Why some people need to avoid nightshades

scoop on nightshades

If you’re following the strict leaky gut or autoimmune diet, you may have noticed nightshades are on the list of foods to avoid. Many common and much-loved vegetables belong to the nightshade family, including eggplants, tomatoes, potatoes, sweet and hot peppers (but not black pepper), and chili-based spices, including paprika. What many people don’t realize is nightshades contain compounds that can contribute to their pain, digestive issues, and inflammation. Some people are sensitive to nightshades so it’s important to determine whether they might play a role in your symptoms.

The word nightshade typically conjures images of notorious toxic plants such as jimson weed, petunias, and deadly nightshade. The nightshade family, called Solanacea, has more than 2,000 species, most of which are inedible and many of which are highly poisonous. However, many edible plants also fall into the nightshade family.

Below are some of the other less well-known nightshades:

  • Bush tomato
  • Goji berries (a.k.a. wolfberry)
  • Naranjillas
  • Pepinos
  • Pimientos
  • Tamarillos
  • Tomatillos

What’s the problem with nightshades?

Several natural compounds in nightshades can make them problematic: saponins, lectins, and capsaicin. These compounds make nightshades a common food sensitivity, and they can lead to leaky gut, a condition in which the lining of the small intestine becomes overly porous. A leaky gut allows unwanted pathogens into the bloodstream, leading to health issues including inflammation, allergies, and autoimmunity.  Researchers also suggest that even moderate consumption of nightshades can contribute to a variety of health conditions, arthritis in particular.

Saponins in nightshades

Saponins are compounds that have detergent-like properties and are designed to protect plants from microbes and insects. When consumed by humans, saponins can create holes in the gut wall, increasing leaky gut and allowing pathogens and toxins into the bloodstream. Saponins also have properties that can encourage the immune system to make inflammatory messengers that cause inflammation in the body.

Peppers are high in saponins. Ripe tomatoes have low levels of saponins, while green tomatoes and hot-house tomatoes (those that are harvested before they are ripe), are exceedingly high in saponins.

Lectins in nightshades

Another compound found in nightshades that can be problematic for some people is lectin. Lectins are a concern because they resist digestion, are able to withstand the heat of cooking (which means they are intact when you eat them), and help create a leaky gut. They can penetrate the protective mucus of the small intestine where they promote cell division at the wrong time and even cause cell death. Lectins can also perforate the intestinal wall, and trick the immune system into thinking there’s an intruder, causing an allergic reaction.

Tomato lectin is known to enter the blood stream relatively quickly in humans, while potato lectins have been found to irritate the immune system and produce symptoms of food hypersensitivity in both allergenic and non-allergenic patients.

Capsaicin in nightshades

Capsaicin is a stimulant found in chili peppers that helps give them their heat. While a variety of health benefits have been attributed to capsaicin, it is also a potent irritant to mucous membranes and may contribute to leaky gut as well.

Yams and sweet potatoes are not nightshades

Yams are in the same family as sweet potatoes; true yams are not very common in the United States. Fortunately, sweet potatoes and true yams are not part of the nightshade family despite their names, and do not exhibit the same tendencies as nightshades toward promoting leaky gut and inflammation in the body.

Anyone wishing to improve digestive health and manage inflammatory conditions, autoimmune diseases, or allergies may want to consider drastically reducing or even eliminating their consumption of nightshades to determine whether they are a problem. Ask my office for more information about the leaky gut, or autoimmune, diet.

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