Everyone from Tom Brady to TikTok health influencers has spoken out about the evils of eating a certain class of plants called nightshades—insisting that they increase inflammation and might contribute to or worsen certain autoimmune conditions, such as psoriasis or inflammatory bowel disease. But are nightshades really a culinary villain? Read on for the dirt.
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First of All, What Are Nightshades?
Nightshades are members of a large family of about 2,300 different varieties of plants (the scientific name is Solanaceae). They got their nickname from the fact that many varieties grow nocturnally, says Kenneth Brown, M.D., a gastroenterologist in Plano, Texas, and the host of the Gut Check Project podcast.
Common nightshade plants include:
- Tomatoes
- Tomatillos
- Potatoes
- Eggplant
- Peppers
- Pepper-based spices (including paprika, chili powder, cayenne powder, red pepper)
- Pimentos
- Goji berries
- Ground cherries
- Huckleberries
- Ashwagandha
- Tobacco
As we mentioned in our guide to nightshades, this family is unique because the plants produce toxic compounds called glycoalkaloids as part of a savvy evolutionary strategy, according to a review published in Processes. These compounds act as "armor" for the plant to fend off certain diseases as well as some insects and animals (who are repelled by it). Solanine is the most prominent glycoalkaloid found in tomatoes, potatoes, eggplant and other edible nightshades at certain points in their ripening process.
Why Do Nightshades Sometimes Get a Bad Rap?
Just like any big family, most of the members are perfectly decent, while a few bad ones can stain the reputation of the entire group, says William W. Li, M.D., a Boston-based internal medicine physician and author of Eat to Beat Disease: The New Science of How Your Body Can Heal Itself.
For example, solanine can cause digestive symptoms such as nausea, vomiting or an upset stomach. But this condition is extremely rare—and it generally only occurs if you eat a whole bunch of young, green potatoes or very old potatoes that have sprouts growing on them. (So: Emphasis on the word "rare" here.) When exposed to UV light, potatoes produce more chlorophyll or sprouted extensions; two signs that their solanine levels are high enough to cause issues.
Other nightshades like tomatoes, potatoes, eggplants and peppers contain alkaloids, or a form of carbohydrate-binding proteins called lectins that can cause inflammation and digestive issues in some people. However, the levels are usually too small to affect most humans, Brown says.
And almost everyone can avoid possible side effects by simply cooking the foods that contain these compounds, adds Akil Palanisamy, M.D., an integrative medicine doctor in San Francisco and the author of The T.I.G.E.R. Protocol: An Integrative, 5-Step Program to Treat and Heal Your Autoimmunity.
So unless you're one of the very few people who have an allergy to eggplants or other nightshades, they're not considered toxic. "As with all foods—not just nightshades—if your body responds negatively, it's best to avoid eating them," Li says.
If you are concerned that nightshades may be a problem for you, talk to your doctor or try a dietitian-guided elimination diet in tandem with a symptom diary. You'll remove various foods and reintroduce them one at a time, noting any symptom changes.
"There has unfortunately been a widespread misunderstanding about nightshades being toxic and dangerous to eat," Li says. "But an enormous volume of scientific and clinical studies on the effects of these foods on health has overwhelmingly shown that they are beneficial to health. In fact, they contain many natural bioactive compounds that improve circulation, assist with gut health, have antioxidant activity, improve immunity and lower inflammation."
Why Nightshades Are Among the Best Foods for Gut Health
In addition to offering various vitamins, minerals and antioxidants for very few calories, nearly all nightshades offer a dose of fiber, which feeds your good gut bacteria and supports digestion.
Will Bulsiewicz, M.D., a Charleston, South Carolina-based gastroenterologist and author of The Fiber Fueled Cookbook, says that in addition to there being no evidence that consuming nightshades in normal amounts is toxic, if you take a step back and think about tomatoes and peppers and eggplants, you're really describing a Mediterranean-style diet—which is known to be among the healthiest eating patterns, if not the healthiest.
Eating a variety of fruits and vegetables, including nightshades, can contribute to a healthier gut microbiome, Brown adds. In fact, compared to people who consume 10 or fewer types of plants per week, people who eat 30 or more (including spices) have healthier microbiomes, according to a May 2018 study published in the journal ASM Journals.
Plus, a diverse diet packed with plants leaves less room for gut-unfriendly items like red meat, artificial sweeteners and alcohol. And getting a range of produce, herbs and spices means that you'll score different types of fiber and nutrients that help your good gut bacteria thrive.
"The more diverse your microbiome, the healthier your gut. This translates into lower inflammation and a reduced risk for chronic diseases like heart disease and type 2 diabetes. It can also promote faster healing, a more streamlined metabolism and even better mood," Li explains.
The Health Benefits of Eating a Plant-Based Diet
The Best Nightshades for Gut Health
While there haven't been any head-to-head studies comparing nightshades in terms of their microbiome benefits, Li says that the following fruits and vegetables are standouts because of the beneficial vitamins, nutrients and other bioactive compounds that they contain. Eat up!
Peppers
"Peppers are generally well-tolerated because they have lower levels of potentially irritating compounds," says Brown, and they're rich in gut-friendly fiber and vitamins, including vitamin C.
Tomatoes
This fruit is also high in fiber and antioxidants like lycopene, which can support gut health, Brown says. In addition, thanks to the vitamins (such as C) and minerals, "intake of tomatoes is associated with lower risk of heart disease, reduced risk of prostate cancer and improved bone health as well," Palanisamy adds.
Huckleberries, Ground Cherries and Tomatillos
These fruits are packed with antioxidants, fiber and vitamins, says Brown, which means they're beneficial for gut health and overall well-being.
Cooked and Chilled Potatoes
While all potatoes come with vitamins, fiber and potassium, leftover spuds (meaning ones that have been cooked and chilled) earn bonus points from Palanisamy, since they're especially high in resistant starch. "The process of cooling cooked potatoes for about 12 hours causes the formation of this resistant starch, which is an excellent prebiotic that feeds and supports the gut microbiome," he says. "Potatoes are pretty unique among plants in terms of being able to synthesize this resistant starch." (Green bananas, black beans, pinto beans, barley and pumpernickel bread are also sources of resistant starch.)
Eggplants
Eggplants are rich in prebiotic factors, such as polyphenols, carotenoids and fiber—all of which help sustain and nurture healthy gut bacteria—which is why this veg has been shown to improve microbiome diversity, notes Li.
If you're feeling inspired to nosh on nightshades, we highly recommend these 18 juicy tomato recipes, our 27 best eggplant recipes for summer, 22 low-calorie potato side dishes and this paprika spice blend you'll want to sprinkle on just about everything.
The Bottom Line
Although some people may need to limit or avoid nightshades, the vast majority of people can benefit from the substantial nutritional benefits that this family of plants provides—including better gut health. And they should absolutely be included as part of a balanced diet, Brown says. And Palanisamy adds that the Mediterranean diet, which includes many nightshades, has been shown to be one of the healthiest diets on the planet—not just for better gut health, but for a better, longer life.
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