What Are Nightshades and Are They Bad for You?

Can eating certain fruits and vegetables do more harm than good? The short answer is no—as long as you're not allergic or have a food sensitivity to them. Unfortunately, though, nightshade vegetables—including tomatoes, potatoes and eggplant—have fallen into a bucket of foods to avoid by some influencers and medical professionals. Imagine—no more salsa and marinara sauce!

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 this family of plants also includes several edible fruits and vegetables, the most common ones being tomatoes, white potatoes, eggplant, bell peppers, chile peppers and tomatillos. Spices derived from nightshades, like paprika and cayenne pepper, are also considered a part of the Solanaceae family.

The nightshade family is unique in that they produce potentially 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 might 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 in Europe—sometimes referred to as hexing herbs.

Adding more subjective fuel to the fire is that some celebrities—like former NFL quarterback Tom Brady—have made it known that they follow a diet that restricts nightshade fruits and vegetables. In Brady's book, The TB12 Method, the seven-time Superbowl champion claims that avoiding nightshades helped his performance and prevented inflammation. It's hard to argue with such a successful high-level athlete—but 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 might also 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 support the notion of nightshades causing inflammation. With that said, 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. But 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. For example, several studies suggest that solanine may help inhibit the growth of cancer cells. And others suggest that solanine has a host of health benefits including it being anti-bacterial, anti-fungal and anti-viral—plus evidence of the compound being beneficial for bones, joints, muscles, nerves and the heart.

Nightshades: Healthy or Harmful?

For most people, there's little, if any, reason to avoid nightshades. In fact, there may be more risk in 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, which act as antioxidants and can exert anti-inflammatory effects on 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. This 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 healthcare practitioner and consider working with a registered 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.

The Bottom Line

While nightshades have gotten a bad rap over the years for various reasons, most of us can eat them without experiencing any issues. There is a wealth of evidence suggesting nightshades are anti-inflammatory and provide health benefits for most people—exceptions might be for those with autoimmune diseases like rheumatoid arthritis. Enjoy nightshades in a variety of recipes, like our Eggplant Parmesan or 3-Ingredient Bell Pepper & Cheese Egg Cups.