Tomatoes, potatoes, eggplant, and a few other foods in this family have a reputation for causing some chronic conditions to flare up.
Is it fact or fiction? Some nutritionists will tell you to eliminate all nightshade plants from your diet. If you read the Old Testament and some Shakespearean works and even writings from Chaucer, you’ll find evidence that nightshades were used as poisons. The chief culprits were belladonna and mandrake. These nightshades were avoided until the 1800s.
Even with more than 3,000 species of nightshade plants, myths still persist that popular nightshade vegetables and fruits, including potatoes, tomatoes, eggplant, peppers, and goji berries should be avoided because they could be toxic.
One study found a link between certain nightshade plants and arthritis. It appears that some nightshade plants can cause inflammation, which affects people with arthritis. Stephanie Vachon, a nursing student, believes that her arthritis gets worse when she eats eggplant, tomatoes, potatoes, peppers, and other nightshade fruits and vegetables. “I did an elimination diet and feel so much better when I don’t eat these fruits and vegetables,” she said.
A later study in the Journal of Nutrition in 2011, showed that yellow and purple potatoes lowered blood markers for inflammation in healthy men. The takeaway from that study showed that some people with arthritis may benefit from nightshades and that some people may be sensitive to certain nightshades.
The information can be confusing. Nightshades have a lot of negatives and some positives. Garrett Smith, a licensed naturopathic physician, writes in his blog that he’s biased against nightshades. “I used to eat a ton of foods in the nightshade family, but now I avoid them as much as possible. I am sensitive to these foods.”
He explained that for him and for his patients, “nightshade avoidance is the answer to long-term relief from pain.”
He agrees with Vachon that eliminating nightshades from your diet can help you avoid muscle pain, morning stiffness, and arthritis.
A main ingredient found in nightshades is glycoalkaloid, a natural pesticide found throughout these plants with high concentrations in the leaves and flowers. According to Georgia A. Ede, MD, in Falmouth, Mass., “Most of us do not associate potatoes with illness, probably because the amount of glycoalkaloid most of us eat every day is not very high.”
She does explain that there are well-documented reports of people getting glycoalkaloid poisoning from eating improperly stored, green, or sprouting potatoes. “At low doses, humans can experience gastrointestinal symptoms, such as vomiting and diarrhea,” she explained.
Higher doses, however, can result in fever, low blood pressure, confusion, and other neurological problems. “We shouldn’t worry about this because if you have a healthy digestive tract, most of the glycoalkaloid won’t make it into your bloodstream,” she said.
If you enjoy eating potatoes, remove the skin because that’s the part with the majority of glycoalkaloids.
Still confused about whether nightshade foods are good or bad for you? Try an elimination diet. For a month remove all nightshade fruits and vegetables. Keep a journal to record how you feel and talk to your doctor or nutritionist about your findings.
You can slowly add one nightshade fruit or vegetable back at a time, and take notice of your well being. Do you feel fine? Do you feel pain?
Symptoms to look for after reintroducing nightshades include: chronic pain, arthritis, joint pain, insomnia, nerve pain, heartburn, or difficulty concentrating. If you are experiencing any of these ailments, eliminate these foods from your diet and talk to your doctor.
September 14, 2016
Janet O’Dell, RN