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How to Do an Elimination Diet, According to a Dietitian

By Elena Donovan Mauer
Reviewed by Daniel Lew, M.D.
April 07, 2022

Many people with chronic conditions wonder if an elimination diet can help them manage their symptoms. Elimination diets are typically used to identify food intolerances and sensitivities, and they may also help people find out which foods trigger symptoms. We spoke with our nutrition expert, Elizabeth DeRobertis, a New York based registered dietitian, to get the full lowdown on how to do an elimination diet and what to expect along the way.

What is an elimination diet, exactly?

An elimination diet is one where you don’t eat any foods that you think your body may not tolerate well. The foods are then reintroduced later, one food at a time, so that you can see if you develop a reaction or symptoms in response to each.

An alternative method of discovery involves removing potentially problematic foods one at a time instead of all at once.

An elimination diet may provide faster relief, but the process of adding back each food will take a little bit longer.

How long should an elimination diet be?

A typical elimination diet lasts five to six weeks; but, some experts say six to eight weeks is even better. The hope is that while you’re on the elimination diet, you will experience a decrease in symptoms. Then, the foods that were eliminated can be added back in one at a time to ideally pinpoint the specific food that your body can’t tolerate well.

Once you identify those trigger foods, you may remove them permanently from your diet, or you may try introducing them again down the line, ideally after six months.

Who is an elimination diet generally recommended for?

An elimination diet is often used when people are having gastrointestinal (GI) issues—such as gas, bloating, diarrhea, constipation, or nausea—and they can’t pinpoint the source of irritation.

Migraine sufferers may try an elimination diet to identify their migraine triggers. Elimination diets are also used to help prevent flare-ups with autoimmune or immune-mediated conditions, such as psoriasis.

It’s important to note that elimination diets shouldn’t be used to pinpoint food allergies. If someone has a documented food allergy, they should not follow an elimination diet, because it includes reintroducing foods that may cause an anaphylactic allergic reaction. Identifying a food allergy should only be done by working with a medical professional. Elimination diets are used to identify sensitivities and intolerances not allergies.

What foods should I avoid?

Which foods you avoid depends on your reason for doing the elimination diet in the first place.

For example, an elimination diet for psoriasis should focus on foods thought to be psoriasis triggers. These may include:

  • Red meat
  • Eggs
  • Dairy products
  • Alcohol
  • Foods high in saturated fat and/or trans fats
  • Refined carbohydrates (such as white flour and white sugar)
  • Nightshade vegetables (such as peppers, white potatoes, eggplant, and tomatoes.)
  • Gluten, which is found in some grains (wheat, rye, and barley)
  • Some condiments and spices. The ones that seem to cause the most trouble for people with psoriasis are pimento, cinnamon, curry, vinegar, mayo, paprika, Tabasco sauce, Worcestershire sauce, and ketchup.
  • Nuts, corn, and soy, if you suspect you’re sensitive to them.

The six-food elimination diet (SFED) is used by people with eosinophilic esophagitis (EoE). This diet eliminates wheat, milk, egg, nuts, soy, fish, and shellfish. An upper endoscopy and biopsy is performed after six weeks of the SFED diet to test for results.

For GI conditions, elimination diets tend to be more restricting. The more foods you remove during the elimination phase, the more likely it is that you will discover which foods trigger uncomfortable symptoms. These foods commonly include:

  • Citrus fruits
  • Nightshade vegetables
  • Nuts and seeds
  • Legumes and soy-based products
  • Starchy foods, including wheat, barley, corn, spelt, rye, and oats
  • Meat
  • Fish
  • Dairy products
  • High-fat foods
  • Alcohol
  • Caffeinated beverages
  • Spices and condiments
  • Sugar and sweeteners

It is important to not only avoid the whole foods you’re eliminating, but to also avoid them as ingredients in other foods. This means you’ll need to check food labels to make sure that the food you’re avoiding is not an ingredient. You may also want to avoid getting takeout or going to restaurants during this process, because you won’t know exactly what ingredients are used to cook your food.

In my office, we also use the low-FODMAP diet for people with complaints of bloating and gas, and irritable bowel syndrome (IBS), as well. FODMAP stands for fermentable, oligosaccharides, disaccharides, monosaccharides, and polyols. Basically, these are short-chain carbohydrates that the body may poorly absorb. Foods high in FODMAP, which should be avoided in a low-FODMAP diet include dairy, wheat, beans, broccoli, onions, apples, and mangoes.

What results can I expect from the elimination diet?

Once all of the trigger foods are eliminated for a couple weeks, ideally, you should be feeling better. If you are, it’s a sign that at least one of the foods you’ve been avoiding was previously causing you symptoms. For example, you may have less gas, bloating, or joint pain. If you have psoriasis, you may see a clearing of the skin.

Any tips for making the diet work?

One of the keys to the elimination diet is keeping a food journal of everything you eat, plus any symptoms you experience. It is really important to write down what you are eating and your symptoms, in order to be able to make specific associations. Things may not be so evident in the moment, but when you look back over a few days, you may notice a trend.

Write down each food as you eat it throughout the day. If you wait until after the fact, it’s easy to forget. You should also jot anything down in your log that is different on those days. Were you under more stress? Did you get less sleep? Did you take any new medications? And then, of course, keep track of any symptoms as they may appear.

Once I’ve eliminated the foods for a while, then what?

The next phase is called the reintroduction phase, where you put the eliminated foods back into your diet one at a time. Each food group should be introduced individually, over two or three days, while you watch for symptoms. This means introducing a new food for two to three days, then removing this food before trying another food group. You can even take longer in between foods, if you like, but it should be gradual. It is also important to start with small portion sizes.

Symptoms to watch for include GI symptoms, such as stomach pain, changes in bowel habits or bloating, but also skin changes, joint pain, and headaches. If one of the foods you reintroduce causes a reaction, then you know it is better to eliminate this food and keep it out of your diet, at least for now. At this point, you should eliminate this trigger food, and wait until your symptoms resolve before reintroducing another food group.

Your next steps depend on what the food is, because it’s important that you are meeting your nutrient needs. If the food that you are sensitive to is corn, for example, and you stick to avoiding corn, you will not have any nutritional deficiencies. However, if the food is in the dairy category, you’ll need to make sure that you identify other sources of calcium.

Also, it doesn’t mean these foods should be eliminated from your diet forever. Every six months, or so, it may be a good idea to try the food again. Often, foods can be tolerated after your body has had a chance to heal, regulate hormones, and the gut microbiome has had a chance to balance itself out.

What else should I know before I try it?

An elimination diet is generally a safe experiment to do for the short term, but be mindful about cutting out too many foods in the long term, as you may create nutrient deficiencies. You can find a registered dietitian to guide you through this process and help ensure you still meet your nutrient needs.

Once you go through this process, you may identify just a couple of triggers, so you may have just a couple restrictions in terms of diet. Most people don’t need to avoid all of the foods they eliminated in the long term.

An ideal outcome would be that you identify a short list of triggers, avoid them for a few months, experience some relief from symptoms, and then eventually add them back in to see if your body has grown to accept them at that time. Some foods may need to be avoided, which will likely be worth it to avoid symptoms and flare-ups.

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