Nightshade sensitivity and thyroid health

Photos: Charles de Luvio and Weak Lifter/Unsplash, Nick Youngson/Alpha Stock Images, and ZooFari. Design: BOOST Thyroid.

Photos: Charles de Luvio and Weak Lifter/Unsplash, Nick Youngson/Alpha Stock Images, and ZooFari. Design: BOOST Thyroid.

How tomatoes, potatoes, and peppers can cause problems with your gut

Nightshades are an extensive plant family, with nearly 4,000 different plant species including tomatoes, potatoes, eggplants, and bell peppers.

Nightshades are rich in vitamins, minerals, and antioxidants, making them desirable health foods. Yet at the same time they contain high levels of lectins and alkaloid molecules that may substantially harm the intestine (1). 

What might happen when you eat nightshades?

Lectins are proteins that help plants fend off pathogens (viruses and bacteria). They’re found in nightshades and for some people they may bind to the gut—this can change the balance of good bacteria, block digestion of other foods, and disrupt hormonal balance (2).

Alkaloids are molecules found in plants. Some of them can be helpful to people, like morphine which prevents pain and quinine which prevents malaria. But most alkaloids taste bitter and are actually slightly poisonous when ingested. Alkaloids affect the gut barrier which can cause problems with digestion. Their impact on the gut may cause ongoing poisoning and inflammation (3, 4).

Both lectins and alkaloids are considered antinutritional. For some people, regularly consuming nightshades throughout long periods of time (weeks, months, or years) can cause significant damage to the gut. Damage to the gut is considered one of the first steps in developing autoimmune conditions (5, 6).

Symptoms of nightshade sensitivity can occur within minutes to a few hours after consumption (7-9): 

  • Nausea

  • Vomiting

  • Diarrhea

  • Bloating

  • Stomach cramps

  • Headache

  • Dizziness 

  • Poor sleep

An elimination diet can help you discover if you have a food sensitivity to nightshades.  But you might not be sensitive to the entire plant family, so try eliminating one nightshade vegetable at a time and allow two to four weeks to see the first results.

If your diet is typically rich in nightshades and you decide to stop eating them, make sure you replace the vitamins and nutrients you formerly received through them.

It’s helpful to talk to your doctor or nutritionist about changes in your diet to make sure you don’t develop nutrient deficiencies.

Track your symptoms in BOOST Thyroid and see if any of your symptoms change when you remove all or a certain nightshade out of your diet.


  1. Lam SK, et al. Lectins: production and practical applications, 2011

  2. Vasconcelos IM, et al. Antinutritional properties of plant lectins, 2004

  3. Iablokov V, et al. Naturally occurring glycoalkaloids in potatoes aggravate intestinal inflammation in two mouse models of inflammatory bowel disease, 2010

  4. Cardenas PD, et al. The bitter side of the nightshades: Genomics drives discovery in Solanaceae steroidal alkaloid metabolism, 2015

  5. Opazo MC, et al. Intestinal Microbiota Influences Non-intestinal Related Autoimmune Diseases, 2018

  6. Campbell AW. Autoimmunity and the Gut, 2014

  7. Messing TT, et al. Potato glycoalkaloids and adverse effects in humans: an ascending dose study, 2005

  8. Diaz GJ. Toxicosis by Plant Alkaloids in Humans and Animals in Colombia, 2015

  9. Myiake K, et al. Lectin-Based Food Poisoning: A New Mechanism of Protein Toxicity, 2007