What Are Nightshades and Are They Bad for You? Here's What a Dietitian Says

Here we address the myths and misconceptions about the "inflammatory" family of veg.

Can eating certain fruits and vegetables do more harm than good? The short answer is no, but that's the question some are asking when it comes to tomatoes, potatoes, eggplant and other produce in the nightshade family. And avoiding nightshades could mean cutting out some of our favorite foods—hello, salsa and marinara sauce! So we did a deep dive into the research on nightshades to understand why they've been labeled "bad" or "inflammatory" by some and if eliminating them is really necessary for good health. Here's what we found.

What Are Nightshades?

Nightshades refer to plants in the Solanaceae family, the majority of which are inedible, like tobacco. But the family includes a handful of edible fruits and vegetables. The most common ones are tomatoes, white potatoes, eggplant, bell peppers, chile peppers and tomatillos, along with spices derived from nightshades like paprika and cayenne pepper. The nightshade family is unique in that they produce toxic compounds known as glycoalkaloids. From an evolutionary standpoint, glycoalkaloids are designed to defend the plant against insects, disease and some plant-eating animals, and thus promote the plants' survival.

The main issue that some people take with nightshades is that these compounds that are toxic to predators can also be toxic to humans—which is where the nightshade debate stems from. While this debate seems as though it should be strictly scientific, it often gets clouded by history since nightshades have long been associated with witchcraft. But also adding more subjective fuel to the fire is the fact that professional football player and celebrity Tom Brady follows a diet that restricts nightshade fruits and vegetables (among many other things) that he claims helps his performance and prevents inflammation. So what does the science suggest?

Are Nightshades Safe to Eat?

Solanine is the primary glycoalkaloid found in tomatoes, white potatoes, eggplant and other edible nightshades. In potatoes, solanine is found in the green skin of young potatoes; you'll usually still see some green skin just under the peel of mature potatoes. Solanine poisoning can cause digestive issues like an upset stomach, nausea and vomiting, but it's also very rare and requires eating a large amount of young, green potatoes or old potatoes with sprouts. Cases of other edible nightshades causing solanine poisoning are also rare.

Do Nightshades Cause Inflammation?

The more recent buzz around nightshades is that they are inflammatory and should be avoided to minimize inflammation, but most research does not suggest that nightshades cause inflammation. However, any irritant in the diet can potentially exacerbate existing inflammatory conditions. This is because the body tends to become hypersensitive when inflammation is present. Consequently, solanine (as well as a host of other natural and processed compounds in foods) may act as an irritant to inflammation that's already present. That said, the concentration of solanine in most edible fruits and vegetables is very low, especially if the produce is ripe.

Perhaps what is more surprising is that some research suggests that nightshades are actually anti-inflammatory for most people. A 2016 study suggests that the compounds in eggplant have anti-inflammatory effects that could possibly be used therapeutically. Similarly, a 2018 study suggests that a solanine could be a "valuable, leading compound" in the treatment of inflammatory diseases. Several studies also suggest that solanine may help inhibit the growth of cancer cells.

Tomatoes on a vine
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Nightshades: Healthy or Harmful?

For most people, there's little (if any) reason to avoid nightshades. In fact, there may be more risk to not including them in your diet. This is because tomatoes, eggplant, peppers and most other edible nightshades are packed with nutrients like vitamin C and phytochemicals like lycopene and beta carotene, and these act as antioxidants and can exert anti-inflammatory effects in the body. Most nightshades are also a good source of fiber, which is an important nutrient for gut health, heart health, longevity and more.

One exception to this is for people with an autoimmune condition such as rheumatoid arthritis or inflammatory bowel disease. While most of the data is anecdotal, some individuals do report unpleasant digestive symptoms or joint-related pain when they consume nightshades, which makes sense considering autoimmune diseases are inflammatory in nature. But even in these cases, the solution doesn't necessarily entail avoiding all nightshades. Many people who experience sensitivity find that their symptoms are triggered by one or two specific nightshades but not by others. Always talk to your doctor and consider working with a dietitian if you're interested in trying an elimination diet yourself. But for most, feel free to enjoy the flavors and health benefits of nightshades in recipes like our Marinated Cherry Tomato Salad and Lemon-Rosemary Melting Potatoes.

Up Next: Do Tomatoes Cause Inflammation? Here's What a Dietitian Has to Say

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