Nightshades

Nightshades (the Solanaceae family) include tomato, potato (white, red, yellow — not sweet potato), eggplant, all peppers (bell, chili, paprika, cayenne), tomatillo, ground cherry, and goji berry. Tobacco is also a nightshade. The family produces glycoalkaloids — naturally occurring defense compounds — most notably solanine in potatoes and tomatine in tomatoes.

Anecdotally, many people with arthritis, autoimmune conditions, or chronic pain report symptom improvement on a nightshade-free diet. The Arthritis Foundation and Cleveland Clinic note the absence of strong clinical evidence for inflammatory effects of nightshades in the general population, but acknowledge individual reactions are real and worth testing if symptoms are persistent.

The science behind the claim

Solanine and similar glycoalkaloids can cause symptoms at very high doses (green or sprouted potatoes, for example), but normal culinary intake is well below toxicity thresholds. The link between nightshades and joint pain or autoimmune flares hasn't been clearly demonstrated in randomized trials. That said, capsaicin in chili peppers can trigger gut symptoms (separate page), and IgE allergy to specific nightshades (especially tomato) does occur.

Try an elimination

For persistent joint pain, eczema, or autoimmune symptoms where conventional triggers have been ruled out, a 4-week complete nightshade elimination followed by structured reintroduction is a reasonable experiment. Eliminate all family members at once (tomato sauce in your usual pasta dish counts), document symptom changes, and add foods back one at a time. The cleanest answers come from a careful trial, not from blanket avoidance.