Nightshades have sort of a bad reputation.
Deadly nightshade (known as Atropa belladonna) was used as poison back in ancient times. And other herbs in the Solanaceae family may be hallucinogenic or narcotic[*][*][*].
But the full list of nightshades includes healthy fruits and vegetables like tomatoes, peppers, and eggplant.
So why are people with chronic inflammation, rheumatoid arthritis, digestive disorders, and other health issues eliminating nightshades from their diet?
And should you?
Before worrying or swearing them off completely, you should learn what nightshades are and what the science says first.
What Are Nightshades?
Nightshades belong to the Solanaceae family, which boasts over 2,700 species of plants, trees, herbs, fruits, and vegetables.
Here’s a quick list of nightshades you’re probably most familiar with:
- Eggplant or aubergine
- Goji berries
- Potatoes (except yams and sweet potatoes)
- Tomatillos, a green veggie similar to tomatoes that’s popular in Tex-Mex and Mexican dishes.
- Peppers including sweet bell peppers, chili peppers, jalapeno, habanero, banana peppers, pimento, etc.
- Red pepper spices such as crushed red pepper flakes, chili powder, cayenne pepper, curry, garam masala, paprika, Chinese Five-Spice powder, and hot sauce.
While peppers are nightshades, black, white, and pink peppercorns are naturally nightshade-free.
The entire list of nightshades also contains plants you may be less familiar with. Pepino, tamarillo, and cape gooseberries (aka ground cherries or golden berries) are all nightshades as well.
Many of these foods have become staples in our modern diet — and for good reasons.
Health Benefits Of The Most Common Nightshades
The most common edible nightshades include potatoes, tomatoes, eggplants, goji berries, and peppers.
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And they each bring unique nutritional strengths to the table:
Potatoes Pack Vitamins B and C
One medium potato (about one cup) contains 70% of your RDA of vitamin C and covers 30% of your vitamin B6 intake[*].
Vitamin B6 plays a role in more than 100 reactions in your body[*]. It helps you metabolize fats, protein, and carbs. And it assists with breaking down stored sugar in your muscles and liver[*].
Since your body needs but can’t produce B6 on its own, you’ll need to get it from your diet or daily vitamin.
And you’ll want to load up on vitamin C from peppers since your body doesn’t make or store that either.
Peppers are Full Of Vitamin C
Turn to both hot peppers and sweet peppers for your daily dose of vitamin C. A 100-gram serving of yellow peppers packs over 300%[*].
Your body uses vitamin C to[*][*]:
- Metabolize protein
- Synthesize collagen
- Enhance immune system function
- Better absorb iron from plant-based sources
Population studies show people with high vitamin C intakes have lower risks of several chronic diseases, including heart disease, cancer, and neurodegenerative conditions[*].
And researchers have learned the capsaicin in hot peppers may combat metabolic syndrome. In one study, capsaicin increased fat oxidation, improved insulin sensitivity, decreased body fat, and lead to better liver and heart function[*].
Higher levels of lycopene have also been associated with better heart health.
Tomatoes: Rich In Potassium and Lycopene
Tomatoes are one of the richest dietary sources of lycopene, which gives tomatoes its signature red color[*].
This antioxidant and phytonutrient is associated with a decreased risk of chronic diseases such as cancer and cardiovascular disease[*]. Low levels of anti-inflammatory lycopene have been linked to heart attacks[*]
Plus, tomatoes are an awesome source of potassium (at 427mg per cup)[*].
Potassium is necessary for your body to maintain optimal blood pressure, heart health, and muscle strength.
If you’re low in this important electrolyte, you may feel:
- Tired, fatigued, and low-energy
- Weakness and widespread muscle pain
- Muscle spasms
- Tingling, crawling, itching, or numb sensations in your extremities
The next nightshade contains a different type of antioxidant.
Eggplant (or Aubergine) May Help Regulate Blood Sugar
Dark, purple eggplant skin contains high levels of anthocyanins, which behave like natural antioxidants[*].
Anthocyanins offer neuroprotection, fight oxidative stress and cancer, prevent heart disease, and improve visual health.
Researchers have even used extracts of anthocyanins found in eggplant to increase insulin sensitivity and prevent diabetes and obesity in rats[*][*][*].
To investigate the effects in humans, scientists gave 58 patients with type 2 diabetes anthocyanins or a placebo twice daily.
After 24 weeks, those taking the anthocyanins had[*]:
- Decreased LDL cholesterol and triglycerides
- Increased HDL cholesterol
- Higher free radical-trapping power
- Lower fasting glucose levels
- A 13% decrease in insulin resistance
These markers signal better health and may increase longevity, which the next nightshade is pretty famous for.
Goji Berries: The Protein-Packed Berry
Dried goji berries (or wolfberries) have been a staple in traditional Chinese medicine for over 2,000 years[*].
Goji berries are a king among berries because they contain 11 essential amino acids[*].
That means while a cup of blueberries or raspberries contains less than 2g of protein, a cup of goji berries boasts almost 11g[*][*][*].
Fans say goji berries promote longevity, fight signs of aging, and increase well-being.
When researchers gave 34 healthy men and women a concentrated goji berry juice for 14 days, participants reported[*]:
- Higher energy levels
- Improved exercise performance
- Better quality sleep
- Lower stress
- Less fatigue
- Greater concentration
- Improved regularity of gastrointestinal function
- Feeling happier, calmer, and more content
The final nightshade may be less popular but it touts similar benefits.
Ashwagandha May Combat Stress
Ashwagandha is an Ayurvedic herb you can find as an extract, supplement, or as a root or leaf powder. This nightshade has been relied on for over 3,000 years[*].
Ashwagandha is considered an adaptogen, so it helps your body get back to normal when you’re stressed.
Specifically, Ashwagandha lowers levels of cortisol (i.e., the stress hormone).
Too much cortisol, like when you’re chronically stressed, not only leads to an increase in mental and physical health issues but also raises your blood sugar[*].
High blood sugar and cortisol levels make it much harder to reach or stay in ketosis or lose weight in general[*].
But Ashwagandha may be able to mitigate this.
One 60-day study of 64 people with chronic stress showed a 69% average reduction in cortisol levels and stress with Ashwagandha supplementation[*].
And researchers in another study discovered Ashwagandha may be able to improve your resistance to stress and lessen symptoms of anxiety and depression[*].
So with all these health benefits found in nightshades, you may be wondering why people are excluding them from their diet.
Should You Avoid Nightshades?
While large, long-term studies are still lacking, people living with certain medical conditions say eating nightshades not only exacerbates their symptoms but causes them.
And they blame it all on alkaloids.
Alkaloids are powerful organic substances produced in the leaves, stems, and edible parts of nightshade plants. And they can be toxic.
Alkaloids act as a defense mechanism for nightshade plants. They can be bitter or spicy, which prevents insects and other herbivores (i.e., plant eaters) from snacking on them.
Eating alkaloids dissolves the insects’ cell membranes from the inside.
In humans and animals, alkaloids are considered antinutritional because they have the potential to cause poisoning. They may also affect your ability to digest or absorb nutrients from your food[*].
The alkaloid tropane is what makes deadly nightshade so toxic and poisonous, for example.
Capsaicin in peppers, the active ingredient responsible for the heat and spiciness, is an alkaloid.
Though not toxic to humans, capsaicin causes a burning reaction which normally deters predators from eating pepper plants.
In true alkaloid fashion, capsaicin may irritate the lining of your stomach and esophagus. And research shows capsaicin can cause heartburn or acid reflux[*].
Nicotine is another alkaloid.
Nicotine is present in the tobacco plant (a nightshade) and in parts of every other nightshade[*].
Though concentrations of nicotine in edible nightshades are much less than what’s found in tobacco, nicotine may still be harmful. It’s a strong neurotoxin and even used in pesticide and insecticide[*][*].
And there are other alkaloids with even murkier resumes.
What You Need To Know About Alkaloids In Nightshades
Alkaloid content in food varies significantly depending on the variety, how it’s grown, where it’s stored, and more.
While the average fruit or veggie may contain far less than a lethal amount, certain ones may contain enough to make you sick.
Solanine, for example, is a different type of alkaloid known as a glycoalkaloid. It’s structurally formed with sugar.
Blueberries, garden huckleberries, okra, and artichokes all contain solanine but they aren’t part of the nightshade family.
Solanine and tomatine (alkaloids found in potatoes and tomatoes) can be highly toxic in excessive amounts.
There’s a famous case of 78 schoolboys falling ill after eating boiled potatoes at lunch. Doctors admitted 17 boys to the hospital and treated them for solanine poisoning. They traced it back to a bag of old potatoes with “excessive” levels of the glycoalkaloid[*].
See, when your body breaks down solanine, it processes out the sugar. Then you’re left with solanidine, which is poisonous and neurotoxic[*][*].
You may not notice any immediate health issues but your body can store solanidine for awhile. One study suggests your body releases these solanidine stores in times of stress and creates harmful consequences for your health[*].
However, this research has not been duplicated and there’s little evidence to suggest the long-term effects are scary.
Solanine poisoning is incredibly rare. Headaches and gastrointestinal symptoms such as severe abdominal pain, vomiting, and diarrhea typically begin two to 24 hours after ingestion[*].
Overall, alkaloids may not affect you. But if you have food sensitivities or an autoimmune disease they may trigger you more.
How Can Alkaloids In Nightshades Affect You?
Certain people report an immune system reaction similar to a wheat or dairy allergy when they eat nightshades.
Just like alkaloids destroy hungry insects, they may behave like a toxin and tear holes in your digestive cell membranes.
Research done on mice with a genetic predisposition for IBD (inflammatory bowel disease) shows glycoalkaloids can poke holes in key membranes, leading to a disruption in gut integrity[*].
This may cause intestinal permeability (aka leaky gut) and create chronic inflammation and digestive troubles.
Evidence definitively connecting glycoalkaloids to causing or making IBD worse isn’t there yet.
But certain people are removing nightshades from their diet regardless.
Are You Sensitive To Nightshades?
According to anecdotal evidence, people who are more sensitive to nightshades or have a higher risk of intolerance include those living with:
- Chronic inflammation
- Autoimmune diseases
- Rheumatoid arthritis (RA)
- Joint conditions
- Digestive disorders such as leaky gut syndrome or IBD
- Food sensitivities and allergies
But what if you don’t have any of those medical issues?
You may want to avoid nightshades if you notice these symptoms after eating them:
- Joint pain and stiffness
- Muscle pain, tension, or tremors
- Brain fog and trouble concentrating
- Digestive issues (such as heartburn, bloating, or stomach discomfort)
- Autoimmune-related flare-ups
- Skin conditions (such as acne, rashes, rosacea, eczema, etc.)
- Depression and mood swings
These reactions after eating nightshades don’t automatically mean you’re allergic or intolerant.
So after consulting with your doctor for medical advice based on your history, you may want to test your nightshade sensitivity to know for sure.
How to Test Your Sensitivity To Nightshades
If you want to know whether your body is sensitive to nightshades, you have to try an elimination diet.
An autoimmune protocol diet (AIP) is a version of a Paleo diet that removes “trigger” foods known to cause poor reactions.
Nightshades are a common trigger, along with dairy, eggs, nuts, and seeds.
So here’s how you begin a nightshades elimination diet:
- Remove all nightshades for at least 30 days and see how your body reacts.
- Start reintroducing nightshades one at a time (because each has a different alkaloid balance) if you feel fine. Eat one nightshade at least three times over two days. Monitor and record your reactions for 72 hours after consuming them.
- If symptoms return, go back to step 1. You may want to try reintroducing a different nightshade 30 days later.
- If you’re symptom-free, you can enjoy nightshades in moderation without worry.
Again, there haven’t been large-scale human studies testing how nightshade vegetables or fruits truly affect the human body.
And current research shows people don’t have an overwhelming response to removing nightshades from their diets.
But you’ll definitely want to limit them if you’re on a low-carb or ketogenic diet.
Are Nightshades Keto?
Though nightshade fruits and vegetables are nutrient-rich, not all of them fit the low-carb macros of a keto diet.
Here’s a list of high-carb nightshade foods to avoid:
- Potato and potato starch. Substitute cauliflower or parsnips for a low-carb alternative.
- Tomato-based products such as ketchup, BBQ sauce, and most store-bought marinara sauce in jars. These typically have added sugars in addition to high carb counts.
- Goji berries. Dried goji berries usually have double your daily sugar intake per serving.
You can use this low-carb list of nightshades to plan your meals:
- Tomato. A small tomato is about 3g of carbs[*].
- Eggplant. One cup of eggplant only clocks in at 2.5 net carbs[*].
- Peppers. One whole, medium bell pepper is less than 5 net carbs[*]
The best way to test your sensitivity to nightshades is to see how you feel after eating these fruits and veggies.
Work Your Way Through This List of Nightshades With These Keto Recipes
Nightshades could be a healthy addition to your keto diet if you’re not sensitive to them. So try out a few low-carb recipes featuring nightshades to see how you react:
This classic keto tomato soup recipe is light years better than the one you pour out of a can.
And this recipe for crispy roasted eggplant chips satisfies potato chip cravings, while this one for celeriac everything fries will replace french fries in your life.
Finally, this ultimate bell pepper sandwich dominates lunch. And this one for spicy keto Italian stuffed peppers covers dinner.
While science says most people don’t have to worry about nightshades, you may want to eliminate them if you have a negative reaction after eating them.
So keep this list of nightshades handy and pay attention to what your body says moving forward.