AIP (Autoimmune Protocol) Diet: A Beginner’s Guide

What is the Autoimmune Protocol Diet?

A healthy immune system is designed to produce antibodies that attack foreign or harmful cells in your body.

However, in people with autoimmune disorders, the immune system tends to produce antibodies that, rather than fight infections, attack healthy cells and tissues.

This can result in a range of symptoms, including joint pain, fatigue, abdominal pain, diarrhea, brain fog, and tissue and nerve damage.

A few examples of autoimmune disorders include rheumatoid arthritis, lupus, IBD, type 1 diabetes, and psoriasis.

Autoimmune diseases are thought to be caused by a variety of factors, including genetic propensity, infection, stress, inflammation, and medication use.

Also, some research suggests that, in susceptible individuals, damage to the gut barrier can lead to increased intestinal permeability, also known as “leaky gut,” which may trigger the development of certain autoimmune diseases (2).

Certain foods are believed to possibly increase the gut’s permeability, thereby increasing your likelihood of leaky gut.

The AIP diet focuses on eliminating these foods and replacing them with health-promoting, nutrient-dense foods that are thought to help heal the gut, and ultimately, reduce inflammation and symptoms of autoimmune diseases (3).

It also removes certain ingredients like gluten, which may cause abnormal immune responses in susceptible individuals (4, 5).

While experts believe that a leaky gut may be a plausible explanation for the inflammation experienced by people with autoimmune disorders, they warn that the current research makes it impossible to confirm a cause-and-effect relationship between the two (2).

Therefore, more research is needed before strong conclusions can be made.

How does it work?

The AIP diet resembles the paleo diet, both in the types of foods allowed and avoided, as well as in the phases that comprise it. Due to their similarities, many consider the AIP diet an extension of the paleo diet — though AIP may be seen as a stricter version of it.

The AIP diet consists of two main phases.

The elimination phase

The first phase is an elimination phase that involves the removal of foods and medications believed to cause gut inflammation, imbalances between levels of good and bad bacteria in the gut, or an immune response (1, 3).

During this phase, foods like grains, legumes, nuts, seeds, nightshade vegetables, eggs, and dairy are completely avoided.

Tobacco, alcohol, coffee, oils, food additives, refined and processed sugars, and certain medications, such as non-steroidal anti-inflammatory drugs (NSAIDs) should also be avoided (1).

Examples of NSAIDs include ibuprofen, naproxen, diclofenac, and high dose aspirin.

On the other hand, this phase encourages the consumption of fresh, nutrient-dense foods, minimally processed meat, fermented foods, and bone broth. It also emphasizes the improvement of lifestyle factors, such as stress, sleep, and physical activity (1).

The length of the elimination phase of the diet varies, as it’s typically maintained until a person feels a noticeable reduction in symptoms. On average, most people maintain this phase for 30–90 days, but some may notice improvements as early as within the first 3 weeks (1, 6).

The reintroduction phase

Once a measurable improvement in symptoms and overall well-being occurs, the reintroduction phase can begin. During this phase, the avoided foods are gradually reintroduced into the diet, one at a time, based on the person’s tolerance.

The goal of this phase is to identify which foods contribute to a person’s symptoms and reintroduce all foods that don’t cause any symptoms while continuing to avoid those that do. This allows for the widest dietary variety a person can tolerate.

During this phase, foods should be reintroduced one at a time, allowing for a period of 5–7 days before reintroducing a different food. This allows a person enough time to notice if any of their symptoms reappear before continuing the reintroduction process (1).

Foods that are well tolerated can be added back into the diet, while those that trigger symptoms should continue to be avoided. Keep in mind that your food tolerance may change over time.

As such, you may want to repeat the reintroduction test for foods that initially failed the test every once in a while.

Step-by-step reintroduction protocol

Here’s a step-by-step approach to reintroducing foods that were avoided during the elimination phase of the AIP diet.

• Step 1. Choose one food to reintroduce. Plan to consume this food a few times per day on the testing day, then avoid it completely for 5–6 days.
• Step 2. Eat a small amount, such as 1 teaspoon of the food, and wait 15 minutes to see if you have a reaction.
• Step 3. If you experience any symptoms, end the test and avoid this food. If you have no symptoms, eat a slightly larger portion, such as 1 1/2 tablespoons, of the same food and monitor how you feel for 2–3 hours.
• Step 4. If you experience any symptoms over this period, end the test and avoid this food. If no symptoms occur, eat a normal portion of the same food and avoid it for 5–6 days without reintroducing any other foods.
• Step 5. If you experience no symptoms for 5–6 days, you may reincorporate the tested food into your diet, and repeat this 5-step reintroduction process with a new food.

It’s best to avoid reintroducing foods under circumstances that tend to increase inflammation and make it difficult to interpret results. These include during an infection, following a poor night’s sleep, when feeling unusually stressed, or following a strenuous workout.

Additionally, it’s sometimes recommended to reintroduce foods in a particular order. For example, when reintroducing dairy, choose dairy products with the lowest lactose concentration to reintroduce first, such as ghee or fermented dairy products.

List of foods to eat and avoid 

The AIP diet has strict recommendations regarding which foods to eat or avoid during its elimination phase (7, 8).

Foods to avoid

• Grains: rice, wheat, oats, barley, rye, etc., as well as foods derived from them, such as pasta, bread, and breakfast cereals
• Legumes: lentils, beans, peas, peanuts, etc., as well as foods derived from them, such as tofu, tempeh, mock meats, or peanut butter
• Nightshade vegetables: eggplants, peppers, potatoes, tomatoes, tomatillos, etc., as well as spices derived from nightshade vegetables, such as paprika
• Eggs: whole eggs, egg whites, or foods containing these ingredients
• Dairy: cow’s, goat’s, or sheep’s milk, as well as foods derived from these milks, such as cream, cheese, butter, or ghee; dairy-based protein powders or other supplements should also be avoided
• Nuts and seeds: all nuts and seeds and foods derived from them, such as flours, butter, or oils; also includes cocoa and seed-based spices, such as coriander, cumin, anise, fennel, fenugreek, mustard, and nutmeg
• Certain beverages: alcohol and coffee
• Processed vegetable oils: canola, rapeseed, corn, cottonseed, palm kernel, safflower, soybean, or sunflower oils
• Refined or processed sugars: cane or beet sugar, corn syrup, brown rice syrup, and barley malt syrup; also includes sweets, soda, candy, frozen desserts, and chocolate, which may contain these ingredients
• Food additives and artificial sweeteners: trans fats, food colorings, emulsifiers, and thickeners, as well as artificial sweeteners, such as stevia, mannitol, and xylitol

Some AIP protocols further recommend avoiding all fruit — both fresh or dried — during the elimination phase. Others allow the inclusion of 10–40 grams of fructose per day, which amounts to around 1–2 portions of fruit per day.

Although not specified in all AIP protocols, some also suggest avoiding algae, such as spirulina or chlorella, during the elimination phase, as this type of sea vegetable may also stimulate an immune response (9).

Foods to eat

• Vegetables: a variety of vegetables except for nightshade vegetables and algae, which should be avoided
• Fresh fruit: a variety of fresh fruit, in moderation
• Tubers: sweet potatoes, taro, yams, as well as Jerusalem or Chinese artichokes
• Minimally processed meat: wild game, fish, seafood, organ meat, and poultry; meats should be wild, grass-fed or pasture-raised, whenever possible
• Fermented, probiotic-rich foods: nondairy-based fermented food, such as kombucha, sauerkraut, pickles, and coconut kefir; probiotic supplements may also be consumed
• Minimally processed vegetable oils: olive oil, avocado oil, or coconut oil
• Herbs and spices: as long as they’re not derived from a seed or a chilli pepper
• Vinegars: balsamic, apple cider, and red wine vinegar, as long as they’re free of added sugars
• Natural sweeteners: maple syrup and honey, in moderation
• Certain teas: green and black tea at average intakes of up to 3–4 cups per day
• Bone broth

Despite being allowed, some protocols further recommend that you moderate your intake of salt, saturated and omega-6 fats, natural sugars, such as honey or maple syrup, as well as coconut-based foods.

Depending on the AIP protocol at hand, small amounts of fruit may also be allowed. This usually amounts to a maximum intake of 10–40 grams of fructose per day, or the equivalent of about 1–2 portions of fresh fruit.

Some protocols further suggest moderating your intake of high glycemic fruits and vegetables, including dried fruit, sweet potatoes, and plantain.

The glycemic index (GI) is a system used to rank foods on a scale of 0 to 100, based on how much they will increase blood sugar levels, compared with white bread. High glycemic fruits and vegetables are those ranked 70 or above on the GI scale (10).

Does the AIP diet work?

Though research on the AIP diet is limited, some evidence suggests that it may reduce inflammation and symptoms of certain autoimmune diseases.

May help heal a leaky gut

People with autoimmune diseases often have a leaky gut, and experts believe there may be a link between the inflammation they experience and the permeability of their gut (2, 3, 11, 12).

A healthy gut typically has a low permeability. This allows it to act as a good barrier and prevent food and waste remains from leaking into the bloodstream.

However, a highly permeable or leaky gut allows foreign particles to crossover into the bloodstream, in turn, possibly causing inflammation.

In parallel, there’s growing evidence that the foods you eat can influence your gut’s immunity and function, and in some cases, possibly even reduce the degree of inflammation you experience (13, 14).

One hypothesis entertained by researchers is that by helping heal leaky gut, the AIP diet may help reduce the degree of inflammation a person experiences.

Although scientific evidence is currently limited, a handful of studies suggests that the AIP diet may help reduce inflammation or symptoms caused by it, at least among a subset of people with certain autoimmune disorders (6, 7, 15).

However, more research is needed to specifically understand the exact ways in which the AIP diet may help, as well as the precise circumstances under which it may do so (2).

May reduce inflammation and symptoms of some autoimmune disorders

To date, the AIP diet has been tested in a small group of people and yielded seemingly positive results.

For instance, in a recent 11-week study in 15 people with IBD on an AIP diet, participants reported experiencing significantly fewer IBD-related symptoms by the end of the study. However, no significant changes in markers of inflammation were observed (15).

Similarly, a small study had people with IBD follow the AIP diet for 11 weeks. Participants reported significant improvements in bowel frequency, stress, and the ability to perform leisure or sport activities as early as 3 weeks into the study (6).

In another study, 16 women with Hashimoto’s thyroiditis, an autoimmune disorder affecting the thyroid gland, followed the AIP diet for 10 weeks. By the end of the study, inflammation and disease-related symptoms decreased by 29% and 68%, respectively.

Participants also reported significant improvements in their quality of life, despite there being no significant differences in their measures of thyroid function (7).

Although promising, studies remain small and few. Also, to date, they have only been performed on a small subset of people with autoimmune disorders. Therefore, more research is needed before strong conclusions can be made.

Possible downsides 

The AIP diet is considered an elimination diet, which makes it very restrictive and potentially hard to follow for some, especially in its elimination phase.

The elimination phase of this diet can also make it difficult for people to eat in social situations, such as at a restaurant or friend’s house, increasing the risk of social isolation.

It’s also important to note that there’s no guarantee that this diet will reduce inflammation or disease-related symptoms in all people with autoimmune disorders.

However, those who experience a reduction in symptoms following this diet may be reticent to progress to the reintroduction phase, for fear it may bring the symptoms back.

This could become problematic, as remaining in the elimination phase can make it difficult to meet your daily nutrient requirements. Therefore, remaining in this phase for too long may increase your risk of developing nutrient deficiencies, as well as poor health over time.

This is why the reintroduction phase is crucial and should not be skipped.

If you’re experiencing difficulties getting started with the reintroduction phase, consider reaching out to a registered dietitian or other medical professional knowledgeable about the AIP diet for personalized guidance.

Should you try it? 

The AIP diet is designed to help reduce inflammation, pain, or other symptoms caused by autoimmune diseases. As such, it may work best for people with autoimmune diseases, such as lupus, IBD, celiac disease, or rheumatoid arthritis.

Autoimmune diseases cannot be cured, but their symptoms may be managed. The AIP diet aims to help you do so by helping you identify which foods may be triggering your specific symptoms.

Evidence regarding the efficacy of this diet is currently limited to people with IBD and Hashimoto’s disease.

However, based on the way in which this diet is believed to function, people with other autoimmune diseases may benefit from it, too.

There are currently few downsides to giving this diet a try, especially when performed under the supervision of a dietitian or other medical professional.

Seeking professional guidance prior to giving the AIP diet a try will help you better pinpoint which foods may be causing your specific symptoms, as well as ensure that you continue to meet your nutrient requirements as best as possible throughout all phases of this diet.

Frequently asked questions

What does an AIP diet consist of?

The AIP diet aims to help manage inflammation through an elimination diet. It involves removing foods from the diet, then replacing them gradually while assessing your body’s reaction. During the elimination phase, you may consume moderate amounts of fresh fruit, bone broth, minimally processed meat, and other items.

What foods should you avoid on an AIP diet?

An AIP diet avoids all processed foods, alcohol, additives, refined sugars, coffee, tea, oils, and certain medications. In the elimination phase, a person will also avoid foods such as grains, legumes, dairy, eggs, and nightshade vegetables, but they may reintroduce these later.

How long can you stay on an AIP diet?

After working through the elimination and reintroduction stages, you can stay on the AIP diet indefinitely. At this point, it becomes similar to the paleo diet. You won’t reintroduce any ingredients that are likely to cause you symptoms, such as refined sugars.

What’s the difference between paleo and AIP?

People on a paleo diet will focus on specific foods, such as eggs, seeds, fruits, vegetables, and minimally processed meat. The person on an AIP diet will move toward a paleo diet, but they will go through a stage of elimination and reintroduction. This means they will eat similar foods to those on a paleo diet, minus the foods that seem to cause symptoms.

The bottom line

The AIP diet is an elimination diet designed to help reduce inflammation or other symptoms caused by autoimmune disorders.

It’s comprised of two phases designed to help you identify and ultimately avoid the foods that may trigger inflammation and disease-specific symptoms. Research on its efficacy is limited but appears promising.

Due to its limited downsides, people with autoimmune disorders generally have little to lose by giving it a try. However, it’s likely best to seek guidance from a qualified health professional to ensure you continue to meet your nutrient needs throughout all phases of this diet.