Pine Nut Syndrome Thesis Completed!

Hello readers!

My 150-page pine nut thesis is finally completed and it has been a huge success 🙂 Thank you all for your contributions to this research: the provision of bitter samples, scientific expertise, industry information, pine nut growing experience, detailed PNS accounts, insightful observations and not to mention the encouragements and friendly email exchanges that fueled my engine over the past 9 nutty months.

I know that many people have been eagerly anticipating the results of the research and I apologize for my long overdue posts! I had intended to get down to it immediately after the defense and critical discussions (on 16 May 2011), but I was immediately whisked away for other academic business in Copenhagen…and a few days after I had my bags packed and started my internship in the hills of Switzerland! Thankfully for a long weekend and for being isolated in this new foreign land, I’ve finally got some quiet time and got right down to writing…

This post first provides an overview of the research and further details will be discussed in greater detail in the different pages. I have revised the old pages with the most updated information from this research. Do check them out!


The main objective of this research was to describe the prevalence and the elements of the syndrome, as well as to establish the source (botanical and industry) of the problem. In simpler terms, I wanted to collect evidence to explain why PNS is a problem to be solved, and then to figure out how it can be solved (i.e. by finding out what change in the industry has resulted in the sales of problem pine nuts and whether the problem seeds can be told apart from non-problem seeds). Based on the detailed information collected, there were several insights into the possible causes and mechanisms of the taste disturbance, however, these hypotheses remain to be tested and we’re currently applying for a grant to continue the research (takes at least a year and it is not guaranteed). Right now, the main goal is to get ’em PNS pine nuts off the market!


The problem was first diagnosed in 2001 by the Belgian Poisons Centre with few cases reported in the number of years following that. Scientific information on the syndrome is lacking and there is a general attitude of dismissal by the authorities and retailers towards PNS being a non-health issue due to the low frequency of reports and due to most (read: BUT NOT ALL) cases resolve on its own within 1-2 weeks. (See page: ‘Health Issue‘ for more information.) Since late 2008/early 2009 there has been a spike in the number of complaints on the Internet and to the authorities. This coincided with the rocketing pine nut prices due to a poor crop in 2009.

“…researchers have not found any safety issues…and it seems to affect a relatively small number of people….” (Whole Foods, USA)
“It is about two years ago…over a long time we ate a lot of pine nuts in dishes, as a snack and so on. I still have complaints (especially bread and wine still taste bitter and like metal)…” (Dutch consumer)


Pine nuts are mostly harvested from natural forests, which bears crops every two years, and good-bad harvests go in periodic cycles of up to 10 years depending on species and environmental conditions. Prices change according to supply (demand is always high) and smaller pine nuts sell for cheaper. There are more than 100 species of pine nuts, of which more than 20 of them are known to be used for food consumption but only a few are distributed internationally with the rest remaining for local consumption. What usually determines the use of a pine species for food production is its economic viability based on factors such as seed size and seed yield. China has a diverse pine nut flora and exports multiple species of pine nuts, however the different species are not differentiated on the commercial market. One problem species has dealt a severe blow to the reputation of all the other good Chinese pine nuts that have been valuable to the market for years. I was told that an abundant crop is expected in Aug-Oct 2011 and hopefully then the pine nut market returns to the pre-PNS state.


There were many reasons for the difficulties in reporting, for instance, (1) trouble establishing link with pine nuts due to the 1-3 days delay of symptoms, (2) pine nuts being previously eaten with no problems, (3) pine nuts tasting fine at point of consumption, (4) lack of awareness of the syndrome both by the public and the medical doctors, (5) not all people being affected, (6) changing of supermarket supplies means that the same brand can differ in composition from batch to batch, (7) some people are only mildly affected and did not seek a diagnosis / did not report, but realized it upon being told by those who were more badly affected. See page ‘Problem Underestimated‘ for more information.

“…This happened to me in 2004 but I didn’t relate the problem to pine nuts. I still am not sure it was that back then, but it lasted 3 months. I went to every medical specialist, had all kinds of tests and nothing turned up. Then it just went away. Now that I look back, I remember just one time ever purchasing a very large bag of pine nuts at Costco because they were a good price for a very large amount. I am thinking now, that I must have munched on them for a period of three months and when they ran out, that was when the symptoms disappeared. This is the weirdest thing I ever heard. Last time I had an MRI of my brain, and an endoscopy. It was very frightening. I had no other symptoms beside taste disturbance.” (American consumer)

The structure of this thesis can be broken down into 3 main studies…


A worldwide survey was conducted and a total of 434 complete case reports from 23 countries were collected for a thorough description of the syndrome (individuals factors, pine nuts consumed, nature of symptoms). Cases involved people of different ages, genders, ethnicity and health conditions with large differences in individual sensitivity towards the adverse taste effect. Both raw and roasted pine nuts, with or without off-flavours and originating from different retail/supply chains were implicated, and the trigger dosage was reported to be as low as 2-3 seeds.

Check out the page on ‘Who Sold Them‘ for a full list of retailers that have sold pine nuts that caused PNS.


A total of 56 complaint samples from 8 countries were collected and 7 different pine nut species (5 species of Chinese origin) were identified amongst the samples. A variety of P. armandii was consistently observed across all the complaint samples. See page Pine Nut Species for details on the outcomes of this study — including a pictures and descriptions of the differences between the commercial pine nut species.


A testing of a fixed dosages from the same non-expired supermarket batch of pine nuts on 21 (willing) human subjects caused symptoms in 19 subjects to varying extents. There was no relation found between genetic bitter taste sensitivity and the ability to be afflicted with PNS.

The details of these studies can be found on the page: ‘Research Findings‘. Do check it out!

The End of a Nutty Chapter

This post ends the first chapter of my active research into the Pine Nut Syndrome. Thank you for accompanying me on this journey! I might not have found a remedy nor the mechanism, but I hope that the information provided here has given some relief to you, and that it will help to prevent more people from having to suffer this syndrome.

As of 1st June 2011, I have begun a new stint at the Nestlé Research Centre in Lausanne, Switzerland, thus my involvements with pine nuts will now have to take a back seat as I invest my full energies for a new cause. Nevertheless, I will continue this blog for the purpose of disseminating information and raising awareness of this syndrome.

Please continue to spread the information and inform your local retailers and authorities! I hope to pursue further research into this, but as academics would be aware of, the first major obstacle is the FUNDING, followed by the TIME that it takes have it approved. Meanwhile, I will continue to run this blog as a comprehensive source of information on PNS, so stay tuned…! 


About grrrrracey

I love to eat, I love to cook, and I love to dig into every mystery about food!
This entry was posted in Announcements, Research Updates, The Great Pine Nut Mystery. Bookmark the permalink.

15 Responses to Pine Nut Syndrome Thesis Completed!

  1. Having been one of the people affected by this strange phenomenon, I truly appreciate all the time and effort put into this study. When I found this study it validated the fact that I was not absolutely crazy and was so happy to have found a reason for the metallic and bitter taste I was experiencing. Congratulations on a job well done!

  2. Deborah says:

    Thank you, Gracey, for all your work and studies! It’s been very interesting to follow your progress and gratifying to know the cause of the taste disturbance!

  3. J Evans says:

    I am two days into this truly terrible experience. The taste in my mouth is nothing short of VILE and I have a pounding headache! And to think I bought and ate pine nuts because I recently heard of the great nutritional benefits of these nuts. (My pine nuts were purchased from Trader Joes in California.) I am so infuriated to find that these tainted pine nuts have been being sold for years! I just called the FDA in California (949)608-3530, and reported my experience. They are aware of the problem and took a full report. The gentleman I spoke with said that it will only be given more attention if EVERYBODY reports it! (He’s taken only 3 reports in the past two days, but suspects there are hundreds more) Please, if you have these terrible symptoms, CALL THE FDA in your state!

  4. Skye says:

    I;ve had it for 20 days now.. It’s not as bad as it first was but I still have a faint metalic taste and my mouth wont stop salivating.. Shoudl I see a doctor? Any remedies? I have tried Charcoal tablets for 3 days.. aloe vera juice and raw garlic..

    Please help

  5. Jac Campbell says:

    I have it right now and I checked my local grocer where I bought the nuts and they were packaged in Wilmar MN – Made in USA. I keep reading that it doesn’t happen with American pine nuts but it surely happened to me. I can drink some liquids but if I eat food the Metallic taste is so foul I feel like vomiting.

    I made Basil Pesto on Sunday with Pine Nuts and the metallic taste started yesterday. I can’t believe that it is a coincidence. I am convinced this is Pine Mouth.

    Thanks for the information. I just wanted to pass this on.

    • leigh13 says:

      The nuts that affected me were also labeled Made in the USA – they were a bag of private label pine nuts from a local grocery chain called Shop Rite. I’m very angry, as it hit me less than a week before Thanksgiving.

    • Hi,
      The pine nuts packed in MN are NOT of us origin. They are import, then pack in the US same with other big brands like Diamond and Fischer. The US production of pine nuts is species specific, P. Monophylla and P.Edulis. New laws in China require species identification and I would hope US pine nut packers would start using the species on the packing. PNS has become such an issue that health inspectors now have specific instructions to declare the product unfit for human consumption if a consumers reports the condition.
      Penny Frazier

  6. I had it last month, from pine nuts from Trader Joe’s in Portland, OR USA. Luckily, I Googled my symptoms and was able to get to the bottom of it pretty quickly, but it was a terrible 3 or 4 days with a bitter mouth! I’m a food blogger, and it was bitterly ironic that this happened to me – I’m writing an essay on the experience for The Farmer General.

    Awesome blog you have – super informative, and my biology background is getting all tingly as I read through. I’m so happy your thesis was so well-received!

    Keep up the good work,

  7. Audrey says:

    27 Aug 2012 Australia – I found you blog because I was very sick yesterday and last night. Yesterday I made Broccoli and Pinenut soup. I ate a couple of handfuls of pinenuts (from Cosco) as I was making it because I hadn’t eaten breakfast. Early in the afternoon I felt unsocial and a bit dull; my lips became cracked and dry, and I was thirsty but felt I couldn’t drink more than a few sips of water at a time without becoming nauseous. By 3 PM I was developing a headache; nausea developed soon after. I went to bed, but my head developed a migraine-like pain which felt like it was centred in the middle of my brain. I dozed off and on and sipped a mouthful of water every now and then. I also had cold-shivers. At 7 PM I vomited more liquid than I thought I had consumed throughout the day – I felt like Mr. Creosote. I then slept for an hour, had a hot drink, then slept for 2 hours, had another hot drink, then slept for another two three hour blocks. by then my dreadful headache had gone.

  8. G-Unit says:

    Thank you! I’ve had moderate symptoms, now on Day 3. I would have had no idea regarding the cause of these symptoms, and might have begun to worry a great deal, if it wasn’t for your website and the information you’ve provided.

  9. Silvia says:

    For Pine nut allergy, there is a new scientific study published in the prestigious journal Molecular Nutrition and Food Research.

    Here is the Pine nut article (safe link)!5BFyCCbY!XXCxNQ-mmunUBnMuH-uHSALM8N4ThgzV0c1HFEdvUO8


  10. TC says:

    I’ve just recently encountered this phenomena and am glad to see that there’s actually research done and causing me less worry over the weird taste bud I’ve been having. I’m on my Day 3 now and hoping for the bitterness to go away. I’ve eaten pine nuts for so long but never encountered this problem before until I bought this huge bag of tiny pine nuts (I’ve always bought the big sized ones). I hope that you’ve actually gotten to do PNS research back in Singapore.

  11. Andy Falzon says:

    Googled bitter mouth. Wow, spot on straight away. I ate some pine nuts the other day that were not the same shape as I’m used to. Hope it passes soon. I wonder if this can’t be developed into a weight loss pill. I’m not rushing to eat anything until this passes 😦

  12. Rachael says:

    Very useful blog. I’m so glad I found it. Struck down with foul bitter taste in mouth after eating pine nuts bought from a leading supermarket chain in Singapore. “Product of China, packed in Singapore” on packaging. It looks like there are a mixture of different species in the pack. Time to call AVA!

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s