The GAPS Diet: An Evidence-Based Review

You’ve heard the phrase “gut instinct.” In fact, you’ve probably experienced it yourself. It’s true that there’s a direct link between the gut and brain, in ways that researchers are only beginning to understand.

Enter the GAPS diet. It’s generating a lot of media buzz by claiming to leverage the gut-brain connection to effectively treat brain- and body- related problems, including anxiety, depression, autism, and ADHD, as well as inflammatory bowel disease and autoimmune illnesses. Here, everything you need to know about the GAPS diet.

What Is the GAPS Diet?

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 (1).

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.

However, it isn’t clear if or how leaky gut plays a role in the development of diseases (2, 3).

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 (4). 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.

Who Is This For? 

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:

  • Autism
  • ADHD
  • Dyslexia
  • Dyspraxia
  • Epilepsy
  • Depression
  • Schizophrenia
  • Bipolar disorder
  • Obsessive-compulsive disorder (OCD)
  • Disordered eating
  • Childhood food intolerance and allergies

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.

Does GAPS Diet Work? 

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: Evidence showed that artificial sweeteners can create imbalances in gut bacteria and increase the risk of metabolic problems (5).
  • Focusing on fruits and vegetables: It was also observed that eating fruits and vegetables can prevent a potentially harmful strain of bacteria from growing in the gut (6).
  • Including probiotics: Probiotics contain many beneficial bacteria. It was suggested that eating probiotic yogurt may help lower blood sugar levels among people with metabolic syndrome (7).

Possibly Managing Some Psychological and Behavioral Conditions

Recent clinical studies have suggested that microbes in the gut can significantly affect brain function (8).

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

A systematic review suggests that probiotics have strong therapeutic potential for treating depressive symptoms (9).

The GAPS Diet and Autism 

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.

A 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 (10). 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 (11).

Findings from a 2014 study that tested more than 130 children found no association between intestinal permeability and the presence of ASD symptoms (12). However, a 2010 pediatric study found different results (13).

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 (14). 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 (15).

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

How To Do the GAPS Diet?

The overall diet is divided into two phases: The Introduction Diet and Full GAPS Diet. According to the GAPS website, the Introduction Diet can be “very overwhelming to patients, parents and children who are used to a traditional Western 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

Once you complete the 6 phases of the Introduction Diet you can then move on to the Full GAPS Diet which is recommended to be followed for between 18 to 24 months. 

During the GAPS diet, avoid all grains, sugars, starchy vegetables, refined carbohydrates, and processed foods.

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

Coming Off GAPS

If you’re following the GAPS diet to the letter, you’ll be on the full diet for at least 1.5–2 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 2–3 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 avoiding all highly processed and refined high-sugar foods, retaining the whole-foods principles of the protocol.

GAPS Supplements 

The diet’s founder states that the most important aspect of the GAPS protocol is the diet.

However, the GAPS protocol also recommends various supplements. These include:


Probiotic supplements are added to the diet to help restore the balance of beneficial bacteria in your gut.

It’s recommended that you choose a probiotic containing strains from a range of bacteria, including Lactobacilli, Bifidobacteria, and Bacillus subtilis varieties.

You’re advised to look for a product that contains at least 8 billion bacterial cells per gram and to introduce the probiotic slowly into your diet.

Essential Fatty Acids and Cod Liver Oil

People on the GAPS diet are advised to take daily supplements of both fish oil and cod liver oil to ensure they’re getting enough.

The diet also suggests you take small amounts of a cold-pressed nut and seed oil blend that has a 2:1 ratio of omega-3 to omega-6 fatty acids.

Digestive Enzymes

The diet’s founder claims that people with GAPS conditions also have low stomach acid production. To remedy this, she suggests followers of the diet take a supplement of betaine HCl with added pepsin before each meal.

This supplement is a manufactured form of hydrochloric acid, one of the main acids produced in your stomach. Pepsin is an enzyme also produced in the stomach, which works to break down and digest proteins.

Some people may want to take additional digestive enzymes to support digestion.

Can GAPS Diet Help You Lose Weight?

The GAPS plan is not a weight-loss diet, and it’s most definitely not a quick fix approach. It’s meant to be followed carefully and long-term. While encouraged by some practitioners, it requires a huge commitment and cannot offer any data or statistics related to its promises.

If you’re still thinking of trying GAPS, talk to your physician first, especially if you’ve been diagnosed with any of the conditions the diet can supposedly cure. If your doctor supports your decision to move forward, work with a registered dietitian, who can guide you in properly following the plan, assess your intake to be sure you’re meeting your nutrient needs, and monitor your progress.

Are There Any Risks Involved? 

Like most diet treatments for autism, the GAPS diet has no rigorous medical studies to back it up. Unfortunately, there’s little medical evidence to indicate that any of Dr. Campbell-McBride’s recommendations, ranging from homemade broth to fermented foods, can help improve symptoms of autism or related disorders.

In fact, some medical professionals warn that cutting out so many healthy foods such as whole grains and legumes can lead to nutritional deficiencies in children and adults who follow the diet. The GAPS diet is extremely restrictive, and also could lead to unintended weight loss.

Finally, the GAPS diet is extremely difficult to follow. You’ll need to cook all your own food from scratch; no store-bought convenience foods, such as broth or most sauces, are allowed. Many parents following the GAPS diet find that they’re spending many more hours in the kitchen than they ever had before.

Should You Try GAPS?

The biggest question regarding the GAPS diet is, does it work? Although Campbell-McBride claims to have clinical experience with thousands of GAPS children and adults around the world, there is no research on the GAPS diet and its outcomes, including reversing intestinal permeability or any of the illnesses the eating plan claims to treat.

Some people are willing to try a diet based on anecdotal reports rather than peer-reviewed research, in the hopes that it may help ease or cure a specific condition, especially if nothing else is working. However, there are a few important things to keep in mind if you decide to give it a go.

In addition to being strict, which may unnecessarily limit certain nutrients, GAPS requires obligations that may not be practical for many people. For example, rather than buying ready-to-eat bone broth and yogurt, you have to make it yourself. The diet also makes dining out difficult because you can’t have farm-raised fish or meat that isn’t organic or grass-fed, and you can only consume certain kinds of cooking oils.

While the list of allowed foods isn’t entirely skimpy, the ingredient sourcing and execution of the diet are far from simple. It’s also not vegetarian or vegan-friendly, for those who are committed to a plant-based diet.

The Bottomline 

Autism, ADHD, and related disorders can be devastating, and it’s understandable that parents would want to do whatever they can to help their children. However, the GAPS diet requires a tremendous, ongoing commitment; it’s not for the faint of heart, nor is it the best diet for a family that’s accustomed to grabbing food on the run.

If you’re considering the GAPS diet, make sure to speak with your doctor or your child’s pediatrician to make certain it’s the best choice for you and your family.

















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