IgG testing results sample

Food sensitivities: Why you react, and how to identify your trigger foods

Food can be a minefield!

Food provides the building blocks for life, can act as medicine, and is associated with celebrations and our most memorable times, sharing with family and friends.

Yet, food can also be a source of fear and confusion, ill-health, and toxicity in the body. We can spiral into a hole of poor gut health and inflammation, reacting to more and more to foods, still not knowing exactly which foods are triggering us. Some people then end up eating a severely restricted diet and become afraid of food in general.

Common digestive symptoms include bloating, wind and diarrhea. We may not have yet connected the dots between what we eat and seemingly unrelated symptoms such as migraines, joint pain, eczema, fatigue or sinus congestion, and mood disturbances.

Adverse food reactions fall into four causal categories.

  1. Immune system mediated – antibodies and inflammation in response to particular foods
  2. Digestive tract mediated – e.g. enzyme dysfunction such as a lactase deficiency which results in an inability to break down lactose, found in dairy
  3. Gut fermentation mediated – high FODMAP foods may lead to a worsening of symptoms. Read about the Low FODMAP diet here.
  4. Something else in the food e.g. salicylates, oxalates, sulfur, histamine, lectins

This article will explain how immune-system mediated over-reactivity comes about, and how to identify which foods are may be affecting you. My aim is help you understand the reasoning behind the interventions I suggest in my second article (released in the next week or so) on lessening these reactions.

Immune Tolerance

A huge proportion of our immune system lives within the lining of the Gastro-Intestinal (GI) tract. The immune cells that line our GI tract have two critical jobs:

1) Defend us from potentially harmful ‘pathogens’ in our guts (e.g. bacteria or viruses that are a threat)

2) To not react to food that we eat, and the bacteria in our gut. The immune system should actively suppresses a reaction to these.

It turns out that most of the time, the role of the immune system is actually NOT to respond to things. It should only react when there actually is a real threat. This concept of an appropriate response to our food and environment is called Oral Tolerance. Oral intolerance normally develops through a baby’s contact with their parents and breastfeeding. The first 1000 days of life are therefore very important in establishing immunity in general.

If we lose oral tolerance, we can start reacting to foods that we eat, and often we also develop increased intestinal permeability (leaky gut), inflammation, and digestive discomfort. This may progress to the stage where our immune system starts targeting our own tissues and organs (auto-immunity). And so it’s important to work on improving gut health not just to reduce food sensitivities themselves, but also to prevent progression of an auto-immune process.

Testing for Food Sensitivities

The first step you should take when working to lessen food sensitivities is to temporarily remove trigger foods from your diet. We can then work to improve your overall gut health so that you are better able to tolerate foods without an exagerated immune response.

But how do you know all the foods that you are reacting to?

One of the best ways to identify food sensitivities is an elimination diet. An elimination diet involves removing all suspect foods, that may be triggering the immune system, for a limited time (at least 3 to 4 weeks, and up to 3 months). After this period, foods are re-introduced systematically, every two or four days whilst keeping a close eye on your symptoms for a reaction to the food. In that way, we can identify which foods that you are react to. How long you avoid the trigger foods before re-introducing them, and how often you re-introduce them will depend on the severity of your symptoms.

Whereas lab testing only tests how certain parts of the immune system (such as IgG) respond to foods, an elimination diet paints the picture of how the body as a whole responds to the food. This is important as there may be other causes of a reaction other than just IgG antibody reactions.

Eight common foods that are often temporarily eliminated by someone suspecting food sensitivities are dairy products, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat and soy containing foods. Other options include the Functional Medicine elimination diet and the Autoimmune Paleo diet, but both of these diets eliminate more than these 8 foods and so are more limiting in what you can eat.

An elimination diet like this can be empowering but it is also restrictive, mentally challenging and time-consuming. An elimination diet, combined with IgG food reactivity lab-testing, provides the most complete view of food sensitivities. If a strict elimination diet is not possible for a person, then lab-testing alone is still a valuable option.

Ultimately, my goal when I work with clients is to get them on the least restrictive and simplest diet possible that has the biggest impact on their health and vitality. It can be beneficial to work with a practitioner as the foods that need to be eliminated varies from person to person, as does how the duration the food re-introduction phase – it can be quite overwhelming with support!

IgE – Allergic Reactions

In this article, I’m not going to go into detail around allergic IgE mediated, but I am going to focus on IgG food sensitivities. The difference between the two is IgE symptoms develop within a couple of minutes to one or two hours after eating a food and include symptoms such as hives, congestion or swelling of the throat. If you suspect a true allergic reaction to a food, please speak to your GP or contact me for further details on lab testing as I’m not going to focus on true allergies in this article. It is also possible to reduce the severity of IgE reactions, but not typically get rid of them, through nutritional support and Functional Medicine.

IgG Food Reactivity Lab-Testing

IgG antibodies tend to be associated with food sensitivities, and are produced from 3 to 72 hours after a food is eaten. At low levels, IgG antibodies are protective and their production is expected but at higher levels, they are associated with inflammation and typical IBS type symptoms. An IgG-mediated reaction to a food may not be noticed until more than 24 hours after eating a food, and remain in the body for weeks after a reaction is triggered, making identification of food sensitivities difficult without an elimination diet or lab testing.

There are many versions of IgG antibody testing to foods, and this diversity of testing can make choosing the right test confusing and overwhelming. Interpretation also benefits from professional help as the key to real improvement is not to only identify and remove trigger foods from the diet, but also support the gut and immune system so that it’s not so reactive. Our intention should always be to eat as varied and nutrient-rich diet as possible.

I recommend food sensitivity testing that measures the response of your immune system to foods (through a blood sample). It’s important that the test measures the IgG antibody reaction and also something call Compliment which measures actual tissue damage.  By measuring both IgG and Compliment simultaneously, we get a much clearer signal of activation of the immune system, giving more accurate results than other IgG food tests that only measure IgG. To find out about or order the food sensitivity testing I recommend, see here.

It is however important to note that some people, that have a severely impaired immune system, may not be capable of launching an immune response to trigger foods. In which case, IgG food sensitivity testing would be essentially useless.

How to Reduce Food Sensitivities

In the second article in this series, I take a deep dive into what you can do to reduce food sensitivities and improve your oral tolerance.

If you have any questions, I’m always happy to help so please get in touch. To know more about how you can work with me, you can find out more here.


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Stephen Ward (MSc) is trained in assessing the root cause of chronic health issues through Functional Medicine.

He uses nutrition, lifestyle changes, and nutraceuticals (targeted supplements) to help you achieve your goals and improve your health.

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