Japanese Knotweed
Japanese knotweed (Polygonum cuspidatum) is a fast-growing perennial plant from East Asia. Its root is a main commercial source of resveratrol.
Also listed as Hu zhang, Polygonum cuspidatum, Bambou Japonais, Japanese Knotwood
What it is studied for
The strongest rated effects first. Bars show the size of the effect, the letter grades the evidence, and each rating lists the studies behind it.
Why is Japanese knotweed in supplements?
Japanese knotweed root supplies resveratrol, a compound used in supplements. Health Canada lists the plant as Reynoutria japonica; the human extract trial uses the name Polygonum cuspidatum. The extract contains a mixture of plant compounds, so its effects cannot automatically be assigned to resveratrol alone. 1 2
Why people take it
SuppCo community snapshot, 2026-09-28. Reasons for use are not evidence that it works.
Questions people ask
Is Japanese knotweed the same thing as resveratrol?
No. The root is one source of resveratrol, while the plant extract contains other compounds too. 1 2
Does it help people live longer?
The cited knotweed trial measured short-term blood markers, not lifespan. It cannot answer that question. 2
Is 150 mg an approved dose for any knotweed product?
No. The EFSA assessment concerns highly purified synthetic trans-resveratrol, not all plant extracts. 3
Can it be combined with medication?
Resveratrol may alter medicine effects. Health Canada recommends discussing such combinations with a health professional. 1