The bad news: After eating pine nuts, some people are reporting a bitter, metallic aftertaste that lingers up to two weeks.

The good news: New Mexico piñon nuts don't seem to cause what is being called "pine mouth."

Marc-David Munk, an assistant professor in The University of New Mexico's Department of Emergency Medicine, began studying the syndrome a year ago after experiencing pine mouth himself after eating some pine nuts at a salad bar.

"It looked like there hadn't been much written about it, so I thought it merited a case report," Munk said this week.

Munk's " 'Pine Mouth' Syndrome: Cacogeusia Following Ingestion of Pine Nuts (Genus: Pinus). An Emerging Problem?"was published in the January edition of the Journal of Medical Toxicology. (Cacogeusia means a bad taste not due to food or drugs.)

As an emergency-room physician, Munk had never seen a case of pine mouth other than his own, but he found numerous cases when he searched on the Internet.

"That was my first tipoff that there might be something going on — that the search volumes for 'pine mouth' went up really dramatically over the last two years," he said. "So either the levels of public awareness of this condition are increasing dramatically, which they probably are given the media coverage, or else this is becoming an increasingly common phenomenon."

A Belgian anesthesiologist first diagnosed the syndrome in 2001. In 2009, blogs began reporting cases in Australia, Europe, the United States "and all over the place," Munk said. "We think this is a fairly widespread issue."

A Google search this week yielded more 22,000 hits for "pine mouth," going back to early 2009, including dozens of bloggers who experienced the syndrome themselves.

A Wednesday article by ABC News quoted San Francisco chef and food critic Jenna VanGrowski, who said she experienced the syndrome after eating pine nuts. She called the taste "almost unbearable" and said not even palate-cleansing foods or toothpaste got rid of it.

"I'm a chef, so I started getting really scared and frustrated because I need to be able to taste to do what I do," she said. "I had no idea what the heck was going on."

But the syndrome, while not pleasant, doesn't seem too serious. National Public Radio reports that of 53 complaints about pine mouth received by the U.S. Food and Drug Administration over the past year, only two involved gastro-intestinal illnesses.

There are two theories for the cause of pine mouth:

u That the reaction is from rancid nuts. Pine oil is notoriously unstable if not kept cold.

u That the reaction is from Chinese pine nuts not traditionally harvested for food.

Researchers at the Nestlé Research Center in Lausanne, Switzerland, recently published identification of the botanical origin of pine nuts found in food products by gas-liquid chromatography analysis of fatty acid profile.The report says the high demand for pine nuts has led to China and Pakistan exporting much of their harvest to Western countries.

"Food safety agencies raised some concerns regarding pine nuts imported from Asia and their association with taste disturbance," the researchers wrote. "However, even though a formal association has not been found to date, the Pinus genus comprises species that are not classified as edible and could be eventually used to adulterate edible species."

The Swiss researchers' analysis found that five of the more than 25 types of pine nuts for sale in groceries included varieties not commonly harvested for food, including the Chinese white pine (Pinus armandii) and the Chinese red pine (Pinus massoniana), both of them cultivated only in China.

Pine nuts are a staple of Mediterranean cuisine. Called pignoli or pignolia, they often are used in salads or mixed with basel or parsley to make pesto. In New Mexico, the nuts are often mixed with fruit or mincemeat to make empanadas.

Neither the species of pine nor their country of origin is listed on pine nuts for sale in bulk at Whole Foods Market in Santa Fe, where shelled, organic pine nuts sell for $34.99 a pound and shelled, nonorganic pine nuts are priced at $24.99 a pound. A grocery manager said Whole Foods' pine nuts are grown in the region that includes Russia, China and North Korea, but he doesn't know their exact country of origin.

Trader Joe's used to carry packages of shelled pine nuts from China — at $7.99 per half pound — but they were pulled from its shelves last month and are "awaiting FDA analysis," according to a notation on Trader Joe's computers.

Piñon nuts — New Mexico law stipulates that only pine nuts grown in New Mexico (Pinus edulis) can be labeled that way — are the object of piñon pickers who roam Northern New Mexico's foothills in the fall.

In season, raw, unshelled piñon nuts typically sell for $10 or more per pound. Maria Varela of Peña Blanca has been selling roasted, unshelled piñons for $20 per pound from her van parked on the far southern end of Santa Fe year-round for the past two years. Meanwhile, the New Mexico Piñon Nut Co. in Albuquerque sells roasted, unshelled piñon nuts for $28.95 per pound.

The state Department of Health hasn't been aware of any reports of pine mouth in New Mexico, spokeswoman Deborah Busemeyer said this week. "Even anecdotally, we haven't heard anything and we haven't had any calls asking about it," she said.

Munk said he's not an agricultural expert, but he agrees that munching fresh, locally grown piñon nuts is probably the safest bet to avoid the problem. "There's nothing better than locally grown produce," he said.

Contact Tom Sharpe at 986-3080 or tsharpe@sfnewmexican.com.