Page 2: 'Pine Mouth': Pine Nuts Can Leave A Bitter Taste That Lingers - ABC News
ABC from July 2010
Also from Wikipedia:
Risks of eating pine nuts:
A small minority of pine nuts cultivated in China can cause taste disturbances, lasting between few days to a few weeks after consumption. A bitter, metallic taste is described. Though unpleasant, there are no lasting effects. This phenomenon was first described in a scientific paper in 2001.[11] Some publications have made reference to this phenomenon as "pine mouth".[12] The Nestlé Research Centre has hypothesized that a particular species of Chinese pine nuts, Pinus armandii, is the cause of the problem. The suspect species of pine nuts are smaller, duller, and more rounded than typical pine nuts.[13] This finding has recently been confirmed.[14] Metallic taste disturbance, known as metallogeusia, is typically reported 1–3 days after ingestion, being worse on day 2 and lasting typically up to 2 weeks. Cases are self-limited and resolve without treatment[15] Möller[16] has postulated an hypothesis that could explain why the bitter taste appears several days after ingestion and lasts for as long. A well known physiological process known as enterohepatic recirculation (EHR) could play a key role in the development of PNS.
The FDA is currently investigating “Pine Mouth”.[17