What Are Nightshades—And Why Are They Off-Limits in So Many Detox Diets?

Spring is just around the corner—and visions of the season’s filmy slip dresses have many of us preparing to embark on detox diets. While skipping gluten and dairy in the name of health is par for the course, one item near the top of many “don’t” lists has us scratching our heads: a category of flowering plants commonly called nightshades. The most famous member of this botanical family, belladonna, can be deadly, but the category also includes foods that are staples in many cultures: potatoes, tomatoes, eggplants, peppers, and goji berries. So what, exactly, is so toxic about the main ingredients in mashed potatoes, salsa, spaghetti sauce, and so many vegan stir-fry dishes?

According to nutritional chef Mikaela Reuben, plants in the nightshade family—a term coined because they tend to grow in shady areas and some flower at night—all naturally produce solanine, a poisonous compound, as part of their defense system to ward off insects prone to snacking on leaves and stems. For anyone sensitive to solanine—especially those with arthritis—nightshades can “cause inflammation, affecting joint pain and digestion,” Reuben says. Not everyone is sensitive to the compound, however, and it’s present in very small amounts in these foods. But as Reuben explains, eliminating potential allergens or inflammatory triggers is a way to jump-start any new health regimen. Test yourself, she advises, by eliminating foods with solanine for a few weeks as part of a cleanse; by doing so, you’ll pay extra attention to eating well, and that leads to brighter skin and higher energy levels.

Reuben isn’t alone in recommending a break from the foods: Dr. Alejandro Junger’s Clean program, favored by Gwyneth Paltrow and Naomi Campbell, forbids nightshades, and the menus of Allen Campbell, personal chef to Gisele Bündchen and Tom Brady, avoids them. But should nightshades really be banished from diets altogether?

Solanine is concentrated in the leafy greens bugs try to eat, one major reason why we only eat the tomato or pepper fruit, not the rest of the plant. It can also be found in foods that aren’t part of the nightshade family, including blueberries, apples, cherries, and artichokes. (And it develops in green potatoes, so discard any tubers with green areas.) But if you’ve tried eliminating them and notice no difference in joint pain or digestion, nightshades can be nutritionally sound additions to basic meals; many of these ingredients are actually high in antioxidants that reduce inflammation.

In other words, nightshades are far from the worst dietary offenders—and cutting those out should be a bigger priority, according to New York City nutritionist Marissa Lippert of Nourish Kitchen + Table. Start off a cleanse by avoiding what she calls “the most prominent potentially allergenic or inflammatory ingredients: dairy, gluten, and soy.” Beyond that, she says, eating wholesome foods in smart ways can improve energy levels, digestion, and metabolism and even stabilize blood sugar. And if you’re not undertaking an elimination diet, Lippert adds, there are a number of very good reasons to eat nightshades. Eggplants, tomatoes, and peppers are antioxidant-rich and a good source of fiber, Vitamin C, and other nutrients. “Everything works together when you eat nutrient-dense foods in smaller portions,” she says.

The takeaway? While it can’t hurt to test for a specific sensitivity to nightshades, for most of us, incorporating them may make meals a whole lot tastier—and likely healthier than a powdered shake or a glass of juice alone.

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