Viscum album – Mistletoe Extract in Medicine

What is Viscum album?

Viscum album, commonly known as European mistletoe or white-berried mistletoe, is a hemiparasitic plant belonging to the family Santalaceae. It grows on various host trees such as apple, pine, oak, and poplar, and is widely distributed across Europe, Asia, and North Africa. Mistletoe has been used in folk medicine for centuries. Today, standardized mistletoe extracts are approved as medicinal products and are primarily used as complementary treatments in oncology.

Active Compounds and Mechanism of Action

The biological effects of Viscum album are attributed to several bioactive constituents:

• Mistletoe lectins (ML I, ML II, ML III): Glycoproteins considered to have immunomodulatory and cytotoxic (cell-damaging toward tumor cells) properties.
• Viscotoxins: Small proteins with cell-damaging effects.
• Polysaccharides: Known to stimulate immune system activity.
• Flavonoids and phenylpropanoids: Plant compounds with antioxidant activity.

Mistletoe lectins are regarded as the primary active substances. They can induce apoptosis (programmed cell death) in tumor cells, stimulate immune defenses, and exert anti-inflammatory effects. An antiangiogenic effect — inhibiting the formation of new blood vessels in tumors — is also under scientific discussion.

Medical Applications

Complementary Cancer Therapy

Mistletoe extracts are used in Germany and other European countries as adjuvant therapy in cancer treatment. The main goals are to improve the quality of life of patients, reduce side effects of conventional chemotherapy or radiation therapy, and strengthen the immune system. Well-known preparations include Iscador, Helixor, and Abnobaviscum.

Administration

Mistletoe extracts are typically administered as subcutaneous injections (under the skin), often several times per week. Dosage is individually adjusted based on tolerability and the patient's response to treatment.

Other Traditional Uses

In folk medicine, Viscum album has also been traditionally used for high blood pressure, arteriosclerosis, and general strengthening of the body. However, scientific evidence for these applications remains limited.

Efficacy and Scientific Evidence

The evidence base for mistletoe therapy is heterogeneous. Some clinical studies report positive effects on the quality of life and well-being of cancer patients. However, sufficient scientific evidence for a direct tumor-inhibiting effect in humans has not yet been established. International medical societies therefore do not recommend mistletoe therapy as a standard treatment but do not categorically exclude it when used as a complement to conventional oncological care.

Side Effects and Risks

Mistletoe extracts are generally well tolerated. Possible side effects include:

• Local reactions at the injection site (redness, swelling, itching)
• Mild fever, especially at the beginning of therapy
• Flu-like symptoms
• Rarely: allergic reactions

Raw mistletoe plant material and especially the berries of Viscum album are toxic and must not be consumed independently. Medical applications should only be carried out using standardized, approved extracts under medical supervision.

Drug Interactions

Patients taking immunosuppressants or suffering from immunological conditions should only use mistletoe therapy after consulting a physician, as mistletoe lectins stimulate the immune system and may interact with existing therapies.

References

1. Kienle GS, Kiene H. Mistletoe in Oncology: Facts and Conceptual Foundations. Schattauer Verlag, Stuttgart, 2003.
2. Ostermann T et al. - Mistletoe therapy in oncology: a systematic review. Cochrane Database of Systematic Reviews, 2020.
3. World Health Organization (WHO) - Monographs on Selected Medicinal Plants, Vol. 4, Geneva, 2009.