Nettle is an annual or perennial herb. For centuries, it has been used as medicine (including nettle leaves, nettle root), food, fiber, dye, and cosmetics.
In empirical medicine, what are the benefits of nettles? Are there side effects of nettles? See the latest analysis in the text for details
What is nettle?
Nettle is an herbaceous plant of the genus Nettle with about 46 different varieties, and the stems and leaves covered with thorny trichomes are recognized as characteristic of this plant.
Nettle and the word nettle are derived from the Anglo-Saxon word “noedl”, meaning “needle”, while its Latin name “urtica” means “burning”. This refers to the tingling sensation caused by the fine hairs on the stems and leaves rubbing against the skin, resulting in a burning sensation and a temporary rash. These fine hairs are used to protect plants from insects.
The most well-known members of this genus are the large nettle (Urtica dioica/stinging nettle) and the small nettle (Urtica urens/annual nettle, also known as urtica/dwarf nettle/dog nettle), which are native to Europe, Africa, Asia and North America.
What are the proven benefits of nettle?
1. Beneficial for blood sugar control
Diabetes mellitus is a metabolic and multifactorial disease characterized by chronically elevated blood sugar levels that develop due to insulin secretion or dysfunction.
From a clinical point of view, diabetes is considered one of the most important risk factors for certain diseases such as nephropathy, retinopathy, neuropathy and cardiovascular disease.
Although the use of insulin and hypoglycemic drugs is the main and effective treatment of diabetes, it may cause different complications such as: increased lipid reserve, lipid contraction at the injection site, hypoglycemic shock… Therefore, alternative or adjuvant therapies are often discussed.
A systematic literature review and meta-analysis (8 randomized controlled trials, 401 people with type 2 diabetes) suggested that supplementation with nettle preparations (daily dose range of 1.5 to 10 g, intervention time of 8 to 12 weeks) significantly reduced fasting blood sugar concentrations compared with placebo. Note 1
HOWEVER, THERE WAS NO SIGNIFICANT EFFECT ON INSULIN LEVELS, HOMEOSTATIC MODELS ASSESSING THE HOMAIR INDEX, OR GLYCOSYLATED HEMOGLOBIN PERCENTAGE.
*Conclusion: For type 2 diabetes, the use of nettle preparations may be positively helpful for glycaemic control, but due to the small sample size, larger and longer trial periods are still needed for further validation
2. Beneficial benign prostatic hyperplasia
Benign prostatic hyperplasia is a common cause of lower urinary tract symptoms in men and is characterized by prostatic stromal cell and epithelial cell hyperplasia in the periurethral transition zone (“normal” prostatic volume is usually 15 to 30 ml in adult men, and glands larger than 30 ml are generally considered “enlarged”).
About 50% of men over the age of 50 will have benign prostatic hyperplasia, and this number increases to 80% when men reach age 80 or older. Symptoms may be obstructive (causing retardation, weakness, tension or duration of urination) or irritation (leading to increased urinary frequency and urgency, nocturia, urge incontinence, and decreased void output), or affect the patient after urination (e.g., trickling or incomplete emptying after urination).
A double-blind, placebo-controlled, randomized trial (6 months, 620 patients with benign prostatic hyperplasia) showed that nettle improved prostate symptom score (IPSS), maximum urine flow rate (Qmax), and post-excretory residual urine output (PVR) compared with placebo. Note 2
Another randomized controlled trial (12-week trial of 60 patients with benign prostatic hyperplasia) showed that Urtica Dioica root extract helped improve prostate symptom scores (IPSS), hypersensitivity C-reactive protein (hs-CRP), malondialdehyde (MDA), and superoxide dismutase (SOD) levels. Note 3
*Conclusion: For benign prostatic hyperplasia, nettle may be a positive help for disease improvement, but limited by the small sample size, more studies are needed for further verification
3. Good for knee osteoarthritis
Knee osteoarthritis is a slow-progressing joint disease characterized by joint pain, cartilage degeneration and inflammation that affects approximately 2 million people worldwide.
A variety of treatment options are available for knee osteoarthritis, from conservative treatment to total knee replacement. Common non-surgical treatments include nonsteroidal anti-inflammatory drugs (NSAIDs), physical therapy, analgesics (such as paracetamol), and intra-articular treatments (such as corticosteroids and hyaluronic acid).
A randomized controlled pilot study (1 week in 42 people with knee osteoarthritis) noted that topical nettle prick therapy helped reduce osteoarthritis pain subscale scores (WOMAC). Note 4
*Conclusion: Due to the small sample size, there is no clear evidence to prove the efficacy and safety of local nettle thorn therapy for knee osteoarthritis, and more studies are needed to further verify
Are there any side effects of nettles?
Oral nettle extract is generally safe, but side effects or adverse effects have been reported as diarrhea, constipation, and stomach upset
In addition, touching a thorny nettle leaf or its juice may cause skin irritation (rash, lump, itching) and, in rare cases, a severe allergic reaction or even life-threatening.
Safety precautions (9 contraindications to use)
1. Do not use by pregnant women (may stimulate uterine contractions and cause miscarriage)
2. Do not use in lactating women (due to unknown safety)
3. Do not use it with lithium drugs, because nettles may have a diuretic effect, which may reduce the speed of the body’s excretion of lithium and cause serious drug side effects.
4. Diabetic patients or those taking hypoglycemic drugs please use with caution, or consult a medical professional before use, because nettle may lower blood sugar, common drugs for diabetes include: glimepiride, glibenclamide, insulin, pioglitazone, rosiglitazone, Chlorpropamide, glipizide, tolbutamide etc.
5. Patients with high blood pressure or those taking blood pressure lowering drugs should use with caution, or consult a medical professional before use, because nettle may lower blood pressure, common drugs for hypertension include: captopril, enalapril, losartan, valsartan, diltiazem, amlodipine, Hydrochlorothiazide, furosemide etc.
6. Do not use with sedative drugs (central nervous system depressants), as large doses of nettle may cause drowsiness and drowsiness, and taking nettle while taking sedatives may cause excessive drowsiness.
7. Do not use it with the anticoagulant drug warfarin, it may reduce the efficacy of the drug, because the aerial part of nettle contains a lot of vitamin K, vitamin K can help blood clotting
8. Nettle may increase the amount of free (active) testosterone, so it may cause worsening health conditions characterized by excess testosterone, such as polycystic ovary syndrome (PCOS)
9. Consult your physician about medications or conditions used before supplementing with nettles to prevent adverse events or unexpected interactions.