Updated: Nov 3, 2018
Many food reactions are not classical IgE-mediated allergies, but instead are food sensitivity/intolerance. So how do you know which foods are problematic to you?
People who are allergic to some food, especially peanut, eggs or shellfish will respond very quickly if they are exposed to a tiny amount of the food allergens causing symptoms such as rashes, swelling, difficulty breathing and anaphylactic shock. This is known as IgE-mediated allergies which can be life-threatening. On the other hand, people may develop IgG antibodies in response to food they usually eat. Symptoms may include bloating, diarrhea, migraine headache, skin and respiratory conditions as well as lethargy. If you experience these symptoms but do not seem to relate them to anything in particular, it is possible that these may be due to food sensitivities.
There are also non-immune mediated food reactions such as lactose intolerance, which is caused by a deficiency in enzyme lactase responsible for digesting certain sugar in milk (i.e. lactose). Undigested lactose cannot be absorbed in the small intestine, and therefore passes into the large intestine where it is fermented by the gut bacteria resulting in unpleasant symptoms such as diarrhoea. Histamine intolerance can be caused by a lack of histamine-degrading enzyme leading to histamine overload in the body which can result in allergy-like symptoms.
One thing to bear in mind is that unlike IgE-mediated allergies, IgG-mediated food sensitivities are usually delayed response meaning that you may notice a reaction several hours or even days after eating certain foods. Also, IgG food intolerance may develop as a result of high levels of exposure to a food allergen (i.e. eating a lot of same food on a regular basis).
“Unlike IgE- mediated allergies, IgG-mediated food sensitivities are usually delayed response meaning that you may notice a reaction several hours or even days after eating certain foods.”
How to test for food sensitivities
There is laboratory testing for IgG and/or IgA antibodies to a range of food antigens (i.e. protein extracts) which can be done using a simple pin-prick blood sample. The test is quite expensive depending on how many foods you want to test (up to 200+ at one time). The methodology of the test is considered plausible based on the premise that elevated IgG and IgA antibodies against food antigens indicate a breakdown in immune tolerance. However, the reproducibility depends on the specific lab procedure which may differ from lab to lab. In addition, the accuracy of the test may be questionable due to factors such as antigen purity and whether the antigens are from cooked, processed or raw foods as their capacity to stimulate an immune response can be affected. IgG food sensitivity testing has been published in peer reviewed journals, and may be used as a guidance for elimination diet. However, it is currently not recognised as diagnosis of food intolerance by allergy and immunology organisations worldwide. More robust and direct clinical evidence linking IgG food sensitivity testing to symptoms is needed.
On the other hand, one clinical trial revealed that patients with irritable bowel syndrome who follow individualized diets based on food sensitivity testing (by measuring white blood cell reaction) achieved significant improvement in their symptoms. The study is claimed to be the first to provide scientific evidence for this medication-free approach to a debilitating condition. However, the results warrant reproducibility in larger and more diverse samples.
Food sensitivity has been shown to be an important trigger for people with an autoimmune condition. A recent observational study concluded that IgG food intolerance testing is a very important tool in patients with autoimmune disease, and should be used to tailor a personalised diet program, which if properly followed, could alleviate symptoms and may stop or slow the the progression of the autoimmune disease.
In fact, the cheapest and most effective way to test if you are sensitive to any food is to keep your food diary and follow elimination diet by removing the suspicious foods from your diet for at least 4-6 weeks, then reintroducing one food at a time to see how your body reacts. Elimination diet can help us understand whether there is a connection between food and symptoms. Common foods that most people are sensitive to include gluten containing grains (i.e. wheat, barley, rye), dairy, corn, soy and egg.
What does it mean if I have multiple food sensitivities?
Multiple food sensitivities may be indicative of increased gut permeability (i.e. leaky gut syndrome), the condition where connections between the cells that line the inside of the gut become looser. When the gut is leaky, it allows large molecules such as improperly digested food particles to pass through the gut wall triggering the immune response and causing inflammation in the body that may manifest in a range of health issues. Irritable bowel syndrome (IBS), migraines and autoimmune conditions are known to be partially caused by immune reactions to foods. Eliminating foods that are aggravating the immune reactions is a way to reduce inflammation and support gut health. It is very important to improve the integrity of gut lining during the elimination period.
At some point, most people should be able to reintroduce foods that once they were unable to tolerate. These foods may be consumed on a long rotation i.e. once every 1-2 weeks, depending on when you discover the level that triggers your symptoms. Bear in mind that some foods, especially gluten has been shown to increase gut permeability in both coeliac and non-coeliac gluten sensitive patients. Notably, it is crucial to rule out coeliac disease (consult with your GP), especially if you have a family history of autoimmune disease as people who have been diagnosed with coeliac disease need to eliminate gluten permanently from their diet.
In conclusion, understanding the relationship between symptoms and foods may help individuals uncover the underlying cause of their health issues. Sensitivities to common foods can stimulate immune response that leads to chronic inflammation in the body. Elimination diet is the gold standard to determine food sensitivities. Although it takes a lot of effort and requires patience, it is accurate and individualised. Everybody is different so do listen to your body.
Last updated 3/11/18