In this episode, we separate fact from fiction, explain who might truly be sensitive to nightshades, and why most of us shouldn’t avoid these nutritious foods.
In this episode, we separate fact from fiction, explain who might truly be sensitive to nightshades, and why most of us shouldn’t avoid these nutritious foods.
Find a full transcript here.
What if the vegetables you’ve been avoiding because they 'cause inflammation' are actually anti-inflammatory? Today, we’re clearing up a persistent nutrition myth about nightshade vegetables, a category that includes some super nutritious options that you don’t want to avoid if you don’t need to (and you probably don’t).
Welcome to the Nutrition Diva podcast, where we take a closer look at nutrition news, research, and trends so that you can feel more confident about what you eat. I’m your host, Monica Reinagel, and today, we’re talking about nightshade vegetables, a topic that I get a lot of questions about.
Tomatoes, potatoes, peppers, and eggplant all belong to a botanical family known as the nightshades. And depending on which corner of the internet you land in, you might hear that these vegetables are a hidden cause of joint pain, digestive issues, or inflammation.
The concern over nightshades as a potential source of inflammation gained traction in the 1980s, largely due to a horticulturalist named Norman Childers, who claimed that eliminating nightshades dramatically improved his arthritis symptoms. He collected thousands of anecdotal reports from others who said the same. But these reports were based on personal experiences, not controlled scientific studies. And as we’ll see, more recent and rigorous research paints a very different picture.
The plants popularly referred to as "nightshades" belong to a large family of plants called Solanaceae–so named because they contain a naturally occurring alkaloid called solanine. This compound acts as a natural insect repellent, protecting the plant from marauding aphids, beetles, and other pests.
In addition to tomatoes, potatoes (but not sweet potatoes), eggplants, tomatillos, and bell peppers, the Solanaceae family also includes chili peppers and spices like paprika and cayenne, as well as non-edible plants like tobacco and petunias.
All told, there are over 2,000 different kinds of plants in the Solanaceae family, including the infamous Deadly Nightshade (aka belladonna).
The ancient Romans reportedly used belladonna as a biological weapon, contaminating enemy food supplies. The wives of Roman emperors Claudius and Augustus are both believed to have used belladonna to poison their husbands. Deadly Nightshade is also thought to be the compound that Juliet uses to fake her own death in “Romeo and Juliet.”
However, it’s not the solanine in Deadly Nightshade that makes it so dangerous; it’s other compounds that work on the central nervous system. One of these, scapolamine, is used pharmaceutically (in carefully controlled dosages) to treat conditions like motion sickness. Another, atropine, is often administered as eyedrops to dilate the pupils before an eye exam.
Solanine can also be toxic to humans if ingested in very high amounts. But most of the solanine is concentrated in the stems and leaves of these plants–which is one of the reasons that we generally don’t eat tomato or potato leaves. (Even if you did, you’d have to eat 1-2 cups of potato leaves to get yourself in trouble). The amount that you’d get from eating the edible parts of nightshade vegetables is much, much less–generally far too low to cause any harm, unless you are among the very small percentage of folks who are sensitive to solanine.
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True allergies to nightshades are extremely rare, estimated to affect less than 1% of the population. These would typically show up as classic allergic symptoms like hives, swelling, or even difficulty breathing shortly after eating the food.
Intolerances, on the other hand, may be a bit more common but they can also be a lot harder to pin down. For one thing, the appearance of symptoms may be delayed by a few hours or a few days—which makes it difficult to make a clear connection to specific foods. For another, food sensitivities can cause a very wide range of symptoms, everything from fatigue to joint pain to belly-aches. Interestingly, most of the documented sensitivities to nightshades involve digestive sysmptoms—things like bloating, nausea, or GI discomfort—rather than inflammatory symptoms like joint pain.
If you suspect that nightshades—or any food, for that matter—might be triggering symptoms, the most reliable way to test that is with an elimination and reintroduction process. This involves removing all nightshades (or whatever food you suspect) from your diet for several weeks, and then gradually reintroducing them one by one while monitoring your symptoms. If your symptoms resolve during the elimination phase and return when a specific food is added back in, that’s a much stronger indication of a sensitivity. But if nothing changes, that suggests that these foods are not a problem for you. And, it appears that this is the case for the vast majority of the population.
In response to persistent concerns about nightshades, organizations like the Arthritis Foundation and the Cleveland Clinic have both gone on record saying there’s no credible research showing that nightshades cause or worsen inflammation or arthritis.
If anything, the opposite seems to be true. Many of these vegetables contain potent anti-inflammatory compounds.
Tomatoes, for example, are rich in lycopene, a carotenoid that has been shown to inhibit inflammatory pathways. Bell peppers are rich in quercetin and luteolin, two other anti-inflammatory flavonoids. Chili peppers contain capsaicin, the compound responsible for their heat—and their anti-inflammatory and pain-relieving properties.
And here’s an interesting twist: even solanine, the compound often blamed for nightshade-related inflammation, has been shown in lab studies to have anti-inflammatory effects, by modulating immune pathways.
Of course, that doesn’t mean everyone responds the same way. But it does challenge the idea that these foods are inherently inflammatory. In fact, foods like tomatoes, peppers, and chilis are often emphasized in diets specifically designed to be anti-inflammatory. Widening the lens a bit more, diets rich in these (and other vegetables) generally reduce the risk of cardiovascular disease and certain cancer.
In other words, for the vast majority of people, eliminating these super-nutritious vegetables is unlikely to reduce inflammation and comes at the expense of a lot of great nutrition. And of course, nightshades aren’t just nutritious—they’re central to so many global cuisines. It’s hard to imagine Indian food without chili, Italian food without tomatoes, or Latin American dishes without peppers.
As I mentioned earlier, if you suspect that you may be among the small minority that is sensitive to solanine, it might be worth a structured elimination and reintroduction protocol to test that theory. But here’s a word to the wise: One common mistake people make with elimination diets is trying to test too many things at once, or not reintroducing foods systematically. That makes it hard to draw clear conclusions. If you’re going to take the time to eliminate a group of foods like nightshades, make sure you have a plan for how you’ll test each one, and ideally, do it under the guidance of a nutrition professional.
But if you’ve never noticed any specific issues and have just been wary of these vegetables because you’ve heard they are inflammatory, you may be doing yourself a disservice. These foods are nutrient powerhouses that can absolutely be part of a healthy diet for most people.
If you have a question you’d like me to answer, you can email me at nutrition@quickanddirtytips.com. If you’d like to find out about having me speak at your next live or virtual event, you can learn more at wellnessworkshere.com
Nutrition Diva is a Quick and Dirty Tips podcast. Holly Hutchings is our Director of Podcasts. Steve Riekeberg is our audio engineer, Morgan Christianson heads up Podcast Operations & Advertising. Thanks also to Nat Hoopes for his support and most of all thanks to you for listening!