The phenomenon of pine mouth, which appeared nearly a decade ago, is still baffling scientists
PESTO MAKERS: beware of where your pine nuts are coming from. The Food Safety Authority has logged 24 cases in less than two years of a strange new phenomenon known as “pine mouth”, which is suspected to be caused by inedible Asian pine nuts having been added to the food chain.
The phenomenon was first noticed nine years ago, and it has baffled scientists and toxicologists in food- safety agencies across Europe. There is, as yet, no clear known cause for the bitter or metallic taste reported by sufferers, which starts one to three days after eating pine nuts and can continue for up to two weeks.
In this writer’s case it resolved itself within four days and started exactly 48 hours after eating a sprinkling of pine nuts in a salad. Symptoms have been reported after eating not just fresh pine nuts but pine nuts processed into pesto, cooked or roasted. The FSA says it’s not aware of any adverse health effects associated with pine mouth. The European Food Safety Authority is currently looking at the issue, and is due to report on its findings before the end of the year.
Earlier this year a Swiss study found that the botanical origin of pine nuts could be identified by checking the fatty-acid profile.
The study found five species of pine nuts on sale, including the Chinese white pine and Chinese red pine, which “are only cultivated in China and are not listed as common sources of edible pine nuts by the Food and Agriculture Organisation”.
In Germany, the Federal Institute for Risk Assessment found that the phenomenon occurred after eating the Korean pine nut, which originates in China or Pakistan, even though this is a pine nut commonly eaten.
Gregory Möller, professor of environmental chemistry and toxicology at the School of Food Science, a joint programme between Washington State University and the University of Idaho, has an interesting article in the May issue of Food Technologymagazine (ift.org) in which he sifts through the various suggested causes of pine mouth.
Prof Möller suggests that the length of time it takes for the symptoms to subside may be due to a process called enterohepatic recirculation (EHR), whereby some chemicals previously processed by the liver are reabsorbed and returned to the liver for another processing. “We know EHR can dramatically extend the residence time of some chemicals or drugs in the digestive tract, and, for toxic compounds there is a potential for enhanced toxicity, especially liver toxicity. There are a good number of known, possibly toxic, compounds in various pine nut species, and some additional laboratory detective work may help isolate the specific offender responsible for PNS (pine nut syndrome).”
In an unpublished update, Prof Möller adds: “We are currently exploring the high levels of a particular oxidised terpene compound, linalool-oxide, that we find in some of our pine nut samples. Linalool is a common natural fragrance found in pines and several other plants, and it is used in many consumer products.
“However, a small percentage of people experience skin sensitivity, including rashes and eczema, when exposed to air-oxidised linalool. Since our skin and gastrointestinal tract are made up of similar cells, there is an intriguing possibility that linalool- oxide may be the offending agent in pine nut mouth.”
Prof Möller advises those who have experienced pine mouth to avoid pine nuts in future, noting that “for those experiencing PNS, pine nuts can be uncomfortably toxic. As we move farther and farther away from the production side of food, we rely more and more on a system of reliable strangers to grow, process, and prepare our food.”
Choose wisely, is his advice.
