The GAPS diet (Gut and Psychology Syndrome) is a nutritional protocol developed by neurologist Dr. Natasha Campbell-McBride. It aims to heal the lining of the digestive tract and rebalance the gut microbiome to improve psychological and physical health issues. The diet operates on the premise that repairing the gut is the most direct way to resolve health problems originating outside the digestive system. This comprehensive elimination diet involves a strict, phased approach that can last up to two years, replacing difficult-to-digest foods with easily absorbed, nutrient-rich alternatives.
Foundational Principles and Core Hypothesis
The theoretical basis of the GAPS diet centers on intestinal hyperpermeability, commonly called “leaky gut.” Proponents suggest that a damaged gut lining allows partially digested food particles, waste products, and toxins to pass directly into the bloodstream. This intrusion is theorized to trigger a systemic inflammatory response and overwhelm the body’s detoxification pathways, leading to chronic toxicity.
This toxicity, combined with nutrient malabsorption, is believed to directly impact brain function. This connection forms the core of the gut-brain axis theory, linking digestive health to neurological and psychological function.
The diet also addresses dysbiosis, an imbalance in the gut’s microbial community characterized by an overgrowth of pathogenic bacteria and yeast. This imbalance is thought to drive intestinal permeability. By correcting dysbiosis and healing the intestinal wall, the protocol aims to prevent the entry of toxins. It is promoted as a method to manage conditions such as autism spectrum disorder, attention deficit hyperactivity disorder (ADHD), and various digestive disorders.
The Three Core Phases of the Diet
The GAPS protocol is structured in three sequential phases: the Introductory Diet, the Full GAPS Diet, and the Maintenance/Exit Diet. This progression gradually increases dietary complexity as the gut lining heals.
Introductory Diet
This first phase is the most restrictive and intensive, consisting of six distinct stages that can take several weeks to months. It begins with highly digestible foods like homemade bone broth, boiled meats, and specific probiotic liquids, such as fermented vegetable juice. As the individual progresses, the diet slowly introduces foods like raw egg yolks, stews with more vegetables, and fermented foods like homemade yogurt or kefir, if tolerated. The purpose of this initial process is to rapidly soothe and seal the gut lining.
Full GAPS Diet
Once the Introductory Diet is completed without digestive distress, the individual moves to the Full GAPS Diet, which typically lasts 18 months to two years. This phase is less restrictive but still eliminates all grains, refined sugar, and processed foods. The emphasis remains on nutrient-dense foods, including meat, fish, eggs, and a variety of cooked and raw vegetables.
Maintenance/Exit Diet
The final stage begins only after an individual has experienced normal digestion for a minimum of six months on the Full GAPS Diet. This phase involves the slow, careful reintroduction of previously restricted complex carbohydrates. Reintroduction starts with foods like properly prepared potatoes and fermented grains. The process is done one food at a time, over several months, to monitor for adverse reactions and ensure the gut remains healed.
Allowed and Restricted Food Groups
The GAPS diet prioritizes foods that are low in complex carbohydrates and easily digestible. Homemade bone broth is a central component, consumed frequently for its collagen, gelatin, and amino acid content, which is believed to support the repair of the intestinal lining.
Allowed Foods
The diet encourages nutrient-dense options, preferably sourced from high-quality, organic, or pasture-raised animals.
- All types of fresh or frozen meats, fish, shellfish, and eggs.
- Natural fats, such as animal fats (tallow, lard, duck fat), coconut oil, and homemade ghee.
- Probiotic-rich foods, including fermented vegetables like sauerkraut and homemade fermented dairy (yogurt and kefir).
- Specific vegetables and fruits, with initial stages favoring cooked, non-starchy varieties.
Restricted Foods
The list of restricted foods is extensive, focusing on eliminating complex carbohydrates and processed items.
- All grains, including wheat, rice, corn, and gluten-free alternatives like quinoa and buckwheat.
- All forms of refined sugar, including high-fructose corn syrup and most artificial sweeteners.
- Starchy vegetables like potatoes, parsnips, and yams, as their complex carbohydrates are thought to feed pathogenic bacteria.
- Most commercial and processed foods, including canned goods and pasteurized dairy products.
Scientific Context and Critical Evaluation
The GAPS diet has gained a following through anecdotal reports, but it lacks validation from large-scale, controlled clinical research. The diet’s foundational theory is often debated, as “leaky gut syndrome” is not a recognized medical diagnosis, although intestinal permeability is a recognized symptom of certain diseases.
There are no published randomized controlled trials (RCTs) specifically examining the efficacy of the entire GAPS protocol for treating the neurological or psychological conditions it claims to address. While general research supports the gut-brain axis and the importance of the microbiome, the specific, multi-phased GAPS diet remains largely unproven by conventional scientific standards.
The highly restrictive nature of the diet raises concerns among healthcare professionals, especially when applied to children, due to the risk of nutritional deficiencies. Eliminating entire food groups, such as grains and starchy vegetables, can lead to inadequate intake of fiber, B vitamins, and certain minerals. Furthermore, following such a demanding regimen for an extended period may contribute to social isolation and potentially foster disordered eating patterns.