What Scientists Have to Say About the GAPS Diet
Proponents of the GAPS diet—a strict, multi-phase elimination diet that involves cutting out grains, pasteurized dairy, starchy vegetables, refined carbohydrates, and more—claim it can successfully treat neurological and psychological conditions, including autism.
But increasing numbers of scientists, doctors, and nutrition professionals are raising concerns about the highly restrictive nature of the diet and the lack of data supporting its supposed benefits.
To help you make sense of the controversy, we explain the origins of the GAPS diet and how to implement the various phases. Then, we dig into the claims about GAPS diet health benefits.
What Is the GAPS Diet?
GAPS, which stands for Gut and Psychology Syndrome, is a term created by Dr. Natasha Campbell-McBride.
Campbell-McBride believes the modern world can damage our gut health in a multitude of ways, and that gut bacteria imbalances are the underlying cause of many health problems, all of which can be treated using the GAPS diet she invented.
According to Dr. Campbell-McBride, imbalances in gut bacteria populations can prevent children from properly digesting and absorbing food, which in turn causes them to develop a variety of symptoms—some related to digestion, and some not. Many of those symptoms, Campbell-McBride says, are caused because harmful gut bacteria transform the undigested food into toxic substances that clog the body and brain. When these toxins flood the brain, they can interfere with sensory processing and keep children from learning and developing skills. This can result in condition such as hyperactivity, dyslexia, and autism.
The purpose of the GAPS diet, Campbell-McBride writes, is “to detoxify the person, to lift the toxic fog off the brain to allow it to develop and function properly. In order to achieve that we need to clean up and heal the digestive tract, so it stops being the major source of toxicity in the body and becomes the source of nourishment, as it is supposed to be. As more than 90% of everything toxic floating in our blood (and getting into the brain) comes from the gut, healing it will drop the level of toxicity in the body dramatically.”
As she concocted the GAPS diet, Campbell-Mcbride drew heavily from the work of Dr. Sidney Valentine Haas. In the early 1900s, Dr. Haas developed a food-based treatment plan for patients with celiac disease that came to be known as the Specific Carbohydrate Diet (SCD). The enduring popularity of the diet is due largely to the efforts of Elaine Gottschall, who claims that when Dr. Hass used the SCD approach to treat her daughter’s severe ulcerative colitis, it brought about miraculous changes. Haas was 92 at the time, and after he passed away, Gottschall decided to devote her life to introducing SCD—which she believed cured her daughter—to others. Based on the testimonials of others who tried SCD, Gottschall promoted it as a treatment for colitis, cystic fibrosis, and autism.
Campbell-McBride learned about SCD when her first child was diagnosed with autism. Frustrated by the lack of effective conventional treatments, she decided to take matters into her own hands. And thus the GAPS diet was born. In her 2004 book, Gut and Psychology Syndrome, she states that the GAPS diet—which is essentially a more restrictive version of SCD—cured her son’s autism.
Though individuals of all ages can and do adopt the GAPS diet, it was designed for children and is still most often sought out by parents whose children have difficult-to-treat conditions.
How the GAPS Diet Works
Following the GAPS diet is a year-long process that requires cutting out all foods that Campbell-McBride believes contribute to gut imbalances. The diet is divided into three phases: the introduction phase, which is intended to detoxify the body; the maintenance phase, during which the gut has time to repair and heal; and the reintroduction phase, for transitioning off the diet.
The GAPS diet prohibits sugars and starches, meaning no bread, pasta, rice, potatoes, or traditional desserts. We’ll get into the specifics of what you can eat later on, but for now, it’s enough to know that the diet centers on broths, meats, fats, nuts, and some vegetables and fruits.
The GAPS Introduction Phase
The GAPS diet intro phase is by far the most intense. The foods you can eat during this phase, which is broken down into six stages, are exceptionally limited. Depending on how your body responds, this phase can last from three weeks to a full year.
Comments from the FAQ section on her website indicate that the introduction phase can be quite brutal. Common side effects include severe stomach pain and bloating, vomiting, diarrhea, and constipation. Campbell-McBride warns that you can also expect “die-off phases”—as harmful bacteria die, she states, they release toxins, causing symptoms to temporarily intensify.
During the introduction phase, you pare your diet back to a few simple liquids. As you move through the stages, you introduce small amounts of a single new food at a time. If you experience a negative reaction, then you should continue to restrict that food for a few more weeks. The standard for determining whether you’re tolerating the foods is whether you’re having normal digestion and bowel movements. You can also test for sensitivities, according to Campbell-McBride, by placing a small amount of a food on your wrist and waiting to see if it causes a reaction. Most medical professionals consider this test useless.
- Stage One: One of Campbell-McBride’s theories is that damage to your gut prevents you from absorbing essential nutrients, so even if you’re eating a normal amount of food, you’re living in a constant state of starvation. To correct that, stage one includes only foods that are extremely easy to digest: room temperature water, homemade meat or fish stock, probiotic juices, and ginger tea with honey. If dairy sensitivity is not an issue, then homemade, unpasteurized kefir and yogurt can be included. It’s also recommended to take probiotic supplements.
- Stage Two: At this stage, you can begin to incorporate raw, organic egg yolk, boiled meats and fish, fermented fish, homemade ghee, and high-fat stews and casseroles loaded with more probiotics.
- Stage Three: When you reach stage three, in addition to the foods already introduced, you can add ripe avocado, special pancakes made with nut butter, eggs, and squash, eggs scrambled in ghee, goose fat, or duck fat, and fermented vegetables like sauerkraut.
- Stage Four: In this stage, you get to experiment with small amounts of roasted or grilled meats, as well as cold-pressed olive oil; fresh-pressed juice made from either carrot, celery, lettuce, mint leaves, or some combination of those ingredients; and a special kind of bread made with nut flour, squash, natural fat, and salt to taste.
- Stage Five: Finally, you can eat fruit again! During stage five, you can eat cooked apple purée, as well as juice made from apple, pineapple, and mango. You can also try eating fresh vegetables, starting with “the softer parts of lettuce” and peeled cucumber, and then moving on to other vegetables like carrots, tomatoes, onions, cabbage, and so on.
- Stage Six: If all is going well, you can try some raw apple, as long as you make sure to peel it first. You can then try other raw fruits, and gradually introduce GAPS diet recipes for cakes and other baked goods made using dried fruit and nut flour.
The GAPS Maintenance Phase
This phase typically lasts between one and a half and two years. While less restrictive than the GAPS diet intro phase, the diet still requires you to restrict yourself to the following foods:
- Hormone-free, grass-fed meat
- Seafood, including shellfish
- Organic eggs
- Animal fats like lard, tallow, lamb fat, duck fat, raw butter, and ghee
- Fermented foods, such as sauerkraut and homemade, unpasteurized kefir and yogurt
- Some vegetables and fruits
- Nuts and nut flours
All other foods should be avoided, especially refined carbohydrates and any preservatives or artificial colorings.
There are also recommendations about what you should eat when. For instance, meals should be made up of meat plus vegetables, and should always include bone broth and healthy fats. You should also consume as much fermented food as you can tolerate. Stay away from packaged and canned foods though, and never eat meat and fruit together.
The GAPS Reintroduction Phase
If you adhere to the full GAPS protocol, you’ll spend a minimum of a year and a half on the diet. After you’ve experienced normal digestion and bowel movements for at least six months, you can begin gradually reintroducing small amounts of prohibited foods. The reintroduction phase can last quite some time. It’s recommended that you introduce each food individually by eating a very small amount, and then, if you experience no digestive issues over the next two to three days, gradually increasing portion sizes for that food. Then you repeat that process all over again to introduce the next food.
The GAPS diet does not prescribe a specific order for reintroducing foods, but does recommend beginning with new potatoes and then trying fermented, gluten-free grains.
Once you’ve transitioned off the diet—which some never do, finding they feel so good on it, they have no desire to try out banned foods—it’s strongly advised that you continue to eat a whole-foods based diet.
A Basic Gaps Diet Foods List
And now, as promised, we’ll cover some of the foods you’re most likely to encounter in GAPS diet recipes. While this isn’t a complete list of all the foods you can eat on the GAPS diet, it does offer a clear picture of what following the diet entails. As you’ll see, grains and starchy vegetables are all out, while meat and healthy fats are liberalized.
- Wild-caught fish: This category includes anchovies, bass, cod, grouper, haddock, halibut, herring, mackerel, mahi mahi, red snapper, salmon, sardines, sea bass, trout, tuna, and walleye.
- Organic, grass-fed meat and poultry: In addition to lots and lots of bone broth, you can also eat beef, bison, chicken duck, lamb, turkey, quail, and venison.
- Organic, unrefined, unpasteurized fats and oils: For instance, avocado, almond, coconut, flaxseed, hempseed, macadamia, olive, sesame, and walnut oils, as well as butter and ghee.
- Raw, grass-fed dairy and pasture-raised eggs: Eggs, ideally pasture-raised are allowed, as are most kinds of cheese, which should be minimally processed. Some cheeses come with specific recommendations regarding the length of time they’re aged, and all should be hormone-free.
- Nuts and legumes, ideally sprouted, soaked, or as nut butter: This means almonds, Brazil nuts, coconut (technically a drupe), hazelnuts, lima beans, macadamia nuts, navy beans, pecans, pine nuts, and walnuts are all good.
- Vegetables: Whether fermented, raw, or cooked, artichokes, arugula, asparagus, avocados (technically a fruit, and also treated as a fat in some instances), beets, bell peppers, bok choy, broccoli, broccoli rabe, Brussels sprouts, cabbage, carrots, celery, collards, cucumbers, eggplant, fennel, garlic, green beans, Jerusalem artichoke, kale, mushrooms,olives, onions, parsnip, pumpkin, radish, romaine lettuce, seaweed, spinach, squash, tomatoes, turnips, and watercress, get approval.
- Fruits, in moderation: While you shouldn’t eat too many (especially citrus fruits), and never with a meal that includes meat, as Campbell-McBride believes fruits interfere with digestion, you can have fruits like apples, apricots, bananas, berries, cantaloupe, cherries, figs, grapefruit, grapes, kiwi, lemons, limes, mango, nectarines, oranges, papaya, peaches, pears, pineapple, plums, pomegranates, rhubarb, and watermelon.
- Spices, herbs, and condiments: Options include apple cider vinegar, basil, black pepper, cilantro, coriander seeds, cinnamon, coconut vinegar, cumin, dill, fennel, garlic, ginger, mint, parsley, peppermint, rosemary, sage, sea salt, tarragon, thyme, and turmeric.
- Flours, in moderation: Only wheat-free, grain free flours, such as those made from coconut, almonds, or nuts are approved for the GAPS diet.
- Sweeteners, in moderation: Small amounts of raw honey, dates made into paste, and other sweeteners made from dried fruit are allowed.
- Beverages: You can drink (or cook with) almond milk, coconut kefir, coconut milk, herbal teas, raw vegetable juices, and, of course, water, both sparkling and still. Adults can also drink wine in moderation.
- Supplements: Some of the recommended supplement include probiotics, digestive enzymes, fish oil and fermented cod liver oil, and L-glutamine powder.
Are There GAPS Diet Health Benefits?
And now, we arrive at the heart of the controversy. Are there GAPS diet health benefits associated with following the highly restrictive protocol? According to Campbell-Mcbride, its creator, using the GAPS diet to heal the gut can treat and even cure conditions such as:
- Attention-deficit disorder (ADD)
- Bed wetting
- Bipolar disorder
- Dyspraxia (a coordination disorder)
- Digestive disorders
- Eating disorders
- Obsessive-compulsive disorder (OCD)
- Tourette’s syndrome
However, there are no published studies to support any of these benefits. While experts agree that there is evidence indicating dietary changes can help children and other individuals dealing with some of the issues Campbell-McBride claims the GAPS diet can treat, the link between diet, gut bacteria, and health outcomes is far more complex than Campbell-McBride claims.
According to Zoe Connor, a leading pediatric dietician who specializes in working with children with autism, some aspects of the GAPS diet could benefit children with undiagnosed food intolerances. She spoke with Anthony Warner, who gained fame “Exposing lies, pretensions and stupidity in the world of food” as The Angry Chef, about the GAPS diet. Connor believes it’s also possible that adopting a low-carbohydrate diet could be a helpful complementary treatment for children with subclinical epilepsy. Changing your diet, and adding probiotics in particular, may even help decrease certain behaviors associated with autism. “Just the action of pushing a child with autism to make significant changes in eating may have a knock on effect in making their behaviour less rigid in other areas or indeed empower parents to feel able to tackle other problems areas,” said Connor. She believes dietary changes should be taken seriously, and seriously studied.
But that’s not to say she’s a fan of the GAPS diet. Far from it. “‘If a child followed GAPS to the letter they could be seriously harmed or even die,” she said. We’ll get into the risks of the diet in the next section. Instead, she hopes researchers will examine why some people feel the diet does work to understand what, exactly, is happening." If it is because they have undiagnosed conditions,” she said, “then we can treat that condition using diet or medications and the child can then have a much more varied, adequate, less expensive and less inconvenient diet with the same improvements.”
Potential GAPS Diet Risks
One of the factors driving the intense outcry surrounding the GAPS diet is that it’s directed toward children. According to Campbell-McBride, the younger a child is when the protocol is adopted, the better the chances of its success. Parents who are desperately looking for a solution to their child’s health issues place them on this extremely limited diet, which has no scientific evidence to support it.
Campbell-McBride states that symptoms such as vomiting, severe stomach pain, distended stomachs, and extreme diarrhea or constipation, as well as increases in the symptoms you’re trying to eliminate with the GAPS diet, are totally normal. Given time, the diet will work and your gut will begin to heal. In the FAQ section of her website, she suggests that parents ignore doctors who tell them their children should be eating more varied diets.
Dieticians have raised concerns that the introductory phase—which can last up to a year, remember—could put people at risk of calcium, iron, potassium, niacin, magnesium, and zinc deficiencies. And the maintenance phase could cause you to overdose on vitamin A, a real possibility if you keep it up for the recommended length of time. Some critics of the GAPS diet also worry that the large amounts of bone broth you consume could increase your lead intake to toxic levels.
Since there’s no hard data on the diet, however, the risks are about as unprovable as the benefits. If embarking on the GAPS diet, it can helpful to supplement with certain nutrients such as essential amino acids to safeguard your health.
On her site, Campbell-Mcbride also makes a number of claims that are bizarre, concerning, and flat-out false. Here’s some of the most striking examples, compiled in part from an excellent article written by Dr. Harriet Hall (aka The SkepDoc), a retired family physician who writes about pseudoscience and questionable medical practices, and in part from The Angry Chef’s article about the GAPS diet mentioned earlier.
- Vaccines should be avoided: Campbell-McBride subscribes to the probably incorrect view that not only the MMR vaccine (which a fraudulent paper claimed caused autism) be avoided, but also all vaccines should be avoided. She claims that vaccinations put “an enormous strain on an already compromised immune system, becomes that last straw which breaks the camel's back and brings on the beginning of autism, asthma, eczema, diabetes, etc.”
- Childhood diseases aren’t that dangerous: This no doubt contributes to the comfort she feels in eschewing vaccines. She admits that the tetanus and polio vaccines are essential, but when it comes to all the other ones, she writes, “It is better to let your child go through those childhood infections. Just make sure that your child is well nourished and he or she will sail through those infections and come out stronger with a more robust immune system.” Dr. Hall is horrified by this stance. “To be clear, she is talking about Meningitis C, Meningitis B, Pneumococcal infections, Measles, Mumps, Rubella, Influenza, Whooping Cough, Haemophilus influenzae type b and others. To claim that children will ‘sail through these infections’ is an insult to the many, many lives that they affect every year.”
- Doctors don’t know what they’re talking about: Except for her, of course. Mainstream doctors who say that the GAPS diet can be dangerous are simply uneducated. Though her point that doctors aren’t extensively trained in nutrition has some validity, she totally disregards the many dietitians and registered nutritionists whose concerns about the GAPS diet stem from their deep knowledge about food and human health.
- Supplements can replace prescription medications: In the FAQs on her site, Campbell-McBride told a patient who shared that they had recently been prescribed Warfarin, a blood thinner, to treat a deep vein blood clot, that they should take fish oil instead. “As you increase the dose of fish oils, you can gradually reduce the dose of Warfarin (and maybe even remove it altogether),” she wrote.
- Desire outweighs food sensitivities: If you listen to your desires for food, you will be able to eat anything you genuinely want to eat. Because you ate it when your body asked for it, it will only benefit your health.
- Perfumes can have side effects: Apparently, perfumes and scented products destroy your sense of smell.
- Olive oil is better than toothpaste: In a strange twist on the Ayurvedic practice of oil pulling, Campbell-McBride suggests that you brush your teeth with olive oil instead of toothpaste to detoxify your mouth.
- Your nervous systems influence which foods you should eat: As your autonomic nervous system shifts between sympathetic and parasympathetic dominance, she claims, you’ll need to adjust your eating habits. One mode requires more meat and fat, while the other requires more plant foods. You’ll be able to sense which mode you’re in and meal plan accordingly.
- Tune into the daily and seasonal cleansing and building cycles: Each cycle, as with each mode of nervous system function, requires different nutrients. For cleansing, you need plant foods. And for building, animal foods.
- It’s safe to eat liver while pregnant: Campbell-McBride advises disregarding doctor’s advice on this, saying that vitamin A only causes damage in processed forms, not the natural forms found in liver. She bases this on the fact that liver has been eaten for centuries by many cultures worldwide.
- You can store bone broth unrefrigerated for up to a year: In response to a question about how to store the large quantities of bone broth the diet requires if you have limited freezer space, she suggests ladling the broth into sterilized glass jars, pressure cooking them, then sealing and storing them at room temperature. “I know a fair bit about food processing,” writes The Angry Chef, “and this is really great advice if you want to die.” The most serious problem with Campbell-McBride’s storage suggestion is that it’s unlikely to kill all pathogenic spores, putting you at risk of contracting botulism, which produces a nerve toxin that’s among the most poisonous substances out there.
- Your ancestry determines your dietary needs: Meaning, if you’re descended from Viking or Eskimo stock, you’ll need to eat lots of fish.
- High blood cholesterol isn’t a problem: Quite the opposite, she writes, “High blood cholesterol is good news: it means that the body is healing itself, repairing damaged tissues.” She also states that as you age, having high cholesterol keeps you healthier and helps you live longer. Plus, testing it can be potentially harmful.
- It’s safe for everyone, including young children, to eat raw eggs: Again, per The Angry Chef, “This is bad advice unless you enjoy the effects of food poisoning. Personally I do not, salmonella kills hundreds of people every year and young children are especially at risk.”
- The Earth’s soils are dangerously depleted: This is the root cause of degenerative disease. Our foods now lack essential minerals and nutrients. To match the nutrition once contained in a single apple, a person living today would need to eat over 4 pounds of apples.
Without testing, it’s impossible to say definitively whether the GAPS diet helps or harms the people who try it. But the concerns raised by various experts make a compelling choice for exploring alternate approaches and waiting to see what the data, if it’s ever collected, reveals.