On Your Health

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What are Nightshades and How Can They Affect Your Gut?

Nightshades like tomatoes, peppers and eggplants have a bad reputation. Even the name "nightshade" sounds ominous. For some people, nightshades have been known to cause digestive issues and even aches and pains. Before you cut these healthy foods out of your diet, here is some information about nightshades and how they can affect your gut.

What are nightshades?

Nightshades are fruits and vegetables in the plant family Solanaceae. With over 2,500 plant species, most Solanaceae are inedible and are instead used in many forms of medicine. However, there are a few nightshades that are edible, below is a list of the most common.

  • Tomatoes – Including ketchup and many sauces.
  • Peppers – Including spices made from peppers such as paprika, cayenne pepper, chilis and chili powder. Keep in mind, spice mixes like Tabasco® are made with these spices as well.
  • Eggplants
  • Potatoes – White, red, yellow and blue-skinned
  • Tomatillos
  • Husk cherries
  • Goji berries
  • Huckleberries
  • Pimentos

Chemicals found in nightshades

bliss potatoes

Almost all the issues tied to consuming nightshades can be blamed on glycoalkaloids. Glycoalkaloids are derived from alkaloids and sugar. Alkaloids are naturally occurring chemical compounds containing nitrogen atoms with acidic properties. With most fruits and vegetables in the nightshade family, you will find the highest alkaloid concentration in the skin, even more so if it's not ripe.

Solanine is a glycoalkaloid poison used by plants as a natural defense mechanism. Solanine helps plants ward off insects and diseases. If you’ve heard of people becoming ill from eating old or rotting potatoes, solanine is to blame. Solanine is present in potatoes once they start turning bright green under the skin and begin to grow sprouts.

Lectins are also found in nightshades, as well as many other plants. Lectins are plant proteins that, in some cases, can have a strong reaction to the body’s cell membranes, increasing their ability to penetrate cell walls. This can ultimately cause allergic reactions to certain foods.

Nightshades and your gut

The big question — how do nightshades affect your gut? The truth is, a healthy gut can handle alkaloids just fine, as long as they are not consumed in irregularly high doses. There is little scientific evidence that you should eliminate nightshades from your diet if you are healthy and can digest nightshades with no side effects. 

However, people who are intolerant to nightshades, meaning they can’t digest them properly, may have a negative reaction. Some of these negative side effects include gas, bloating, diarrhea, heartburn, nausea and joint pain due to inflammation.

There are many factors to nightshade intolerance because every individual’s digestive system is unique. However, research suggests underlying issues may be the real cause of the intolerance. For example, if you have a pre-existing digestive issue like Crohn's disease or an autoimmune disease like rheumatoid arthritis, nightshades can enhance the irritation. In this case, acidic alkaloids can harm the cells lining the intestinal tract, leading to intestinal permeability or leaky gut syndrome.

How to manage nightshades in your diet

Now that you know all about nightshades, should you cut them out of your diet? We suggest starting with a detailed food log. If you experience any symptoms after eating foods in the nightshade family, keep a record of what you ate, what symptoms you experienced and then speak with your healthcare provider. Keep reading On Your Health blogs for more health and wellness information.