Healthy People Don't Need to Avoid Nightshade Vegetables
Tomatoes, eggplants, and peppers do not cause inflammation.
Welcome to Wellness Lies, our list of the most pervasive misfires in the effort to feel and look better. We asked the experts and consulted the best science on all the questions you have about each of these wellness fads. Read the whole list and share with your most misinformed friends and family members.
Even if you don’t spend your nights reading tarot cards and charging your crystals by the light of the full moon, you may have heard of the poisonous plant belladonna. Many of us have seen Practical Magic, in which Sally (Sandra Bullock) accidentally kills her sister’s abusive boyfriend when she slips a little too much belladonna into his tequila. Some people think the purple plant was the mystery drug involved in Juliet’s ill-fated plan to fake her own death in Romeo and Juliet.
Belladonna has another name: deadly nightshade. It’s just one in a family of more than 2,000 plants known as nightshades. Though most aren’t edible, some of them have probably passed through your gut countless times. If you’ve eaten tomatoes, tomatillos, eggplant, potatoes, bell or hot peppers, or goji berries, then you, my friend, are intimately familiar with nightshades.
So how is it that you haven’t died? Well, tomatoes obviously aren’t poisonous like belladonna. But some people claim that all of these plants can have dangerous consequences. New England Patriots quarterback Tom Brady, for example, has famously cut nightshades out of his life. “No tomatoes, peppers, mushrooms, or eggplants,” Brady’s chef, Allen Campbell, told Boston.com in 2016. “Tomatoes trickle in every now and then, but just maybe once a month. I’m very cautious about tomatoes. They cause inflammation.”
Brady and his chef get that idea because poisonous nightshades like belladonna contain extremely high levels of compounds called alkaloids, which can be dangerous in high doses. But edible nightshades like tomatoes have very small amounts of these compounds to begin with, and the concentration of alkaloids falls even more when you cook them or do things like remove the skin and eyes from a potato, says Reyna Franco, a registered dietician nutritionist in New York City.
Nightshades also contain higher amounts of another compound some people worry about called lectins. Singer Kelly Clarkson made headlines in 2018 when she claimed that going on a lectin-free diet cured her thyroid problems. Some people argue that lectins are an “anti-nutrient” that’s making us all sick, the theory being that because the purpose of lectins is to protect plants from being eaten and digested, consuming them causes inflammatory reactions. But, like alkaloids, lectins break down when they’re processed or cooked. Even if you do end up eating raw lectins in foods like uncooked tomatoes, the amount you'd have to eat to feel any negative effects is much higher than a typical diet would include, according to the Mayo Clinic.
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Still, there is anecdotal evidence that eating nightshades can contribute to painful flares in people who have chronic inflammatory diseases like psoriasis and rheumatoid arthritis, says Gerard Mullin, associate professor of medicine and gastroenterology at The Johns Hopkins Hospital. Some people feel they have a sensitivity to nightshades, he says, and for those people, it might make sense to cut these foods out of their diets. “I’ve had people come into my office and say they feel better [when they stop eating nightshades],” Mullin says.
In one 2017 survey of 1,206 people with psoriasis, about 52 percent said they eliminated nightshades from their diets in an effort to quell flare-ups. Yet, neither this survey or any other research has found a clear reason why avoiding tomatoes, potatoes, peppers, and other nightshades would help people with autoimmune disorders, Mullin says. There’s no science to back up that choice. Maybe it’s a placebo effect, or maybe experts just doesn’t have an explanation yet. (Also worth noting: some people with acid reflux are told not to eat tomatoes because they're acidic.)
What we do know is that it’s not necessary for everyone to stop eating nightshades. In fact, it’d be kind of ridiculous if we did. “I’m in the camp of, if you can eat it, don’t restrict it,” says Stacy K. Leung, a registered dietician nutritionist based in New York City. Of course, you probably still want to limit low-nutrition snacks like potato chips and gummy bears, but unless you have a reason to stop eating healthy, whole foods—like if onions give you gas, or your face swells up when you eat peanuts—there’s no reason to restrict them.
Maybe people who already have arthritis and other inflammatory diseases notice they feel better when they eat fewer tomatoes, but even chomping on tomatoes won’t cause arthritis, Franco says. Think of it this way: Some people have the autoimmune disorder celiac disease or have a gluten sensitivity, so it makes sense for them to stop eating wheat, barley, and rye. But when perfectly healthy people hop on the gluten-free bandwagon, it does nothing more than deny them the deep pleasure of eating bread (and getting the nutrients from whole grains).
Any nutritionist will tell you that it’s best to strive for a balanced diet featuring plenty of fresh fruits and vegetables—and nightshades are certainly included in that recommendation. “When we look back at our ancestors’ cultural cuisines, a lot of these foods are integrated. They provide good nutrition and I believe that there’s a place for them in everyone’s diet,” Leung says.
Tomatoes are chock full of an antioxidant called lycopene. Peppers are loaded with vitamin C. Potatoes have more potassium than a banana. And eggplant is a great source of B vitamins and manganese. If you were to stop eating these foods for no real reason, and without carefully replacing them with similar foods, you could be missing out on those valuable nutrients. Besides, why would anyone choose to live without mashed potatoes if they don’t have to?
So feel free to ignore any wacky, restrictive diet recommended by a celebrity or when someone spouts off about which foods are “good” and which foods are “bad.” Ask yourself: Does this food make me feel itchy, nauseous, swollen, [insert negative adjective here]? If the answer is no, go ahead and eat it. You’ll be fine.
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