Nightshade Vegetables and Fruits: Avoid or Include in Your Diet?

You may have heard that some people avoid “nightshades” like eggplant, peppers and tomatoes. Why on earth would you avoid such nutrient-rich vegetables? Is this a fad diet or are nightshades dangerous?

To put it simply, nightshade vegetables are completely healthy for most people, but for a few it can act as a trigger similar to wheat or dairy and cause major immune reactions.

If you are a person that struggles with certain food sensitivities and allergies, autoimmune disease, inflammatory bowel disease or leaky gut syndrome, then there is a chance that nightshades could be contributing to your health condition.

When it comes to each plant in the nightshade family, everyone’s body responds in a unique way, but for most people these vegetables are not an issue. Nonetheless, you will want to look out for any warning signs after eating nightshades such as joint pain, digestive issues, reddening of your skin or any type of inflammatory response.

Learn more about nightshades and why they would they cause a reaction.

What Are Nightshade Plants?

Nightshade vegetables are part of the Solanaceae (Solanum dulcamara) plant family, which contains about 98 genera and well over 2,000 different species.

The family Solanaceae variety extends well beyond vegetables to include innocuous flowers, such as morning glories, and even toxic herbs, such as Atropa belladonna. There are even nightshade trees.

Still, the vegetables are a prominent part of the family, so much so, that Solanaceae is sometimes called the “potato family” or “tomato family.” Technically tomatoes are fruit, so nightshades include fruits as a result. The main edible nightshade members include potatoes, tomatoes, eggplant and peppers.

Nightshades contain chemical compounds called alkaloids, which contain nitrogen. They help protect the plant from disease and insects, and give the plants a slightly bitter taste.

Nightshade Vegetables and Fruits

There are over 2,000 species of nightshades, herbs and non-edibles included. Here’s a list of commonly eaten nightshade vegetables and fruits:

• Tomatoes
• ­White potatoes
• ­Eggplant
• ­Okra
• ­Peppers, including serrano, poblano and jalapeno
• ­Tomatillos
• ­Sorrel
• ­Gooseberries*
• ­Ground cherries
• ­Pepino melons
• Tobacco
• ­Paprika
• ­Cayenne pepper
• Capsicum
• Ashwagandha

* Note that blueberries, goji berries and huckleberries all include similar alkaloids, even though they are not considered nightshades.

Also anything that might contain potato starch as a thickener or filler — including medications, baking powders and even envelope glue — may contain similar alkaloids.

Benefits

While nightshades get unfair scrutiny, they actually provide many health benefits. Some medications even use nightshade derivatives, such as nicotine being evaluated for its potential to reduce risks of disease and solanine being actively studied as a plant source for pharmacological agents.

Nightshade vegetables and fruits are also very high in nutrients. For example, tomatoes are good source of vitamin C and vitamin K, and one of the best sources of the phytonutrient lycopene. Scientific evidence indicates that higher lycopene intake can help protect against lung, stomach, colon, oral, breast and cervical cancers.

Peppers contain few calories but add tons of flavor alongside vitamins A and C, plus potassium and folic acid. Dozens of varieties exist, and studies show that they can help boost the immune system due to their high-antioxidant levels.

Eggplants contains also contain a high amount of antioxidants and special phytonutrients, including phenolic compounds such as nasunin. According to studies, nasunin is a potent fighter of inflammation and oxidative stress, acting as an oxygen scavenger and an iron “chelator,” which can protect against lipid peroxidation.

Nightshade Alkaloids

Most often, alkaloids are identified molecularly by a ring with a nitrogen atom and are derived from amino acids, though there are exceptions to this structure. Alkaloids are known for being the strongest, riskiest components in herbal medicine. In fact, some of strongest “recreational” or medicinal herbs are from this family.

Tropane alkaloids (such as hyoscyamine) are also found in the nightshade family of plants (and are quite dangerous, hence the name “deadly nightshade” given for the Eurasian perennial Atropa belladonna), but they are not necessarily in nightshade vegetables.

The most common nightshade vegetable alkaloids include the following:

1. Solanine (and tomatine)

Solanine is a type of steroid alkaloid known as a glycoalkaloid — an alkaloid merged with a sugar. When the body begins to metabolize solanine, the sugar separates and solanidine is left. While not immediately toxic in the amounts ingested in nightshade vegetables, solanidine can store in the body and may release during times of stress, to the detriment of the body.

Solanine is primarily found in potatoes; the tomato counterpart of this solanine is tomatine.

Both steroid alkaloids are produced similarly to chlorophyll, which means there will be more concentrated amounts of them in the green portions of the plant. Even potatoes beginning to sprout or green spots on potatoes could represent more concentrated solanine amounts.

Solanine and the other nightshade steroidal alkaloids can irritate the gastrointestinal system and act as acetylcholinesterase inhibitors — affecting neurotransmitters. Actual solanine poisoning is rare, but has been documented to include severe vomiting and diarrhea, central nervous system depression, and even death.

2. Capsaicin

Capsaicin is the active ingredient in hot peppers and is most commonly recognized for its anti-inflammatory properties, but it should also be noted that it is an alkaloid. Anyone who has eaten a ghost pepper or habanero can attest to the irritation they can ignite. When your lips are burning after a bite of too-hot salsa, there’s more than a taste sensation at work.

Capsaicin’s irritant properties actually cause a release of substance P — a neuropeptide that plays a role in the communication of pain messages. After the initial irritation of contact with capsaicin and the release of substance P, there is a refractory period of deadened sensation. This reaction chain is why capsaicin is often used topically as an analgesic for osteoarthritis.

3. Nicotine

Nicotine is an alkaloid substance in the tobacco plant, which happens to be a nightshade. While nicotine is an addictive stimulent and the main psychoactive ingredient in tobacco products, this alkaloid is present in all parts of nightshade vegetables.

Nightshade Allergy and Sensitivities

Keep in mind that nightshades include quite deadly plants as well as generally safe vegetables. Not all of these compounds are present in every nightshade plant, and even when they are present, not all are strong enough to feel immediate effects.

Meanwhile, a true nightshade allergy, like any food or environmental allergy, should be taken seriously. However, it may not be easy to pinpoint.

While many allergens are easy to single out — think tree nuts or dairy — nightshade vegetables are not readily associated with one another. If you or a loved one is exhibiting signs of a food allergy, nightshade vegetables should be considered in any elimination diet and food allergy testing plans.

Those exhibiting apparent sensitivities to nightshade vegetables often have similar complaints as gluten sensitive reactions. Nightshade vegetable sensitivity reactions can include:

• irritable bowel disorders and other gastrointestinal issues
• heartburn
• nerve sensitization
• joint pain

A 2002 study monitored the gut permeability of mice to determine how nightshades would affect irritable bowel syndrome or irritable bowel disease (IBS or IBD). Using potatoes as the nightshade of choice, they found that existing IBD was aggravated, or even served as a catalyst for symptoms for the mice that were predisposed to having IBD.

Meanwhile, the alkaloid capsaicin is tied to issues with acid reflux and heartburn. Most individuals can limit the amount of capsaicin they intake to minimize this discomfort, but a true sensitivity will require its elimination.

Do nightshades cause joint pain? To date, there is no direct evidence of nightshade vegetables causing arthritis or joint pain.

Lastly, for those who suffer from an autoimmune disease, a healthcare provider can help look into whether or not nightshade vegetables may cause or “trigger” existing inflammation in the body and, thus, contribute to the symptoms. The autoimmune protocol diet (AIP) was developed because many foods allowed on the Paleo diet — such as nuts, seeds, dairy products, eggs and yes, nightshade vegetables — could also trigger symptoms in those with an autoimmune disease.

Nightshade Substitutions

If you seek to eliminate nightshades from your diet, allow around three months for your elimination to fully be complete before you make a judgment or begin trials because solanine can store in the body for some time.

This list of nightshade vegetable substitutions should help you adjust to your new diet:

• Sweet potatoes, yam and purple potatoes
• Cauliflower
• Celery
• Radishes
• Fresh fruit like blueberries, grapes, orange slices and melon
• Mushrooms
• Spices like black and white pepper instead of red pepper

Conclusion

Clearly, nightshade vegetables are not universally dangerous. Many of them have strong health benefits to offer the body. Even the alkaloid compounds cannot be completely cast aside — capsaicin can be a useful analgesic, and even nicotine has been evaluated for its potential to reduce risks of disease.

However, if you are suffering from symptoms that could be tied to nightshade sensitivity, taking the time to eliminate them from your diet and give your body a chance to recover might save a lifetime of pain and discomfort.