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Knotweed Extract

Also known as: Polygonum aviculare, Fallopia japonica, Japanese knotweed, Reynoutria japonica, Hu Zhang, resveratrol source

Evidence under review. — Not yet rated

Traditional herb with very limited clinical research; sometimes used for male fertility and as a resveratrol source.

  • What it does

    Knotweed extract comes from plants in the Polygonum or Fallopia genus and has a long history of use in traditional Asian medicine. One animal study suggests an aqueous extract may help improve...

  • Evidence quality

    Evidence base hasn't been formally rated yet. See research below.

  • Clinical dose

    No established dose

See full breakdown ↓ Methodology →

What the Science Says

Knotweed extract comes from plants in the Polygonum or Fallopia genus and has a long history of use in traditional Asian medicine. One animal study suggests an aqueous extract may help improve sperm motility in chemotherapy-induced fertility damage, but no human clinical trials have been identified in the available research. It is also commonly marketed as a natural source of resveratrol, a polyphenol compound, though the clinical significance of this in supplement form is not well established.

What It Doesn't Do

Not proven to boost testosterone or male fertility in humans — the only study was in rats. Not a proven resveratrol delivery system with confirmed human benefits. No evidence it treats any disease or condition. Don't confuse animal data with human clinical proof.

Evidence-Based Benefits

May improve sperm motility in chemotherapy-damaged fertility — in rats only, not humans.

Weak Evidence

Effective at: No established dose

Absorption & Bioavailability

Unknown — no human pharmacokinetic data available from provided studies. Resveratrol from plant sources is generally considered to have low oral bioavailability.

Red Flags to Watch For

  • Japanese knotweed is an invasive species; sourcing and quality control can vary widely between products
  • Only one animal study available — no human clinical trials support use for any health condition
  • Often marketed as a resveratrol source, but resveratrol content and bioavailability in extracts is inconsistent and rarely verified
  • May interact with blood thinners or medications metabolized by the liver — consult a doctor before use
  • Limited published research available; most health claims are based on traditional use, not clinical evidence

Research Sources

  • PMID: 11276309
  • General knowledge — limited published research available

This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-05-25