Far from being bad for you, nightshade vegetables confer a number of health benefits because they are often rich in vitamins, minerals, and other useful compounds. As is the case with all elements of the human diet, however, some people find that they feel healthier when they do not eat these vegetables. For people with conditions that are sometimes made worse by what they eat, it may help to use an elimination diet to zone in on foods which cause complications and discomfort.
Nightshade vegetables are actually fruits, not vegetables — except in the case of the potato, which is a tuber — but because they are cooked and treated like vegetables, most people refer to them with this term. Eggplant, tomatoes, peppers, and potatoes are all members of the nightshade family that are used for food, and tobacco is another member that is cultivated for use by humans. All of these products contain trace amounts of alkaloids that can be harmful in heavy concentrations.
As a general rule, people should avoid consuming the leaves, stems, and flowers of members of the nightshade family, and they should only eat fruits that are fully ripened, without any green spots. Some members of the nightshade family, such as peppers, can be green when fully ripe, but green spots on tomatoes, potatoes, and eggplant are not desirable, as they can contain high concentrations of alkaloids. On potatoes, the green spots indicate that the tubers have been exposed to sunlight, and the potato has developed alkaloids as a self defense mechanism to make it unappealing to animals that might want to eat it.
The natural toxins present in trace amounts in mature nightshade vegetables do not appear to be harmful when these foods are eaten as part of a balanced diet. A high concentration of such food in the diet could cause issues in some people, especially if the food is underripe or poorly handled. Consumers can avoid problems by using fresh, fully ripened vegetables and carefully trimming away any green spots on potatoes.
Some researchers have suggested that these vegetables can be involved in gastroesophageal reflux disease (GERD), along with the more mundane heartburn. They may also be a culprit in inflammatory processes, such as those observed in arthritis, and some people believe that these foods can also exacerbate acne. While people may not want to take recommendations to eliminate nightshade vegetables from their diets at face value, going through an elimination diet can be a good idea, as it can help identify any problem foods.