The Uncanny Nightshades - Healthy or Harmful to Eat?

The Uncanny Nightshades - Healthy or Harmful to Eat?

Every creature, plant or animal, needs protection from something that wants to attack them, and in plants, that defense mechanism is often a biochemical weapon. For humans that consume organic materials to sustain ourselves, we need to be aware of what the plant contains that may be harmful to us.

What you don't know can hurt you!

Case in point is the nightshade family of plants. You may have heard the name from stories of witchcraft or espionage where the deadly nightshade (or belladonna) was used for nefarious purposes because of its nature (it produces atropine, which is a deadly poison.) But you may not know that many of the foods you regularly consume belong to this family. Despite long having had exaggerated negative connotations attached to them by often poorly informed people (the eggplant was named the mad apple as it was believed to cause madness), these plants do actually cause significant problems for many people.

So why is there a problem eating nightshades?

Beyond belladonna, the nightshade, or Solanaceae family, includes over 2800 plants such as tomatoes, peppers, potatoes, eggplant, and tobacco to name the most common. The traits at issue that these plants share is their defense against attackers. They produce glycoalkaloids like solanine, chaconine, or tomatine, natural pesticides concentrated in leaves, flowers, and ripening fruits. These alkaloids defend against bacteria, viruses, fungi, and insects. 

Glycoalkaloids bind to cholesterol in the cell membranes, disrupting the structure and causing them to leak or burst upon contact. They also act as neurotoxins, blocking the enzyme cholinesterase, which is responsible for breaking down acetylcholine, a vital neurotransmitter that sends signals between nerve cells and muscle cells. This causes acetylcholine to accumulate, electrically overstimulating an invader's muscle cells and leading to convulsions, paralysis, respiratory arrest, and even death. These alkaloids are very good at keeping both viral, bacteriological and physical attackers at bay. Our nerve gas weapons work in this fashion.

Clearly glycoalkaloids are dangerous to tiny creatures, but our interest lies in their effects on humans.

Clinical research done on this group of alkaloids shows that it really can impact nerve, muscle, joint, and digestion function in humans. Dr. Norman Childers (The Arthritis Nightshades Research Foundation) warns they cause inflammation and stress, particularly by disturbing calcium metabolism in the body, resulting in aches and pains in the joints, skin problems, and a host of potential adverse reactions. Lectins in nightshades are pro-inflammatory and have the ability to increase intestinal permeability, causing digestive health issues (Carreno-Gómez B et al. “Studies on the uptake of tomato lectin nanoparticles in everted gut sacs.” Int J Pharm. 1999 Jun.)

The problem is that with sufficient consumption, it is possible that the low-level toxic properties of nightshade vegetables contribute to a variety of health issues over time in pretty much anyone. Even for people with lesser sensitivity, glycoalkaloids can still lead to problems, and removing certain nightshade vegetables from a diet has been known to significantly reduce inflammation and joint pain, as well as some symptoms of digestive discomfort and leaky gut.  Dr Childers suggests if you suffer from an any auto-immune disease such as lupus, arthritis, osteoporosis or any chronic inflammation, you should eliminate all nightshades completely.

My own story with nightshades bears recounting. For a long time when I was younger I suffered with knee pain that I attributed to the years of playing volleyball. I was always active and the pain would often interfere with many activities. When I spoke to an herbalist friend, he suggested that before I take drastic measures, I should consider my nightshade intake. Like most people, I looked at him as though he was speaking another language. What was this and how much could I be eating to cause a problem anyway?

What I learned was that my Greek heritage meant that my diet consisted of large amounts of tomatoes, eggplant, peppers, potatoes, cayenne, paprika and chili. I particularly ate a lot of tomatoes. I always believed this was a good thing. After all these are healthy vegetables right? 

Wrong for me!

I also learned from my friend that nightshade plants commonly cause inflammation, and maybe that was my concern. I wanted to avoid injections or surgery, so I figured I would try adjusting my diet as he recommended. It was tough, believe me, but it was easier than heading straight for more serious choices. After 6 months of keenly controlling the amounts of tomatoes, peppers, potatoes, and chili-based spices I consumed, I discovered something wonderful. The constant pains I got in my knees started to fade. Since I made the changes, my pain is basically gone. I cannot remember the last time I suffered. Sure it's not clinical, but my body tells me I did the right thing.

That was me. But should everyone cut out nightshades?

Firstly, not all nightshade foods are problematic. The levels of glycoalkaloids is so low in blueberries, huckleberries, okra, cherries, sugar beets, and artichokes that you do not need to worry.

For the rest of them, it really varies by person and by the plant. Some plants have higher levels of glycoalkaloids. The only way to find out for yourself is to see what changes to your diet do for your symptoms. Even if you have no symptoms, controlling edible nightshades is a smart choice. Use moderation and employ variety. Even just watching your ketchup and tomato-based sauce intake may have benefits.

Choose ripe nightshades since solanine levels are highest in unripe ones. For example, eat red tomatoes instead of green tomatoes, or red peppers instead of green. Cooking nightshades is also a good idea as it reduces alkaloid content by up to half.

Finally, if you still want to get the nutrients into your diet from these othwerwise healthy foods, drying and powdering them also reduces the glycoalkaloids considerably while still maintaining broad nutrient value. Look for a high quality vegetable supplement to assist in more safely getting the good stuff while minimizing the bad.

Related Posts: 
The Importance of Being Alkaline - Know Your pH ! 
For the Love of Food, What We Eat Can Heal

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Childers N.F. A relationship of arthritis to the Solanaceae (nightshades). J Intern Acad Prev Med 1979; 7:31-37
Hopkins, J. The glycoalkaloids: naturally of interest (but a hot potato?). Food Chem Toxicol. 1995 Apr; 33(4):323-8.
Dalvi, R. R. and Bowie, W. C. Toxicology of solanine: an overview. Vet Hum Toxicol. 1983 Feb; 25(1):13-5.

The opinions expressed in this article are of the author. Content and other information presented on the site are not meant to be medical advice or any substitute for professional advice, counseling, diagnosis, or treatment. Never delay or disregard professional medical or mental health advice from your physician or other qualified health provider.


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