Nightshades are plants in the Solanaceae family, a group of over 3,000 species that includes some of the most popular vegetables in the world: tomatoes, potatoes, peppers, and eggplants. The family also includes toxic wild plants like belladonna and several common herbs and spices. If you’re trying to figure out which foods on your plate are nightshades, or which ones aren’t, here’s the full picture.
Common Edible Nightshades
The nightshades you’re most likely eating regularly include:
- Tomatoes (all varieties)
- Potatoes (white and yellow, but not sweet potatoes)
- Bell peppers
- Eggplants
- Chili peppers (jalapeños, habaneros, serranos, and all other hot peppers)
- Tomatillos
- Pimientos
- Goji berries
Several spices come from nightshade plants too: paprika, cayenne pepper, crushed red pepper, and chili powder are all made from dried peppers in the Solanaceae family. These are easy to overlook if you’re trying to avoid nightshades, since they show up in spice blends, sauces, and processed foods without being obvious.
Foods Often Confused for Nightshades
Sweet potatoes are not nightshades. Despite sharing the word “potato,” they belong to the morning glory family and are botanically unrelated. Regular white and yellow potatoes are true nightshades; sweet potatoes and yams are not.
Black pepper (the kind in your pepper grinder) is also not a nightshade. It comes from an entirely different plant family. The confusion is understandable since chili peppers and bell peppers are nightshades, but black peppercorns have no relation to them. Similarly, blueberries are sometimes mistakenly listed as nightshades. They’re not.
Toxic and Wild Nightshades
The Solanaceae family gets its ominous common name from its more dangerous members. Deadly nightshade (belladonna) is the most notorious. It’s a medium-sized shrub with purple bell-shaped flowers and sweet-tasting purplish-black berries that have poisoned people, especially children, for centuries. Every part of the plant is toxic, and even handling it can cause skin irritation or allow toxins to be absorbed through the skin. Poisoning symptoms include rapid heartbeat, dilated pupils, hallucinations, delirium, vomiting, and in severe cases, death from respiratory failure.
Other toxic nightshades include jimsonweed (sometimes called thorn apple), bittersweet nightshade, and henbane. Tobacco is also a nightshade, and its addictive compound, nicotine, is one of the alkaloids characteristic of this plant family.
What Makes a Plant a Nightshade
All nightshades share a distinctive flower structure: five fused petals, five fused sepals, and five stamens arranged around a two-part ovary. If you’ve ever looked closely at a tomato blossom or a potato flower, you’ve seen this pattern. The fruits are typically berries (in the botanical sense), which is why tomatoes, peppers, and eggplants are technically berries even though we treat them as vegetables in the kitchen.
The family’s defining chemistry involves alkaloids, naturally occurring compounds that affect animal nervous systems. Different nightshades produce different alkaloids. Potatoes and tomatoes contain solanine, peppers produce capsaicin (the compound that makes them spicy), belladonna produces atropine, and tobacco produces nicotine. In edible nightshades, these compounds are present at low enough levels to be safe for the vast majority of people.
Solanine in Potatoes: When It Matters
Commercial potatoes contain less than 0.2 mg/g of solanine, well below levels that cause problems. But when potatoes are exposed to light, damaged, or allowed to sprout, solanine concentrations can jump to 1 mg/g or higher. That green tint under the skin of an old potato is a visible signal that solanine levels have risen.
Toxic symptoms in adults can appear at doses of 200 to 400 mg, and doses around 600 mg are considered potentially lethal. For context, in one documented case in Canada, 61 schoolchildren became sick after eating baked potatoes that contained about 50 mg of solanine per 100 grams. They experienced nausea, vomiting, abdominal cramps, and headaches. A quick test: if a potato tastes bitter or causes a burning sensation in your mouth, it likely contains elevated solanine and shouldn’t be eaten. Cutting away green areas, removing sprouts, and peeling the skin reduces solanine content, but heavily greened or sprouted potatoes are better discarded.
Nightshades, Inflammation, and Sensitivity
Some people report that nightshade vegetables worsen joint pain, digestive symptoms, or autoimmune conditions. The theory is that alkaloids in these foods can stimulate the immune system and trigger inflammation. A small number of people do have genuine allergies to nightshade alkaloids, with symptoms including hives, itchiness, nausea, and joint aches.
The clinical evidence, however, is limited. The Arthritis Foundation has stated there is no evidence that nightshades worsen rheumatoid arthritis and recommends people with arthritis continue eating them as part of a healthy diet. A 2017 study found that people with inflammatory bowel disease reported reduced symptoms on an elimination diet that removed nightshades along with alcohol, legumes, and other foods, but since multiple foods were removed simultaneously, it’s hard to pin the improvement on nightshades specifically.
For most people, nightshade vegetables are nutrient-dense foods with clear health benefits. Tomatoes are rich in lycopene, peppers are packed with vitamin C, and potatoes are an excellent source of potassium. If you suspect nightshades bother you, an elimination diet (removing them for two to three weeks, then reintroducing one at a time) is the most practical way to test your own sensitivity.