Nightshade vegetables
Top 10 in Top 10 Foods to Avoid on the Paleo Diet
On some highly strict paleo diets, nightshade fruits and vegetables, such as peppers, potatoes, tomatoes, eggplant, and tobacco, are seldom allowed. Eating nightshades vegetables is completely safe for the vast majority of people. However, for people with autoimmune diseases or leaky gut, eating these veggies might induce excruciating discomfort.
Although research is limited, it is widely recognized that alkaloids, a chemical component found in nightshade plants, are what make the veggies dangerous for some people. The high alkaloid content of nightshades is what gives the plant its lethal qualities.