Japanese knotweed is one of the richest natural sources of resveratrol, the same antioxidant compound found in red wine and grapes, but in far higher concentrations. Its root has been used in traditional Chinese medicine for centuries under the name Hu Zhang, and modern research is beginning to confirm some of those uses. The plant also happens to be edible, with young spring shoots that taste similar to rhubarb.
Key Compounds in the Plant
The root of Japanese knotweed contains three compounds that drive most of its health-related uses. Resveratrol, found at roughly 1.8 mg per gram of dried root, acts as a potent antioxidant and anti-inflammatory agent. Polydatin, a closely related compound, is present at even higher levels (about 13 mg per gram) and converts to resveratrol in the body. The third major compound, emodin, is an anthraquinone that contributes anti-inflammatory and mild laxative effects.
Most resveratrol supplements on the market actually source their resveratrol from Japanese knotweed rather than grapes, because the plant provides a much more concentrated and cost-effective supply.
Traditional Chinese Medicine Uses
Hu Zhang has a long history in Chinese herbal medicine, where it’s typically combined with other herbs rather than used alone. Practitioners have prescribed it for hepatitis, jaundice, joint pain, cough, skin burns, snake bites, and high cholesterol. In the framework of traditional Chinese medicine, the root is considered useful for clearing heat and toxins, promoting blood circulation, and reducing phlegm. While these traditional categories don’t map neatly onto Western medicine, they overlap with some of the anti-inflammatory and liver-protective effects that lab studies have since identified.
Anti-Inflammatory Properties
The strongest scientific support for Japanese knotweed centers on its anti-inflammatory activity. Emodin, one of its main compounds, reduces levels of key inflammatory signaling molecules including TNF-alpha and interleukin-6. In animal studies, emodin also suppressed the activation of inflammatory pathways that drive tissue damage, particularly those involved in scarring and fibrosis. Resveratrol contributes its own anti-inflammatory effects through overlapping but distinct mechanisms.
This combination of anti-inflammatory compounds may explain why the plant has historically been used for joint pain and inflammatory conditions, though human clinical trials remain limited.
Lyme Disease and Antimicrobial Activity
Japanese knotweed has gained significant attention in the Lyme disease community, largely through the work of herbalist Stephen Buhner. Lab studies have provided some basis for this interest. In a review published in Integrative Medicine, Japanese knotweed was identified as one of the most potent herbal compounds tested against the Lyme bacterium (Borrelia burgdorferi) in laboratory dishes, showing minimum inhibitory concentrations as low as 0.03% to 0.06%. Only one other herb, cryptolepis, showed comparable potency.
The plant demonstrated antibacterial, anti-borrelia, and anti-inflammatory activity in vitro. Its two active constituents in this context are emodin and resveratrol. However, killing bacteria in a test tube is very different from treating an active infection in the human body, and no clinical trials have confirmed these effects in people with Lyme disease. Many people with persistent Lyme symptoms use knotweed extracts as a complementary approach alongside conventional treatment.
Brain Health Potential
Early research suggests Japanese knotweed compounds may support brain health by restoring the integrity of the blood-brain barrier, the protective lining that controls what enters the brain from the bloodstream. Network pharmacology analysis indicates the plant’s constituents may reduce inflammatory activity in the brain through a signaling pathway called PI3K-Akt, which plays a central role in cell survival and inflammation. These findings are preliminary and based on computational modeling rather than human studies, but they align with the broader body of research on resveratrol’s neuroprotective effects.
Eating Japanese Knotweed
The young shoots that emerge in early spring, when they’re under about 8 inches tall, are the edible part. They have a tart, tangy flavor often compared to rhubarb and can be used in similar ways: stewed into compotes, baked into crumbles, or made into jam. Some people sauté the shoots or pickle them.
One important caution: Japanese knotweed is high in oxalic acid, roughly comparable to rhubarb. If you avoid rhubarb or spinach because of kidney stones or oxalate sensitivity, you should avoid knotweed too. Cooking does not significantly reduce oxalic acid content. Fermenting may lower levels somewhat, but this hasn’t been well quantified. The oxalic acid is present throughout the plant but tends to be highest in the leaves, which most foragers avoid eating entirely.
Safety Considerations
Japanese knotweed root extract is generally well tolerated in moderate amounts, but it carries a few risks worth knowing about. Emodin has a natural laxative effect, meaning higher doses of knotweed supplements can cause digestive upset, cramping, or diarrhea.
More importantly, emodin inhibits certain liver enzymes (CYP1A2 and CYP3A4) that metabolize a wide range of medications. If you take prescription drugs, particularly those processed by the liver, knotweed supplements could alter how quickly your body breaks down those medications, potentially increasing their levels in your bloodstream. This is especially relevant for blood thinners, certain antidepressants, and some heart medications. Resveratrol itself can also enhance the effects of blood-thinning drugs.
Pregnant and breastfeeding women are typically advised to avoid knotweed supplements, partly due to the laxative compounds and partly because of insufficient safety data.