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Standardized Nettle Root Extract

Also known as: Nettle root extract, Stinging nettle root extract, Urtica dioica

Overview

Standardized nettle root extract is derived from the roots of *Urtica dioica*, commonly known as stinging nettle, a perennial herbaceous plant found in temperate regions. This extract is distinct from leaf extracts and is primarily used for managing lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH). It also shows potential benefits for metabolic syndrome, including anti-diabetic effects, and may modulate testosterone levels. The extract contains bioactive compounds such as lignans, polysaccharides, and sterols, which are believed to influence hormone binding and inflammation. Research on nettle root extract is moderately mature, with several randomized controlled trials and meta-analyses supporting its efficacy for BPH-related outcomes, while evidence for metabolic and hormonal effects is emerging but less robust.

Benefits

Nettle root extract offers several evidence-based benefits, primarily for men with benign prostatic hyperplasia (BPH). Meta-analyses indicate that it significantly improves lower urinary tract symptoms (LUTS) compared to placebo, with modest but clinically relevant effect sizes, and a favorable safety profile. For instance, symptom scores have shown improvements of approximately -5.7 points with nettle root extract versus -4.8 points with placebo. The strength of evidence for LUTS/BPH is high, supported by multiple systematic reviews and meta-analyses. Additionally, animal studies and some clinical trials suggest anti-diabetic effects, including increased insulin secretion and pancreatic β-cell proliferation, which could benefit individuals with metabolic syndrome. However, human evidence for these metabolic effects requires further validation. Secondary benefits include potential testosterone modulation, where animal studies suggest nettle root extract may increase free testosterone by blocking sex hormone-binding globulin (SHBG), but human evidence remains inconclusive and limited. The primary beneficiaries are middle-aged and older men with BPH, with potential benefits for diabetic animal models.

How it works

Nettle root extract exerts its effects through several biological pathways. For benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS), its compounds are believed to inhibit aromatase and 5-alpha reductase enzymes, which are involved in hormone metabolism. It also reduces inflammation and may block sex hormone-binding globulin (SHBG), potentially increasing free testosterone and modulating androgen receptor activity within prostate tissue. For metabolic effects, nettle root extract appears to enhance insulin secretion and promote pancreatic β-cell regeneration, possibly through its antioxidant and anti-inflammatory properties. Standardized extracts ensure consistent levels of these bioactive compounds, and the root extracts are generally well absorbed orally.

Side effects

Standardized nettle root extract is generally well tolerated, with no significant hepatotoxicity or serious adverse events reported in randomized controlled trials lasting up to one year. The most common side effects, occurring occasionally, include mild gastrointestinal discomfort. Uncommon side effects (1-5% frequency) are rare allergic reactions. No serious adverse events have been documented at frequencies below 1%. Caution is advised regarding potential additive effects with other BPH medications. Due to possible mild blood-thinning effects, individuals taking anticoagulants should consult a healthcare provider. The primary contraindication is a known allergy to nettle or related plants. Safety in pregnant or breastfeeding women has not been established, and therefore, use in these populations is not recommended.

Dosage

For the management of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH), the minimum effective dose of standardized nettle root extract observed in clinical trials is approximately 300–600 mg per day. Most randomized controlled trials utilize dosages within this range, often administered in divided doses. Long-term studies up to 52 weeks at these dosages have demonstrated good safety and tolerability; however, data for higher doses are insufficient. Consistent daily dosing is recommended, as the beneficial effects tend to accumulate over several weeks. Standardized extracts with defined active compounds are preferred to ensure reproducibility and consistent efficacy. Oral administration with food may help improve gastrointestinal tolerance. No specific cofactors are identified as necessary for its efficacy.

FAQs

Does nettle root extract increase testosterone in humans?

Current human evidence is inconclusive. While animal studies suggest potential increases in free testosterone by inhibiting SHBG, clinical trials in humans have not definitively confirmed this effect.

Is nettle root extract safe for long-term use?

Yes, randomized controlled trials lasting up to one year have shown good safety and tolerability, with no serious adverse events reported during prolonged use.

How long before benefits on urinary symptoms appear?

Improvements in urinary symptoms are typically observed within a few weeks of consistent use and are sustained with continued administration.

Can nettle root extract be used with other BPH medications?

It is often used in combination, but patients should consult their healthcare provider due to potential interactions and to ensure appropriate management of BPH.

Research Sources

https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0297839 – This systematic review, while focused on medicinal plants for allergic rhinitis, highlights the rigorous Cochrane methods used for evidence synthesis. It underscores the importance of standardized extracts and adequate controls in clinical research, principles that are crucial for evaluating nettle root studies.
https://www.ncbi.nlm.nih.gov/books/NBK589898/ – This source references a long-term randomized controlled trial published in the World Journal of Urology (2005). It involved 219 men with BPH treated with a combination of sabal and nettle extracts for 96 weeks, demonstrating maintained symptom improvement and no serious adverse events or hepatotoxicity, indicating a robust design.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9282742/ – This review from Iran J Basic Med Sci (2022) summarizes animal and limited human data on nettle's metabolic effects. It indicates nettle's role in enhancing insulin secretion and β-cell regeneration, contributing to hypoglycemic effects, and calls for more randomized controlled trials in humans to confirm these findings.
https://www.hims.com/blog/stinging-nettle-testosterone – This article discusses the potential of nettle root extract to increase free testosterone by blocking sex hormone-binding globulin (SHBG). It notes that while animal studies show this potential, human evidence remains inconclusive and limited, requiring further definitive research.
https://journals.athmsi.org/index.php/ajtcam/article/view/3330 – This meta-analysis published in the African Journal of Traditional, Complementary and Alternative Medicines (2016) included multiple RCTs on nettle root extract for LUTS/BPH. It found significant improvements in LUTS symptom scores versus placebo with good safety, though it noted heterogeneity in extract formulations as a limitation.