Vegetables like potatoes and tomatoes are common but can cause some people dietary distress. Here’s what you need to know.

Nightshades, a category of vegetables that includes potatoes and tomatoes, are one of the latest food groups on the chopping block in many fad diets. They’re joining the likes of gluten, carbs and canola oil as foods that allegedly cause dietary issues and inflammation in the body.

But are nightshades really something you need to cut out of your diet? Might this be the last straw for your red pizza or French fry fanaticism?

Below, we dig into the science of nightshades to discover the truth.

What are nightshades?

Nightshade is a botanical family of plants. It includes vegetables such as potatoes, eggplants, tomatoes and peppers. It also includes highly toxic plants such as belladonna, mandrake and tobacco.

Despite their dangerous relatives, the common nightshade vegetables that you know and love are safe to eat. They are an excellent source of nutrients such as:

• Vitamin C (bell peppers), which helps protect your body’s cells against free radicals that may play a role in cancer and heart disease
• Potassium (potatoes), a mineral that helps keep your heartbeat regular, among other things
• Lycopene (tomatoes), a type of chemical that may help prevent certain types of cancer and heart issues

Most people can enjoy nightshades without worry. But some may be sensitive or even allergic to certain nightshades.

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Nightshade allergies

It’s possible to have a nightshade allergy, but it’s rare, says Payel Gupta, M.D. She’s a spokesperson for the American College of Allergy, Asthma and Immunology, and a clinical instructor at Mount Sinai Hospital. She’s also an assistant clinical professor at SUNY Downstate Medical Center in New York City. She notes that allergies to milk, eggs, soy, sesame, wheat, fish, shellfish, tree nuts and peanuts are the most common food allergies.

“Signs and symptoms of nightshade allergies mimic other food allergies,” says Tiffany Leon, R.D. She’s the assistant director of training and professional programs at Food Allergy Research & Education. If you’re allergic, you might experience these symptoms when you eat a nightshade vegetable:

• Tingly or itchy feeling in the mouth
• Swelling around your mouth, face or throat
• Itchy swellings or rashes on your skin
• Vomiting, diarrhea or abdominal cramps
• Tightening of the throat and trouble breathing
• Coughing or wheezing

If you suspect that you have a nightshade allergy, Leon advises that you see an allergist — a doctor trained in food allergies. And keep a diary of the foods you eat and any reactions you have to them. She points out that it’s rare to be allergic to all nightshade vegetables. An allergist should be able to pinpoint exactly what you are allergic to, she says. They can run skin or blood tests and go over your food diary.

Food allergies are managed by avoiding any foods that you are allergic to. “That means staying away from the food and all foods that are made with, cooked with, or in cross-contact with the allergen,” says Leon. Dr. Gupta adds that you’ll need to read food labels carefully to make sure they do not contain any of your allergens.

If you have a serious food allergy, you should also carry an epinephrine device, such as an EpiPen, with you, says Dr. Gupta. Epinephrine helps to relax the muscles in your airways and tighten your blood vessels.

Some allergens can trigger a life-threatening reaction called anaphylaxis, which can cause everything from a rash and vomiting to difficulty breathing. An EpiPen is a shot you can give yourself (or someone can give you) if you’re having that type of serious allergic reaction. “Epinephrine can help stop a reaction and save your life,” says Dr. Gupta.

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Nightshades and inflammation

Nightshades contain chemical compounds called alkaloids. You’ve probably heard of a couple of them. Nicotine (in tobacco) and capsaicin (in hot peppers) are alkaloids. Toxic nightshade plants have high doses of alkaloids that can be deadly if you consume them.

But the nightshades that we typically eat have low doses that are generally harmless. That said, some people may be sensitive to nightshades. They could cause problems for people with inflammatory or autoimmune conditions like inflammatory bowel disease, arthritis or psoriasis. There is very little evidence proving a connection, but many people claim that avoiding nightshades has helped ease their symptoms.

If you suspect that you’re sensitive to nightshades, the first step is to test for an allergy. Once that has been ruled out, you can try an elimination diet. That means trying to cut out suspected foods from your diet for a few weeks, then adding them back one by one, watching carefully for any symptoms.

Food sensitivities are hard to diagnose. There are no evidence-based tests. An elimination diet is the best way to figure out what (if any) foods are causing you trouble. It’s best to do this with the help of a doctor or dietitian. They can help you figure out which foods to cut. And they’ll help you understand any symptoms you may have as you put them back in your diet.

Unlike allergies, food sensitivities won’t cause a life-threatening reaction. You don’t need to be as diligent about avoiding certain foods as you are with certain allergies. You may even be able to tolerate small amounts of the foods that you’re sensitive to. Once you know what’s causing your symptoms, you can decide the extent to which you need to avoid those foods.

Because nightshades include common vegetables such as potatoes and tomatoes, that also means they are most likely present in foods such as tater tots and marinara sauce, to name a few. Most people do not need to cut nightshades out of their diet, though some may have rare allergies or sensitivities to them.

Talk to your doctor — or ask them about a referral to a dietitian or an allergist — if you think nightshades may be causing health problems for you. Or you can always cut them out of your diet. But you’ll want to consult a doctor before making any changes to your diet.

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For informational purposes only. This information is compiled by UnitedHealthcare and does not diagnose problems or recommend specific treatment. Services and medical technologies referenced herein may not be covered under your plan. Please consult directly with your primary care physician if you need medical advice.

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Cleveland Clinic. “Arthritis: Should you avoid nightshade vegetables?” March 15, 2023. Retrieved from https://health.clevelandclinic.org/arthritis-should-you-avoid-nightshade-vegetables

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MedlinePlus. “Low blood potassium.” June 12, 2023. Retrieved from https://medlineplus.gov/ency/article/000479.htm

MedlinePlus. “Vitamin C.” January 19, 2023. Retrieved from https://medlineplus.gov/ency/article/002404.htm

Oregon State University Linus Pauling Institute. “α-Carotene, β-carotene, β-cryptoxanthin, lycopene, lutein, and zeaxanthin.” October 2023. Retrieved from https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/carotenoids

U.S. Department of Veterans Affairs. “Elimination diet.” May 1, 2024. Retrieved from https://www.va.gov/WHOLEHEALTHLIBRARY/tools/elimination-diets.asp

U.S. Food & Drug Administration. “Food allergies.” April 12, 2024. Retrieved from https://www.fda.gov/food/food-labeling-nutrition/food-allergies

U.S. Forest Service. “The powerful solanaceae.” Retrieved from https://www.fs.usda.gov/wildflowers/ethnobotany/Mind_and_Spirit/solanaceae.shtml. Accessed on December 3, 2024

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