Solanaceae, also known as nightshades, are a family of flowering plants that include a number of important agricultural crops as well as many toxic plants. The family includes Datura (Jimson weed), Mandragora (mandrake), Belladonna (deadly nightshade), Lycium barbarum (Wolfberry), Physalis philadelphica (Tomatillo) , Physalis peruviana (Cape gooseberry flower), Capsicum (all peppers including chili peppers, habenero, cayenne pepper and paprika, but not peppercorns), Solanum (potato, tomato, eggplant, but not sweet potatoes or yams), Nicotiana (tobacco), and Petunia. With the exception of tobacco (Nicotianoideae) and petunia (Petunioideae), most of the economically important genera are contained in the sub-family Solanoideae. Solanaceae are characteristically ethnobotanical, that is, extensively utilized by humans. They are important sources of food, spice and medicine. However, Solanaceae species are often rich in alkaloids whose toxicity to humans and animals ranges from mildly irritating to fatal in small quantities.
Why should you care about this? It’s likely that you enjoy eating these foods and can’t imagine that they are bad for you in any way. Well, if you suffer from inflammation, joint pain and cracking, avoiding nightshades will lessen your pain, whether or not the nightshades are the true source of the pain. Are you sensitive to weather changes? This can be an indication of nightshade sensitivity. Muscle pain and tightness, morning stiffness, poor healing, arthritis, insomnia and gall bladder problems—these can all be caused by nightshades. Nightshades can also cause heart burn or GERD—a lot of people already know they react this way when they eat peppers or tomatoes. Scleroderma is a widespread connective tissue disease that involves changes or hardening in the skin, blood vessels, muscles and internal organs. All nightshades contain nicotine, which is why they can be addictive.
I have some occasional joint pain, which I've attributed to exercise and aging. Less explainable are some random skin irritations that occur at odd places - one side of my chin gets extremely irritated when I shave and I have a quarter-sized circle of tough dry skin on my ankle, where I fractured a bone many years ago. I've tried topical creams, soaking the areas in black tea, but nothing worked. So giving up nightshades in order to fix up these minor irritations seemed worth a try.
At the beginning of this month, we decided to cut out nightshades from our diet and see what happened. It has been tough. Turns out that many of these items show up in almost everything we like to eat. Some of it has been easier than others - I love pizza with Alfredo sauce, so giving up tomatoes has not been that bad. The most difficult for me? By far hot peppers - I live on them, using them on everything short of cereal. It's been tough to forego the hot sauce when eating asian or latin meals.
It's been 3 weeks and I'm not certain that I feel any different, but the article Laima cited says it takes a good 6 weeks for the effects to become noticeable. I'll report back then and let you know what I think. If nothing else, cutting out nightshades has made us more aware of their ubiqity, and paying attention to one's diet is never a bad thing. Plus, all that nicotine can't be good for us anyway.
Sources: http://en.wikipedia.org/wiki/Solanaceae http://www.westonaprice.org/food-features/nightshades