They may sound like sunglasses you wear after dark, but nightshades aren’t the subject of an 80s pop song. Instead, nightshades are a family of plants, many of which are staples in human diets around the world.
Despite this, nightshades are often the subject of food controversy. On one side of the argument, they are touted for their tremendous health benefits, while the other side claims nightshades promote inflammation, are high in dangerous antinutrients, and may be damaging to your health.
So what’s the truth about nightshades? Are they good for you, bad for you, or somewhere in between? And should everyone avoid them — or not?
What Are Nightshades in Food?
Nightshades actually belong to a scientific family of plants called Solanaceae, which includes thousands of species, such as fruits, vegetables, herbs, shrubs, and weeds.
Nightshades are unique in that they all grow five petal flowers and alternate leaves that grow in a staggered fashion on the stems.
Most nightshades are toxic to humans, insects, and animals on some level, such as tobacco and the belladonna plant (ominously and accurately known as deadly nightshade). One of the biggest reasons these plants are not ingested is because of compounds called tropane alkaloids. These substances can have hallucinogenic effects, damage organs, and negatively impact the functioning of the central nervous system and digestive system.
Only a handful of nightshades are actually safe for humans to eat, which may be part of the reason many people are skeptical about nightshades in the first place. (That or the fact that they were also associated with witchcraft in the Middle Ages. More on that later!)
Nightshade Vegetables
It’s likely that edible nightshades are already a regular part of your diet. Some of the most popular types of nightshade vegetables include:
- Bell peppers, hot peppers, sweet peppers
- Spices that come from peppers, such as cayenne and paprika
- Eggplant
- Potatoes (excluding sweet potatoes)
- Tomatoes
- Tomatillos
Health Benefits of Edible Nightshade Vegetables
Like all whole plant foods, vegetables that also happen to be nightshades are still great sources of nutrients such as vitamins, minerals, protein, and fiber. And eating more fruits and vegetables is associated with a reduced risk of chronic disease and mortality.
Let’s examine what we know about nightshade foods and their benefits.
Peppers
Green, red, and yellow aren’t just for traffic lights. Peppers enjoy these colors, too. Research shows the different colors of fruits and vegetables are linked to specific phytonutrients, each with its own health-promoting superpowers.
Nutritionally, peppers are also a great source of vitamins A, C, E, K, and B6, along with potassium and folic acid. And they’re high in antioxidants that can help prevent and perhaps even reverse a number of diseases, like heart disease and cancer.
One of the most beneficial compounds found in hot peppers, specifically, is capsaicin. Although we know it as the spiciness factor in peppers, capsaicin also has applications that range from pain relief to weight loss.
Eggplants
Eggplants are rich in fiber, potassium, and vitamins B1, B6, and K. Although eggplants come in a variety of colors, the most common is purple. Eggplants’ purple color comes from their anthocyanin content — an antioxidant and phytochemical that may protect against inflammation, cancer, heart disease, and type 2 diabetes. In fact, eggplant consumption may be a valuable tool in treating metabolic syndrome — a condition involving type 2 diabetes, obesity, high cholesterol, and high blood pressure.
Tomatoes
Tomatoes are an excellent source of vitamin C and potassium, along with the powerful eye-health-promoting antioxidants lutein and zeaxanthin. They’re also one of the best sources of lycopene, an antioxidant that reduces inflammation as well as conditions related to oxidative stress.
To enhance your absorption of lycopene from tomatoes, cook them and eat them with a healthy source of fat. Traditional cultures seem to have known this intuitively — classic Italian dishes pair olives with stewed tomatoes, and Mexican cuisine combines avocados and various tomato-based sauces and spreads.
A 2016 meta-analysis found that tomatoes may be protective against cancer, especially that of the prostate. This likely has something to do with their lycopene content, which has been shown to slow the progression of cancer cells. Tomatoes also appear to benefit heart health by lowering both your LDL (“bad”) cholesterol and blood pressure, among other cardioprotective effects.
Potatoes
Different colors of potatoes offer different health benefits, but they’re typically all good sources of fiber, potassium, vitamin C, and vitamin B6. Potatoes are an abundant source of resistant starch, which is good for digestion and may even play a role in reducing the risk of colon cancer. Their peels are also rich in nutrients important for bone health, like iron, phosphorus, calcium, magnesium, and zinc. Red and purple potatoes are a source of antioxidants, especially carotenoids, which have been widely researched for their protective effects against chronic diseases and inflammation. Purple and blue potatoes have been shown to reduce oxidative damage and inflammation.
Why Do People Think Nightshades Are Bad?
Nightshades’ bad rap likely stems from the infamy of one plant, in particular: deadly nightshade or Atropa belladonna. Its botanical name comes from Atropos, one of the three fates in Greek mythology who is in charge of ending a life, and belladonna, which means “beautiful woman” in Italian. As its name suggests, it’s a beautiful but deadly plant that’s toxic when ingested. Nevertheless, that didn’t stop people from using it for both good and evil.
Some of its more nefarious uses were to induce hallucinations in ancient Grecian cults and to allow witches to fly (or think they were flying), cast spells, and commune with the devil. It was also the poison of choice in ancient Rome, and many people speculate that the sleeping draught Juliet takes in William Shakespeare’s Romeo & Juliet was derived from deadly nightshade.
But Atropa belladonna also had cosmetic and medicinal purposes as well. During the Renaissance period in Europe, women allegedly used it to dilate their pupils, making their eyes appear larger and more doll-like. Atropine sulfate eye drops (originally derived from the deadly nightshade plant) are still used by eye doctors to dilate pupils before an eye exam. And atropine is commonly used to treat bradycardia (slow heart rate) as well as organophosphate poisoning (a pesticide and nerve agent that can affect the heart, excretory glands, and muscles).
The New Myth of Nightshade Foods Being Bad for You
Nowadays, there’s a new spokesperson for the “all nightshades are dangerous” perspective: Dr. Stephen Gundry, the physician behind the “Gundry Way” eating plan and The Plant Paradox book. A quick Google search will unveil the many claims he has emphasized about nightshades causing inflammation and generally being unhealthy and disastrous to your body, especially your digestive system.
According to Dr. Gundry, there are two main reasons to avoid nightshades: lectins and alkaloids. You may have heard of these being referred to as “antinutrients,” meaning that they may compete with nutrient absorption in the body.
Lectins are proteins found most densely in nightshade peels and edible seeds like cereal grains and legumes. Gundry claims that lectins are toxic and inflammatory and that they are resistant to your digestive enzymes, making them impossible to properly break down in the body. If you eat a lot of lectins, he says, you will experience major discomfort. Therefore, he advocates for a lectin-free diet.
Alkaloids include plant compounds such as solanine, nicotine, and capsaicin. Gundry claims that some people may not be able to digest these properly, either, and that they may cause vomiting, diarrhea, and abdominal pain.
Dr. Gundry also notes that some people have nightshade sensitivity and may not realize it due to its similarity to other conditions. For instance, he says nightshade sensitivity may present itself as diarrhea, heartburn and acid reflux, nausea, irritable bowel, joint pain, and swelling.
So What’s the Truth About the Compounds in Nightshades?
This all brings us to the most important question: What does the research actually say about the compounds found in nightshade vegetables? Are lectins and alkaloids truly dangerous to your health? Should we all be avoiding tomatoes and potatoes from here on out? Let’s see what the research tells us.
Lectins
Lectins are proteins present in many plants and concentrated in beans, whole grains, and certain fruits and vegetables. Excessive amounts of certain kinds of lectins can, indeed, be problematic. For example, one of the lectins found in kidney beans, phytohaemagglutinin, can make people sick if it’s consumed raw.
I don’t know anyone who’s actually in the habit of eating raw kidney beans. But some people don’t cook them properly, and this can allow a small amount of dangerous lectins to remain. For all legumes, it’s best to cook them well (in a pressure cooker if you have one) until they are fork-tender. (Lectins aren’t a concern with canned beans because all canned beans are thoroughly pressure cooked.)
Some research indicates that ingesting large amounts of raw lectins can cause harm. However, soaking, processing, and cooking lectins breaks them down and minimizes any risk.
For a comprehensive look at this topic, check out our article, The Truth About Lectins: What Are Lectins, and Are Lectins in Food Bad For You?
Alkaloids
Alkaloids are, in fact, toxins that can be dangerous to humans and animals when eaten in very large doses. In vegetables, the primary toxic alkaloid is solanine, which is found in high levels in certain foliage. Some fruits also contain trace amounts of solanine.
How much solanine would you have to eat for it to be risky? For the average adult, potentially life-threatening, toxic intakes would be around 400 mg. But since nightshade vegetables typically contain from 2–13 mg of solanine each, you would have to eat over 35 raw eggplants to pose any risk to your well-being. And I’m guessing that’s not on your menu tonight. Just to put your mind at ease, there are no recipes on this website that call for an entire shopping cart full of raw eggplants for a family of four!
As to Gundry’s claims that alkaloids cause joint pain, arthritis, and gastrointestinal effects, there are no scientific studies to back up these claims, nor does the Arthritis Foundation agree.
That’s not to say that some nightshades can’t have excessive alkaloid content. Have you ever seen a potato that looks slightly green? This can happen due to light exposure and may show up in certain areas of the potato or in patches that you can typically see on the skin. Potatoes that have turned green for this reason should be avoided, as they contain high levels of the glycoalkaloids chaconine and solanine, which can be dangerous for humans to eat. The concentration of solanine in green or blighted potatoes has been shown to increase sevenfold. Studies have found that doses of glycoalkaloids as low as 1–5 mg per kilogram of human body weight can be acutely toxic. But unless you eat green potatoes, this is unlikely to be a concern.
Who (if Anyone) Should Avoid Nightshades?
Although nightshade vegetables aren’t actually bad (and, in fact, are mighty healthy) for most people, there are some people who may want to steer clear of them.
For instance, if you have a food allergy or sensitivity to specific nightshade foods, you’ll want to limit or avoid these in your diet. It is possible to have an acute allergic reaction to a nightshade like tomato or eggplant, so if that’s you, then, by all means, steer clear!
There are also anecdotal reports claiming that when people eliminate nightshades from their diet, they stop experiencing painful inflammatory symptoms. People with inflammatory bowel diseases like Crohn’s disease or ulcerative colitis may find that they do better when they avoid nightshades. Some of these conditions can cause intestinal permeability. And a number of test-tube and animal studies suggest that excessive intake of the alkaloids in potatoes, fiber in tomatoes, and capsaicin in peppers can negatively impact intestinal permeability. (Our view on the use of animals in medical research is here.)
Although primarily anecdotal, some people with autoimmune diseases report feeling fewer symptoms when they eliminate nightshades from their diet. Whether it’s from the placebo effect or not, paying attention to how particular foods make you feel is always a wise approach.
How to Prepare Nightshade Vegetables
If misconceptions have had you on the fence about eating nightshades, we hope you’re now convinced that tomatoes, eggplant, peppers, and potatoes can be a nourishing addition to your diet, adding more diversity and nutrients to your plate. Below you’ll find a Vegetable Breakfast Casserole, which is scrumptious any time of day; Roasted Balsamic Tomatoes, which will have your mouth watering the moment you take them out of the oven; and Eggplant and Chickpea Mnazaleh, a Middle Eastern dish that includes a blend of spices, textures and flavors, making each bite a delight.
1. Vegetable Breakfast Casserole
What better way to start your day than with fiber-filled and nutrient-packed veggies? Vegetable Breakfast Casserole includes several nourishing nightshade vegetables, including potatoes, peppers, and tomatoes, that are combined with pungent onions, umami mushrooms, crunchy asparagus, protein-rich tofu, and fragrant rosemary and thyme. The casserole is baked until golden crisp, then topped with avocado, chives, and a dash of hot sauce for a delectable breakfast experience.
2. Roasted Balsamic Tomatoes
Umami tomatoes, sweet basil, and figgy balsamic vinegar come together to create a heavenly tomato experience that can be used on top of plant-based cheese and whole grain bread, legume pasta, or a summer salad. Packed with lycopene, iron, and zinc, this meal-topper provides as much nutrition as it does flavor!
3. Eggplant and Chickpea Mnazaleh
Embrace the comforting nourishment of Mnazaleh, a Middle Eastern eggplant and tomato stew that’s a kaleidoscope of healing spices and robust flavors. Hearty eggplant, rich stewed tomatoes, protein-packed chickpeas, and tender spinach are infused with warming cinnamon, clove, turmeric, and a hint of nutmeg. Prepare to be enveloped by the welcoming aromas that will fill your kitchen and permeate your home, promising a culinary journey that is as nourishing as it is delightful.
Should You Eat Nightshades?
If you’re generally a healthy person and enjoy nightshades without any negative impacts, there’s no reason to eliminate them from your diet. However, we don’t recommend eating 35 eggplants at a time, or a bunch of green potatoes for that matter. But nightshades like potatoes, tomatoes, eggplant, and peppers are all plant foods that offer important nutrients and health benefits in a well-balanced diet. Plus, they’re easy to prepare. On the other hand, if you’re not a fan of nightshades or you feel like you may be sensitive to them, there are plenty of other healthy and delicious vegetables to choose from.
Tell us in the comments:
- Did you know about the controversy around nightshades before reading this article?
- Do you eat nightshade vegetables? Why or why not?
- What are your favorite ways to prepare tomatoes, peppers, eggplant, and potatoes?
Featured Image: iStock.com/ilbusca
