The GAPS diet theory says that eliminating certain foods, such as grains and sugars, can help people treat conditions that affect the brain, such as autism and dyslexia.

The term "GAPS" stands for "gut and psychology syndrome." The GAPS diet follows the premise that gut health is linked with overall physical and mental health.

In this theory, improving gut health can improve other health conditions.

Researchers have not yet fully explored this diet and there are some concerns around the premise of this diet.

In this article, we look at the evidence for the GAPS diet's claims, how to follow it, and its possible benefits. We also provide example food lists and meal plans.

Ginger tea which is a part of stage 1 of the gaps dietShare on Pinterest
The GAPS diet involves replacing foods that are difficult to digest with nutrient-rich food.

Dr. Natasha Campbell-McBride, who invented the GAPS diet, believes that poor nutrition and a leaky gut, or increased intestinal permeability, are responsible for many psychological, neurological, and behavioral issues.

At the core of the GAPS diet, people avoid foods that are difficult to digest and might damage the gut flora or gut lining. They replace them with nutrient-rich foods that help the gut heal.

According to the GAPS theory, a leaky gut releases harmful bacteria and toxins into the bloodstream, which then travel to the brain and interfere with the brain functioning. The theory says that eliminating foods that damage the gut could help treat conditions such as autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and dyslexia.

Although current research suggests that there is a connection between the brain and the gut, particularly for conditions such as anxiety and depression, research is mixed on certain aspects of the diet. While there are many testimonials of improvement, there is limited published evidence to suggest that following all components of the GAPS diet is required to improve psychological or behavioral conditions.

Dr. Campbell-McBride originally designed the GAPS diet with the aim of treating her son's autism. Some people also use the GAPS diet as an alternative therapy for a range of psychological and behavioral conditions, including:

Dr. Campbell-McBride's initial aim with the GAPS diet was to help children with behavioral and mood disorders. However, some adults now use it to improve digestive problems.

Dr. Campbell-McBride believes that children develop autism due to poor nutrition and leaky gut syndrome. She claims that the GAPS diet can "cure" or improve symptoms of autism.

ASD causes a range of symptoms that affect how a person experiences the world and interacts in social settings. Scientists believe that a combination of genetic and environmental factors contribute to the development of ASD.

Most experts agree that there is no cure for ASD. It is possible, however, to improve health conditions associated with ASD, such as gastrointestinal (GI) problems.

One 2014 systematic review found that children with ASD had significantly higher rates of GI symptoms than those without. The authors say that children with ASD were more prone to abdominal pain, constipation, and diarrhea. Some research suggests these symptoms are linked to unbalanced gut microbiota or dysbiosis.

One case study reported that a 12-year-old boy with ASD and celiac disease showed significant reductions in GI symptoms and core autism symptoms after 4 weeks of probiotic treatment.

Findings from a 2014 study that tested 133 children found no association between intestinal permeability and the presence of ASD symptoms. On the contrary, a 2010 pediatric study found different results.

Nearly thirty-seven percent of patients with ASD and twenty-one percent of their first-degree relatives showed altered intestinal permeability (IPT) suggesting a hereditary factor. Patients with ASD on a gluten and casein free diet had lower IPT levels than those who ate unrestricted. The authors conclude that a gluten-free diet could benefit a subgroup of patients with ASD.

Another case study of a 5 year old boy had significant improvement in GI symptoms, development and cognition when his undiagnosed celiac disease was diagnosed and treated with a gluten-free diet. The authors suggest that all children with neurodevelopmental delays be screened for malabsorptive conditions and nutritional deficiencies that could heavily influence cognition.

Autoimmune conditions have also been associated with ASD and a study published in Nutritional Neuroscience found a significant number of autism patients had elevated antibodies simultaneously to gliadin protein present in gluten-containing foods and cerebellar cortex neurons.

More research is needed to elucidate what other dietary changes may be effective to substantially affect ASD.

There is no evidence to suggest that all components of the GAPS diet can help treat the conditions it claims to.

Following this diet could, however, improve a person's gut health. It encourages people to eat fewer processed foods and more fruits, vegetables, and natural fats. These simple dietary changes could improve gut health and overall health.

However, GAPS diet guidelines do not explicitly account for all nutritional needs. When following this diet, people should make sure that they are getting enough vitamins and minerals to avoid developing nutritional deficiencies.

The following sections discuss the evidence for possible benefits of the GAPS diet.

Improving gut health

The GAPS diet could improve gut health in three main ways:

  • Eliminating artificial sweeteners: According to some animal studies, artificial sweeteners can create imbalances in gut bacteria and increase the risk of metabolic problems.
  • Focusing on fruits and vegetables: A 2016 study involving 122 people showed that eating fruits and vegetables can prevent a potentially harmful strain of bacteria from growing in the gut.
  • Including probiotics: Probiotics contain many beneficial bacteria. One study suggests that eating probiotic yogurt may help lower blood sugar levels among people with metabolic syndrome.

Possibly managing some psychological and behavioral conditions

According to a review study, recent clinical studies have suggested that microbes in the gut can significantly affect brain function.

The researchers suggest that gut imbalances could contribute to schizophrenia and other complex behavioral conditions.

Findings from a 2019 systematic review suggest that probiotics have strong therapeutic potential for treating depressive symptoms.

To follow the GAPS diet, eliminate grains, sugar, soy, pasteurized dairy, starchy vegetables, and processed foods from the diet.

The diet is restrictive and may take up to 2 years to complete.

There are three stages to the GAPS diet:

1. The introduction diet

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A person can add avocado at stage 3 of the introduction diet.

Dr. Campbell-McBride recommends that many people follow the introduction diet before starting the full GAPS diet.

While highly restrictive, this phase aims to heal the gut and reduce digestive symptoms quickly. It can last anywhere from a few weeks to 1 year.

The introduction diet has six progressive stages. Each stage introduces new foods but foods within each stage are individualized to each person based on tolerance.

People should not progress to the next stage if they experience digestive symptoms, which may include:

  • diarrhea
  • bloating
  • gas
  • constipation
  • abdominal pain

Stage 1

In stage 1, the diet consists of:

  • homemade meat stock
  • boiled meat or fish
  • well-cooked vegetables
  • probiotics, such as fermented vegetable juices, yogurt or kefir, and homemade fermented whey
  • ginger or chamomile tea with raw honey
  • purified water

Stage 2

In stage 2, add the following foods:

  • raw, organic egg yolks
  • casseroles made with meats and vegetables
  • fermented fish
  • homemade ghee

Stage 3

In stage 3, add the following foods:

  • avocado
  • sauerkraut and fermented vegetables
  • GAPS pancakes
  • scrambled eggs made with ghee, goose fat, or duck fat
  • probiotic supplements

Stage 4

In stage 4, add the following foods:

  • roasted or grilled meats
  • cold-pressed olive oil
  • freshly pressed carrot juice
  • GAPS milkshake
  • GAPS bread

Stage 5

In stage 5, add the following foods:

  • cooked apple purée
  • raw vegetables, such as lettuce and peeled cucumber
  • pressed fruit juice

Stage 6

In stage 6, add the following foods:

  • raw, peeled apple
  • raw fruit
  • increase honey
  • baked goods sweetened with dried fruit

After completing the introduction diet, many people move onto the full GAPS diet.

2. The full GAPS diet

During the GAPS diet, avoid all grains, sugars, starchy vegetables, refined carbohydrates, and processed foods. This stage lasts 18–24 months but is individualized and may require less time for some.

Acceptable GAPS foods include:

  • eggs
  • meat, fish, and shellfish (fresh or frozen only)
  • fresh vegetables and fruit
  • garlic
  • natural fats, such as olive oil, coconut oil, and ghee
  • a moderate amount of nuts
  • GAPS baked goods made using nut flour

The GAPS diet also recommends that people:

  • use organic food as often as possible
  • avoid all processed and packaged foods
  • eat fermented food with every meal
  • drink bone broth with every meal
  • avoid eating fruit with meals
  • combine all protein food with vegetables, which the theory says will keep body acidity levels normal

3. The reintroduction phase

After at least 6 months of normal digestion, people can choose to move on to the reintroduction phase.

The final stage of the GAPS diet involves gradually reintroducing food items over the course of several months.

The diet recommends starting with potatoes and fermented grains. Start with small portions and gradually increase the amount of food, as long as no digestive issues arise. Continue this process with starchy vegetables, grains, and beans.

After completing the GAPS diet, many people continue to avoid refined, highly processed foods.

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People can eat eggs on the GAPS diet.

People can eat the following foods on the GAPS diet:

  • meat stock (cooked shorter than broth and contains less glutamates)
  • meats, preferably hormone-free or grass-fed
  • fish
  • shellfish
  • animal fats
  • eggs
  • fresh fruits and non-starchy vegetables
  • fermented foods and beverages
  • hard, natural cheeses
  • kefir
  • coconuts, coconut milk, and coconut oil
  • nuts
  • dry wine
  • white navy beans

Foods to avoid on the GAPS diet include:

  • sugar and artificial sweeteners
  • syrups
  • alcohol, but adults can have a glass of dry wine occasionally
  • processed and packaged foods
  • grains such as rice, corn, wheat, and oats
  • starchy vegetables, such as potatoes and yams
  • milk
  • beans, except white and greens beans
  • coffee
  • strong tea
  • soy

Start the day with one of the following:

  • a glass of filtered lemon water and kefir
  • a glass of freshly pressed fruit and vegetable juice

For breakfast:

  • GAPS pancakes topped with butter or honey
  • one cup of lemon and ginger tea

For lunch:

  • meat or fish with vegetables
  • one cup of homemade meat stock
  • one serving of probiotics, such as kimchi, sauerkraut, yogurt, or kefir

For dinner:

  • homemade vegetable soup made with meat stock
  • one serving of probiotics, such as kimchi, sauerkraut, yogurt, or kefir

The GAPS diet claims to help treat autism and other behavioral and psychological conditions. While some aspects of the GAPS diet show promising results, more research is needed to validate that all components of the GAPS diet are necessary for the benefits it claims.

People should therefore proceed with caution.

Those interested in trying the GAPS diet can consult a licensed GAPS practitioner to learn more. However, people should first consider consulting a registered dietitian or other healthcare provider.