Japanese knotweed is a supplement traditionally taken for heart health and circulation as well as for gastrointestinal health.
Japanese knotweed (Polygonum cuspidatum) is an herb used in Traditional Chinese Medicine and contains resveratrol — a naturally occurring compound found in the skin of grapes and other plant sources, known for its antioxidant, anti-inflammation, heart-protective and immune-stimulating properties (1).
While limited trials have been performed in humans, researchers believe Japanese Knotweed’s benefits are attributed to the presence of resveratrol.
Over 67 polyphenols including quinones, stilbenes, flavonoids, coumarins and ligans have also been identified in Japanese Knotweed (2).
With the help of future studies, researchers will be able to better understand how these compounds contribute to this herb’s pharmacological effects.
Japanese knotweed improves inflammation and alleviates oxidative stress. Chronic inflammation is a contributing factor of age-related diseases and conditions such as diabetes, cardiovascular and autoimmune diseases (3). Inflammation and oxidative stress go hand-in-hand in that the inflammatory process induces oxidative stress, which in turn reduces the antioxidant defense system.
The aim of a 2010 study was to evaluate the effect of a Polygonum cuspidatum extract on oxidative and inflammatory stress in overall healthy participants.
Twenty adults were randomized to receive placebo or Polygonum cuspidatum extract containing 40 mg resveratrol daily for six weeks.
At the end of the study, supplementation with the extract resulted in a significant reduction in all the testing parameters for oxidative and inflammatory stress (4).
In another study, topical application of Polygonum cuspidatum extract inhibited the development of ear edema (swelling caused by the buildup of excess fluid in the body’s tissues) and inflammation in a mouse model (5).
Japanese knotweed promotes cardiovascular health. The results of a systematic review and meta-analysis of randomized, controlled, clinical trials revealed that when taken in high doses, resveratrol had a cardioprotective effect specifically in people with diabetes.
Dosages of ≥300 mg/day had a systolic blood pressure-lowering effect (6).
Japanese knotweed can be a potential treatment for rheumatoid arthritis. An arthritis- and inflammation-induced animal model used in a recent study revealed the ability of ethyl acetate extract of Polygonum cuspidatum to reduce inflammation and alleviate pain.
Researchers found the extract to be effective in providing pain relief in the animal hot plate test and tail-flick test at a dosage of 200 mg/kg. It did not, however, provide pain relief in the acetic acid-induced writhing test.
To evaluate the extract’s ability to reduce inflammation, researchers relied on a serotonin-induced paw edema model and Freund’s complete adjuvant (FCA)-induced adjuvant arthritis model.
It was found that the extract inhibited the swelling inflammatory response within 12 minutes after the serotonin injection, at both 100 and 200 mg/kg doses. In the FCA-induced adjuvant arthritis model, 100 mg/kg resulted in significantly suppressed joint swelling within five days, while 200 mg/kg of the extract showed the similar result within three days (7).
These results are encouraging especially for rheumatoid arthritis sufferers who, among other symptoms, experience joint pain and swelling.
Japanese knotweed may help speed the healing time of wounds. Polygonum cuspidatum extract has long been used in Traditional Chinese Medicine as a treatment to induce wound healing. In 2012, researchers set out to investigate its wound healing activity in a clinical setting using a rat study.
Results showed that in comparison to the control group, wound healing rates in the group treated with topical Polygonum cuspidatum extract were significantly higher at three, seven, 14 and 21 days.
In addition, microscopic studies revealed more well-organized bands of collagen, more fibroblasts and hair follicles and less inflammatory cells in the extract group (8).
Japanese Knotweed is also being studied for its possible role as a skin lightening agent.
Japanese knotweed helps to prevent the growth of human cancer cells. Results from in vitro and animal studies show resveratrol’s potential role in preventing and treating certain types of cancer (9). Researchers have found that resveratrol has an antitumor effect on neuroblastomas in mice; dose dependently inhibits the growth of estrogen receptor(ER)-positive MCF-7 cells (a breast cancer cell line used for clinical study); and induces human promyelocytic leukemia (HL-60) cell death.
Japanese knotweed may help prevent flu viruses. In 2015, researchers tested the effects of over 300 traditional Chinese medicines on the replication of various influenza virus strains in a lung cell line. Impressively, of all the tested medicines, Polygonum cuspidatum and its active components, resveratrol and emodin, were found to effectively inhibit influenza virus replication, specifically the influenza A virus, including such strains as H1N1 (13).
Japanese knotweed may help treat allergies. Researchers have found that emodin, an anthraquinone compound present in Japanese knotweed, has the potential to prevent and treat allergic reactions. Using an in vivo passive anaphylaxis animal model and in vitro mouse bone marrow-derived mast cells, researchers noted that emodin has the ability to suppress activation of mast cells and thereby the anaphylactic reaction (14).
There is limited information on the side effects of Japanese knotweed supplementation.
While further human clinical trials are needed to understand the full scope of possible side effects, supplementation may cause mild to moderate gastrointestinal symptoms.
This is due to the resveratrol content, which has been associated with such symptoms as diarrhea when taken at high doses (15).
Due to a lack of clinical studies of Japanese knotweed use in humans, recommended dosages are not yet available.
Japanese knotweed (also known as Polygonum cuspidatum) is a supplement traditionally taken for heart health and circulation. Researchers have attributed the presence of the naturally occurring compound, resveratrol to this herb’s medicinal benefits.
Resveratrol is commonly found in the skin of grapes, and is known for its antioxidant, anti-inflammation, heart-protective and immune-stimulating properties.
Early findings also show that Japanese knotweed has the potential to treat and prevent several other diseases and conditions.
It is being studied for its ability to treat inflammation and alleviate oxidative stress; promote cardiovascular health; treat rheumatoid arthritis; heal wounds; and prevent and treat allergic reactions.
This resveratrol-rich nutraceutical also shows promise as a potential cancer chemopreventive agent.
Researchers note the need for larger-scale cohort studies to validate these early findings.