The nightshade family as a category actually comprises more than fruits and vegetables. There are over 2,800 species of plants including herbs, shrubs and trees.
Common edible nightshades are eggplant, potatoes, tomatoes, and all peppers with the exception of black pepper. Perhaps less well known nightshade foods or products include cayenne pepper, garden huckleberry, ground cherries, paprika, pimentos (also called pimientos), pepinos, tamarios, tomatillos and Tabasco sauce.
Nightshades belong to the scientific order Polemoniales. Their scientific family is Solanaceae. They all contain alkaloids which is where the potential trouble arises.
Alkaloids are actually quite beneficial to the plant, since these alkaloids are a defense against insects. And many people will never experience distress from eating nightshades.
But for those who are sensitive to the alkaloids in them, it's another story.
Alkaloids can affect nerves and muscles, causing convulsions, twitching, trembling and breathing problems. They can cause problems with digestion for both animals and human beings, and may cause heartburn or gastroesophageal reflux disease (GERD).
Alkaloids may also cause inflammation in the joints. They may be factors in calcium loss from the bones, and calcium deposited where it should not be, in soft tissue.
It is recommended that people with conditions like gout, osteoarthritis and rheumatoid arthritis think about avoiding nightshades. An elimination of nightshades for two to four weeks may be long enough to tell you whether or not these foods have been contributing to your pain.
For those who don't suffer any sensitivity at all to nightshades, it may seem hard to believe that there could be a problem. For these folks, nightshades are tasty and nutritious.
But even these friends of nightshades should be careful not to eat any green spots on eggplant, potatoes or tomatoes. Those green spots indicate a high concentration of alkaloids.
The nightshade debate goes like this. One person says they can't eat nightshades, because of pain in their joints. Another person says there is no proof of this.