Have you ever heard that some foods are considered nightshades?
The term nightshade refers to the Solanaceae family of plants, a diverse array of flowers, shrubs, and trees. Nightshades all share certain properties, most famously (or infamously) that they contain chemicals called alkaloids. High levels of alkaloids (for example, in belladonna, known as deadly nightshade) make some of them extremely toxic to humans. The tobacco plant is a nightshade and contains high levels of the alkaloid nicotine. At very low concentrations, alkaloids are used as medicines.
Nightshade vegetables are edible and quite common in our everyday diet, including tomatoes, white and red potatoes (not sweet potatoes), bell and chili peppers, and eggplant. They contain very small amounts of alkaloids. These nightshade foods are packed with healthy compounds, particularly vitamins A and C, other carotenoids, and antioxidants.
However, some people (and fad diets) may avoid nightshades because they are reputed to cause inflammation. As mentioned in The Science of Living Well: Beyond Cancer, chronic inflammation is associated with many modern diseases (cancer, heart disease, diabetes), and we are trying to eat foods that help reduce inflammation, not increase it. However, there is no significant scientific evidence supporting a connection between normal consumption of nightshade vegetables and inflammation. Furthermore, nutrients in nightshades—such as carotenoids in tomatoes and bell peppers, and anthocyanins in eggplant—act as antioxidants to protect cells and DNA when inflammation is present. Concerned about dietary links to inflammation? The evidence connecting sugar and saturated fat with inflammation is much stronger.
You may have heard or read that if you have an autoimmune disorder, nightshades purportedly pose a risk of exacerbating symptoms as a result of their alkaloid content. However, no large-scale controlled studies have found that nightshades are bad if you are not someone with an autoimmune disorder. In fact, some edible nightshades—tomatoes, for one—are staples of the Mediterranean diet, often held as being one of the most life-extending diets on the planet!
As always, check with your doctor to make sure these vegetables mesh with your personal nutrition needs.