The GAPS diet is promoted as a natural treatment for people with conditions that affect the brain, such as autism spectrum disorder. But it’s a controversial therapy that has received a lot of criticism for its restrictive regimen.

The Gut and Psychology Syndrome (GAPS) diet is a type of elimination diet created in 2004 by Dr. Natasha Campbell-McBride.

Dr. Campbell-McBride theorized that a leaky gut causes several conditions that affect the brain, such as autism spectrum disorder (ASD).

Leaky gut syndrome is a term sometimes used to describe an increase in the permeability of the gut wall, but it’s not recognised as an official medical diagnosis.

The GAPS theory claims that a leaky gut allows chemicals and bacteria from your food and environment to enter your blood when they wouldn’t normally do so. Once they do, they can supposedly affect brain function and development, causing “brain fog” and conditions like ASD.

The GAPS protocol is designed to help heal and seal the gut wall, prevent toxins from entering the bloodstream, and lower “toxicity” in the body.

However, it isn’t clear if or how leaky gut plays a role in the development of mental or neurological conditions, and the research on the effectiveness of the GAPS diet is limited.

Keep reading to learn more about the features of the GAPS diet, and whether there’s evidence behind its purported health benefits.

In her book, Dr. Campbell-McBride states that the GAPS dietary protocol treated her first child of autism spectrum disorder (ASD).

The diet is now promoted as a natural cure for many other psychiatric and neurological conditions that primarily affect children, including:

Despite Dr. Campbell-McBride’s claims, research on whether a leaky gut causes ASD is limited and mixed.

ASD is a condition that results in changes to brain function that affect how the person experiences the world. Its effects can vary widely, but, in general, autistic people have difficulties with communication and social interaction.

It’s a complex condition thought to result from a combination of genetic and environmental factors.

Some research suggests that up to 7 in 10 autistic people are likely to experience gastrointestinal symptoms like diarrhea, constipation, abdominal pain, acid reflux, and vomiting. This may lead to more severe behaviors, including increased irritability, aggressive behavior, social withdrawal, and hyperactivity.

A 2020 review also found that some children with ASD may have increased intestinal permeability, but older studies have found no difference between intestinal permeability in children with and without ASD.

While some animal studies suggest a link, no studies have confirmed the presence of leaky gut before the development of ASD. So even if leaky gut is linked to ASD in some children, it’s not known if it’s a cause or a symptom.

Overall, the claim that leaky gut is the cause of ASD is controversial. This explanation also oversimplifies the causes of a complex condition. More research is needed to understand the role of leaky gut and ASD.

How the diet works

Following the GAPS diet can be a years-long process. It requires cutting out all foods Dr. Campbell-McBride thinks contribute to a leaky gut, including grains, pasteurized dairy, starchy vegetables, and refined carbs.

The GAPS protocol is made up of three main stages:

  • introduction diet
  • full GAPS
  • reintroduction phase

The introduction phase is the most intense part of the diet because it eliminates the most foods. It’s called the “gut healing phase” and can last from 3 weeks to 1 year, depending on your symptoms.

This phase is broken down into six stages:

  • Stage 1: Consume homemade bone broth, juices from probiotic foods and ginger, and drink mint or chamomile tea with honey between meals. People who are not dairy intolerant may eat unpasteurized, homemade yogurt or kefir.
  • Stage 2: Add raw organic egg yolks, ghee, and stews made with vegetables, meat, or fish.
  • Stage 3: All previous foods plus avocado, fermented vegetables, GAPS-recipe pancakes, and scrambled eggs made with ghee, duck fat, or goose fat.
  • Stage 4: Add in grilled and roasted meats, cold-pressed olive oil, vegetable juice, and GAPS-recipe bread.
  • Stage 5: Introduce cooked apple purée, raw vegetables starting with lettuce and peeled cucumber, fruit juice, and small amounts of raw fruit, but no citrus.
  • Stage 6: Finally, introduce more raw fruit, including citrus.

During the introduction phase, the diet requires you to introduce foods slowly, starting with small amounts. You may move on to the next phase once you can tolerate the foods you have introduced. You’re considered to be tolerating a food when you have a normal bowel movement.

Once the introduction diet is complete, you can move to the full GAPS diet.

The full GAPS diet lasts 1.5 to 2 years. During this period, people are advised to base the majority of their diet on the following foods:

  • fresh meat, preferably hormone-free and grass-fed
  • animal fats, such as lard, tallow, lamb fat, duck fat, raw butter, and ghee
  • fish
  • shellfish
  • organic eggs
  • fermented foods, such as kefir, homemade yogurt, and sauerkraut
  • vegetables

Followers of the diet can also eat moderate amounts of nuts and GAPS-recipe baked goods made with nut flours.

There are also a number of additional recommendations that go along with the full GAPS diet. These include:

  • Do not eat meat and fruit together.
  • Use organic foods whenever possible.
  • Eat animal fats, coconut oil, or cold-pressed olive oil at every meal.
  • Consume bone broth with every meal.
  • Consume large amounts of fermented foods, if you can tolerate them.
  • Avoid packaged and canned foods.

While on this phase of the diet, you should avoid all other foods, particularly refined carbs, preservatives, and artificial colorings.

If you’re following the GAPS diet properly, you’ll be on the full diet for at least 1.5 to 2 years before you start reintroducing other foods.

The diet suggests that you start the reintroduction phase after you have experienced normal digestion and bowel movements for at least 6 months.

Like the other stages of this diet, the final stage can also be a long process as you reintroduce foods slowly over a number of months.

The diet suggests introducing each food individually in a small amount. If you don’t note any digestive issues over 2 to 3 days, you may gradually increase your portions.

The diet doesn’t detail the order or the exact foods you should introduce. However, it states that you should start with new potatoes and fermented, gluten-free grains.

Even once you’re off the diet, you’re advised to continue limiting ultra-processed and refined high-sugar foods, retaining the whole-foods principles of the protocol.

The most important aspect of the GAPS protocol is the diet itself. Theoretically, these whole foods should provide your body with all of the nutrients it needs to heal.

However, the GAPS protocol also recommends a few supplements for Phases 1 and 2 to possibly help balance the bacteria, acids, and enzymes in your gut. Some supplements may include:

It’s important to speak with a healthcare professional before taking any supplements, especially if you’re taking any medications. Supplements aren’t regulated by the Food and Drug Administration (FDA), and they may interact with some drugs.

As of 2025, very limited research has examined the effects of the GAPS dietary protocol on the symptoms and behaviors associated with ASD.

Some studies suggest that it may help manage gastrointestinal symptoms, which can, in turn, prevent or reduce the severity of certain behaviors.

Other studies performed by the International Society for Orthomolecular Medicine found that the GAPS diet had a positive effect on conditions like PANDAS, tic-related disorders, and various chronic diseases.

However, studies have been small, and dropout rates are high, so it’s still unclear whether these diets may work and which people they may help.

More research is needed to understand the role of the GAPS diet in managing neurodivergent conditions.

Can dietary supplements help with ASD?

The effect of probiotics on the gut may be a more promising line of research.

For instance, a 2019 study found that children with ASD had different gut microbiota compared to neurotypical children, and probiotic supplementation was beneficial. Other studies from 2017 and 2019 found similar results.

The GAPS diet also suggests taking supplements of essential fats and digestive enzymes.

A small 2021 study found that taking omega-3 fatty acid supplements had some positive effect on ASD behaviors. Older studies on the effects of digestive enzymes on ASD found similar results, but further research is needed.

The GAPS diet is a very restrictive protocol that requires you to cut out many nutritious foods for long periods of time. It also provides little guidance on how to ensure your diet contains all the nutrients you need.

Because of this, the GAPS diet may increase the risk of malnutrition. This is especially true for children who are growing fast and need a lot of nutrients, since the diet is very restrictive.

Additionally, those with ASD may already have a restrictive diet and may not readily accept new foods or changes to their diets. This could lead to extreme restriction.

Some people feel they’ve benefited from the GAPS diet, though these reports are anecdotal.

The GAPS diet is extremely restrictive for long periods of time, making it difficult to stick to. Since this restrictiveness may lead to deficiencies in nutrition and growth, it may be especially dangerous for the exact population it’s intended for.

Some health professionals have criticized the GAPS diet because many of its claims are not supported by scientific studies.

If you’re interested in trying it, speak with a healthcare professional beforehand. They can make sure you’re meeting your nutritional needs.