Mistletoe is best known for facilitating kisses during the holiday season, but the berried plant may do more than light up your love life. For hundreds of years, mistletoe has been used to treat a variety of medical conditions, including epilepsy, asthma, hypertension, headaches, menopausal symptoms, infertility, dermatitis, arthritis, and rheumatism, according to the National Cancer Institute (NCI).

Mistletoe extracts - nci.

Mistletoe plants and berries are considered to be poisonous, according to the National Capital Poison Center. That said, mistletoe extracts, typically administered via injection, may have powerful health benefits. In recent years, scientists have mainly been exploring the use of mistletoe extracts as a complementary or alternative therapy for cancer. Growing evidence suggests that certain compounds in the plant can boost the immune system and fight cancer.

Staupe H, Buentzel J, Keinki C, Buentzel J, Huebner J. Systematic analysis of mistletoe prescriptions in clinical studies. J Cancer Res Clin Oncol. 2023;149(9):5559-5571.

Szurpnicka A, Kowalczuk A, Szterk A. Biological activity of mistletoe: in vitro and in vivo studies and mechanisms of action. Arch Pharm Res. 2020;43(6):593-629.

Mistletoe is not approved for use as a treatment for cancer—or any other medical condition—in the United States; however, in Europe, mistletoe extracts are prescribed to patients with cancer. “As with many therapies [that] fall outside of the current standard of care, we need more research. However, we have had evidence for quite some time to suggest that mistletoe has a beneficial effect against cancer,” Jonathan Stegall, MD, an integrative oncologist and founder of the Center for Advanced Medicine in Johns Creek, GA, tells MDLinx.

Friedel WE, Matthes H, Bock PR, Zänker KS. Systematic evaluation of the clinical effects of supportive mistletoe treatment within chemo- and/or radiotherapy protocols and long-term mistletoe application in nonmetastatic colorectal carcinoma: multicenter, controlled, observational cohort study. J Soc Integr Oncol. 2009;7(4):137-145.

Some studies conducted on mistletoe identified anticancer effects

The bulk of research exploring the health benefits of mistletoe extracts has been conducted in Europe. Some reports have found that mistletoe extracts have a potent anticancer effect, according to the NCI.

Mistletoe extracts - nci.

One report, for example, found that women with breast cancer who took mistletoe along with their standard cancer treatments developed significantly less adverse drug reactions associated with conventional treatment. Another discovered that people with breast cancer who took mistletoe along with their standard treatment had improved survival and/or quality of life compared to those who did not take mistletoe. However, the reliability of the findings in some of these studies has been questioned.

Mistletoe extracts (Pdq®) - nci

Reports have found that mistletoe extracts, taken in conjunction with conventional treatments, boosted survival rates in people with colorectal cancer and pancreatic cancer. According to the NCI, clinical trials have commonly reported better quality of life and improved survival among cancer patients who took mistletoe extracts. On the other hand, some studies have determined that mistletoe extracts had no apparent impact on quality of life or survival among people with certain cancers, such as non-small cell lung cancer and melanoma.

Mistletoe extracts - nci.

Clinical trials are currently being conducted in the US. A 2023 trial conducted by researchers at Johns Hopkins Kimmel Cancer Center, for example, found that patients with cancer tolerated the treatment well, reporting control of their cancer and improved quality of life, according to Dr. Stegall. “Based on these encouraging results, they recommended that additional studies be conducted,” he says.

According to the NCI, mistletoe extracts, in general, are associated with few side effects and are well-tolerated. “When given at appropriate doses, mistletoe is generally well-tolerated without significant side effects,” says Neha Bhatt, MD, a naturopathic medicine specialist and resident physician at Sonoran University of Health Sciences. Side effects may include soreness and inflammation at injection sites, headache, fever, chills, nausea, and lethargy. According to Dr. Stegall, these symptoms result from mistletoe's ability to evoke an immune response. “As with any substance, there is a risk of allergic reaction, which has been reported in the literature,” he says.

Mistletoe extracts - nci.

Here’s why mistletoe might help treat cancer

According to Dr. Bhatt, mistletoe extracts may have immune-stimulating and anti-inflammatory effects, giving it an anti-cancer effect.

Huber R, Rostock M, Goedl R, et al. Mistletoe treatment induces GM-CSF- and IL-5 production by PBMC and increases blood granulocyte- and eosinophil counts: a placebo controlled randomized study in healthy subjects. Eur J Med Res. 2005;10(10):411-418.

Some evidence suggests that certain compounds found in mistletoe, including viscotoxins and lectins, inhibit tumour growth. Mistletoe may also improve the quality of life in people with cancer by treating symptoms, such as fatigue, nausea, vomiting, depression, anxiety, and side effects of other treatments like chemotherapy and radiotherapy, research shows. Other reports suggest that mistletoe also boosts the efficacy of cancer treatments, Dr. Stegall notes.

Szurpnicka A, Kowalczuk A, Szterk A. Biological activity of mistletoe: in vitro and in vivo studies and mechanisms of action. Arch Pharm Res. 2020;43(6):593-629.

Cebović T, Spasić S, Popović M. Cytotoxic effects of the Viscum album L. extract on Ehrlich tumour cells in vivo. Phytother Res. 2008;22(8):1097-1103.

Thronicke A, Oei SL, Merkle A, Matthes H, Schad F. Clinical safety of combined targeted and viscum album l. Therapy in oncological patients. Medicines (Basel). 2018;5(3):100.

Dr. Stegall utilizes mistletoe extracts, given subcutaneously and intravenously, in his cancer treatment protocols, along with chemotherapy and immunotherapy. He says that the health effects depend on the specific Viscum species used. “For example, in my integrative oncology clinic, we use Viscum mali intravenously for its cytotoxic (cancer cell–killing) effect, and we use Viscum abietis as a subcutaneous injection for its immune-boosting properties,” Dr Stegall tells MDLinx. 

He believes that the plant has helped many of his patients with cancer. “I've found it to be quite safe and well-tolerated,” he says.

Should people consider taking mistletoe extracts?

More research is needed to uncover the health benefits. Future trials, hopefully, will help scientists determine whether mistletoe can be useful in the treatment of certain cancer patients.