Ask The RDN: Food Sensitivity Tests For Athletes

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Many runners feel lost when it comes to figuring out their gastrointestinal system woes.  They might try to remove multiple food groups and spend copious amounts of money on testing to try to figure out a connection to their stomach pains and emergency pit stops on runs.  All too often, this leads to more confusion, a rocky relationship with food and the potential for nutrient deficiencies to develop.

To understand what’s behind your digestive woes, it is important to differentiate between a true food allergy and a food sensitivity or intolerance.

If you have a true food allergy the response is based in the immune system, while food sensitivities and intolerances stem from the digestive system.   When you have a food allergy and your body encounters a small amount of this food, it produces a histamine response and symptoms such as dizziness, swelling, nausea and hives can occur. With a food sensitivity or intolerance, the digestive system can’t properly break down a particular food. This can be due to a lack of enzymes to digest a certain food, food chemical & preservative sensitivity or lack of ability to process certain types of carbohydrates.

Traditional food allergy testing is done by a skin prick or blood test and measures a protein called Immunoglobulin E or IgE. The presence of IgE antibodies usually indicates a true immune response. Food sensitivity tests usually measure the presence of IgG antibodies, not IgE, and these antibodies have not been reliably shown to identify food allergies or sensitivities. In fact, many people produce IgG antibodies just after eating food.  Unfortunately, restrictions suggested by the IgG antibody tests can cause people to unnecessarily restrict foods that have no impact on their stomach woes.

What Next?

It may not be the answer that many runners want to hear, but a traditional elimination diet and food journal is currently the best way to go.  If you haven’t tried this method before, it is pretty straightforward.

#1) Keep a detailed food journal for a few weeks, and include when you experience stomach issues

#2) Try to hone in on potential food or beverage triggers. Once these are identified, remove all suspected food triggers for 2-3 weeks.

#3) After 2-3 weeks time, reintroduce specific foods in an organized manner.  Typically, it is a good idea to reintroduce a small amount of a food on the first day of reintroduction, a medium amount on the second day, and a large amount on the third day.  Journal if you have symptoms while reintroducing so that you can pinpoint actual triggers. If you do identify trigger foods, you will need to eliminate it from your diet to avoid future problems. It is important to keep in mind that you do not want to reintroduce multiple foods at one time or you will not be able to successfully determine what is causing your problems.

Sometimes elimination diets can become overwhelming or confusing, especially if you are eliminating multiple food groups at one time.  If this is the case for you, reach out to a doctor or sports dietitian to help with the process and avoid nutrient deficiencies.

Do you have a question for our RDN? Send your trail-running-nutrition quandaries to

Kylee Van Horn is a licensed Sports Registered Dietitian and competitive trail runner.

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