers an allergic reaction as a result. They usually develop in childhood, and are not necessarily something you can overcome, although some people do seem to grow out of them.

On the other hand, food intolerances are an adverse reaction to a food that does not involve the immune system. Reactions can be immediate or delayed up to 20 hours after a food is eaten...hence being difficult to pinpoint the culprit in many cases. The good thing about food intolerances is that they can be temporary, and are more a sign of dysfunction in the digestive system. The key to overcoming them, is to identify why you have lost the ability to digest certain foods in the first place. Avoiding them in the short term helps a lot with reducing symptoms, but it’s not a good long-term solution, as most people will slowly become intolerant to more and more foods over time and end up on a very limited diet which isn’t fun, or beneficial for your health in the long term.


The only accurate way to identify food intolerances is through an elimination diet. Unfortunately tests that claim to identify food intolerances are not reliable and often leave you with a long list of random foods to exclude from your diet, which in many cases is unnecessary, and misses the foods that are actually problematic.

Why are the common food intolerance tests not helpful? Let's take a look.

ELISA and ALCAT are both blood tests that claim to identify food intolerances. They look at how your blood responds when exposed to a specific food. ELISA measures IgG antibody reactions. ALCAT measures white blood cell reactions. These sound like plausible theories, right? Antibodies and white blood cells are part of your immune system. If your immune system reacts to a food, that would obviously signify intolerance. It turns out that some studies show that an IgG response to a food actually indicates tolerance. And white blood cells constantly change shape and activity anyway, so if they do that in the presence of a food, that doesn’t mean the food was the trigger. Not surprisingly, both tests are notorious for inconsistent results.


The most common causes for food intolerances are related to dysfunction in the gut. You may have an overgrowth of bacteria in the small intestine (SIBO), which means that when you eat foods that are normally broken down by gut bacteria in the large intestine, this starts to happen in the small intestine. The result is gas production, and when this happens in the small intestine, it can result in extreme bloating, uncomfortable gas and changes to bowel movements.

Another common cause for developing food intolerances is nervous system dysfunction, which is generally driven by stress and anxiety. To put it simply, your nervous system may often be in a state of ‘fight or flight’, which results in your digestion being “switched off”, leading to lower production of HCl in the stomach, and pancreatic enzymes, needed to break down the foods you eat, as well as changes to motility, causing your digestion to either slow down (constipation), or speed up (diarrhea).


As you can see, it is really important to address the underlying issue, rather than stop at simply eliminating foods you are intolerant to. However, working out your food intolerances can help to reduce your symptoms in the short term, and reduce inflammation in the gut.

As I mentioned before, the only accurate way to do this is to work through an elimination diet, and starting with the most common foods that people with digestive issues are intolerant to is a great place to start.


I recommend beginning with gluten, dairy, and FODMAPs. It is important to note that gluten is not a FODMAP, but it is common for those