The AIP Diet 101: My Opinion as a Dietitian

If you have experienced digestive issues, or other uncomfortable symptoms related to food in the past, and searched for answers online, it’s likely you have come across the AIP diet.

The Autoimmune Protocol Diet or “AIP” diet is an anti-inflammatory diet that is a more restrictive version of the well known Paleo diet. The AIP diet gained popularity around 2011 as a way to reduce inflammation and manage autoimmune disease symptoms. According to the NIH, autoimmune disease is on the rise in the United States.

Autoimmune diseases include:

• Hashimoto’s Thyroiditis
• Crohn’s Disease
• Ulcerative Colitis
• Sjogren’s
• Multiple Sclerosis
• PCOS
• Type 1 Diabetes

The AIP diet is viewed as more of a lifestyle than just a diet by many.  This is because the AIP approach encourages consuming nutrient dense foods such as organ meats, fish, and vegetables- as well as getting adequate sleep, managing stress, and prioritizing natural movement.  The goal of the AIP lifestyle is to improve digestive and immune health to reduce or eliminate symptoms.

AIP diet phases

The diet consists of 2 main phases: the “elimination phase” which is the most restrictive portion of the diet and often what is referred to as the AIP diet.  It’s recommended to follow this portion for 30-90 days, while some may comply longer. 

The second phase is the reintroduction phase.  During this portion of the program, you can reintroduce foods one by one to monitor if you experience any reactions.

AIP diet food lists for beginners

The quality of food that you consume on the AIP diet is just as important as the types of food you are consuming.

Since the AIP diet uses many principles of the paleo diet as its foundation, one of the fundamental principles of AIP is consuming foods that are as close to nature as possible.  High quality standards include grass-fed, wild caught, pasture raised, organic, and non-GMO food sources.

Note: While the goal is to consume only the highest quality foods, this is not always possible in some communities due to resources and availability.

Foods to include on an AIP diet

• Most vegetables (except for nightshades)
• All fruit
• Proteins:
  • Poultry- chicken, turkey, duck, cornish hen
  • Beef
  • Venison
  • Fish
  • Shellfish
  • Pork
  • Lamb
  • Bone broth
  • Organ meats
• Healthy Fats/oil
  • Olive oil
  • Avocado Oil
  • Coconut Oil
  • Rendered animal fat from duck, beef etc

Foods to avoid on an AIP diet

• Eggs
• All Nuts
• All Seeds
• Gluten
• Dairy
• Legumes
• All Grains
• Nightshade vegetables
• Coffee
• Alcohol
• Sugar and Sugar substitutes
• Artificial colors or additives
• Refined vegetable oils or trans fats
• Processed or refined foods

The AIP diet is not a long term solution

Because the AIP diet excludes multiple food categories,  this diet is not meant to be lifelong intervention, but rather a therapeutic, short term diet.

How does the AIP diet work?

Autoimmune and other inflammatory diseases have been increasing over the last 30 years.  The term “leaky gut” has been used to describe a damaged intestinal epithelial lining.  When this lining is damaged and becomes permeable or “leaky” small particles of undigested food, toxins, and bacteria enter the bloodstream which can cause inflammation.

A large percentage of our immune system is in the digestive system, therefore supporting proper gut health can play a role in alleviating symptoms.

The AIP diet is believed to work by eliminating pro-inflammatory foods as well as supporting the body with large amounts of nutrient dense foods.  Through this approach, the goal is to repair any damage that has occurred to the mucosal lining of the intestines aka “leaky gut”.

A small study in 2018 that was conducted on participants with Ulcerative Colitis found that there were positive changes linked to reduced T-cell mediated inflammation and mucosal healing after an 11 week program following the AIP diet. The study used clinical biposies and colonoscopies both at baseline and completion of the study to verify results.  While controlled clinical studies are needed these finding are promising to

What Does the Science Say?

The AIP diet is relatively new and therefore few clinical studies have been done to prove it’s efficacy.  Some small sample size studies have been completed on using the AIP diet in relation to certain autoimmune conditions.

AIP and Hashimoto’s

A 2019 study that investigated if the AIP diet helped women with Hashimoto’s Thyroiditis was conducted.  This study had 16 female participants who all had a  normal or overweight BMI with a previous Hashimoto’s Thyroiditis diagnosis.  The participants followed the elimination phase of the AIP diet for 10 weeks and were aided by online health coaching.

To measure the participant’s health outcomes, blood tests including CBC, CMP, Thyroid panel, and CRP along with Medical Symptoms Questionnaires (MSQ) were used both before and after the program.

The study found that while there was no statistical improvement in blood lab markers or improvement in thyroid function, there was a decrease in CRP markers and white blood cell count changes that can signify a reduction in systemic inflammation.  Furthermore, participants also reported lower MSQ scores which correlate with lower symptom burden, and better quality of life.

AIP and IBD

A small study conducted with participants that all had Irritable Bowel Disease (IBD), Ulcerative Colitis (UC), or Crohn’s Disease (CD) was published in 2019.

This study used the AIP diet elimination phase with participants for 6 weeks followed by an additional 5 weeks of a maintenance phase without any food reintroductions.

The Short Inflammatory Bowel Disease Questionnaire (SIBDQ) was completed at baseline, and weeks 3, 6, 9, and 11 to measure each participant’s symptoms.

The study included 6 UC and 9 CD participants.  The study found that results from the SIBDQ mean score improved significantly from baseline by more than 15 points- from 46.5 to 61.5.

The study found that by week 3, participants experienced improvements in bowel movement frequency, stress, and ability to perform leisure/sport activities in both participants with CD and UC.

Consuming an AIP diet allowed participants to have fewer symptoms and improve quality of life as early as week 3 of following the protocol.

These studies show promising results, however, these were in very small sample sizes and it warrants conducting larger clinically controlled studies to validate the diet’s efficacy.   

Who is the AIP diet right for?

Those with an autoimmune disease or chronic illness that have explored other diet options without finding relief may benefit from a trial of the AIP diet.  The AIP diet should not be used on anyone that has a history of disordered eating or food fear, unless working directly with a qualified provider.  As a dietitian, the AIP diet  is not usually my first suggestion, but I have found it to be a useful tool in my nutrition toolbox for specific clients that may benefit.

My experience with AIP as a dietitian

I provided a nutrition consultation to a female patient that was previously diagnosed with Hashimoto’s Thyroiditis and was experiencing fatigue, bloat, joint pain, digestive issues, and inflammation for several years without relief.  She had previously tried several elimination diets but did not see any notable improvement in symptoms.  We worked together and completed a 4 week trial of  the AIP diet.  The patient saw significant improvement in her digestive issues, bloat, joint pain and fatigue.  Once improvement was seen and she felt she was at a stable baseline, she did a systematic reintroduction of each food and food category.

The reintroduction process is where the most valuable information comes out.  The process of adding each food back into the diet one by one allows the patient to notice if any specific food is causing symptoms to flare up.

The patient shared with me that the reintroduction was the most helpful portion, as she was able to identify several foods that cause worsening of symptoms for her.  Now she is able to be symptom free without severely restricting her diet unnecessarily.

More research needed

The AIP diet is now well-known and frequently used by both individuals and providers to gain relief from uncomfortable symptoms related to inflammatory, autoimmune, or other diseases.  While more research is needed to validate the diet’s efficacy, self-reports and anecdotal evidence does support the use of the diet for gut health support and symptom relief.