Could a Christmas Kiss Prove Fatal?
Mistletoe means romance and goodwill. It is also genuinely poisonous— here is the molecular reason its toxins can tear a cell membrane apart.
By Samantha Pinto & Arianna Aggarwal
Edited by Emma Goodland
What happens if you eat it?
Mistletoe is a well-known Christmas decoration, and“ kissing under the mistletoe” is a familiar tradition— one derived from a Norse legend in which the goddess Frigg declared mistletoe a symbol of“ love triumphing over death” after her son was brought back to life, having been killed by an arrow of mistletoe wood. Cherished as it is, mistletoe remains poisonous. This article looks at what makes it dangerous: the chemicals it contains, how they affect the body, and what can be done about them.
What are the poisonous substances?
The two main toxins in mistletoe are phoratoxin and viscotoxin, both members of the thionin family of basic, cysteine-rich peptides. They are found mostly in the stems and leaves— not, as is commonly believed, the berries. American mistletoe generally contains more phoratoxin than European mistletoe, but European mistletoe also contains lectin, a glycoprotein toxin that raises poison levels further. Lectins irreversibly inhibit protein synthesis in the ribosome once they enter the cell, leading to the cell’ s death.
Should you decide to snack on mistletoe after your Christmas kiss, the phoratoxins and viscotoxins enter the body through the digestive system. Although they are peptides made of amino acids, strong disulphide bonds make them relatively resistant to digestion by proteases. Once absorbed into the bloodstream, the thionins reach major organs such as the liver and heart, accumulating in excitable tissue— cardiac muscle, neurons and gastrointestinal mucosa— which explains a range of symptoms: raised blood pressure and a slowed heart rate; blurred vision; diarrhoea, nausea, vomiting and stomach pain; and drowsiness.
Treatment
• There is no specific antidote to mistletoe poisoning, though it can be managed.
• Activated charcoal may be given to reduce absorption of the poison.
• Electrolytes may be administered to counteract the ion imbalance caused by the toxins.
So, unfortunately, your Christmas kiss would not have the fairytale ending you imagined— more likely a Christmas spent in hospital, and a lasting aversion to mistletoe.
CATALYST 14