Are Nightshade Plants Harmful?

According to a US doctor, nightshade plants such as tomatoes, peppers, and potatoes are harmful. They contained unhealthy lectins. If you avoid lectins, you can free yourself from numerous chronic diseases. Is he right?

What are nightshades?

The nightshade family (Solanaceae) is a plant family of many hundreds of plant species. These include mostly ornamental plants (such as petunia or angel’s trumpet) and wild plants, some of which are considered to be clearly poisonous, such as black nightshade, deadly nightshade, or henbane.

List of edible nightshade plants

The following list shows the most important foods from the nightshade family:

  • tomatoes
  • paprika
  • eggplants
  • chili
  • Potatoes (sweet potatoes are not part of the nightshade family)
  • Physalis (also called Andean berry or Cape gooseberry)
  • goji berry
  • Tree Tomato (also known as Tamarillo)

Why are nightshade plants actually called nightshade plants?

The exact origin of the name “Nightshade” is not known. It’s just speculation. Originally, however, it was only used to describe the black nightshade (Solanum nigrum) – and not an entire plant family, as is the case today.

The term is said to come from Old High German, so shade could also mean harm and night indicates a type of mental derangement that overtakes one when eating the unripe berries of black nightshade.

Another explanation is that some wild nightshade plants (e.g. deadly nightshade, henbane, and black nightshade) were used to make healing potions in the Middle Ages to drive away nightmares (shadows at night).

It is interesting here that even the black nightshade, which is known as a poisonous plant, is a vegetable and fruit plant in some countries. Its leaves are cooked like spinach (the cooking water has to be changed and thrown away several times) and it’s ripe(!) berries are eaten as fruit. Since the black nightshade is extremely drought tolerant, it is not surprising that it is used as food, especially in African countries.

How is it that nightshade vegetables are labeled as harmful?

Actually, there have long been voices that are not so well disposed toward the nightshade family. Rudolf Steiner (1861 – 1925), the founder of anthroposophy, advised against excessive consumption of nightshade vegetables. He considered the potato particularly unfavorable. Because while the root of a plant (e.g. radishes or carrots) promotes spiritual development, a tuber is something that never quite became the root and therefore promotes a more materialistic way of thinking. The spirit, on the other hand, gets no more nourishment. He also considered the other nightshade vegetables to be largely detrimental to mental development.

Steiner based his teaching on the knowledge that he gained in a supernatural way. Former cardiologist Dr. Steven Gundry (*1944), however, describes specific ingredients in the nightshade plants as problematic, if not harmful.

It is also he who triggered the current anti-nightshade and anti-lectin hype with his book “The Plant Paradox”. The title of the German edition of Gundry’s book is telling: “Bad Vegetables: How Healthy Foods Make Us Sick”. The book was published in February 2018.

Lectins belong to the proteins

after dr In Gundry’s view, lectins are THE cause of chronic diseases such as arthritis, diabetes, autoimmune diseases (e.g. Hashimoto’s), and cardiovascular disorders, but also of obesity. If you avoid foods containing lectins, you will become slim and healthy in no time at all in an almost miraculous way.

Lectins belong to the proteins, with each plant containing its species-specific lectin. So there are many different lectins, some of which have completely different properties.

Lectins are there to protect the plant from predators, it is said again and again. From the point of view of the plant, humans are also among the enemies – according to Gundry – and must be expelled or damaged, which the plant tries to implement with the help of lectins.

But what uses is a strategy for the plant that people don’t even notice. After all, hardly anyone gets sick immediately after eating tomatoes, peppers & Co. – with the exception of allergy sufferers. The damage develops – if at all – gradually over many years. So hardly anyone avoids these foods. The thesis with the protective substances against predators must therefore be strongly questioned in relation to humans.

Why can lectins be harmful?

It is now said that lectins bind to the mucous membrane cells of the intestine and restrict their function. This loosens the intestinal barrier and promotes leaky gut syndrome. The lectins could then also get into the bloodstream, where they bind to blood cells and cause them to clump together.

Incidentally, because of this property, the blood group diet developed by Peter J. D’Adamo, who believed that it depends on the blood group which foods one tolerates or which lectins one reacts to sensitively. However, this thesis has not yet been scientifically proven.

Lectins could also bind to other cells and in this way lead to organ damage or insulin resistance (precursor to diabetes). Overall, lectins are said to have pro-inflammatory, neurotoxic, and cytotoxic properties and to be able to unbalance the immune system.

Dangerous lectins are found in uncooked beans

Lectins that are actually dangerous (the so-called phasin) are found in raw beans (heart beans and green beans). Therefore, everyone knows that beans should only be eaten when they are cooked, otherwise they can lead to diarrhea and extreme nausea, or even death, depending on the amount eaten.

Which foods contain lectins?

However, Gundry says that not only legumes, but many other foods are also rich in lectins and should therefore be avoided or specially prepared in the future (see below):

  • Legumes (including peanuts and soy products (except fermented soy products such as tempeh))
  • nightshade family
  • all cereals (except millet), especially whole grain products, while white flour is great, and according to Gundry you can also eat polished basmati rice now and then
  • Pseudo-cereals (quinoa, amaranth, buckwheat)
    many types of nuts (e.g. walnuts, cashew nuts, etc.)
  • Oil seeds (pumpkin seeds, sunflower seeds, chia seeds, etc.)
  • Pumpkins (incl. zucchini)
  • cucumbers
  • melons and
  • any fruit including berries (except avocados)

Some of these foods could still be eaten if you pay attention to a certain way of preparation.

No study has proven the harmfulness of nightshade plants

Scientific evidence that edible nightshades, or the lectins ingested from these vegetables, are inherently harmful to everyone, as Dr. Gundry claims there isn’t. He was only able to make similar observations in himself and later also in his patients, to whom he recommended a lectin-free diet (LFE) and who allegedly got better quickly – no matter what they had previously suffered from.

However, there is a 1993 study related to arthritis. It states that diet is an important causal factor in the development of arthritis, which of course is not disputed, as we have already explained here.

Based on surveys of 1,400 volunteers over a period of 20 years, it was shown that regular consumption of nightshade plants can contribute to arthritis in sensitive people (!). However, smoking was also one of them (since tobacco is also a nightshade plant?). Eliminating nightshades from the diet (along with other dietary changes) has seen a marked improvement in arthritis and overall health.

Who Should Eat a Lectin-Free Diet?

However, since the LFE is preceded by a detoxification cure, grain and thus gluten is avoided, less meat is eaten and only dairy products of selected quality are served, lots of vegetables and plenty of salads are on the menu, all ready meals including sugar are taboo and Gundry also recommends intermittent fasting, it may well be that even these extremely health-promoting measures lead to the appropriate recovery – and would do so even if you were also eating nightshade vegetables.

Anyone who has not noticed any improvement after switching to a “normal” healthy diet for several weeks should try out for themselves whether the foods Gundry considers problematic should be avoided.

Of course, if you read this article and immediately say, oh yes, I have never tolerated tomatoes, peppers and aubergines well, you can of course start with the LFE right away or at least avoid the nightshade vegetables and see whether this is actually the right recovery concept for him/her could be.

How to remove lectins from food

Lectins are found in particular in the skin and cores of vegetables, i.e. precisely there where many valuable vital substances are found so that the question arises as to whether the food is not devalued much more if these parts are removed. Because that’s exactly what you should do if you eat a diet low in lectins and still want to eat nightshades.

Before eating, tomatoes are placed in boiling hot water for half a minute, then quenched in ice water, skinned, halved, and pitted with a spoon. Peppers should also be skinned, of course, they will be deseeded anyway.

Potatoes should first be boiled and peeled. The cooking water is discarded (which is usually done anyway) since lectins and solanine are dissolved in it.

Evidently, lectins in grain cannot be reduced/removed. According to Gundry, pseudo-cereals like buckwheat and quinoa simply have to be prepared in a pressure cooker, where the lectins in these seeds are destroyed. Millet is naturally lectin-free since it is only commercially available shelled anyway and most lectins are in the shell. Gundry’s free pass should not apply to brown millet that is unpeeled.

core beans such as B. Red kidney beans should be cooked for one hour (if not soaked first; overnight soaking would reduce cooking time to about 15 minutes). Then there are no more lectins. In the pressure cooker, 30 minutes should be sufficient for non-soaked beans. Canned or jarred beans no longer need to be cooked. They are already lectin-free.

Small amounts of lectins can also be beneficial

As is the case everywhere, lectins can be dangerous if consumed in excess – with e.g. B. a salad made from raw core beans (which is generally considered poisonous and therefore not recommended even in small quantities).

However, in the quantities that lectins are contained in a healthy wholefood diet, these substances actually have health advantages rather than disadvantages. Studies have shown that some lectins improve bowel function, curb cancer growth, specifically protect against colon cancer and help reduce obesity.

How useful and credible are lectin studies?

Studies that show that lectins can be dangerous, as well as studies that attest to the lectin’s positive effects, have always been carried out with isolated and concentrated lectin preparations, mostly in test tubes with cell cultures, but not with lectin-containing foods in humans or animals.

Lectin studies also often use lectins that do not come from our food plants at all, but from other very lectin-rich plants (e.g. from the pencil bush), since one would like to check whether pharmaceuticals can be produced from these highly effective lectins.

It is interesting that galactose, a carbohydrate found in many vegetables and fruits (including nightshade vegetables, legumes, etc.), can bind to some carcinogenic lectins and thus protect against cancer – a possible indication that nature has taken precautions and not the harmful potential of an individual substance should be considered, but the food in its entirety.

Is solanine in nightshade plants harmful?

In addition to the lectins, a possible solanine content is also criticized in the edible nightshade plants. Solanine is a plant substance from a group of alkaloids. Poisoning with solanine is almost non-existent today, as modern tomato and potato varieties are extremely low in solanine.

If you then make sure not to eat green tubers with potatoes and remove any sprouting and also make sure you only use ripe tomatoes, solanine is no longer an issue today – unless you are hypersensitive to solanine and thus to foods containing solanine.

Just like lectins, solanine is held responsible for inflammatory diseases – from fibromyalgia and migraines to joint pain and depression, there is almost nothing that relevant portals do not blame solanine for.

Since not only nightshade plants but also other foods can contain solanine, such as blueberries, apples, cherries, and okra, these foods are of course also discouraged, although there is not a single scientific evidence that these fruits can harm in any way. On the contrary, here, too, the advantages clearly outweigh the disadvantages – but of course not for those people who may have developed an individual intolerance here.

Do nightshades contain calcitriol?

Another disadvantage of nightshade plants is that they contain calcitriol, according to the critics (including the Weston A. Price Foundation, which is already known for its soy bashing and recommends a diet rich in meat, offal, bone marrow broth, and contains dairy products).

Calcitriol is the active vitamin D (1,25-dihydroxycholecalciferol). It is therefore not vitamin D3 (from e.g. food supplements), which first has to be converted into the active vitamin in the liver and then in the kidneys in several steps, but the already activated final form of this vitamin. It is calcitriol to which all the positive vitamin D properties are attributed, such as improved calcium absorption from the intestine.

And exactly this calcitriol is said to be contained in tomatoes and other nightshade vegetables. At first glance, that sounds very good. Because why not absorb the active vitamin right away so that the body doesn’t have to laboriously convert it first? However, conversion has a very important purpose. It prevents an overdose of active vitamin D and ensures that only those amounts of vitamin D that the body needs are activated.

Therefore, there are no dietary supplements that contain calcitriol directly, but only preparations with the precursor vitamin D3. Otherwise, the wrong dosage could quickly lead to dangerous side effects, such as excessive calcium absorption from the intestine, which can then lead to so-called calcinosis, a pathological deposit of calcium salts in the blood vessels (arteriosclerosis, coronary heart disease), the skin ( scleroderma), the kidneys (nephrocalcinosis) and also in the joints (rheumatism).

So it is said that if you eat nightshade vegetables, over the years this would lead to exactly this calcinosis with all its pathological symptoms.

However, when looking for evidence of a relevant calcitriol content in nightshade vegetables, one only finds studies showing that the leaves and stems of nightshade plants contain calcitriol, but not the fruit. And since nobody eats tomato plants or aubergine leaves, studies on this topic are only available in connection with the nutrition of livestock. Here the carcinogenic effects of various nightshade plants that are not relevant for human nutrition, such as Solanum glaucophyllum and others, were investigated.

A detailed study on vitamin D in plants (from 2017) reports an investigation in which rats (with vitamin D deficiency) were given an extract from tomato leaves. The calcium level in the blood rose significantly, which indicates that the tomato leaves may actually contain calcitriol, i.e. active vitamin D. However, the administration of tomato fruits showed no such effect!

So it can be assumed that nightshade critics are referring to the calcitriol content of the plants/leaves (which, however, are highly toxic and therefore not consumed). However, the fruits of the typical nightshade vegetables from human nutrition (tomatoes, aubergines, etc.) are most likely free of calcitriol and therefore probably do not harbor the risk of insidious calcinosis.

Should you definitely avoid nightshade plants and lectins?

As mentioned several times above, there can of course also be individual intolerances to the group of nightshade vegetables or to foods containing lectins in general. In general, however, both the edible nightshade plants and foods containing lectins are considered very healthy.

Tomatoes, for example, are known for their anti-cancer properties and are recommended for a heart-healthy diet. Its high lycopene content is also responsible for a positive effect on the prostate.

There are also numerous studies that show that a diet rich in vegetables and also a diet rich in fiber, which e.g. also contains nightshade plants and whole grain products rich in lectins, is associated with better health, so for this reason, too it cannot be assumed that these foods are fundamentally harmful.

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Written by Micah Stanley

Hi, I'm Micah. I am a creative Expert Freelance Dietitian Nutritionist with years of experience in counseling, recipe creation, nutrition, and content writing, product development.

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