The GAPS Diet: Complete Guide, Benefits, Risks, and Evidence-Based Analysis

The Gut and Psychology Syndrome (GAPS) diet has gained attention as an alternative approach for managing various neurological and psychiatric conditions. Developed by Dr. Natasha Campbell-McBride in 2004, this dietary protocol is based on the theory that intestinal health directly impacts brain function and mental well-being.

While some families report positive experiences with this diet, it remains a controversial treatment approach with limited scientific validation. Understanding what the GAPS diet entails, who it’s designed for, and the current state of research can help you make informed decisions about whether this dietary approach might be appropriate for your situation.

What Is the GAPS Diet?

The GAPS (Gut and Psychology Syndrome) diet is an elimination diet protocol created by Dr. Natasha Campbell-McBride, a neurologist and nutritionist. The diet is founded on the hypothesis that increased intestinal permeability—commonly referred to as “leaky gut”—allows harmful substances to enter the bloodstream, potentially affecting brain function and development.

According to the GAPS theory, when the gut lining becomes compromised, toxins, undigested food particles, and bacteria can pass through the intestinal wall into the bloodstream. These substances may then travel to the brain and contribute to various neurological and psychological conditions.

The GAPS protocol aims to “heal and seal” the gut lining through a structured dietary approach, thereby reducing the entry of harmful substances into the bloodstream and potentially improving symptoms associated with various conditions.

It’s important to note that “leaky gut syndrome” is not recognized as an official medical diagnosis by mainstream medicine, though research into intestinal permeability and its health implications continues to evolve.

Who Is the GAPS Diet Designed For?

The GAPS diet was originally developed as a treatment for autism spectrum disorder (ASD), based on Dr. Campbell-McBride’s experience treating her own child. Over time, proponents have promoted it as a potential intervention for numerous other conditions, including:

• Autism spectrum disorder (ASD)
• Attention deficit hyperactivity disorder (ADHD)
• Attention deficit disorder (ADD)
• Dyslexia and dyspraxia
• Depression and anxiety
• Obsessive-compulsive disorder (OCD)
• Schizophrenia and bipolar disorder
• Tourette syndrome
• Eating disorders
• Food allergies and intolerances
• Digestive disorders
• Chronic inflammatory conditions

The diet is primarily marketed toward parents of children with these conditions, though adults with similar diagnoses may also consider following the protocol.

Understanding the Gut-Brain Connection

Research has established that a relationship exists between gut health and brain function, often referred to as the “gut-brain axis.” Some studies indicate that children with autism spectrum disorder experience gastrointestinal symptoms at higher rates than neurotypical children, with up to 70% experiencing issues such as constipation, diarrhea, abdominal pain, or acid reflux.

However, the exact nature of this relationship remains unclear. While some research suggests that certain individuals with ASD may have increased intestinal permeability, other studies have found no significant differences in gut barrier function between autistic and neurotypical children.

Importantly, no research has definitively established that increased intestinal permeability causes autism or other neurological conditions. Even if a correlation exists, it’s uncertain whether gut issues are a cause, a symptom, or simply a co-occurring condition.

The Three Phases of the GAPS Diet

The GAPS protocol consists of three distinct phases, each with specific goals and dietary guidelines. The complete protocol can last anywhere from two to several years, depending on individual progress and symptom improvement.

Phase 1: The Introduction Diet (Elimination Phase)

The introduction phase is the most restrictive part of the GAPS protocol and can last from three weeks to one year. This phase is divided into six progressive stages, with each stage introducing new foods gradually:

Stage 1

The diet begins with homemade meat or fish stock (bone broth), consumed frequently throughout the day. Participants also drink ginger tea, chamomile tea, or mint tea with honey. Probiotic foods like homemade sauerkraut juice may be added in small amounts. Those who tolerate dairy may include homemade yogurt or kefir.

Stage 2

Raw organic egg yolks, ghee (clarified butter), and stews made with well-cooked vegetables and meat or fish are added. Fermented foods continue in increasing amounts.

Stage 3

The diet expands to include avocado, additional fermented vegetables, pancakes made with nut flours and eggs, and scrambled eggs cooked in animal fats like duck fat or ghee.

Stage 4

Grilled and roasted meats, cold-pressed olive oil, freshly pressed vegetable juices, and bread made with GAPS-approved ingredients (typically nut flours) are introduced.

Stage 5

Cooked apple puree and small amounts of raw vegetables (starting with lettuce and peeled cucumber) are added. Fresh fruit juice and small portions of raw fruit (excluding citrus) may be included.

Stage 6

Additional raw fruits, including citrus fruits, are gradually introduced.

Progression through these stages depends on individual tolerance. You move to the next stage only when you can consume the current stage’s foods without digestive symptoms, typically indicated by normal bowel movements.

Phase 2: The Full GAPS Diet (Maintenance Phase)

The full GAPS diet typically lasts 1.5 to 2 years and is less restrictive than the introduction phase, though it still eliminates many common foods. The diet focuses on nutrient-dense, whole foods, including:

• Fresh meat, preferably grass-fed and hormone-free
• Wild-caught fish and shellfish
• Organic eggs
• Animal fats (lard, tallow, duck fat, ghee, raw butter)
• Non-starchy vegetables
• Fermented foods (sauerkraut, kimchi, kefir, yogurt)
• Nuts and seeds in moderation
• Honey as a sweetener
• Bone broth

The diet strictly prohibits several food categories:

• All grains (wheat, rice, corn, oats, etc.)
• Starchy vegetables (potatoes, sweet potatoes, yams)
• Processed and refined sugars
• Most dairy products (except fermented dairy for those who tolerate it)
• Canned and packaged foods
• Artificial ingredients, preservatives, and colorings
• Beans and legumes (except white navy beans and lentils after a certain point)

Additional Guidelines for the Full GAPS Diet

Followers are encouraged to:

• Consume bone broth with every meal
• Eat large quantities of fermented foods daily
• Include healthy fats at every meal
• Choose organic foods whenever possible
• Avoid combining meat and fruit in the same meal
• Prepare foods at home rather than purchasing prepared items

Phase 3: Reintroduction and Coming Off GAPS

After maintaining the full GAPS diet for at least 1.5 to 2 years and experiencing normal digestion for at least six consecutive months, you may begin gradually reintroducing previously eliminated foods.

This phase involves introducing one new food at a time in small amounts, waiting 2-3 days to monitor for any digestive reactions before increasing portion sizes or adding another food. The protocol recommends starting with new potatoes and fermented gluten-free grains.

Even after completing the diet, followers are advised to continue limiting ultra-processed foods, refined sugars, and artificial ingredients, maintaining the whole-foods foundation established during the protocol.

GAPS Diet Supplements

While the GAPS diet emphasizes obtaining nutrients from whole foods, the protocol recommends several supplements during the first two phases to support digestive function and gut healing:

• Probiotics: High-quality, multi-strain probiotic supplements to support beneficial gut bacteria
• Essential fatty acids: Particularly omega-3 fatty acids from fish oil or cod liver oil
• Digestive enzymes: To support the breakdown and absorption of nutrients
• Betaine HCl with pepsin: To support stomach acid production
• Bile salts: For those who have had gallbladder removal or have difficulty digesting fats

Before taking any supplements, it’s essential to consult with a healthcare professional, especially if you’re taking medications or have underlying health conditions. Supplements can interact with certain medications and may not be appropriate for everyone.

Does the GAPS Diet Work? What Does the Research Say?

As of the most current research, scientific evidence supporting the GAPS diet’s effectiveness remains extremely limited. Very few peer-reviewed studies have examined the protocol’s impact on autism spectrum disorder or other targeted conditions.

Limited Research on the GAPS Protocol

The research that does exist is primarily limited to small case studies and reports from the International Society for Orthomolecular Medicine. These studies have suggested possible benefits for certain conditions, but they involve very small sample sizes and lack the rigorous controls needed to draw definitive conclusions.

Additionally, studies examining similar elimination diets for autism spectrum disorder have reported high dropout rates, suggesting that the restrictive nature of these protocols makes them difficult to maintain long-term.

Research on Individual Components

While evidence for the complete GAPS protocol is lacking, some research supports certain elements of the approach:

Probiotics and Gut Health

Several studies have found that children with autism spectrum disorder may have different gut microbiome compositions compared to neurotypical children. Some research suggests that probiotic supplementation may provide benefits for gastrointestinal symptoms and potentially some behavioral aspects of ASD, though more research is needed.

Omega-3 Fatty Acids

Limited research has examined the effects of omega-3 fatty acid supplementation on autism spectrum disorder symptoms, with some small studies suggesting possible benefits for certain behaviors. However, results have been mixed, and larger, more rigorous studies are needed.

Digestive Enzymes

Some smaller studies have explored whether digestive enzyme supplementation might benefit individuals with ASD, particularly those experiencing gastrointestinal symptoms. Results have been inconclusive, and further research is necessary.

The Challenge of Proving Causation

A fundamental challenge in evaluating the GAPS diet is the lack of evidence that intestinal permeability causes the conditions the diet claims to treat. While some individuals with autism spectrum disorder may experience increased intestinal permeability, research has not established whether this is a cause, a consequence, or simply a co-occurring condition.

Autism spectrum disorder is a complex neurodevelopmental condition influenced by multiple genetic and environmental factors. The GAPS theory that a single mechanism—leaky gut—causes such a multifaceted condition represents an oversimplification that is not supported by current scientific understanding.

Potential Benefits of the GAPS Diet

Despite limited scientific validation, some individuals report experiencing benefits from the GAPS protocol. Potential advantages may include:

Elimination of Processed Foods

The GAPS diet eliminates ultra-processed foods, refined sugars, and artificial additives—dietary changes that may benefit anyone, regardless of whether they have a specific diagnosis. Reducing these foods and increasing whole food consumption aligns with general nutritional recommendations.

Increased Nutrient Density

The emphasis on nutrient-dense foods like bone broth, organ meats, vegetables, and fermented foods may increase intake of vitamins, minerals, and beneficial compounds that some people may lack in a typical Western diet.

Identification of Food Sensitivities

The structured elimination and reintroduction process may help identify specific food sensitivities or intolerances that could be contributing to digestive symptoms or other health issues.

Improved Gastrointestinal Symptoms

For individuals experiencing digestive problems, the diet’s focus on easily digestible foods, bone broth, and fermented foods may provide relief from symptoms like bloating, constipation, or diarrhea.

Risks and Concerns About the GAPS Diet

The GAPS diet carries several significant risks and concerns that should be carefully considered before starting the protocol:

Nutritional Deficiencies

The diet’s extreme restrictiveness—particularly during the introduction phase—creates a significant risk of nutritional deficiencies. By eliminating entire food groups for extended periods, including all grains, legumes, and starchy vegetables, followers may not receive adequate amounts of certain nutrients.

Children are particularly vulnerable to nutritional deficiencies because they require adequate nutrition for growth and development. The GAPS diet provides little specific guidance on ensuring nutritional adequacy, increasing this risk.

Disordered Eating Patterns

The diet’s extreme restrictions, rigid rules about food combinations, and emphasis on “healing” through specific eating patterns may contribute to unhealthy relationships with food or disordered eating behaviors, particularly in susceptible individuals.

Special Concerns for Autistic Individuals

Many autistic individuals already have selective eating patterns or sensory sensitivities related to food. The GAPS diet’s restrictions may exacerbate these challenges, potentially leading to even more limited food acceptance and increased nutritional risk.

Additionally, autistic individuals may find the constant dietary changes during the introduction phase particularly challenging, as many prefer routine and predictability.

Financial and Time Burden

The GAPS diet requires significant financial investment and time commitment. The protocol emphasizes organic foods, grass-fed meats, and homemade preparations—all of which can be expensive and time-consuming. Many families may find these requirements unsustainable.

Social Isolation

The diet’s restrictions can make social situations involving food—such as birthday parties, school lunches, or family gatherings—extremely challenging. This social isolation may be particularly difficult for children who are already experiencing challenges with social situations.

Lack of Professional Guidance

Unlike established medical treatments, the GAPS diet typically lacks oversight from healthcare professionals trained in nutrition and dietetics. Without proper guidance, families may inadvertently create nutritional imbalances or miss important warning signs of complications.

Delayed Evidence-Based Treatment

Perhaps most concerning, families who pursue the GAPS diet as a treatment may delay or forgo evidence-based interventions that could genuinely benefit their child, such as behavioral therapies, educational support, or medical treatments for co-occurring conditions.

Practical Considerations Before Starting the GAPS Diet

If you’re considering the GAPS diet despite its limitations and risks, several important steps can help protect your health or your child’s health:

Consult Healthcare Professionals

Before starting the GAPS diet, consult with your doctor and, ideally, a registered dietitian who can assess your nutritional status, identify any specific concerns, and help monitor for deficiencies during the protocol.

Get Baseline Testing

Consider getting baseline laboratory tests to assess nutritional status before starting the diet. This can include tests for vitamin D, iron, B vitamins, and other nutrients. Regular monitoring can help identify deficiencies early.

Keep Detailed Records

If you proceed with the diet, keep detailed records of foods consumed, symptoms experienced, and any changes in behavior or health. This documentation can help you and your healthcare providers assess whether the diet is beneficial or harmful.

Set Clear Goals and Timelines

Establish specific, measurable goals for what you hope to achieve with the diet and set realistic timelines for evaluating progress. This can help you make objective decisions about whether to continue rather than persisting with an ineffective intervention.

Maintain Evidence-Based Treatments

Don’t abandon proven treatments in favor of the GAPS diet. If you or your child is receiving beneficial therapies or medical care, continue these while implementing dietary changes.

Be Prepared for Challenges

Understand that the GAPS diet is extremely demanding. Be realistic about whether you have the time, financial resources, and family support necessary to sustain the protocol for the recommended timeline.

Alternative Approaches to Consider

If you’re interested in exploring the potential connection between gut health and neurological or psychiatric conditions, several less restrictive approaches may be worth considering:

Working with a Registered Dietitian

A registered dietitian can help you identify food sensitivities through proper testing and elimination protocols while ensuring nutritional needs are met. This individualized approach may be more appropriate than a one-size-fits-all restrictive diet.

Addressing Specific Gastrointestinal Symptoms

Rather than following a restrictive protocol, work with a gastroenterologist to properly diagnose and treat any gastrointestinal issues. Addressing constipation, diarrhea, or other digestive problems through evidence-based approaches may improve quality of life without extreme dietary restrictions.

Optimizing Overall Diet Quality

Focus on improving overall diet quality by increasing vegetables, fruits, whole grains, lean proteins, and healthy fats while reducing ultra-processed foods and added sugars. This balanced approach provides benefits without the risks of extreme restriction.

Probiotic Supplementation

If you’re interested in supporting gut health, consider discussing probiotic supplementation with your healthcare provider. Some research suggests benefits for certain conditions, and probiotics carry fewer risks than extreme dietary protocols.

What Healthcare Professionals Say About the GAPS Diet

The GAPS diet has received criticism from many healthcare professionals, nutritionists, and medical organizations. Common concerns include:

• The lack of scientific evidence supporting the diet’s theoretical foundation
• The absence of peer-reviewed research demonstrating effectiveness
• The significant risk of nutritional deficiencies, particularly in children
• The potential for the diet to delay evidence-based treatments
• The oversimplification of complex conditions like autism spectrum disorder
• The financial exploitation of vulnerable families seeking solutions for their children

Many healthcare professionals emphasize that while gut health is important and emerging research on the gut-brain connection is promising, the GAPS diet represents an extreme approach that is not justified by current evidence.

The Bottom Line

The GAPS diet is an extremely restrictive dietary protocol based on the theory that increased intestinal permeability causes various neurological and psychiatric conditions. While some individuals report benefits, scientific evidence supporting the diet’s effectiveness remains very limited.

The diet carries significant risks, including nutritional deficiencies, disordered eating patterns, social isolation, and financial burden. These risks may be especially concerning for children, who are the primary target population for this intervention.

Current research has not established that leaky gut causes conditions like autism spectrum disorder, and the GAPS theory represents an oversimplification of complex conditions influenced by multiple genetic and environmental factors.

If you’re considering the GAPS diet, it’s essential to consult with qualified healthcare professionals, including your doctor and a registered dietitian. They can help you weigh the potential risks and benefits, ensure nutritional needs are met, and explore alternative approaches that may be more appropriate for your specific situation.

Remember that evidence-based treatments—such as behavioral therapies for autism spectrum disorder or appropriate medical care for other conditions—should not be abandoned in pursuit of unproven dietary interventions.

While optimizing gut health through diet may play a role in overall wellness, extreme restriction is rarely necessary or beneficial. A balanced approach that improves overall diet quality while maintaining variety and nutritional adequacy is more likely to support long-term health without the significant risks associated with highly restrictive protocols like the GAPS diet.

Sources:

• National Center for Biotechnology Information – Autism Spectrum Disorder
• Frontiers in Neuroscience – Intestinal Permeability in Autism
• PMC – Probiotics and Autism Spectrum Disorder
• PMC – Intestinal Permeability Research
• PMC – Elimination Diets and Autism
• GAPS Diet Official Website
• FDA – Dietary Supplements Information
• PMC – Feeding Difficulties in Autism