Nightshades

Nightshades are a diverse group of foods, herbs, shrubs, and trees that have fascinated scientists, doctors, and nutritionists for centuries.

They get their name because these plants prefer to grow in the shade and their flowers open or bloom at night. Some believe the name reflects the spooky or dangerous reputation of wild plants in the Solanaceae family, which contains powerful toxins used in narcotics, sedatives, and painkillers, including belladonna and mandrake, which add to their mysterious and dark reputations.

Nightshade vegetables include potatoes, tomatoes, sweet and hot peppers, eggplant, tomatillos, tamarinds, pepinos, pimentos, paprika, and cayenne. The specific substances in these foods are called alkaloids and can affect nerve-muscle and digestive functions in humans and may also compromise joint function. Because the amounts of alkaloids are very low in nightshade foods compared with other nightshade plants, health problems from nightshade foods may occur only in individuals who are especially sensitive to these alkaloids. 

The steroid alkaloids in nightshades have been studied for their health effects in two areas. First, they can block the activity of an enzyme in nerve cells, cholinesterase, by inhibiting it. If cholinesterase activity is too strong, the nervous system becomes disrupted, and muscle twitching, trembling, paralyzed breathing, or convulsions can result. 

A potentially related problem is joint damage caused by inflammation and altered mineral status. Some researchers have speculated that nightshade alkaloids may contribute to excessive calcium loss from bone and soft tissues. For this reason, it is recommended that nightshade foods be eliminated from the meal plans of all individuals with osteoarthritis, rheumatoid arthritis, and joint problems.

If you have existing joint problems, temporarily eliminate nightshade foods from your meal plan to determine if they contribute to them. The same recommendation would apply to individuals with existing nervous system problems.