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Edible Dictionary: Pine Mouth

What a nagging metallic taste in your mouth could say about the global supply and demand for the seeds of certain pine trees.


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Pronounciation: paɪn mauθ
Etymology: pine (< classical Latin pīnus) + mouth (cognate with Old Frisian mūth)

1. A temporary distortion of taste probably caused by eating the seeds of certain pine tree species.

2009 Christopher Middleton The Daily Mail. The first reports of "pine mouth," as it has been dubbed, began last winter in the U.S. from those who had eaten imported Chinese pine nuts.

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The symptoms of “pine mouth,” or pine nut syndrome, are reported as follows: Approximately 24 to 72 hours after eating pine nuts—those sweet, little seeds plucked from mature pine tree cones—patients begin to detect a metallic taste in their mouth.

If you drink beer, it tastes bitter and metallic. If you eat an apple, it tastes bitter and metallic. Same thing with spicy pho or chocolate. When I experienced it last November, I thought I had early stages of tongue cancer or something terrible. I tried brushing the metallic taste off my tongue, but even peppermint toothpaste had a metallic aftertaste. Then a week later, everything was back to normal.

Medical researchers in Europe first reported taste disturbances associated with pine nuts in 2001. In 2010, Marc-David Munk published the first case study on a single patient's experience with pine nuts and metallogeusia (metallic taste). Munk conducted physical, dental, neurological, and other sensory examinations, but nothing appeared to be amiss. The patient's symptoms went away so Munk was forced to turn to another tool: Google Trends. He found that searches for “pine mouth” had peaked in the second quarter of 2009. (A spokesman at the Food and Drug Administration told me they have recorded more than 100 reports of pine mouth since data collection began in 2009. If you experience the problem, you can file reports here.)

Why did "pine mouth" happen? And why does it continue to happen? No one really knows. It's possible that batches get contaminated or go rancid, or it could be an allergic response or a psychogenic reaction. In a lengthy review of the research, food scientist Gregory Möller writes, "PNS is an idiosyncratic adverse food sensitivity arising from a bioactive natural chemical or group of chemicals in a newly introduced dietary pine nut species." In other words, the chemical makeup of the pine nuts we're eating is changing, and that may be distorting our sense of taste.

The world has 120 known species of pine tree in the Pinus genus, but only 29 have a history of being eaten, according to the UN's Food and Agriculture Organization, and five of those—P. pinea (Italian pignolis), P. koraiensis (Korean pine nuts), P. sibirica (Siberian), P. gerardiana (Chilgoza), and P. edulis (pinyons)—have significant commercial harvests. Because the demand for pine nuts has grown and appears to be outpacing local production, especially in the United States, seeds from other pine trees species are being introduced. The average shopper, presumably, wants a familiar-sounding "pine nut" rather than a lesson in dendrology. But studying pine tree varieties is important. Pine nuts from two Chinese trees—P. armandii and P. massoniana—appear to contain different fatty acid profiles, which may be a factor in increasing bile production and creating the temporary, bitter disruption of taste.

While the perplexing chemical cause-and-effect in the body is still being unraveled, it's worth considering how the popularity of pine nuts, pignolis, and pesto may inadvertently be leaving a bitter taste in our mouths.

Photo: Harvesting Pinus sibirica in Siberia, via A.N. Arbachakov "Harvesting of Siberian Pine Nuts in Mountain Shoria: Traditions and Nowadays." © 2009 Elsevier

Edible Dictionary is a newish series from GOOD's Food hub that investigates obscure food terminology in an attempt to shed light on the lesser-known workings of our food system. Our most recent entry defined "carnery."