Why are there no nightshades on AIP?

Over 24 million Americans have an autoimmune disease, and for some, diet can play a significant role in managing symptoms. The Autoimmune Protocol (AIP) is an elimination diet designed to calm inflammation, which is why there are no nightshades on AIP in the initial phase.

Quick Summary

The AIP diet removes nightshades, such as tomatoes, peppers, and potatoes, due to compounds like alkaloids and saponins that can cause inflammation and gut irritation in sensitive individuals. Their elimination aims to reduce autoimmune symptoms and support gut healing.

Key Points

• Alkaloids and Saponins: Nightshades contain natural compounds like alkaloids (solanine) and saponins that can increase intestinal permeability, or "leaky gut," in sensitive individuals.

• Inflammation Trigger: For those with autoimmune conditions, these compounds can exacerbate inflammation and trigger an immune response, worsening symptoms.

• Elimination and Reintroduction: The AIP diet's approach is to eliminate nightshades temporarily to allow the gut to heal, followed by a careful reintroduction phase to test for individual tolerance.

• High-Risk Individuals: While nightshades are healthy for most, people with conditions like inflammatory bowel disease (IBD) or arthritis may be more susceptible to their inflammatory effects.

• Nutrient Alternatives: The AIP ensures a nutrient-dense diet even without nightshades, recommending alternatives like sweet potatoes for vitamin A and citrus fruits for vitamin C.

• Personalized Diet Plan: The protocol is not a one-size-fits-all solution; it is a personalized roadmap that helps identify specific foods that cause issues for an individual.

Understanding the Autoimmune Protocol (AIP)

The Autoimmune Protocol (AIP) is a specialized version of the Paleo diet focused on reducing inflammation and promoting gut healing for those with autoimmune conditions. The diet's core principle is to eliminate foods that are known to be potential triggers of inflammation and immune responses. The AIP is not meant to be a permanent, restrictive lifestyle but rather a temporary, structured elimination diet followed by a systematic reintroduction phase to identify individual food sensitivities. The foods most often removed during the initial phase include grains, legumes, dairy, eggs, nuts, seeds, and, crucially, nightshade vegetables.

The Compounds in Nightshades that Trigger Symptoms

Nightshade vegetables, which belong to the Solanaceae family, contain several natural compounds that are suspected of triggering inflammation and adverse reactions in people with autoimmune diseases. While these compounds pose no issue for most healthy individuals, those with compromised gut health or an overactive immune system may be particularly sensitive.

• Alkaloids: Nightshades contain alkaloids like solanine and tomatine, which are thought to be the plant's natural defense against insects. For sensitive individuals, these substances may increase intestinal permeability, also known as "leaky gut". An increase in intestinal permeability allows undigested food particles and bacteria to enter the bloodstream, which can trigger an immune response and increase inflammation. In potatoes, the highest concentration of solanine is found in the skin, especially in any green spots.
• Saponins: Found in the seeds and skin of many nightshades, saponins are another compound that can affect the intestinal barrier. Saponins have an adjuvant effect, meaning they can stimulate and exaggerate an immune response. This can cause the body to produce antibodies that mistakenly attack its own tissues, a defining feature of autoimmune disease.
• Lectins: Another class of proteins found in nightshades, lectins, can resist digestion and bind to the lining of the gut. This can interfere with nutrient absorption and further contribute to intestinal inflammation, triggering flare-ups.
• Capsaicin: The compound responsible for the heat in chili peppers, capsaicin, can act as a mucosal irritant for some people. This can be particularly problematic for individuals with inflammatory bowel disease, causing discomfort and potential irritation of the digestive tract lining.

Nightshade Elimination vs. Nightshade Inclusion

Aspect	Nightshade Elimination (Initial AIP Phase)	Nightshade Inclusion (For Tolerant Individuals)
Core Purpose	Reduce potential inflammatory triggers and promote gut healing.	Leverage the nutrient density and flavor of these vegetables.
Targeted Population	Individuals with autoimmune diseases who are experiencing active symptoms.	The general population and those who have successfully reintroduced nightshades.
Underlying Principle	Avoidance of compounds like alkaloids and lectins to calm the immune system.	Consumption of antioxidants like lycopene and vitamin C, and dietary fiber.
Duration	A temporary phase (typically 30-90 days or until symptoms improve) followed by reintroduction.	No restriction, with ongoing monitoring of symptoms.
Food Substitutions	Creative alternatives are used, such as sweet potatoes for white potatoes or pesto for tomato sauce.	None needed, as nightshades are part of the diet.
Risk of Nutrient Deficiency	Managed by ensuring a varied intake of other nutrient-dense, AIP-compliant foods.	None, as nightshades provide valuable vitamins and minerals.

The Reintroduction Process

The goal of AIP is not permanent elimination, but rather to identify which specific foods trigger an individual's symptoms. After a period of 30 to 90 days on the elimination phase, or once symptoms have stabilized, nightshades can be reintroduced one at a time. The process must be slow and methodical to accurately pinpoint which, if any, nightshades cause a reaction.

1. Assess Readiness: Ensure symptoms are stable for at least 4 to 6 weeks before starting reintroduction.
2. Choose One Nightshade: Start with a single food, such as a cooked and peeled white potato.
3. Start Small: Eat a very small amount (e.g., a quarter serving) and monitor for symptoms over the next 72 hours.
4. Observe and Record: Keep a detailed food and symptom journal, noting any changes in digestive issues, joint pain, skin reactions, or energy levels.
5. Increase Portion (If Tolerated): If no symptoms occur after 72 hours, try a slightly larger portion. If still no reaction, you can begin to incorporate that food back into your diet.
6. Reintroduce Next Food: Wait at least a week after a successful reintroduction before testing the next nightshade.

Conclusion

The temporary removal of nightshades during the initial AIP phase is a targeted strategy to help reduce potential inflammatory triggers for sensitive individuals with autoimmune disease. While nightshades offer many nutritional benefits for the general population, the alkaloids, saponins, and lectins they contain can exacerbate symptoms and intestinal permeability in some. The protocol's structured elimination followed by careful reintroduction is a powerful tool for personalization, allowing individuals to determine their specific tolerances. This process enables them to build a sustainable, nourishing diet that minimizes symptoms and supports long-term health.

Sources

• PrimeHealth Denver. "What Are Nightshades? List & Impact on Autoimmune Issues." Accessed October 14, 2025. https://primehealthdenver.com/blog/nightshades/
• Eat G.A.N.G.S.T.E.R.. "Why Aren't Tomatoes Allowed on AIP?." Accessed October 14, 2025. https://eatgangster.com/blogs/blogs-and-articles/why-arent-tomatoes-allowed-on-aip
• Healthline. "AIP (Autoimmune Protocol) Diet: A Beginner's Guide." Accessed October 14, 2025. https://www.healthline.com/nutrition/aip-diet-autoimmune-protocol-diet
• EatLove. "Beginner’s Guide to the AIP Diet." Accessed October 14, 2025. https://www.eatlove.is/blog/aip-diet
• Meridian Health Clinic. "Are Nightshade Vegetables Increasing Your Pain and Inflammation?." Accessed October 14, 2025. https://meridianhealthclinic.com/are-nightshade-vegetables-increasing-your-pain-and-inflammation/
• Banner Health. "What You Should Know About Nightshade Vegetables." Accessed October 14, 2025. https://www.bannerhealth.com/healthcareblog/teach-me/what-you-should-know-about-nightshade-vegetables
• EatingWell. "What Are Nightshades and Are They Bad for You?." Accessed October 14, 2025. https://www.eatingwell.com/article/7999760/what-are-nightshades-and-are-they-bad-for-you/
• Joanna Frankham. "Autoimmunity and the Removal of Nightshades From Your Diet." Accessed October 14, 2025. https://joannafrankham.com/autoimmunity-and-the-removal-of-nightshades-from-your-diet/
• Wild Zora. "Change Your Life Go Nightshade Free Diet - Wild Zora." Accessed October 14, 2025. https://wildzora.com/blogs/news/how-a-nightshade-free-diet-can-change-your-life
• Joanna Frankham. "Autoimmunity and the Removal of Nightshades From Your Diet." Accessed October 14, 2025. https://joannafrankham.com/autoimmunity-and-the-removal-of-nightshades-from-your-diet/
• Chomps. "AIP Reintroduction Phase: How to Reintroduce Foods on AIP." Accessed October 14, 2025. https://chomps.com/blogs/nutrition-sustainability-news/aip-reintroduction
• Healthline. "Nightshade Vegetables: Risks, Examples, and Substitutes." Accessed October 14, 2025. https://www.healthline.com/nutrition/nightshade-vegetables
• Shelley Cavezza, PhD. "How to Reintroduce Nightshades and Eggs on an AIP Diet Safely." Accessed October 14, 2025. https://www.drshelleycavezza.com.au/how-to-reintroduce-nightshades-and-eggs-on-an-aip-diet/
• Natural Endocrinology Specialists. "Autoimmune Paleo Diet (AIP): Free Downloadable PDF." Accessed October 14, 2025. https://www.nesaz.com/autoimmune-paleo-diet/

Frequently Asked Questions

What are nightshades that are excluded from AIP?

Nightshades excluded from the AIP diet include tomatoes, white potatoes, peppers (bell, chili, cayenne, paprika), eggplant, tomatillos, and goji berries.

Are sweet potatoes considered nightshades?

No, sweet potatoes are not nightshades. They are a root vegetable from a different plant family and are allowed on the AIP diet.

What are alkaloids, and why are they a concern?

Alkaloids like solanine are natural compounds in nightshades that can irritate the gut lining and increase intestinal permeability (leaky gut) in sensitive people, triggering an immune response.

How long do I need to eliminate nightshades on AIP?

The elimination phase typically lasts between 30 to 90 days, or until a person experiences a noticeable reduction in their autoimmune symptoms.

What happens if I reintroduce nightshades and have a reaction?

If you experience negative symptoms after reintroducing a nightshade, you should eliminate that food again. You can try reintroducing it again after a few weeks or consult a healthcare professional.

What can I use as a substitute for tomatoes on AIP?

For a tomato-like flavor, you can use a puree of roasted beets, carrots, and butternut squash. Pesto made with AIP-compliant herbs is another excellent alternative.

Is nightshade sensitivity the same as a food allergy?

No, a sensitivity is not the same as an allergy. A sensitivity can cause inflammatory symptoms, while a severe allergy can cause hives, swelling, and difficulty breathing. It is important to differentiate between the two.