Nutrition glossary
What is an elimination diet?
An elimination diet is a short-term test where you cut out one or more foods you suspect are causing symptoms, then add them back one at a time to see which, if any, bring the symptoms back. It's a way to find a trigger, not a long-term way of eating.
When people use an elimination diet
You might try one, ideally with a doctor or dietitian, if you have symptoms that seem to follow certain foods, such as:
- Bloating, wind, tummy pain or diarrhoea, including irritable bowel syndrome (IBS)
- Suspected lactose intolerance
- Some skin flare-ups or headaches that seem linked to meals
Foods most often tested include dairy, wheat, eggs, soy, nuts and, for IBS, a group of fermentable carbs called FODMAPs. The low FODMAP diet is itself a structured elimination diet, and the NHS recommends doing it with a dietitian.
The three phases
- Elimination. Remove the suspect food or foods completely, usually for two to six weeks. This means reading labels, since milk, wheat and egg turn up in sauces, bread, biscuits and ready meals.
- Reintroduction. If your symptoms have clearly improved, bring back one food at a time. Start with a small portion, increase it over a couple of days, and watch for symptoms. Wait until you're back to normal before testing the next food.
- Personalisation. Keep eating everything that didn't cause problems. For foods that did, find out how much you can tolerate. Many people with lactose intolerance can handle a splash of milk in tea or some hard cheese, even if a large glass of milk causes trouble.
If your symptoms don't improve at all during the elimination phase, the food you removed probably isn't the cause, and it's time to look elsewhere with your doctor.
A sample dairy elimination timeline
| When | What you do |
|---|---|
| Week 0 | Keep a food and symptom diary for a week as a baseline |
| Weeks 1 to 3 | No milk, cheese, yogurt, butter or foods with milk in the ingredients; use calcium-fortified plant milk |
| Week 4, days 1 to 3 | If symptoms have eased, reintroduce milk: half a glass on day 1, a full glass by day 3 |
| Week 4, days 4 to 7 | Note any symptoms, then test yogurt or cheese separately once you feel normal again |
| After | Keep the dairy foods you tolerate and limit only those that clearly cause symptoms |
A diary makes all the difference. Write down what you ate, when, and any symptoms with a rough 1 to 10 rating. Memory is unreliable, especially over weeks.
Common mistakes
- Cutting out too many foods at once without a plan, which makes it hard to eat well and harder to pin down the cause.
- Skipping the reintroduction and avoiding foods for good that you may never have needed to avoid.
- Adding back several foods on the same day, so you can't tell which one caused a reaction.
- Not replacing lost nutrients. Dropping dairy can leave you short of calcium and iodine; dropping wheat can cut your fibre.
Safety first
If you think you might have coeliac disease, get tested before cutting out gluten, because the blood test only works while you're still eating it. If you've ever had a serious allergic reaction, such as swelling of the lips or throat or trouble breathing, never test that food at home; allergies need an allergy specialist. Elimination diets for children, during pregnancy or for anyone with a history of an eating disorder should be supervised by a doctor or registered dietitian.
Common questions
How long should an elimination diet last?
The elimination phase usually lasts two to six weeks, long enough to see whether symptoms settle. Reintroduction then takes several more weeks, depending on how many foods you test.
Is an elimination diet good for weight loss?
It isn't designed for it. Any weight change usually comes from eating fewer processed foods, not from removing a specific trigger. If weight loss is your goal, a steady calorie deficit is a better approach.
Can I do an elimination diet without a dietitian?
A simple one, like cutting out dairy for a few weeks, is often done at home with a diary. Bigger ones, like low FODMAP or cutting several food groups, are much easier and safer with a dietitian's help.
Related
Read do you need a dietitian to start a diet and are online diet plans safe. To keep your meals balanced while you test, see healthy eating basics and diet quality. For more terms, browse the nutrition glossary or how to choose a diet.