I have recently been alerted of a large-scale French study of which the results were released in a report just a few days ago. It was really nice to know that there is indeed ongoing work on this problem! You can download the paper here. A survey was conducted with several thousands of PNS sufferers to describe the syndrome and the results are consistent with what I see from your responses so far. Still, please do continue to fill in my survey, as I have formulated the questions to help answer some of my hypotheses of the mechanisms. I would really like to find out the WHATs WHYs and HOWs of the unusual symptoms.
It was hypothesized in the French report as well as the research of the Nestle Research Centre that a particular species of Chinese pine nuts is the cause of the problem. There isn’t a proven answer on the causative agent yet, but for now, I would advise that it is best to avoid pine nuts that look like these ones in the pictures I have attached. They are smaller than normal (0.7-1.0cm length), duller in colour, oval-ish in shape, have a strange-looking tip, but don’t taste that much different from the other pine nuts. I have observed that suppliers / distributors that have many complaints (e.g. Trader Joe’s) contain solely such pine nuts, whereas others are mostly a mixture with the medium-sized angular ones that I believe are the Korean pine nuts that have been on the market for eons.
Picture 1 (above) shows the appearance of pine nuts from some of the brands I have received. The only exception is from Delhaize of Begium, where Italian pine nuts were implicated. I am still looking into this special case.
Picture 3 (left) is a close-up of the funny-looking Chinese pine nut tip and…my big fat finger tips.
Picture 4 (right) is a comparison of the size of a Chinese pine nut with that of an Italian one. The Italian / Mediterranean pine nuts are larger, of a more long-ish shape, and do not have a brown tip. They are a pretty ‘safe’ bet.
My recommendations at the moment are that it is best that you avoid these Chinese pine nuts (not necessarily boycotting China altogether) and return to the more expensive European pine nuts (weren’t pine nuts expensive all along, anyway?) I hope that my descriptions and pictures are clear enough to help you identify which pine nuts NOT to buy. You could also refer to my newly compiled list of supermarkets /suppliers that provide these particular small, oval, dull-coloured, brown-tipped pine nuts and just avoid those brands. Even though Trader Joe’s declare ‘Product of Korea and/or Russia’ on their packaging, they ARE belonging to the same pine nut species that is declared on other packaged brands as a ‘Product of China’.
For those of you who have had previous reactions to pine nuts or reacted immediately upon consuming minute amounts (2 or 3 seeds), it is probably safer to avoid pine nuts or perhaps consider testing for an allergy. Update: It seems now that 2-3 of the problem seeds CAN cause a taste disturbance. Do give me a few more weeks to look into this. Meanwhile, I would play on the safe side by avoiding the Chinese pine nuts… How about trying cashew nuts!