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Is the IgG Food Intolerance Test Reliable?

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Many individuals experience strong reactions to certain foods, but they often confuse a food allergy with a food intolerance or use these terms interchangeably. A food allergy occurs when the body initiates an immune response, producing IgE antibodies. Conversely, a food intolerance does not involve this immune reaction, meaning no antibodies are generated. However, confusion arises as some laboratories conduct tests for food "intolerance" using IgG antibodies. This raises the question: if antibodies such as IgG, IgE, IgA and IgM indicate an immune response, why test for IgG antibodies for a food intolerance which is not considered a immunologic reaction? Can IgG tests accurately identify a food allergy? If not, why are they offered?

It is normal that our immune system produces antibodies to foreign proteins, such as those in food, therefore, when we consume food, our bodies may react to the proteins present by producing IgG antibodies. This process, the production of IgG antibodies to food, is part of the normal functioning of the immune system. For this reason, IgG testing lacks reliability and is not recommended for determining the presence of a food intolerance, as a food intolerance is not considered an immunologic reaction to begin with. In addition, an IgG test cannot test for a food allergy either, as food allergies are specifically connected to IgE antibodies, not IgG antibodies.

Interpreting IgG Results

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IgG tests look at lots of different foods and tell people which ones they might be "intolerant" to. Interestingly, the results often show that individuals are intolerant to foods they really like or eat often. But as mentioned in the previous paragraph, IgG might just show that that these foods have been eaten, not that there is an intolerance or allergic reaction to these foods. Could this explain why the results seem to line up with people's favorite or regular foods?

As mentioned before, IgG shows the body's normal response to food. But how strong this response is doesn't seem to relate to any health problems. In other words, there's no evidence to suggest that having higher or lower IgG responses means you're healthier or unhealthier.

Why Individuals Feel Improvement After Following IgG Food Elimination

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If IgG testing isn't proven to be reliable for finding food allergies or intolerances, why do many people say they feel better after cutting out foods from the list? And when they start eating those foods again after a break, some say they don't have any food-related problems anymore. How does that work?

Whenever someone makes changes in their daily routine, they often feel better, even if it's just because they believe they will. This is called the placebo effect. In food allergies, this effect can be quite strong, with about half of the people feeling better after they cut out certain foods. But to really know if someone has a food allergy or intolerance, doctors need to do a special test where neither the patient nor the doctor knows if they're eating the problematic food or not.

Some individuals find relief by cutting out gluten and high lactose foods, but IgG tests often lead to over-restriction or removal of too many other unnecessary foods, which often pose no issues to an individual, affecting quality of life. Changes in diet may alter gut bacteria, potentially reducing sensitivity to certain foods over time. Other reliable and scientifically accepted exclusion methods, such as elimination diets under professional guidance, are more targeted based on personal signs and symptoms and can achieve improvements without the drawbacks of IgG testing.

Is There Any Reliable Food Hypersensitivity Test?

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Is there a single test that accurately identifies which foods someone is allergic or intolerant to? If not, what are the scientifically validated diagnostic methods for detecting these conditions?

The most reliable test for confirming a food allergy or intolerance is the double-blind placebo controlled food challenge. However, this procedure is time-consuming and impractical for everyday use.

For food allergies, additional diagnostic tests include the skin prick test and specific IgE detection in the blood. These tests only detect sensitization, and clinical relevance must be confirmed through a reliable history or the food challenge test mentioned earlier.

Food intolerance can only be confirmed through provocation tests, such as the hydrogen breath test for e.g. lactose intolerance. However, an elimination diet under professional guidance is widely accepted as the most reliable method for identifying food intolerances.

Are There "Silent" Food Hypersensitivities?

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Food allergies or intolerances typically lead to noticeable signs like itching, swelling, rashes, or digestive issues. However, some claim that intolerances may not always show obvious symptoms, prompting tests to identify "silent" damage or metabolic blockages caused by food. Is there a test for this?


Given food's vital role in life and quality of life, the body usually shows clear objective symptoms if food or its ingredients cause harm. Thus, "silent" food hypersensitivities lack scientific evidence. 


Genetic Testing

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Does genetic testing provide more benefits than traditional diagnostic methods?


Currently, there's little evidence supporting the use of genetic testing for common lifestyle-related diseases like metabolic syndrome, type 2 diabetes, or cardiovascular diseases. It doesn't seem to offer significant advantages over methods like family history or blood glucose tests. Despite substantial investments and research on risk alleles, genetic testing hasn't notably enhanced diagnoses.

Is Genetic Testing Useful for Personalized Nutrition?

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The connection between nutrition and our genes works in two ways. Our genes determine how we react to certain nutrients, as genetic testing shows. Conversely, nutrients and other environmental factors can influence how our genes function, known as epigenetics, which is the opposite effect. Since this relationship could lead to ongoing changes in our genes, how useful is genetic testing for personalized nutrition when it only considers one side?

Most studies investigating the impact of genetic information on counseling haven't found evidence that people are more likely to follow dietary advice or improve their lifestyles. This was also the main finding in Food4me, the largest study on personalized nutrition to date. While some individuals may benefit from knowing this information, for the majority, it doesn't seem to make a difference.
Additionally, considering that many diseases, such as cancer, involve many risk genes, and are constantly influenced by external factors (epigenetics), the complexity of DNA and the usefulness of DNA testing raises critical concerns. Following traditional approaches with less rigid parameters may therefore be preferable for the time being.

The Issues of Direct-To-Consumer (DTC) Genetic Testing

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Direct-to-consumer (DTC) genetic testing, offered by sequencing companies, raises ethical concerns regarding potential misinterpretation of genetic information without professional guidance. What are the risks?


In the case that a genetics test is done, it is strongly advised that genetic counseling should be carried out by a professional to provide proper context and risk perception for the findings. 



Can A Gut Microbiota Test Show Me The Health of My Gut Microbiota?

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The importance of a healthy gut microbiota is becoming more and more popular. Can I therefore do a gut microbiota test to see if I have a healthy gut microbiota? 


Gut microbiota tests are not generally advised for several reasons. 

  1. Uncertain Science: The science around gut microbiota and its impact on health is still evolving. While we know that a healthy gut microbiota is generally diverse, the clinical significance of specific microbial compositions is often unclear.

  2. Individual Variability: Gut microbiota can vary widely between individuals and can even change within the same individual over time. Each person's gut microbiota is unique, similar to a fingerprint, which makes it difficult to establish a standard for what constitutes a "healthy" gut microbiota.

  3. Limited Evidence: There is limited evidence to suggest that altering gut microbiota based on test results leads to meaningful health improvements. While some studies have shown associations between certain microbial patterns and health conditions, causation has not always been established.

  4. Questionable Tests: Many gut microbiota tests marketed to consumers lack scientific validation and may provide misleading or inaccurate information. Without proper validation and standardization, the reliability and accuracy of these tests are questionable.

Given these factors, it's important to approach gut microbiota testing, food intolerance testing and genetic testing with caution. Consulting with a licensed nutrition professional, such as a Certified Nutrition Therapist, can offer guidance on individual health and provide recommendations for improving gut health, as well as improving signs and symptoms of food hypersensitivities, that are in accordance with widely accepted and reliable methods, as well as established principles of nutrition and lifestyle.

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