The Gut and Physiology Syndrome (GAPS) diet, created by Dr. Natasha Campbell-McBride in 2004, is presented as a natural treatment for conditions affecting the brain, such as autism spectrum disorder (ASD). It is a type of elimination diet that involves cutting out refined carbs, starchy vegetables, pasteurized dairy, grains, and processed foods.
The GAPS Theory: Linking Gut Health and the Brain
Dr. Campbell-McBride theorized that a leaky gut causes several conditions that affect the brain, such as autism spectrum disorder (ASD). 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.
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 protocol is designed to help heal and seal the gut wall, prevent toxins from entering the bloodstream, and lower “toxicity” in the body.
Conditions the GAPS Diet Claims to Address
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:
- Attention deficit disorder (ADD)
- ADHD
- Dyspraxia
- Dyslexia
- Depression
- Schizophrenia
- Tourette syndrome
- Bipolar disorder
- Obsessive-compulsive disorder (OCD)
- Eating disorders
- Gout
- Childhood bedwetting
- Food intolerance or allergy
The GAPS Diet Protocol: Stages and Recommendations
The GAPS diet unfolds in three main stages: the Introduction Phase, the Full GAPS Diet, and the Reintroduction Phase. Each stage has specific guidelines and recommended durations.
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The Introduction Phase: Healing the Gut
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.
The Full GAPS Diet: Maintaining Gut Health
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:
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- 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.
The Reintroduction Phase: Expanding the Diet
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.
Scientific Evidence and Criticisms
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.
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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.
The Role of Supplements
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.
Criticisms of the GAPS Diet
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 health professionals have criticized the GAPS diet because many of its claims are not supported by scientific studies.
Practical Considerations and Potential Drawbacks
The GAPS diet is very restrictive, this goes without saying. So I freely admit that when I saw the length of time for which this restriction should ideally continue, I balked! Then, as if that wasn't daunting enough, when it comes to the food itself, there are absolutely no shortcuts. Basically you can seemingly never just buy anything and eat it ever again. You must instead make absolutely everything from scratch.
For instance, fermented dairy products such as yoghurt or kefir, are much easier for the human gut to handle, and even come with a host of beneficial healing properties. However, commercially available fermented dairy products are not fermented long enough to make the milk suitable for GAPS people, and they are also often pasteurised, which kills off the good bacteria and enzymes etc that make it beneficial. As a result, only home-fermented dairy products are recommended for the GAPS diet. The same applies for things such as ghee, sauerkraut, meat stocks and broths.
While I can fully appreciate the reasoning behind this, it just adds to the daunting feeling, as it is made abundantly clear how much time and effort is required in order to commit to this diet. Yes, improving your health is absolutely something you should spend a lot of time and effort on, no argument. However, my worry with very strict and restrictive long-term regimes is what happens when there is inevitably a day where said time and effort cannot be spent, when life gets in the way? Personally, when I have been restrictive with my diet and have fallen off the wagon, the fall has been hard, and getting back on the wagon even harder. Hence my concern and trepidation.