Covid-19: Stinging Nettle Lectin


“Out of this nettle – danger – we pluck this flower – safety.” — William Shakespeare

When I think of nettles, I remember an observation one of my student classmates at John Bastyr College shared with me that he had learned in an undergraduate botany class. Stinging nettles (Urtica spp.) have fine hairs on the leaves and stems that contain irritating chemicals, which are released when the plant comes in contact with the skin. When a forest is disturbed by fire the first plants that grow in the burnt, broken underbrush are nettles. Nettles are renowned for their stinging ability. In fact Roman soldiers in Northern England used to rub their legs with nettle to cause flushing and ward off the cold northern winds. My friend’s botany teacher saw this as a perfect example of Gaia, the concept of the Earth as a living organism: The fast-germinating nettles act like barbed wire, preventing animals from rooting around in the disturbed area until it could begin to regenerate itself.

Nettle leaves have a long history as a potherb. They can be sautéed, or par-boiled in salted water, and have a taste beween spinach (perhaps with a bit more of an ‘iron’ taste) and arugula (bit more peppery). The leaves have a long history of use in herbal medicine, where it has been used for osteoarthritis and skin inflammations. Nettle capsules can be used to reduce sneezing and itching in people with hay fever, and this likely constitutes its most frequent modern use.

Nettle root also has medicinal usage, predominantly for benign prostatic hypertrophy, where it is thought that elements in the root reduce symptoms such as frequent urination. It may be because it contains chemicals that affect hormones (including testosterone and estrogen) by interacting with sex hormone binding globulin (SHBG).

The root also possesses what I consider one of the most interesting plant lectins, known as Urtica Dioica Agglutinin (UDA). UDA is known in immunology as a superantigen, a lectin that induces cell growth and division (clonal activation). When these lectins induce specific white blood cells to multiply, they are known as mitogens . Many plant lectins are mitogens; Poke Weed (Phytolacca spp.) and Jimson Weed (Datura spp.) come to mind, but UDA is unique. It activates CD8+ T cells (often called cytotoxic T lymphocytes, or CTLs), which are very important for our immune defense against intracellular pathogens, including viruses and bacteria.

Which brings us this blog. For all intents and purposes, UDA lectin has properties that may make it worthy of consideration as an anti-coronavirus agent. It has been studied and shown to possess antiviral activity against HIV, CMV, RSV, H1N1 and SARS-CoV.

Two targets of possible antiviral intervention were identified in the replication cycle of SARS-CoV. The first target is located early in the replication cycle, most probably viral attachment, and the second target is located at the end of the infectious virus cycle. This study also showed that UDA was a potent and selective inhibitor of SARS-CoV strain Frankfurt-1.

Plant lectins like UDA probably target viral attachment and fusion, and its eventual exit (exocytosis or egress) from the cell. In an article entitled ‘Ready, Set, Fuse! The Coronavirus Spike Protein and Acquisition of Fusion Competence’ the authors noted that lectins such as UDA do not affect binding of the S-protein to the ACE2 receptor, but rather seem to inhibit viral entry at some undefined later stage.

In a separate study UDA lectin was tested for efficacy in lethal SARS-CoV-infected mice. All virus-infected mice receiving UDA treatments were also significantly protected against weight loss and had effectively reduced lung pathology scores. At day 6 after virus exposure, all groups of mice receiving UDA had much lower lung weights than did the placebo-treated mice, which indicates that their lungs were not filling up with liquids. The authors concluded that UDA inhibited severe acute respiratory syndrome (ARDS) associated with coronavirus replication. However, when UDA was exposed to the amino sugar N-acetylglucosamine the UDA lectin did not inhibit the virus infection.

UDA was reported to inhibit coronaviruses in vitro with some selectivity in mice. The researchers concluded that UDA was a potent and selective inhibitor of SARS-CoV strain Frankfurt-1. The reduction of IL6 in lungs along with 50% survival of mice in this study was thought to provide evidence to support further investigation of UDA treatment regiments as potential antiviral therapies.

So what’s the take home message for the man (and woman) in the street? I think nettle root may have significant benefit as a potential safe, low cost and readily available traditional medicine for Covid-19. Health authorities should include this traditional medicine in the evaluation panels exploring potentially effective treatments for Covid-19. Nettle root can obviously be found in its native form and simply lightly cooked and used with the greens as a potherb, or can be purchased as a nutritional supplement from any number of vendors. We would need to insure that the formula was from the root. A sure sign that the supplement contains the root would be a claim that the formula was useful for ‘prostate health’.

As with all medicines, natural or otherwise, please consult with experts who are experienced in their actions, interactions, contraindications and potential side effects before starting this or any other supplement program.

16 comments on “Covid-19: Stinging Nettle Lectin”

  1. Mark Reply

    Thank you for this piece.
    You mention Nettle root as a possible aid against COVID19, but what about Nettle leaf, which is much easier to find?
    Do high lectin plants tend to have more lectins in their roots in general?
    Thank you

    • Nancy Reply

      I am wondering about the leaf also as I have been picking these last two weeks, making broth and eating leaves. Thank you for this info!

  2. Carri Overstreet Reply

    Would nettle root still be beneficial for a person with sarcoidosis? Thank you for this read.

  3. Helen Steiner Reply

    My nettle supplements state organic nettle tops including Urtica dioica. Are these as good as the root? Thank you.

  4. D Allen Reply

    Dosage in mg from root. A human is not a mouse. The mouse model was well constructed. NIH is interested. I know. That said finding nettle root isn’t the issue. .What is the percentage of UDA in the root per g or kg? Is there a known toxicity level for uda or the root as a whole.Based on the animal study a reasonable effective dose can be guessed.

    Between 5 -10 mg/kg was deemed most effective for mice with 20 mg/kg being the upper tolerated level with side effects. Since nettle root isn’t standardized a reasonable guess is the only option. Do you know of any studies analyzing nettle for component break down by wt. Otherwise it is a stab in the dark.

    • Peter D'Adamo Reply

      Concentrations vary widely from 0 -.05% to maybe as high as high as 3-4% depending a variety of environmental factors and possibly in certain stressful growing circumstances (wet, warm, fungal) may be significantly higher.

      I’m a computer scientist, not a mathematician, so my napkin calculations will likely be off. Say an average person is 70kg. According to the study (5mg/kg) we’d need a dose of 350mg UDA. Let’s say our nettle root sample is 2% UDA , the we need to multiply the 350mg dose requirement by what we’ll need in raw material to achieve it (50x in this case). This yields 17,500 mg raw material needed. Freeze-drying might cut that down a bit, but no matter, that is a LOT of nettle root.

      However lectins are quite promiscuous and highly reusable. Due to receptor capping, they can disassociate after the agglomerated receptors drop the binding covalence; then they’re free to do it all over again. So it’s not inconceivable that repeated smaller doses may bioaccumulate over time.

      Finally UDA has other actions of interest in Covid19: ACE2 receptor inhibition, fusion inhibition, viral entry inhibition (in both an ‘early’ and ‘late’ stage, whatever they are.) The lectin is endocytosed, so uptake is probably not be an issue.

      • Jamie Reply

        > 17,500 mg raw material needed […] that is a LOT of nettle root.

        Not really! I just went into the garden and collected 4 small/medium plants. Removed and weighed the roots; yielded 9g. So you’d need 8 plants to get the 17,500mg. Not too bad IMO?

  5. Denise Allen Reply

    Thanks so much. Straight up multiplication is not how the FDA calculates initial trial doses. I’ll find the formula and post the calculation tomorrow with the reference.

    Thanks for the information.

  6. Gregory Kelly, ND Reply

    Peter in one of the studies you linked to (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7114093/) they found that the lectin in leek was more active at a lower concentration and more selective for SARS-CoV-1 than stinging nettle (and every other lectin they tested). I haven’t been able to find much info about this lectin, but assume it might be more concentrated in the bulb than the green stalks. Do you happen to know? “The most potent lectin against the SARS-CoV-induced cytopathicity is the mannose-specific plant lectin isolated from leek (APA) with an EC50 of 0.45 μg/ml and a selectivity index of >222. In addition, the N-acetyl glucosamine-specific lectins isolated from the stinging nettle (UDA) and from the tobacco plant (Nictaba) are also markedly active against the SARS-CoV with a selectivity index of >77 and >59, respectively. “

    • Peter D'Adamo Reply

      Greg, although I cannot say for sure, I think your hypothesis that the bulb would have higher lectin content is likely true.

      • Gregory Kelly, ND Reply

        Thanks Peter. The quality of what you’ve been posting is amazing … that is, of course, not at all surprising to me.

  7. Jill H Fusia Reply

    Hi Dr. D’Adamo,

    I learned a lot from your webinar with Dr. David Brady. I was wondering if women would need to be concerned about increasing their testosterone levels when taking Stinging Nettle Root? Thank you. Jill Fusia RD,IFNCP

    • Peter D'Adamo Reply

      I think that, if it has effects, nettle roots would likely be most useful as a treatment for the early stages of infection, hopefully canalizing the course of the infection towards a milder outcome. Since this implies very short term use, I suspect that, while possible, the effects on SHBG would be mild and reversible upon discontinuation.

      • Denise Allen Reply

        From a study I have seen

        https://www.ncbi.nlm.nih.gov › pub…
        Web results
        Inhibition of severe acute respiratory syndrome coronavirus replication in a lethal SARS-CoV …

        The journal is decent and study is well constructed.

        Again I am NOT a doctor or medical person. This is SARS 1 .It uses the same ace2 receptor infection mechanism. There has been about 17 percent divergence, but UDA seemed quite helpful in early phase by binding to glycoslated portions of the virus.

        The study is worth the read. The FDA gives the math to turn a mouse into a human. Again I am not a DOCTOR. Take it for what you want.

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