Understanding Food Sensitivities

In a broad approach to nutrition, foods are labeled good or bad based on their macro and micronutrient content (carbs, fats, proteins, vitamins and minerals). But foods can’t be labeled as good or bad without the context of a person. Because different people respond differently to the same food. For example, some people can eat tomatoes with no ill effects and the lycopene and other flavonoids are beneficial. For other people, eating tomatoes may lead to joint pain.

I’m talking about food sensitivities. You have probably heard about food sensitivities and you have probably been told that figuring out your food sensitivities is the key to optimal health. But that isn’t necessarily true and issues with food are more complicated than that.

Allergy vs Sensitivity vs Intolerance

There are two types of food allergies: immediate and delayed onset. Immediate food allergies involve antibodies called IgE that cause swelling, hives, restriction in airway and other severe and potentially life threatening symptoms. These symptoms occur within seconds to minutes of ingestion. Delayed onset involves a different type of antibody called IgG that causes vague symptoms like digestive discomfort, brain fog, joint pain, and skin issues. Reactions can occur days after ingestion. 

Intolerances are when the reaction is due to lack of an enzyme or a nutrient deficiency. For example. lactose intolerance occurs when your body does not produce sufficient lactase to break down lactose.

Sensitivities are a broad classification that can include the delayed onset food allergies, food intolerances, and other adverse food reactions mediated by other mechanisms. 

Identifying food sensitivities

When it comes to identifying food sensitivities, most people want the quick and easy answer. So they turn to blood testing. Blood tests can measure IgA, IgE, and IgG antibodies against specific foods. BUT this isn’t necessarily an accurate or reliable way to assess your food sensitivities. These tests are notoriously unreliable and different labs will provide different results for the same patient. Also, your immune system has plenty of other ways in which it can react to food, so this may miss some key physiology (mast cell degranulation, for example). This is why I don’t put much stock in food sensitivity testing.

So the gold standard to identify food sensitivities is a methodical elimination diet. This involves eliminating specific foods for 2+ weeks and then reintroducing one food at a time in 3-7 day intervals while assessing symptoms.

For the most part, I don’t advise most patients to do testing or a full elimination diet. I often advise modified eliminations diets based on the research associated with specific diagnoses. For example, I advise my Hashimoto’s patients to eliminate gluten, dairy and soy while undergoing treatment. BUT most food sensitivities are simply a symptom of a deeper imbalance in physiology. So rather than put energy and time into identifying food sensitivities, we focus on correcting the root cause.

Root Causes of Food Sensitivities

For many food sensitivities (but not all), the root cause is increased intestinal permeability. This means that the lining of your gut is not intact. There are holes between gut cells or even through gut cells. This allows undigested food and bacterial proteins to interact with your immune system in a way they normally wouldn’t, leading to immune responses to food (aka food sensitivities).

So why is the gut leaky? You may have been told that food sensitivities are what cause leaky gut. But that isn’t necessarily true. Consuming foods that your immune system is reacting to will promote inflammation and maintain the leaky nature of the gut, but the food itself often didn’t start this vicious cycle.

So what is the most common root cause of leaky gut? Imbalances in gut bacteria. If you have too many bacteria that produce a toxin called LPS, you will have impaired intestinal permeability. Inflammatory LPS is primarily produced by bacteria in the Proteobacteria phylum. This includes Escherichia, Klebsiella, Pseudomonas, Enterobacteri, Bilophila, and Desulfovibrio species.

So the key to resolving your food sensitivities and your gut health is not necessarily to eliminate more and more foods from your diet. The key is keep your gut bacteria healthy and happy.


  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3562736/

  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3562736/

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I'm Dr. Carly and my mission is to create a health revolution. I believe that another prescription is not the answer. I believe in using natural therapies that go beyond the symptoms. And I believe that doctors should spend way more than 7 minutes with a patient.