The nightshade family includes tomatoes, peppers, potatoes (not sweet potatoes or yams), eggplant, goji berries, and even tobacco. Anecdotal reports indicate that consumption of these either cause or aggravate certain chronic medical conditions, such as arthritis, chronic fatigue, or irritable bowel syndrome.
Georgia Ede, M.D., has an article on medical effects of nightshades at her website. The potentially offensive chemicals in nightshades are called glycoalkaloids. I looked into this issue when deciding whether to include potatoes in my version of the paleo diet. (They’re included).
Dr. Ede’s writes:
As with any food sensitivity, the only way to find out is to remove nightshades from your diet for a couple of weeks or so to see if you feel better. There are ZERO scientific articles about nightshade sensitivity, chronic pain, or arthritis in the literature, however, the internet is full of anecdotal reports of people who have found that nightshades aggravate arthritis, fibromyalgia, or other chronic pain syndromes.
I bet I could eat a couple potatoes and tomatoes every day without ill effect. And there’s Chris Voigt, head of the Washington State Potato Commission, famous for his 60-day potato diet. As they say, your mileage may vary.
Some of the nightshades, such as potatoes, supply a major carbohydrate load that can spike blood sugars too high in many diabetics. Be careful. And use your home glucose monitor.