The elimination diet explained

Could the food you eat be the cause of your unidentified symptoms? Find out how an elimination diet may help you discover if you might have a food intolerance or food allergy .

Food provides nutrients your body needs, but some of it can trigger negative reactions. If digestive symptoms plague you after meals, you may have a food allergy or be one of the approximately 15 to 20 percent of the population who has a food intolerance.

To diagnose the culprit, your doctor may suggest an elimination diet. “There are many different types, and the plan will be personalized to you and your individual triggers,” says Tamara Duker Freuman, a registered dietician and author of The Bloated Belly Whisperer.

Can an elimination diet help identify the cause of your symptoms? Here’s what you need to know about these medically supervised eating plans.

What is an elimination diet?

An elimination diet is a short-term eating plan that takes out certain foods (or groups of foods). “Generally, elimination diets are for people who have a digestive issue and cannot pinpoint the source of the problem,” says Natalie Rizzo, a registered dietician in New York City. When you remove suspect foods for a certain period of time and then reintroduce them, you can better determine what might be causing symptoms or making them worse. However, not all digestive problems are related to food, so it’s important to work with a medical professional before starting an elimination diet.

Food allergies vs. intolerances

Food allergies and intolerances are different, but in some cases, the symptoms may be similar. An allergic reaction is an immune system response: The body produces antibodies to fight off a substance in an offending food that it believes is harmful. Symptoms of an allergic reaction may affect the skin, digestive system, respiratory system, or entire body. If you’re allergic to a food, eating it may cause hives, stomach pain, diarrhea, itchy skin, shortness of breath, chest pain, and swelling of the airways. If not treated, some allergic reactions result in anaphylaxis, a life-threatening condition.

An estimated 32 million Americans suffer from a food allergy. The eight most common food allergens are milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and soybeans, according to the U.S. Food and Drug Administration. Food allergies are diagnosed by a doctor, usually using a combination of skin and/or blood tests as well as an elimination diet.

A food intolerance, or sensitivity, is caused when your body has trouble digesting a food—either because you don’t have an enzyme to break down a specific compound or your body reacts negatively to an additive or naturally occurring compound in the food. Symptoms of a food intolerance are often digestive—such as nausea, stomach cramps, gas, bloating, vomiting, heartburn, and diarrhea—but they may also include headaches, irritability, and nervousness. There is no medical test for food sensitivities, so doctors use elimination diets to identify them.

How to do an elimination diet

A doctor (often a gastroenterologist or allergist) or a registered dietician nutritionist should design and supervise your elimination diet. The plan will be divided into two phases that last approximately three weeks each, Rizzo says. Before you begin an elimination diet, your doctor or nutritionist may have you keep a log of everything you eat—as well as any symptoms you experience—to help narrow down which foods to eliminate during the first phase of the plan. Ideally, at the end of the diet, you will have a better idea of which foods cause adverse reactions so you can avoid them.

The elimination phase

During the elimination phase, you cut out the foods your doctor or nutritionist suspects might be causing your symptoms. (For example, to test for lactose intolerance, you’d remove all dairy from your diet during this period.) This first phase lasts two to three weeks, since it takes that long for foods to completely clear out of your system so your symptoms improve, Rizzo says.

The reintroduction phase

If your symptoms improve, that indicates a certain food was the culprit—and this second phase will help identify it. During the reintroduction period, you’ll eat a small amount of one restricted food for a day or two and record any symptoms you experience. If you feel okay, you’ll increase the amount. You’ll continue introducing one of the eliminated foods every two to three days until all of the potentially problematic foods have been tested.

Foods you can eat on an elimination diet

There’s no set list of foods you’re allowed to have while on an elimination diet, since the plan is customized for every person. However, there are some foods that are less likely to cause negative reactions, and will likely be on your approved list. They include:

  • Vegetables: Most veggies are allowed on elimination diets, but there are a few exceptions. Some people are sensitive to tomato, eggplant, mushroom, and cruciferous veggies, so they might be on your off-limits list.
  • Fruit (except citrus): Like vegetables, fruit is usually a safe food for people on an elimination diet. But you’ll probably have to stay away from citrus, Rizzo says, because its high acidity can cause digestive symptoms.
  • Rice: This is a gluten-free, whole-grain food that is unlikely to cause adverse reactions.
  • Potato: Similar to rice, potatoes are gluten-free, provide complex carbohydrates, and don’t usually cause negative reactions.
  • Meat and poultry: Chicken, turkey, and pork are usually safe foods. However, some people are intolerant of the amine compound in beef, so red meat is sometimes eliminated.
  • Plant milks (except soy): Assuming your doctor has ruled out an allergy to tree nuts, milks from almonds, cashews, and oat are good sources of protein and calcium.

Foods you can’t eat on an elimination diet

Your doctor or nutritionist will compile your personalized list of foods to avoid during the elimination phase, based on your diet and symptoms. But these eight most common allergens are often on the do-not-eat list, Rizzo says.

  • Dairy: Lactose intolerance is one of the most common food sensitivities. By cutting out milk and other dairy items (such as yogurt and cheese), it should be relatively easy to pinpoint if dairy is your culprit, Rizzo says.
  • Eggs: If you’re eliminating eggs, be sure to read labels—eggs are a common ingredient in many foods, including baked goods and baking mixes, as well as some breads and pastas.
  • Fish: Don’t assume you’re not allergic to tuna, cod, or salmon simply because you’ve been eating it your entire life. An estimated 39 percent of people with fish allergy experience their first allergic reaction as adults.
  • Shellfish: Eliminating shellfish goes beyond not eating shrimp and crabs—you’ll need to check the labels on your vitamin and mineral supplements as well, since shellfish are a common ingredient in supplements.
  • Wheat, rye, barley, and oats: These grains contain gluten, a protein that might contribute to intolerance. (A gluten intolerance is different from an allergy and Celiac disease.)
  • Tree nuts: You may need to eliminate almonds, Brazil nuts, cashews, hazelnuts, pecans, pistachios, and walnuts—as well as their butters—from your diet.
  • Peanuts: Allergies to peanuts are common and potentially lethal.
  • Soybeans: Soy is a common allergen and trigger for intolerances, so it’s often avoided during an elimination diet.

Potential benefits of an elimination diet

The goal of an elimination diet is to determine which foods, if any, are causing you discomfort. When done correctly, this type of short-term eating plan can reduce or eradicate the following symptoms associated with problem foods.

Reduce symptoms of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal condition that causes symptoms such as abdominal pain, cramping or bloating, excessive gas, diarrhea or constipation, and mucus in the stool. It affects roughly 14 percent of people worldwide, according to a report published in Gastroenterology and Hepatology, and it must be diagnosed by a doctor. Food intolerances often manifest themselves in digestive issues, so cutting out certain foods can reduce symptoms of IBS.

Reduce bloating

Some foods—including dairy, broccoli, Brussels sprouts, and cauliflower—can increase gas build-up in the stomach and intestines. Eliminating these foods from your diet may reduce bloating.

Reduce excessive gas

Excessive gas—belching or flatulence more than 20 times per day, according to the Mayo Clinic— can be caused by your body’s inability to digest certain foods. You might experience excessive gas if you have a food or lactose intolerance, so eliminating the trigger foods can reduce the symptom.

Prevent abdominal pain and diarrhea

Abdominal pain and diarrhea are common symptoms of food intolerance, and may be alleviated when the offending food is removed from your diet.

Reduce migraines

There’s a connection between some food intolerances and migraines, but there’s little research that explains why, Rizzo says. A small study published in the Journal of Headache Pain found that people who suffered from migraines experienced symptom relief after following a low-fat plant-based diet. And another study found that a significant proportion of people who suffer from migraines have celiac disease, and that a gluten-free diet may improve migraines in these people.

Reduce rheumatoid arthritis joint pain

Inflammation can worsen symptoms of rheumatoid arthritis, so cutting back on these foods that cause inflammation may reduce joint pain. For example, following a gluten-free, vegan diet helped relieve symptoms of rheumatoid arthritis in a study published in Rheumatology.

Potential risks of an elimination diet

An elimination diet can help boost your well being, but it may have negative effects—that’s why it’s important to only follow one under a doctor or nutritionist’s supervision. Some risks include:

  • Unintentional weight loss: “Elimination diets are very restrictive in terms of what you can eat at first,” Rizzo says. By cutting out so many food groups, especially high-calorie ones like dairy, you run the risk of unintentional weight loss.
  • Malnourishment: When you severely restrict what you eat, you may end up short on important vitamins and minerals, as well as protein, carbs, and fat.
  • Headaches and constipation: If you’re not eating enough, or you’re not getting enough fiber, you might experience symptoms like headache or constipation. Because these are also signs of an intolerance, they can make it harder to identify offending foods.
  • Unhealthy relationship with food: Elimination diets are very restrictive, which makes them risky for people who have a history of disordered eating or are struggling with an eating disorder, Duker Freuman says.
  • Cutting out too many foods: Sometimes people assume several foods were the cause of their symptoms and continue to eliminate them. “Then the patient is stuck with a heavily restricted diet,” Duker Freuman says. “Relatedly, some people might not feel fully better, leading them to conclude they haven’t eliminated enough foods and then further restriction takes place.”

Other food elimination diets

If your doctor determines your symptoms are caused by FODMAPs, gluten, or dairy, you may be put on a diet to eliminate only those ingredients. Here’s the lowdown on each of these common plans:

  • Low-FODMAP diet: FODMAPS are types of carbohydrates that are difficult to digest, causing gas and bloating in some people. A low-FODMAP diet eliminates many foods—such as milk, yogurt and ice cream; wheat-based products; beans and lentils; artichokes, asparagus, onions, and garlic; and apples, cherries, pears, and peaches—and then slowly reintroduces them.
  • Gluten-free diet: Gluten is a protein found in most grains, including wheat, barley, and rye. People who suffer from the autoimmune condition called Celiac disease must avoid gluten, since it can trigger a reaction that damages the small intestine. But there are gluten intolerances and allergies, too, and a gluten-free diet may help identify them. Keep in mind that the only way to properly diagnose Celiac disease is through blood work, and in order for the result to be accurate you have to have gluten in your system—so don’t start a gluten-free diet unless your doctor recommends it.
  • Dairy-free diet: Lactose intolerance is a very common intolerance that affects the digestive system. There is a breath test to determine whether you suffer from lactose intolerance, which means you lack or don’t have enough lactase, the enzyme that breaks down lactose. If you’re diagnosed as lactose intolerant, your doctor may suggest a dairy-free diet that cuts out milk, yogurt, ice cream, cream, cheese, and butter.

The upshot: Could an elimination diet work for you?

An elimination diet can help pinpoint foods that are causing certain symptoms—largely those affecting the digestive system—so you can feel better, Rizzo says. But remember: An elimination diet isn’t a one-size-fits-all solution. Everyone’s nutritional needs, symptoms, and possible problem foods vary. If you’re experiencing symptoms that you suspect are related to food, see your doctor.

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Heather Mayer Irvine is the former food and nutrition editor for Runner’s World and the author of The Runner’s World Vegetarian Cookbook. Her writing has appeared in Bicycling, Cooking Light, Popular Mechanics, The Boston Globe, Glamour, and more.