Elimination diets may promise to cure bloat, brain fog and breakouts, but do they actually live up to the hype? Before you try out an elimination diet, it's important to know what they are, how they work — and why you should only do them under a health care provider's supervision.
What Are Elimination Diets?
Elimination diets are meal plans that remove specific foods or food groups from the diet in order to determine the source of a person's food intolerances. They can be pretty useful when you consider that some 15 to 20 percent of the population deals with food intolerances, per a December 2014 review in Alimentary Pharmacology & Therapeutics.
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The goal of an elimination diet is to identify the foods that may be triggering a range of unwanted symptoms.
"Various elimination diets are recommended at times for acne, migraines, inflammation and more," says Anna Kippen, RDN, LD, a registered dietitian at the Cleveland Clinic. Chronic pain and fatigue may also lead people to try elimination diets.
But gastrointestinal problems are among the most common reasons people try elimination diets. The low-FODMAP diet, for example, is designed to help people with irritable bowel syndrome (IBS) pinpoint specific carbohydrates that they are unable to tolerate. Another example is cutting out dairy to see if GI symptoms like bloating, gas and diarrhea resolve when the milk sugar lactose is removed from the diet.
"You could even argue that the Paleo, Whole30 and gluten-free diets are all elimination diets," says Shanti Eswaran, MD, a gastroenterologist and associate professor at Michigan Medicine.
After all, these meal plans remove food groups from the diet. The difference with plans like Whole30, though, is they're typically intended for weight loss, whereas elimination diets are not.
Unlike diets designed for people with food allergies that require long-term adherence, elimination diets are meant to be temporary. They also reintroduce potential trigger foods as a means of testing whether or not they bring on symptoms. Diets for those with food allergies, on the other hand, remove allergens altogether. Since food allergies can trigger potentially fatal immune reactions, reintroducing allergens to test one's reactions to offending foods is not recommended.
How Do Elimination Diets Work?
There are typically three phases of elimination diets: elimination, reintroduction and individualization.
Phase 1: Elimination
"The goals of the elimination phase are to remove all offending foods from the diet and see a complete or near-complete resolution of symptoms," Kippen says. "This is typically done for about four to six weeks, but most patients will begin seeing an improvement in symptoms within the first two weeks depending on their adherence."
Estimates vary, but research suggests that somewhere from 50 to 86 percent of people with IBS respond to the elimination phase of the low-FODMAP diet, per a January 2017 Gastroenterology & Hepatology review.
"We don't exactly know why some people respond and others don't, though it's probably because IBS itself is quite variable," Dr. Eswaran says. "In some people, diet may be driving symptoms, while in others it might be stress or medications."
The general rule of thumb is that if you don't experience symptom improvement within two to six weeks of the elimination phase, there's no reason to continue on the diet.
Remember, symptom relief isn't linear or immediate. "Nerves and bacteria in the GI tract take time to adapt to changes in the diet," Dr. Eswaran says. "You might feel good one day but not the next."
That's why sticking with an elimination diet for more than just a few days is necessary in order to fully assess its effects on symptoms.
Phase 2: Reintroduction
The second phase of elimination diets consists of the slow and steady reintroduction of foods. According to Kippen, this phase matters most.
"If done incorrectly, it will render the elimination useless and all symptoms may return with no information provided to us," she warns. "The goal here is to carefully reintroduce one food at a time in order to gauge whether that food is a trigger."
Reintroducing foods one by one is critical. For the low-FODMAP diet, for example, the best approach is to eat one new food from a certain FODMAP group every three days (with a three-day "washout period" — where you revert back to the elimination phase — in between each new addition).
If a reintroduced food does not result in symptoms, it can remain in the diet long-term. However, if consumption brings on bad reactions, Kippen says the full elimination diet should be restored until all symptoms resolve.
"Once they've resolved, I advise people to do the same food trial again. I recommend doing a food trial at least three times before adding something to the 'no' or 'trigger' list."
Why? It can be tough to know whether or not that food was the true culprit. Plus, cutting out any food for the long haul is not ideal, so it's important to be sure before going down that route.
When working on phase two, it's important to make sure the foods you reintroduce only contain one of the potential triggers you're monitoring. For example, try watermelon (a high-FODMAP food) instead of a piece of bread, which may also contain wheat, gluten, dairy and/or eggs.
"It's also helpful to keep a food journal to document symptom severity and duration [during the reintroduction phase]," Kippen says. "Sometimes we will have a symptom and be so distracted or 'used to it' that we miss it until we're asked to pick up a journal and document it."
Phase 3: Individualization
The final phase of an elimination diet is all about personalization.
"Once we have completed reintroduction and identified food triggers, we work on creating a nutrition plan that limits or eliminates certain food triggers but still has variety, is balanced and also promotes overall health based on one's specific medical status and goals," Kippen says.
Whether foods need to be eliminated for life depends on the person and the condition. When you're allergic to a food, there's no option to 'just have a taste.' The food must be avoided. However, if you're dealing with an intolerance or IBS, there may be some wiggle room.
Say you discover that apples (a high-FODMAP food) cause you mild bloat. It may be possible to have a small portion of your favorite Honeycrisp every now and then and still feel comfortable.
"Many people will be able to have small amounts of offending foods after doing the elimination diet and not suffer from intense symptoms," Kippen says.
Remember: Digestive issues are extremely individual, so there's no one-size-fits-all approach to designing a gut-friendly diet.
Pros and Cons of Elimination Diets
As long as elimination diets are performed correctly, they shouldn't come with major health risks, Dr. Eswaran says. That said, it's crucial to follow the strict protocols surrounding the meal plans.
Elimination diets should not be done without guidance from a health care professional. Kippen says she always does a comprehensive assessment to determine a person's food preferences, dietary patterns and medical history before initiating an elimination diet.
It's also important to remember that elimination diets are temporary and should not be followed for long periods or to lose weight.
"Potential risks can also pop up with nutritional deficiencies or negative changes to the gut microbiota if someone sticks to an elimination diet for a long time," Dr. Eswaran says.
Low fiber intake (in the case of the low-FODMAP diet) and undesirable weight loss can occur if an elimination diet is followed for an extended period of time or completed incorrectly, adds Kippen.
Elimination diets are not recommended for people who struggle with disordered eating patterns, as the meal plans can be extremely restrictive and may therefore contribute to unhealthy relationships with food.
Yet for some, elimination diets can significantly improve both health and quality of life. "For the majority of my patients, they experience an improvement or complete resolution of symptoms," says Kippen. "They feel so much better that the [dietary restrictions] do not feel as intense."
Foods You Can’t Eat on Elimination Diets
There's no single elimination diet, but foods that are commonly cut out include:
1. Common allergens: These include wheat, soy, dairy, eggs, peanuts, tree nuts, fish, shellfish and sesame
2. FODMAP foods: FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. Here's what these consist of:
- Oligosaccharides: Wheat, rye, onions, garlic and legumes
- Disaccharides: Lactose in milk, yogurt and cheese
- Monosaccharides: Fructose in honey, apples, watermelon, mango, pears and plums
- Polyols: Sorbitol and mannitol found in some fruits and vegetables; sugar alcohols and artificial sweeteners
6. Added sugars
The Bottom Line
There is no single elimination diet, but these types of meal plans share common characteristics. Most are meant to be short-term and aim to identify foods that may be contributing to symptoms like skin flare-ups, bloat, headaches or fatigue.
While elimination diets can be extremely helpful — particularly for those dealing with GI issues — they are not perfect and leave considerable room for error.
"It is very easy to do an elimination diet incorrectly and cause a host of issues as a result," says Kippen.
If an elimination diet seems like the right choice for you, pursue the meal plan with the help of a doctor or registered dietitian who can guide you through the process and provide recommendations so you maintain a balanced diet and a healthy relationship with food.
- Alimentary Pharmacology & Therapeutics: "Review Article: The Aetiology, Diagnosis, Mechanisms and Clinical Evidence for Food Intolerance"
- Gastroenterology & Hepatology: "Controversies and Recent Developments of the Low-FODMAP Diet"
- Monash University: "FODMAPs and Irritable Bowel Syndrome"
- University of Virginia School of Medicine: "When a Registered Dietitian Becomes the Patient: Translating the Science of the Low FODMAP Diet to Daily Living"