Elimination Diet 101 for Discovering Food Allergy or Intolerance

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We hear it often in food allergy circles - If you think you're allergic to a food, just do an elimination diet. 

What I find is, while we toss the term around freely, many are confused about exactly what an elimination diet is and how to conduct one to determine if a food is causing symptoms of intolerance or an allergic reaction. 

Here, we'll clear up those gray areas and cover the basics about elimination diets to detect food allergy or intolerance.

NoteIf you are unsure about conducting an elimination diet, or if you believe you have a life-threatening food allergy, DO NOT begin an elimination diet. See your physician first.

What is an Elimination Diet? 

Eliminating a particular food from the diet for a short time – usually two to four weeks – is a useful approach to determine whether a particular food is the source of symptoms of food allergy or food intolerance.

{food allergy ~ an adverse immune response to a food, usually a food protein. For example, breaking out in hives after exposure to peanuts.}

{food intolerance ~ adverse digestive system response to a food; not an immune response. For example, abdominal bloating after consuming milk is an example of a food intolerance (specifically, lactose intolerance)}

When is an Elimination Diet Useful?

There are several instances when allergists find elimination diets useful in accurately diagnosing patients with (or ruling out) food allergy or sensitivity.

1. When allergy testing is inconclusive.

Negative test results with symptoms.

If food allergy tests come back negative when an individual continues to experience symptoms, an elimination diet may help identify food allergy or sensitivity the test did not detect.

Positive test results without symptoms.

If food allergy tests come back positive when an individual experiences no allergic reaction or apparent sensitivity to the food in question, an elimination diet may help rule out food allergy or sensitivity.

2. To determine if symptoms are caused by something other than food sensitivity.

Other medical conditions can mimic food allergy or sensitivity symptoms.

For example, an individual with gallstones may experience diarrhea, abdominal pain and bloating after eating a food like pizza and attribute it to a sensitivity to dairy (cheese). However, it may not be dairy causing the issue at all. Instead, it may be the pizza contained a high amount of grease, which is known to aggravate gallstones.

This is a great example of why it is always important to speak to your physician when you suspect a food allergy or intolerance.

If you do so and you both determine an elimination diet is the next step to diagnosis for you, here is an overview of how an elimination diet works. 

How does an Elimination Diet Work?

A single food is completely removed from the diet for two to four weeks.

During the elimination period:

  • Remove all forms of the offending food from the diet.

This means “whole” sources of the food as well as secondary sources.

For example, if you are eliminating soy, avoid obvious sources like whole soybeans and soymilk, but also be sure to avoid soy in foods like canned tuna, Asian dishes and foods with added hydrolyzed vegetable protein, which also contain soy. (Note: this is an example and by no means an inclusive list of all sources – whole or secondary – containing soy.)

  • Keep the rest of your diet the same as before the elimination.

Changing more than one food at a time makes it impossible to know which food is causing issues.

Eat simple foods you prepare yourself, to avoid the possibility of cross-contamination.

  • Keep track of your symptoms and any changes in them during the elimination.

A food journal is a useful tool for doing this.

Write down what you eat at each meal and how you’re feeling.

Be specific about symptoms, their severity and duration. Note if symptoms decline or are absent.

Keep your food journal handy during the elimination period so you’re able to record all foods eaten and any reactions or symptoms. 

What Happens at the End of the Elimination Period?

If symptoms do not improve during the elimination period, the food in question is likely not causing the symptoms.

That means it is time to look to the next possible culprit in your diet.

However, if your symptoms improve or go away entirely, it is a good indicator you have an allergy or intolerance to the eliminated food.

Next, you may consider a reintroduction. 

What is Reintroduction?

Some physicians recommend reintroducing the eliminated food to confirm it causes your symptoms.

Suspect foods are typically reintroduced gradually in small amounts. (This is also called a “challenge”.)


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