Study identifies previously unrecognised cause of persistent coughing

Generally in practice we’re able to make significant headway with all sorts of people with all sorts of health issues be they a 57 year-old man with type 2 diabetes or a 23 year-old woman with irritable bowel syndrome. And yet, I do inevitably come across patients I don’t seem to be able to help in any meaningful way, and this includes a handful of patients I’ve known over the years that suffer from a chronic, dry, tickly cough. These are individuals for whom conventional causes of cough, such as asthma, have been investigated and excluded.

I have, with these individuals, tried the sorts of approaches that one might expect from a naturally oriented doctor (e.g. identification and elimination of foods that might be triggering the problem, immune support if there’s any suspicion of compromise here, herbals approaches to soothe the throat and surrounding regions). But I have to say, hand on heart, that the results have generally not been good. Reading a study published yesterday on-line in the American Journal of Clinical Nutrition, I feel I may have found a missing piece in the puzzle regarding the causes of, and potential cure for, a persistent dry cough.

This study focused on vitamin B12, and the fact that a deficiency in this nutrient can lead to nerve damage. Could B12 deficiency lead to enhanced reactivity in and around the throat? And if so, might B12 supplementation help reduce this as well as the symptoms of chronic cough? [1].

This study focused on 42 individuals with chronic, unexplained cough. 27 of these were found to be deficient in vitamin B12 (<200 pmol/L). The remainder (15 people) were not B12 deficient.

The investigators found ‘laryngeal hyper-responsiveness’ (to histamine) was significantly more common in individuals with B12 deficiency than those without.

This finding is interesting, I think, and consistent with the investigators’ underlying hypothesis. But all this finding does, in essence, is link B12 deficiency with hyper-responsiveness in the throat – that does not mean that B12 is causing the hyper-responsiveness.

However, the investigators went a step further by treating the participants of this study with B12 to judge the effect. Individuals were treated with the following protocol:

1000 micrograms (1 mg) of B12 (in the form of cyanocobalamin) by intramuscular (IM) injection daily for 5 days, followed by;

1000 micrograms of B12 by IM injection weekly for 3 weeks, follow by;

1000 micrograms of B12 by IM injection once a month thereafter.

In the individuals who were not B12 deficient to start with, this treatment regime essentially did nothing for them. However, it was a different story in the group who were deficient: Here, B12 therapy reduced the ‘hyper-responsiveness’ in the throat significantly. Perhaps most importantly of all, cough symptoms reduced by about half in this group (though was unchanged in the group who were not B12 deficient to start with).

This is just one study, and as the authors point out, there is no other study like it (apart from one in Columbian children which found that giving them nutrient-fortified (including B12) snacks reducing coughing. However, bearing in mind how persistent cough symptoms can be, I know I’ll be on the lookout for B12 deficiency in the future.

I’ll be particularly keen to explore this possibility in individuals who fall into an at risk category. In this study, the most likely underlying cause of B12 deficiency was “inadequate intake of foods from animal origin”. Another potential underlying factor was low stomach acid secretion (stomach acid is required for the efficient absorption of B12).


1. Bucca CB, et al. Unexplained chronic cough and vitamin B12 deficiency. AJCN 19 January 2010 [epub before print]

21 Responses to Study identifies previously unrecognised cause of persistent coughing

  1. Bill Rowles 21 January 2011 at 5:49 pm #

    On B12 absorption the following link is interesting.

    Not easy to come by, B12!


  2. David Brown 21 January 2011 at 7:18 pm #

    B12 could indeed be part of the problem. Until last Winter I had a persistent cough, but ONLY in Winter. My problem, however, was too much omega-6 intake in the form of almost daily peanut butter sandwiches for lunch. When I stopped eating peanut butter, my cough stopped also. In addition, the pain in my legs subsided and my gingivitis went away.

    Dr. Briffa, you might want to have your patients’ omega-6/omega-3 tissue and/or blood ratios measured to see if they’re in balance. [1,2]

    Suggest you Google “”


  3. Barbara Kell 21 January 2011 at 8:12 pm #

    B12 injections have helped me tremendously with my ME. I inject every day and have been doing so for over two years. If I have a virus I up the dose to twice a day.
    I also know many others who have been helped by simple B12 but we are refused this medication by our doctors (UK) and have to source from overseas.

  4. Kathy Hall 21 January 2011 at 11:19 pm #

    My husband had a chronic cough while taking Zocor and it totally went away when he stopped it. I’m pretty sure it was a side effect of statins.

  5. Valerie H 21 January 2011 at 11:42 pm #

    A few months ago, Blogger Jimmy Moore did a podcast with the author of a book about B12.

  6. Valerie H 21 January 2011 at 11:45 pm #

    I meant to also include the link to Jimmy’s show

  7. Chmee 22 January 2011 at 12:21 am #

    Interesting post. I used to have a persistent cough, maybe half a dozen times a year, no rhyme or reason to it. Anyway, a few years ago my GP told me I had pernicious anaemia and started me on IM B12. The cough has not troubled me since. ( Touch wood – let’s not tempt fate. ) Yes, anecdotal, but… BTW I now take a 1000 microgram tablet every five days approximately, feel even better and my B12 levels are much more stable. I believe this method of delivery is quite common in Canada and Scandanavia, where it is preferred to injections.

  8. Stephen Hoyt 22 January 2011 at 3:04 pm #

    I always enjoy your interesting newsletter;

    I have been experiencing a persistent cough for a few winters now and this year my family doctor prescribed “AVAMYS” a medically controlled product available here in Canada described as a “fluticasone furoate nasal spray”.

    I decided to take this product as my cough attacks were persistent, becoming very aggressive and causing much discomfort. I was advised by my MD to use the product up completely (27.5 ml bottle) and was also given one refill of this “by prescription only” medication, in case my cough persisted and I needed to continue a secondary round of treatment.

    After the prescribed once a day usage of this medication for a few weeks, the cough did become more manageable and less severe. I have been using this treatment for about four weeks now, but my coughing has not completely abated.

    After reading your article, I think I will look into this more natural treatment of using B12 tablets, which are readily available here (over the counter) to see if this can better manage my persistent, dry cough in a gentler, more natural manner.

    Stephen H

  9. Margaret 22 January 2011 at 4:01 pm #

    If you have pernicious anaemia, you cannot supplement B12 by taking a tablet orally. Pernicious anaemia is an autoimmune disease where the body is producing antibodies which destroy the intrinsic factor which is necessary for the gut to absorb B12. That is why you were given intramuscular injections of B12 by your GP. It may be possible to supplement B12 via sublingual B12 which is absorbed via the mucosa or tissue lining the mouth.

    Also worth considering that the opinion of many interested in evolutionary medicine is that many autoimmune diseases (not just coeliac disease) are triggered by gluten.

  10. patricia 22 January 2011 at 11:42 pm #

    I always thought it was frowned on to take a single B vitamin? Do I need to take a “complete” B vitamin in order to gain the benefits of B12? or if not, where can I buy B12 in the UK? thanks

  11. Chmee 23 January 2011 at 10:02 pm #


    Yes, I know what pernicious anaemia is – I read lots about it….. 🙂 In fact, it seems you can take it orally; you just need to take very large doses. Some of it, despite the lack of intrinsic factor ( the ‘carrier’ moelcule that takes it from the gut to the bloodstream ) gets through, and since you only need a few mcg a day, it works. Pubmed will give you lots of papers supporting this, and as I said, it is very common in some other countries, e.g. Scandanavia.

    I hated the injections, as they were scheduled every 12 weeks, but by about week 8, I started to feel horrid again. So I looked into it, told my doctor what I was planning and started oral B12. My doctor ( who really is marvellous btw ) thought it worth a try and agreed to keep checking my levels. 1000 mcg a day sent me over the top of the normal range – just – and taking one every other day gave a level that was still a little high in his opinion, so I’ve settled at around 1000 every 4 or 5 days, depending if I remember etc ! It took a few months. I usually just let them dissolve under my tongue, as you suggest, but swallowing them gives much the same results. I don’t eat much by way of gluten incidentally, and avoid bread etc – other than on very rare occasions ( I just love home made garlic bread ! 🙂 ). I follow a low carb diet.


    Lots of things are ‘frowned on’ – usually by the same people who gave us the current appalling nutritional guidelines, so I really don’t care what they think. I do care that there is reputable evidence ( as in proper published studies; ideally RCTs etc ), and in this case there is. As a general principle, I would much rather get what my body needs from my diet, but in this case I can’t. Though I do eat red meat, shell fish, other fish ( salmon is good), and so on.

    I really dislike liver, which would be best of all for B12. Many years ago, prior to injections of B12, if I remember correctly, the only hope for people with pernicious anaemia was to eat lots of this ( As in pounds. Every day. Raw…….). The B12 I use is by Solgar, and Google wil give you suppliers in the UK. It’s not expensive and delivery usually only takes a couple of days. Let me know if you can’t find a reliable supplier.

    To both you: I hope this helps.

  12. Sandra Lawrence 1 February 2011 at 9:56 pm #

    I have a consistent dry, tickly chronic cough, which for the past 31/2 years which seems to be getting more intense and sometimes associated with mild shortness of breath.
    I have done various chest xrays, CT scan which is all clear. I have taken various medications, using inhalers etc. without any success. I am now really very anxious to ge a solution to this problem since this cough has taken over my life.
    Any suggestion is appreciated.

  13. Daniella 25 March 2011 at 12:56 am #

    Very good book ” could it be b12″ by Sally pacholok and Jeffrey Stuart , one of those rare books everyone should read.

  14. Phil Ambler 2 September 2011 at 9:30 pm #

    Since all our vegies are sprayed with pesticides that break down vit b12.
    Since we rinse off more by washing our greens.
    Due to a cultural lack of village life and pigshit mud wrestling;walking barefoot in the dairy;or picking mushrooms in season:
    “All Western Industrialised populations are vit b12 deficient.”

  15. Gwen 21 September 2011 at 9:46 pm #

    I have a cough when laying down that produces clear phlegm. I’ve been to an ENT who said it was Reflux, Pulmonary doc did a breathing test and found acute asthma, and recently had blood work where my GP found B12 deficiency. I googled cough and B12 and was shocked at where it took me. I am shocked that I actually found a clear reason for this and will try the B12. Interesting also is that I have psoriasis an that is also linked to autoimmunity disease.


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