Fireweed

BotanicalBest taken away from food

What is it

Fireweed (Epilobium angustifolium, also known as Rosebay Willowherb) is a tall pink-flowered plant native to northern hemispheres. Its aerial parts are used in traditional herbal medicine, primarily for urinary and prostate complaints.

Evidence for 2 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Benign prostatic hyperplasia (BPH)

Mixed Evidence

Mechanistic studies suggest fireweed extracts inhibit 5-alpha-reductase, but rigorous human trials are sparse and inconsistent. Use is mostly traditional.

Urinary tract symptoms

Mixed Evidence

Folk medicine uses fireweed tea for mild urinary irritation. Clinical evidence is anecdotal.

How it works

Fireweed contains tannins (notably oenothein B), flavonoids and phytosterols. Oenothein B has been studied in vitro for its inhibition of 5-alpha-reductase and aromatase, enzymes involved in androgen and estrogen metabolism that are relevant to benign prostatic hyperplasia (BPH). Lab studies also report antioxidant and anti-inflammatory effects on prostate tissue. Whether enough of these compounds reach systemic circulation after typical oral doses, and whether they produce clinically meaningful changes, is largely untested in humans.

Dosage

There is no established RDA, AI or UL. Traditional infusions use roughly 2-3 g of dried herb per cup, taken 1-3 times daily. Supplement label doses vary widely and most products are unstandardized.

When and how to take it

No established timing. Tea is often taken between meals to limit tannin interference with mineral absorption.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Dried herb / tea

Aerial parts brewed as an infusion.

Traditional preparation.

Standardized extract

Used in capsule supplements aimed at prostate health.

Sometimes standardized to oenothein B.

Safety

Generally well tolerated short-term as a tea. High tannin content can cause stomach upset, nausea or constipation. Long-term safety has not been characterized.

Who should be cautious

Avoid in pregnancy and breastfeeding due to lack of safety data. Caution in people on iron supplements or medications sensitive to tannin binding.

Interactions

No significant interactions reported. Tannins may theoretically reduce absorption of iron and some medications if taken at the same time.

Food sources

Fireweed tea (Ivan Chai)

Amount
1 cup of brewed leaf tea
%DV
—

Frequently asked questions

Does fireweed shrink the prostate?⌄

Lab studies show enzyme effects relevant to prostate size, but human evidence for shrinking the prostate is weak.

Can I drink fireweed tea every day?⌄

Short-term daily use is common in folk practice; long-term daily intake has not been well studied.

References

Fireweed on Wikidata — Wikidata link

Fireweed on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Fireweed (PubMed search) — PubMed link

Track Fireweed with Pilora

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.