DOES IT WORK?Mistletoe and cancer
KISSING UNDER the mistletoe is an ancient tradition, more recently limited to Christmas time. The ancient Greeks associated mistletoe with marriage and fertility. In Scandinavia, mistletoe was a plant of peace under which truces were declared – both by warriors and spouses. Another custom is that mistletoe was not supposed to touch the ground, which may reflect the way it grows naturally.
Mistletoe is botanically unusual, being a plant which feeds off various trees. It puts its roots into the tree to obtain water and nutrients, and can also produce some food through photosynthesis. For this reason mistletoe is called a hemi-parasite.
This parasitic nature also led to the suggestion that mistletoe might treat cancer. Rudolf Steiner developed a spiritual philosophy that became known as anthroposophical medicine. Mistletoe’s colonisation of a tree was said to resemble the way cancer spreads in the body. Based on the homeopathic principle of “like curing like”, extremely dilute solutions of mistletoe were believed to cure cancer.
While the reasoning was based on Steiner’s philosophy and not biology, some recent scientific studies are supporting the connection. Extracts of mistletoe have thus become one of the most popular herbal remedies for cancer, especially in continental Europe.
The name mistletoe is used for a number of different species. European mistletoe (Viscum album) is used to make the extracts used for cancer. These are sometimes known by their acronym, VAE (Viscum album extract). American mistletoe looks similar, but is a completely different species (Phoradendron leucarpum).
Mistletoe extracts have been scientifically studied for many decades, especially in Germany. Numerous compounds have been found that kill cancer cells or stimulate the immune system when tested in tissues or animals. Depending on the tree upon which the mistletoe grew, the compounds found in an extract vary considerably, leading to inconsistent results.
Overall, studies in cancer patients have not produced the expected positive results. There is clear evidence that mistletoe does not help patients with head, neck, pancreatic or bladder cancers. Studies involving other types of cancer have had some beneficial results.
In the area of breast and gynaecological cancer, a systematic review earlier this year identified 19 randomised studies. The strongest evidence of benefit was found for patients’ quality of life and the tolerability of conventional chemotherapy.
Compared to those taking placebos, patients taking mistletoe extracts reported improvements in tiredness, appetite, sleep patterns, depression, anxiety and general wellbeing.
In addition, the severity of adverse effects from conventional chemotherapy was sometimes reduced by mistletoe, although this benefit was not found in all studies. However, the cancer itself and patient survival times showed very little change or improvement.
Clinical studies have found that mistletoe extracts produce few adverse effects other than some flu-like symptoms when they were given by injection.
Regarding the plant material, European mistletoe should not be confused with American mistletoe. The berries of both are poisonous, as is the rest of the American mistletoe plant. American mistletoe contains compounds that stimulate the heart and uterus.
Although sometimes used to treat heart failure, uncertainty about the amount of active ingredients in the plants has led to serious adverse cardiac effects and miscarriages.
Early studies led to much hope that mistletoe would provide a novel anti-cancer treatment. The results in human studies have been disappointing. The most important ingredients may be proteins, which might explain the lack of effectiveness as proteins are destroyed when taken orally.
The gene for one of these proteins has been identified and used to make pure protein synthetically (called aviscumine). An injectable formulation of this is currently being tested for its anti-cancer activity.
This approach of testing purified compounds appears to offer the most potential. At the same time, currently available mistletoe extracts may help improve cancer patients’ overall quality of life even if they do not impact the cancer itself.
Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He is author of
Alternative Medicine: The Christian Handbook
, Updated and Expanded Edition, Zondervan, 2007
