Japanese knotweed is well-known as an invasive weed; however, this plant has strong medicinal properties.
This article will dive into the health benefits of Japanese knotweed, its safety, and its traditional uses.
Table of Contents
- What is Japanese Knotweed?
- Health Benefits of Japanese Knotweed:
- Japanese Knotweed Safety:
- Naming & Taxonomy:
- History & Traditional Use:
What is Japanese Knotweed?
Japanese knotweed is a perennial plant that is considered an invasive weed. It’s native to Japan, North China, Taiwan, and Korea.
The Latin name for this herb is Polygonum cuspidatum.
Other common names for Japanese knotweed include bushy knotweed, Mexican bamboo, Chinese knotweed, Hu Zhang, Kojo, Itadori, and Hojang.
Japanese knotweed is commonly used in Traditional Chinese Medicine (TCM) for treating various conditions and in western herbalism for treating Lyme disease.
There are over 60 known plant compounds in Japanese knotweed, some including:
- Gallic acid
Health Benefits of Japanese Knotweed:
Below are the top research-backed health benefits of Japanese knotweed and its active compounds.
1. May Treat Lyme Disease
Borrelia burgdorfer is a bacteria transmitted by ticks that cause Lyme disease. Lyme disease is the most common vector-borne disease in the United States.
One of the first signs of Lyme disease includes erythema migrans (EM), a “bullseye” rash that appears at the tick bite site. The rash may accompany flu-like symptoms such as fever, headache, stiff neck, fatigue, discomfort, muscle aches, or joint stiffness; however, one may also be asymptomatic. A typical late Lyme disease sign is arthritis and joint swelling, primarily affecting large joints such as the knees.
Researchers have studied numerous botanicals, including Japanese knotweed, to help treat individuals with Lyme disease.
An in vitro study evaluated several botanicals, including Polygonum cuspidatum (Japanese knotweed), Cryptolepis sanguinolenta, Juglans nigra (Black walnut), Artemisia annua (Sweet wormwood), Uncaria tomentosa (Cat’s claw), Cistus incanus, and Scutellaria baicalensis (Chinese skullcap) on their effectiveness against Borrelia burgdorferi. It was shown that Japanese knotweed has a strong ability to halt the growth of Borrelia burgdorferi.
Emodin is one of the Japanese knotweed’s active chemical compounds. A study examined specific chemical compounds on the activity against Borrelia burgdorferi and found that emodin effectively ceases the bacteria’s growth.
Babesia duncani is a parasite that causes babesiosis, an illness similar to malaria that may be transmitted by a tick. Babesia duncani may co-mingle with Borrelia burgdorferi, thus causing Lyme disease co-infections.
An in vitro study tested several botanicals, including Japanese knotweed, against the Babesia duncani. Japanese knotweed was shown to be able to stop the growth of this bacteria.
Lyme disease expert and author Stephen Buhner states that Japanese knotweed also helps to improve blood flow throughout the body. Thus, it is effective for the treatment of Lyme disease as the bacteria is often “hidden” in these areas of the body.
Japanese knotweed can specifically help the treatment of Lyme disease in the following ways:
- Improve circulation/blood flow
- Reduce inflammation
- Correct and protect heart function
- Reduce autoimmune reactions
- Provide anti-bacterial and anti-viral activity
- Promote immune function
- Act as a synergist with other herbs and drugs
- Protect endothelial integrity
- Act as an anti-biofilm agent
Furthermore, Buhner notes that the essential functions of Japanese knotweed on Lyme disease are its cytokine modulation and neuroprotective and regeneration effects.
Summary:Research shows that Japanese knotweed may be beneficial in treating Lyme disease.
2. Anti-Inflammatory Properties
Japanese knotweed may be one of the most beneficial herbs for reducing inflammation.
A randomized, controlled trial studied athletic men and Japanese knotweed extract’s effect on inflammation. Those who took 200mg of Japanese knotweed daily (which contained a high dose of resveratrol) had significantly reduced markers of inflammation.
A randomized, double-blind, cross-over trial studied resveratrol’s anti-inflammatory and antioxidant effects on 50 adult smokers. Resveratrol significantly reduced the inflammatory marker C-reactive protein (CRP), decreased triglycerides, and increased overall antioxidant levels.
An animal study examined the analgesic (pain-relieving) and anti-inflammatory effects of Japanese knotweed for the treatment of arthritis. Results revealed that within three days of treatment, joint swelling was significantly reduced, in addition to decreased inflammatory markers C-reactive protein and Rheumatoid factor (RF).
Summary:Japanese knotweed may be able to reduce inflammation, although additional studies would be beneficial in confirming this finding.
3. May Support Brain Health
Studies show that Japanese knotweed may work to improve cognitive function by decreasing oxidative stress, benefiting memory, and supporting brain health.
A double-blind study examined resveratrol on mild-to-moderate Alzheimer’s disease. Results were remarkable, revealing that resveratrol can decrease neuroinflammation and promote adaptive immunity. In addition, resveratrol displayed the ability to restore the integrity of the blood-brain barrier.
An animal study looked at the effects of resveratrol on overall cognition. Results showed that resveratrol intake decreased oxidative stress, enhanced brain function, and positively affected learning and memory, specifically long-term memory.
Another animal study examined the compound resveratrol extracted from Japanese knotweed on the aging brain. Findings showed that resveratrol can improve neuromuscular coordination, sensorimotor ability, learning, and memory.
Summary:Japanese knotweed has been shown to increase brain function, however, further human studies are needed for verification.
4. Anti-Viral Properties
An in vitro study showed that Japanese knotweed demonstrated anti-HIV activity. The plant’s chemical compounds resveratrol, 5,7-dimethoxyphthalide, catechin, and emodin exhibited potent antiviral activity against HIV.
Another in vitro study examined the anti-viral effects of Japanese knotweed and its compounds resveratrol and emodin. Researchers identified anti-influenza activity among its compounds, including inhibiting the growth and replication of the influenza viruses.
A recent in vitro study investigated Japanese knotweed on COVID-19. Findings showed that Japanese knotweed and its flavonoids, polydatin, and resveratrol had anti-viral activity by suppressing virus replication and potentially inhibiting coronavirus infections.
Summary:According to several studies, Japanese knotweed may have anti-viral effects.
5. Other Health Benefits
- May Improve Heart Health: An animal study showed that the compound polydatin from Japanese knotweed can help reduce triglycerides, total cholesterol, and LDL cholesterol.
- May Improve Eye Health: An animal study revealed that Japanese knotweed might be a suitable treatment to reduce dry eyes, decrease inflammation, and protect against apoptosis.
- Anti-Tumor Properties: A promising animal study found that the compound resveratrol extracted from Japanese knotweed can remarkably reduce tumor volume by 42%, reduce tumor weight by 44%, and reduce metastasis to the lungs by 56%.
Summary:Japanese knotweed may support heart and eye health, as well as having anti-tumor properties. Human clinical research is needed to confirm these findings.
Japanese Knotweed Safety:
Japanese knotweed is considered a very safe herb.
The potentially toxic dose of this plant is 75 grams.
Those taking blood-thinning medications should not consume Japanese knotweed.
Pregnancy & Lactation:
Japanese knotweed is not suitable for pregnancy.
There is unknown data on the safety while breastfeeding.
The following dosages are recommended by Stephen Buhner:
For Lyme infections:
- Standardized tablets (Resveratrol): 1-4 tablets three to four times per day.
- May begin using a lower dose and work up to a larger quantity.
- Powder: 1 tbsp. of powder in liquid (juice or water) three times per day.
- May begin with 1 tsp. and work up to a larger dose.
- May take up to 8-12 months to resolve symptoms.
- Tincture (1:5, 60% alcohol): ½ to 1 tsp. three to six times per day.
- Decoction: Add 4oz of herb to 32oz water, simmer for 20 minutes, strain, cool, divide into four doses, and drink throughout the day.
- Traditional Chinese Medicine (TCM): 9-30 grams of root per day.
Please note that these dosages may vary depending on the person and condition.
Japanese knotweed is not on the United Plant Saver’s “at-risk” list of plants that are sensitive to the impact of human activities.
This plant is considered one of the world’s most invasive species.
Naming & Taxonomy:
Japanese knotweed’s scientific name is Polygonum cuspidatum. It belongs to the Polygonaceae (i.e., buckwheat) family of plants.
The plant’s Chinese name, Hu Zhang, means ‘tiger stick.’ It is a traditional Chinese herb listed in the Pharmacopoeia of the People’s Republic of China.
‘Hancock’s curse’ is another nickname for Japanese knotweed, which may be from the man who originally planted it in the United Kingdom.
Japanese knotweed is very leafy and has bamboo-like stems. It can grow nine to twelve feet in height.
History & Traditional Use:
Japanese knotweed has been used for over 2,000 years in Asia as food and as medicine.
The plant was first introduced as an ornamental in Britain in 1825 and in the United States in the late 1800s.
In Korea, the root of the plant is used for dental diseases as it’s said to help decrease plaque formation.
In India and Southeast Asia, the leaves are used for smoking.
Hu Zhang is used in Traditional Chinese Medicine (TCM) to ‘clear heat,’ promote blood circulation, and ‘expel dampness.’ The plant treats conditions such as coughs, phlegm, hepatitis, jaundice, amenorrhea, snake bites, and joint stiffness.
Japanese knotweed is a safe medicinal herb that has shown remarkable findings in the treatment of Lyme disease and its symptoms.
As always, make sure to consult with your physician before making any changes to your diet or adding a new herbal supplement to your regimen.
Buhner, S. H. (2015). Healing Lyme: Natural healing of Lyme borreliosis and the coinfections chlamydia and spotted fever rickettsioses (2nd edition). Raven Press: Boulder, CO.
Shapiro E. D. (2014). Borrelia burgdorferi (Lyme disease). Pediatrics in review, 35(12), 500–509. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029759/
Zhang, H., Li, C., Kwok, S. T., Zhang, Q. W., & Chan, S. W. (2013). A Review of the Pharmacological Effects of the Dried Root of Polygonum cuspidatum (Hu Zhang) and Its Constituents. Evidence-based complementary and alternative medicine: eCAM, 2013, 208349. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3806114/