Japanese knotweed – ingredients, effects and application

Japanese knotweed is an invasive plant in Central Europe that displaces native species and is therefore combated. However, this “troublemaker” has a variety of medically effective substances. However, in most cases the effectiveness for humans and the application are not proven.

Characteristics

• Scientific name: Fallopia japonica
• Common names: Japanese knotweed, Japanese knotweed, Kamchatka knotweed
• Family: Knotweed family (Polygonaceae)
• Distribution: Originally East Asia (Japan, Korea, China), now in Central Europe and parts of Canada as an invasive neophyte.
• Plant parts used: All parts of the plant
• Ingredients: Polyphenols such as Reservatrol, oxalic acid, anthraquinone, emodin, rutin, phytoestrogens, tannic acids, proteins, vitamins, minerals
• Areas of application (selection): Inflammation, joint pain due to osteoarthritis, diabetes/blood sugar, heart health, wound healing, pain during menopause and postmenopause.

Japanese knotweed – an overview

• Knotweeds that occur in this country are the Japanese knotweed (Fallopia japonica), the Sakhalin knotweed (Fallopia sachalinensis) and the Bohemian knotweed (Fallopia x bohemica), a hybrid of both species.
• Japanese knotweed is an invasive neophyte. It spreads very quickly, grows rapidly and prevails over the competition. It displaces native species and damages buildings, roads and river banks.
• Japanese knotweed needs light, warmth and moisture. It thrives on nutrient-rich and slightly acidic soils.
• The resveratrol it contains is an antioxidant phytoalexin and protects the plant from parasites and fungal infections. Effects against diseases in humans are controversial.
• In the countries of origin, knotweed is used in traditional medicine, among other things, for gastrointestinal complaints and to detoxify the blood.
• In the kitchen, the stems can be used in a similar way to rhubarb.
• Like rhubarb, knotweed contains a lot of oxalic acid. Therefore, older stems should not be used.

ingredients

Japanese knotweed contains polyphenols such as reservatrol. It also contains anthraquinone, emodin (anthraquinone derivative), rutin, phytoestrogens, tannic acids, oxalic acid, proteins, minerals and vitamins among the ingredients.

Medical effect and application

Japanese knotweed ingredients have antioxidant and anti-inflammatory properties. A variety of medical effects are associated with the plant, but have not been sufficiently scientifically investigated or proven.

Areas of application include inflammation and urinary retention. The plant is also said to have positive effects on cholesterol levels and blood sugar. Effects for reducing fever, accelerating wound healing and pain relief are also reported. In addition, the plant substances contained in it are said to help laxatives and regulate menstruation.

The plant contains powerful antioxidants that are generally known to slow down harmful cell changes and thus potentially prevent cancer. Heart health should also be promoted.

According to a 2021 review, the greatest therapeutic potential lies in its antioxidant, antimicrobial, anti-inflammatory and anti-cancer effects.

It has not been proven that knotweed regulates blood sugar and helps against diabetes. The effect is attributed to the substance emodin, although its antidiabetic potential could also be attributed solely to a reduction in appetite.

The high content of tannic acid, which has a contracting effect on blood vessels, can accelerate wound healing. Therefore, fresh leaves are crushed and used as a dressing for skin diseases and superficial skin wounds.

With its ingredients, Japanese knotweed offers a high potential for medicinal effects – but only a few have so far been proven for use in humans. (Image: Madeleine Steinbach/stock.adobe.com/own editing heilpraxis.de)

Reservatrol

Reservatrol, contained in high concentrations in Japanese knotweed, is used to prevent or treat heart disease and diabetes, as well as to improve memory and relieve joint pain due to osteoarthritis.

Antioxidant, anti-inflammatory and antiproliferative properties are proven for Reservatrol. However, many properties have not been confirmed to achieve corresponding effects in humans. Anti-aging effects have not been proven, nor have any improvement in cognitive function in older adults or cardioprotective effects. Positive effects on diabetes have not yet been proven undisputed.

What is likely, however, are pain-relieving effects in women during menopause and postmenopause, as well as bone-protective effects and improvements in symptoms of (osteo-)arthritis.

Trans-resveratrol from Japanese knotweed is approved as a dietary supplement for adults as tablets or capsules in a dose not exceeding 150 mg per day.

Knotweed in Ayurveda and Chinese Medicine

The root of knotweed is particularly used in India and China. This is processed into extracts or powders that are intended to detoxify the blood, are taken for gastrointestinal complaints and serve as daily medicine for a long life.

Side effects and contraindications

Japanese knotweed contains a lot of oxalic acid. This can be reduced if the cooking water is thrown away when preparing it as food and foods that contain a lot of fiber are consumed with the knotweed.

Because of the oxalic acid, you should not consume Japanese knotweed if you suffer from the following illnesses: gout, osteoarthritis, rheumatism, kidney stones and kidney problems that prevent excretion via the kidneys.

Side effects of high doses of resveratrol can include nausea, bloating, stomach pain and diarrhea.

Japanese knotweed in the kitchen

Japanese knotweed is popular in the cuisine of Japan, China and Korea. The young shoots are usually used for this. These are peeled and cooked like asparagus, then soaked in water and salt to preserve them. This vegetable, called “Itadori”, is used, for example, to fill sushi and spring rolls.

In Central Europe there are now experimental recipes for lemonades, compotes, jams, cakes and relish and some also use the young sticks as a vegetable. The stems are hollow and can therefore also be filled.

The fresh root sprouts can be baked, fried or breaded. Japanese knotweed is a healthy source of nutrition, and this vegetable provides the human body with important vitamins, minerals and, above all, phytochemicals. Consuming foods containing resveratrol is generally safe.

An invasive neophyte

Japanese knotweed is considered one of the most harmful neophytes in Central Europe. Such invasive species are animal and plant species that, as they spread, affect habitats, species or ecosystems and can therefore harm biological diversity.

A plant is considered a neophyte if it has been introduced to us since the beginning of global trade and has spread as a “new plant” outside of its natural area of ​​origin. Many of these plants do not harm the ecosystems in the newly populated countries. However, invasive neophytes, such as Japanese knotweed, are so competitive that they spread rapidly and displace native plants.

Japanese knotweed is very adaptable and often overgrows sensitive biotopes on river banks and streams. It also damages human infrastructure as the stems penetrate walls, asphalt and pipes.

It is difficult to fight because the smallest piece of a rhizome sprouts into a new plant. It is best to pull out the plants in their entirety and dig them up. None of the rhizome should remain in the ground. (Dr Utz Anhalt)