The Dark Myth of the Poinsettia

The common myth of the Christmas flower poisoning originated in 1919 when authorities mistakenly claimed that an American child's death was caused by the ingestion of poinsettia (Euphorbia pulcherria) leaves. Ever since then, the festive plant that decorates our houses during the winter has earned a dark reputation. The poinsettia is labeled as a toxic household plant on a myriad of poison control websites.

However, the claim of the poisonous poinsettia is in fact entirely unfounded. The Poisindex Information Service, which is the research source used by most poison control centers, notes that a 50 pound child would have to eat more than 500 poinsettia bracts before crossing a toxic threshold. The Poisindex Information Service also claims that the ingestion of poinsettia leaves may cause nausea and vomiting in people and direct contact with the plant may cause irritation. So what exactly is the truth behind the chemical compounds of the poinsettia?

As a member of the Euphorbiaceae plant family, the poinsettia's cousin is the rubber tree (Hevea brasiliensis). It has been found that the stems and leaves of plants in the Euphorbiaceae family contain milky saps, which contain bitter and irritating substances. These latex saps are a mixture of water with tiny rubber particles. Other water-insoluble solids and liquids are dispersed and suspended throughout the mixture, creating the "milky appearance." Plants of the Euphorbia family, also known as spurges or wolf's milk, are notorious for their extremely irritating saps that contain cardiac glycosides, organic compounds that act on the contractile force of the cardiac muscle. Cardiac glycosides act as secondary metabolites in plants, and they play an important role in plant chemical defense mechanisms. When eaten by animals, the slightly toxic chemicals can cause indigestion or a bitter taste. The saps stored in the stem of poinsettias are dispersed throughout the veins of the plant's leaves. Thus when a leaf is broken, the irritating sap is produced. Although the saps of the poinsettia plant may not qualify as being lethal, this surely does not mean that the leaves are edible.

A 20-year long study conducted by the American Association of Poison Control Centers (AAPCC) analyzed approximately 27,000 encounters involving poinsettias, holly, and mistletoe. The AAPCC found that roughly 90 percent of people involved in the study had no symptoms and only 30 individuals, or 0.1 percent of the total sample became seriously ill.

Beyond the latex saps of the poinsettia, another prominent chemical can be found in their bright red leaves. Predominant in teas, wines, berries, and nuts, anthocyanins are members of the flavonoid group of phytochemicals. Anthocyanin pigments are responsible for the red, purple, and blue colors of a variety of different plants. To date, there have been more than 635 anthocyanins identified in nature. Based upon many human and animal clinical trials, it has been suggested that anthocyanins possess anti-inflammatory and anti-carcinogenic properties and cardiovascular and neurodegenerative disease prevention. There have been no indications of anthocyanins crossing a toxic threshold. The dark myth of the holiday Christmas star should be thrown out once and for all!

References:

Kew Royal Botanic Gardens. Euphorbia pulcherrima (poinsettia).

National Center for Biotechnology Information. Safety and whole-body antioxidant potential of a novel anthocyanin-rich formulation of edible berries. (2006).

National Center for Biotechnology Information. Irritant and co-carcinogenic diterpene esters from the latex of Euphorbia cauducifolia L. (2010).

Princeton University. Cardiac glycoside. (2014).

Khan, A. Q. et al. A New Macrocylic Diterpene Ester from the Latex of Euphorbia tirucalli. Journal of Natural Products 53, 728-731 (1990).

Labos, C. "Poinsettias, mistletoe, and holly not as poisonous as once feared." The Boston Globe. December 17, 2014.

Sequin, M. The Chemistry of Plants: Perfumes, Pigments and Poisons. Royal Society of Chemistry, 2012.

Images Credits:

1. Latex sap of Euphorbia family image is by Steadygrowpro blog user dshinall and is in the public domain.