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 allergy or intolerance.
Published 18 November 2020

Food provides nutrients your body needs, but some foods can trigger adverse reactions. If digestive symptoms occur after meals, you may have a food allergy or intolerance.

To diagnose the culprit, your doctor or dietitian may suggest an elimination diet. “There are many different types, and the plan will be personalised to you and your individual triggers” says Tamara Duker Freuman, a registered dietitian.

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 digestive issues and cannot pinpoint the source of the problem,” says Natalie Rizzo, registered dietitian. 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 seek advice from 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 occurs when your body mistakenly identifies a food or food substance as harmful. Symptoms of an allergic reaction may affect the skin, digestive system, respiratory system, or the entire body. If you’re allergic to a food, eating it may cause hives, stomach pain, diarrhoea, 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.

Food allergy occurs in around 10% for infants, 4-8% of children, and about 2% of adults in Australia and New Zealand according to the Australasian Society of Clinical Immunology and Allergy (ASCLA). The nine most common food allergens are peanut, tree nuts, milk, eggs, sesame, fish, shellfish, soy and wheat. 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 food compound or your body reacts 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 diarrhoea—but they may also include headaches, irritability, and nervousness. There is no medical test for food intolerances, so doctors use elimination diets to identify them.

How to do an elimination diet

A doctor (often a gastroenterologist or immunologist) or a registered dietitian should design and supervise your elimination diet. The plan will be divided into two phases that last approximately three to four weeks each, Rizzo says. Before you begin an elimination diet, your doctor or dietitian 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 or reduce them.

The elimination phase

During the elimination phase, you cut out the foods your doctor or dietitian 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 can last for up to two to four 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 typically 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 week 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 customised for every person. However, there are some foods that are less likely to cause adverse reactions, and will likely be on your approved list. They include:

  • Some vegetables: Veggies are allowed on elimination diets, but this can differ depending on your symptoms and the type of elimination diet you do. Some people are sensitive to tomato, eggplant, mushroom, and cruciferous veggies, so they might be on your off-limits list.
  • Some fruits: Like vegetables, fruit is allowed but the types may vary. 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, wholegrain food that is unlikely to cause adverse reactions.
  • Potato: Similar to rice, potatoes are gluten-free, provide complex carbohydrates, and don’t usually cause adverse 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 dietitian will compile your personalised 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 yoghurt and soft 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 per cent of people with fish allergy experience their first allergic reaction as adults.
  • Shellfish: Eliminating shellfish goes beyond not eating prawns 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 coeliac 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 resolve 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, diarrhoea or constipation. It affects roughly 14 per cent 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 or reducing certain foods can help to manage symptoms of IBS.

Reduce bloating

Some foods—including dairy, broccoli, Brussels sprouts, and cauliflower—can increase the build up of gas 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 diarrhoea

Abdominal pain and diarrhoea 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. However, further research is needed to explore this.

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 wellbeing, but it may have negative effects—that’s why it’s important to only follow one under a doctor or dietitian’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 energy dense foods 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 fibre, you might experience symptoms like headaches or constipation. Because these are also signs of an intolerance, they can make it harder to identify trigger 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 symptoms such as abdominal pain, cramping or bloating, excessive gas, diarrhoea or constipation in some people. A low-FODMAP diet eliminates many foods—such as milk, yoghurt and ice cream; wheat-based products; legumes 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 coeliac 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 coeliac disease is through blood tests and a small bowel biopsy, 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, yoghurt, ice cream, cream and certain cheese.

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 trigger foods vary. If you’re experiencing symptoms that you suspect are related to food, see your doctor.