What are Nightshades?

Solanaceae, the scientific name for the group of plants known as nightshades comes from the genus group Solanum. The term ‘nightshades’ derives from the plant family’s tendency to grow in shaded locations and bloom at night.

The International Society for Horticulture concludes that there are 98 genera and 2,700 species of Solanaceae. And while nightshade species such as the belladonna, popularized in Macbeth for being used as a deadly poison, give the group a bad rap, many of the commonplace food varieties eaten everyday produce no harmful side effects and therefore should be distinguished from the poisonous plants of the family.

Common veggies of the nightshade family include the potato, tomato, eggplant and pepper—all of which offer nutritional benefits necessary in a healthy diet. Tomatoes and peppers contain phytochemicals that can lower cancer risk, potatoes offer vitamin C, B6, and potassium, and the eggplant is a source of Vitamin K.

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Rosane Oliveira, DVM, PhD, Founding Director of UC Davis Integrative Medicine, dispels some common misconceptions about the nightshade family. She notes that while nightshades have been attributed to causing arthritic pain and migraine headaches, no definitive scientific proof has been reported. Oliveira also disputes the claim that nightshades contribute to osteoporosis (some folks point to their high oxalic acid content which, they contend, could block absorption of calcium necessary for bone strength).

Lastly, she states that although some nightshades do contain solanine, a toxic alkaloid meant to protect the plants from insects, tomatoes, peppers and eggplant are not among the plants that contain this compound, so no caution is needed there. The one exception we do eat would be the potato. If it contains green spots or sprouts on the skin, it should be avoided, as these telltale signs point to the existence of solanine. If absent, potatoes are perfectly safe to ingest.

Having said this, it is possible to have food sensitivities or adverse reactions to any particular plant within this family. If you experience digestive problems or migraines after eating any, it would be best to remove nightshades from your diet for a period of two to three weeks to see if you notice a difference.