Nightshade vegetables come with a certain air of mystery. Add in the fact that certain high profile athletes and celebrities remove them from their diets and this group of vegetables becomes even more intriguing. But, in actuality, they’re pretty common. There are over 2,000 species of nightshade vegetables and herbs. The four most common species are white potatoes, tomatoes, eggplant, and peppers. However, the list goes on to include okra, capsicum, cayenne pepper, paprika, goji berries, ground cherries, and tomatillos. You probably eat foods that fit into the nightshade classification on the regular.
“Rumor has it that these veggies could increase inflammation, particularly the discomfort from arthritis, but the benefits of these nightshade foods may outweigh their potential risks,” says Bonnie Taub-Dix, RDN, creator of Better Than Dieting and author of Read it Before You Eat It: Taking You from Label to Table.
Some of the most common nightshade vegetables are known to have health benefits:
- Chili Peppers. The capsaicin within chili peppers may relieve arthritis pain and inflammation, says Taub-Dix.
- White Potatoes. “White potatoes contain fiber and vitamin C, and one medium potato has about twice the potassium of a banana,” says Taub-Dix. Potassium is a nutrient that most of us don’t get enough of.
- Tomatoes. Tomatoes have been shown to reduce inflammation. “They contain the powerful antioxidant, lycopene, [that is] thought to play an important role in cancer prevention, help curb heart disease, and boost immunity,” she says.
- Eggplant. Eggplant, a fruit often thought of as a vegetable, contains a variety of essential nutrients and is low in calories, she adds. Some studies have shown that eggplant might reduce inflammation. This is due to an antioxidant found in the purple skin of eggplants, called nasunin, that fights inflammation and oxidative stress.
Yet regardless of the health benefits, studies have shown that the same vegetables can be harmful and cause digestive issues. So what gives?
Why do some people avoid nightshades?
People may avoid nightshades due to an allergy, a food sensitivity, or a histamine intolerance. “Histamine is a chemical in the body that can elicit an inflammatory response,” says Jessica DeLuise, MHS, PA-C. She explains that people who have histamine intolerance can experience abdominal cramps, abnormal menstrual cycles, anxiety or depression, sleep disturbance, digestive disturbances, dizziness, vertigo, skin flushing, fatigue, nasal congestion, acid reflux, sinus issues, rapid heart rate, sneezing, tachycardia, swelling, and joint pain.
“Just like any food, some people may just be allergic to nightshade vegetables, so, of course, that would be a reason to avoid them,” says Alix Turoff, a registered dietitian and nutritionist. Interestingly, “[Some] people report that they are sensitive to nightshade vegetables after completing an elimination diet to determine food sensitivities,” says Turoff. Although there may not be significant scientific evidence that shows nightshade vegetables actually cause inflammation, some people—such as those with inflammatory diseases and disorders, including arthritis, ulcerative colitis, Crohn’s Disease, and asthma—may be sensitive to nightshade vegetables and should avoid eating them.
How do nightshade vegetables impact inflammation and gut issues?
It is difficult to determine exactly which nightshade vegetables could be causing adverse reactions. A 2002 study tested how nightshades affected irritable bowel diseases (IBD). The study used potatoes, finding that they did make IBD worse. This is due to the solanine in the potatoes. To best explain this, let’s start from the beginning. Solanine, also called glycoalkaloid, is a type of steroid alkaloid. An alkaloid, though a derivative of amino acids, has a different molecular structure. This structure is what makes alkaloid potentially more dangerous to consume. A glycoalkaloid is an alkaloid that has been combined with a sugar molecule. When breaking solanine down, the body separates the solanine from the sugar and stores it. Solanine, along with other steroidal alkaloids, could be the culprit behind your gastrointestinal irritation.
Another alkaloid found in nightshade vegetables, most commonly in peppers, is capsaicin. This alkaloid is the culprit for the tingling and burning sensation on your lips after you eat something particularly spicy. Those with heartburn or acid reflux may want to watch how much capsaicin they are consuming. It can irritate both the lining of your esophagus and stomach.
Follow an elimination diet.
It may not always be clear what’s causing your food allergies and sensitivities. Determining a food sensitivity can be done by following an elimination diet for a specified period of time. “By systematically eliminating these foods from the diet and then assessing whether symptoms have gotten better, we can determine if a person might be sensitive to nightshades,” says Turoff. “I would recommend experimenting by [reintroducing] one of these veggies [into your diet] at a time and then pay attention to whether your symptoms seem to escalate,” says Taub-Dix. “Don’t assume that if one nightshade food bothers you, that you’ll need to take the rest off your shopping list,” says Taub-Dix. These foods could play an important, nutrient-rich part of your diet if you tolerate them.
What are the benefits?
For those who can safely consume nightshades, individuals can report improvements in digestion, weight loss, and joint pain, among many other benefits. “Nightshades possess a variety of healthy attributes, such as vitamins A, E, and C, and antioxidants. For example, lycopene in tomatoes or beta-carotene in peppers,” says DeLuise. “As a healthcare practitioner, I recommend as many fruits, vegetables, and nutrient dense foods as possible, so avoiding them is never a good idea if there is no reason to do so.” Before eliminating foods or changing dietary practice, it is always a good idea to speak with your practitioner or dietitian.
So, should we be avoiding nightshade vegetables?
The jury is still out, but experts agree that you should only be cutting these out if you need to. “Some experts do recommend avoiding them if you have any inflammatory disease. But most will just advise patients to avoid them if they can suss out a true sensitivity,” says Turoff.
For most people, nightshade vegetables should be included in a healthy diet. There is no reason for most people to avoid them. That said, if you feel you might be sensitive to them, it doesn’t hurt to eliminate them and monitor symptoms. Most experts would probably agree that if it’s not broke, don’t fix it!