Alternate Title

  • Fallopia japonica

Related Terms

  • Anthraquinones, astringin, emodin, Fallopia japonica, flavonoid, fuyanke granule, Hu chang, Hu zhang, Phellodendron chinense, physcion, phytoalexin, phytoestrogens, piceatannol, piceid, polydatin, Polygonaceae (family), Polygoni cuspidati radix, Polygonum cuspidatum roots, Polygonum cuspidatum water extract, Polygonum cuspidatum, polyphenolic hydroxyanthraquinones, polyphenolic phytoalexin, Protykin®, resveratrol, Reynoutria japonica, stilbenes.

Background

  • Japanese knotweed (Polygonum cuspidatum), a perennial herb native to Japan, China and Korea, was imported into Great Britain and the United States in the 1800s as an ornamental plant. The shoots, leaves, and stems are edible, but contain oxalic acid, a chemical that may hinder calcium absorption. The three Latin names of Japanese knotweed are used in different regions of the world: Reynoutria japonica in much of Europe; Polygonum cuspidatum, in North America; and Fallopia japonica, in Britain.
  • Japanese knotweed is a common commercial source of resveratrol, a chemical well-known for its presence in red wine. Resveratrol, which is available as a dietary supplement, has reported antiaging, antioxidant, anti-inflammatory, anticancer, and lipid-lowering effects.
  • Traditional medicinal uses of Japanese knotweed root extracts include improvement of oral hygiene and cardiovascular health and treatment of acute hepatitis, high cholesterol, inflammation, skin rash, and constipation.

Evidence Table

    Disclaimer

    These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

*Key to grades:

Tradition

    Disclaimer

    The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Dosing

    Disclaimer

    The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

  • Adults (18 years and older)

    • There is no proven safe or effective dose for Japanese knotweed in adults.
  • Children (under 18 years old)

    • There is no proven safe or effective dose for Japanese knotweed in children.

Safety

    Disclaimer

    The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

  • Allergies

    • Avoid with known allergy or hypersensitivity to Japanese knotweed, its components, or members of the Polygonaceae family. Some people who ingested Japanese knotweed and were exposed to sunlight developed a rash.
  • Side Effects and Warnings

    • Use cautiously in patients with blood clotting disorders or in those taking blood thinners.
    • Use cautiously in fair-skinned patients or in individuals using photosensitizing agents. Photosensitivity has been reported in some people who have ingested Japanese knotweed extracts.
    • Avoid with known allergy or hypersensitivity to Japanese knotweed, its components, or members of the Polygonaceae family.
    • Avoid during pregnancy and breastfeeding.
  • Pregnancy and Breastfeeding

    • Avoid during pregnancy and breastfeeding due to a lack of sufficient data.

Interactions

    Disclaimer

    Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

  • Interactions with Drugs

    • Japanese knotweed may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (“blood thinners”) such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
    • Because Japanese knotweed contains estrogen-like chemicals, the effects of drugs believed to have estrogen-like properties may be altered.
    • Japanese knotweed may also interact with antibiotics, anticancer agents, antiviral drugs, anti-inflammatory agents, cardiovascular drugs, cholesterol lowering drugs, drugs used for osteoporosis, lipoxygenase inhibitors, and photosensitizing agents (agents that cause sun sensitivity).
  • Interactions with Herbs and Dietary Supplements

    • Japanese knotweed may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
    • Because Japanese knotweed contains estrogen-like chemicals, the effects of herbs and supplements believed to have estrogen-like properties, such as phytoestrogens, may be altered.
    • Japanese knotweed may also interact with antibacterials, anticancer herbs and supplements, antioxidants, antivirals, anti-inflammatory herbs and supplements, cardiovascular herbs and supplements, cholesterol lowering herbs and supplements, herbs and supplements used for osteoporosis, herbs and supplements that cause sun sensitivity, and resveratrol.

Attribution

  • This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration ().

Bibliography

    Disclaimer

    Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to . Selected references are listed below.

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    View Abstract
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    View Abstract
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    View Abstract
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    View Abstract
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    View Abstract
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    View Abstract
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    View Abstract
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    View Abstract
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    View Abstract
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    View Abstract
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    View Abstract