Yoghurt and pine nut dip.
Yoghurt and pine nut dip. Photo: Marcel Aucar

It is known for its buttery texture and delicate flavour but the humble pine nut could be causing havoc to tastebuds across the country.

An unusual malady called “pine mouth” is literally leaving a bad taste in the mouths of some nut fans. While not believed to pose a danger to the health of consumers, the condition can render even the most palatable flavours revolting for up to several weeks.

A 35-year-old Sydney office administrator, Thea Naghten, was affected early in March after she added a “mountain of pine nuts” to a salad. A few days later, she started tasting a strong metallic flavour, known medically as metallogeusia.

The pine nuts do not taste any different at the time of consumption and not everyone will be affected.

“I went out for a meal and, I feel very bad about it now, but I actually sent it back thinking there was something wrong with it,” Naghten said.

“Everything tasted bitter and metallic. Then for the next six or seven days everything I ate had that same bitter, metallic taste.”

Naghten tried to wash the flavour away with water but the bad taste lingered. After suspecting the pine nuts could be to blame she read about the condition online and realised she could do little but wait it out.

“Your tastebuds are replaced about every seven to 10 days normally so … essentially the tastebuds turn over and [the taste] goes away,” said Merlin Thomas, an adjunct professor of preventive medicine at Baker IDI Heart and Diabetes Institute in Melbourne.

A paper published two years ago by the NSW Food Authority suggested the most likely culprit was a particular species called Pinus armandii, which is imported from the Shaanxi and Shanxi regions of China. Traditionally considered inedible, it can make its way into the supply of edible species. How exactly it impairs people's taste is not known but the problem is unlikely to be caused by rancid nuts, which have an immediate unpleasant flavour.

First recorded in Brussels in 2001, the syndrome experienced a global spike eight years later with hundreds of cases in France, Britain and the US. In Australia, the NSW Food Authority has recorded fewer than 50 incidents since its first case in May 2009 while the Department of Health in Victoria has received nine calls in the past 15 months. It is likely many cases remain unreported, however.

Although awareness of the condition was fairly recent, the phenomenon itself was unlikely to be new, Professor Thomas said. While humans have eaten pine nuts since Palaeolithic times only recently have they grown and sold them in mass quantities on supermarket shelves. This surge in popularity allowed greater opportunity for the odd bad nut to taint supply, he said.

“The more you use the greater the chance you'll have of having quality control issues,” Professor Thomas said.

The NSW Food Authority has not singled out one particular brand or retailer as being affected. Trying to identify the root of the problem was difficult because batches of different nuts were often mixed however authorities in China have taken preventative steps such as accrediting exporters of pine nuts, its report said. In recent years some Australian retailers and suppliers have emphasised measures to maintain quality as well.

“The NSW Food Authority is working with industry and is currently monitoring reported incidents of pine mouth,” a spokesperson for the organisation said. “Given the relatively low numbers of reported cases in NSW the authority is continuing to monitor overseas experience, trends and research.”

Consumers who noticed taste disturbance after eating pine nuts could contact the authority to report their experience but anyone concerned about their symptoms should consult a doctor, the spokesperson said.

One home remedy Professor Thomas suggested was brushing your tongue thoroughly with mouthwash. This encouraged the turnover of tastebud cells, which might shorten the length of time people suffer from pine mouth.

But don't let a fear of pine mouth spoil your love of pine nuts, Professor Thomas said. “I wouldn't give up on pine nuts. They're yummy.”