Coughs, colds, and the “appealing but mistaken concept of boosting the immune system”

I came down with a nasty cold before the holidays – so bad that I briefly thought I had the flu, and was cursing myself for having waited so long to get the flu shot, which I’d received just before the symptoms began.

Amidst all the sniffling and groaning and self-pitying, it occurred to me that, while we’ve spent a lot of time this season talking about influenza, we haven’t much covered the common cold.  There are reasons for that of course.  Though sometimes as unpleasant as influenza, colds rarely kill.  There’s also no organized movement attempting to subvert public health initiatives related to the common cold, as there is with the flu.  So the stakes are certainly lower.

Yet there are an awful lot of cold products on the market, and as is often the case when symptoms are inherently self-limiting, many of these treatments are highly questionable.  That goes for pharmaceutical products as well as alternative ones, as the following roundup of popular remedies illustrates:

  • Vitamin C – the grand-daddy of all cold treatments, taking mega-doses of Vitamin C to fight the cold was popularized by Nobel prize-winning chemist Linus Pauling in the 60’s, proving Ben Goldacre’s maxim that having a PhD is just a risk factor for being correct.  Subsequent research over the last 50 years has failed to show any effect – a fact that has been widely covered yet has done only minor damage to the treatment’s appeal.
  • Echinacea (Flu Shield, etc.) – popular when I was still wearing Eddie Bauer plaid, Echinacea has very much lost its lustre of late.   The evidence was never great, but the recent (and thankfully, widely reported) study published in the Annals of Internal Medicine seems to put the nail in the coffin.
  • Cold-FX – this ginseng-based product promises to strengthen the immune system to “stop colds & flu in their tracks”.   Scott does a detailed review over at Science-Based Pharmacy, noting that the clinical evidence is mixed, and all of the studies have methodological problems, so it’s hard to separate the data from the noise.  However, even on the most charitable read of the evidence, most people won’t get much benefit out of the product for the $400 worth of pills it takes to prevent a single cold.
  • Oscillococcinum – the new “it” remedy promises cough, cold and flu relief for children with “no known side-effects, no risk of overdose, no contra-indications”.  No wonder –  it’s a 200C homeopathic dilution of duck heart and liver – that’s one part in ten thousand trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion.  As Scott points out while taking Health Canada to task for approving this product, “It is mathematically impossible that there is any of the original fermented goo in the final product.”
  • OTC Remedies for Children – Oscillococcinum’s new children’s version is largely the result of recent evidence showing that OTC pharmaceutical remedies (expectorants, cough suppressants, decongestants, and first generation antihistamines) provide no benefit in children.  Children’s doses of these medicines have now been pulled from pharmacy shelves, leaving a void in the market that Oscillococcinum has been all too happy to fill with lactose.  (And they say we skeptics only question natural remedies.  I guess my cheque for being a Big Pharma shill won’t arrive this month.)

Of course, people are free to spend their money on unsubstantiated treatments if they like.  There’s little risk in any of these treatments (with the exception of the children’s OTC products), and I’m the first to admit that cold symptoms are precisely the type that the placebo effect works best on.  In some ways ignorance may indeed be bliss, and my intent today is not simply to write a consumer protection piece.  Rather, what I’m hoping to explore is the incorrect assumption at the heart of these treatments – an assumption that’s repeated widely and without question both in the media and in the individual discussions we all have about health and illness.

Immune to Evidence

With the exception of the now-removed children’s OTC products, all of the above remedies have one thing in common: they claim to work by boosting the immune system, making it better able to fight off viruses before they can cause unpleasant symptoms.  This seems like an inherently reasonable proposition – we have a natural defense system, so why not help it do its job better?

And in fact, that’s exactly what we do when we vaccinate.  By injecting dead or critically weakened viruses into our body, our immune system does indeed learn how to fight that virus when it later sees it live and full strength.  Of course vaccination isn’t feasible for the common cold – between the healthcare costs and the known risks (however rare), it’s hard to make a case for public health intervention to avoid a benign, if unpleasant, illness.

But immune boosting in common parlance (and in cold product marketing materials) is different from vaccination in a very critical way.  Vaccination teaches the body how to respond to a specific threat, whereas these cold products claim to boost the immune system’s general ability to respond to any threat.  And that’s where the marketing disconnects from the science.

I was first made aware of this disconnect by the inimitable Mark Crislip, an infectious disease specialist who writes over at Science Based Medicine, in a post from last September.  (Skeptoid later took up the topic, but relied primarily on Mark’s original).  While I have immense respect for Mark, and am inclined to trust his opinions within his field of expertise, I have to admit I was reticent to accept his assertions because they fly so directly in the face of the “received wisdom” on the subject.  So I made a mental note to look more closely at the data at some point…which I then promptly forgot.  (Maybe I should have taken my Ginko biloba).

I was reminded again when a co-worker, commenting on my aforementioned cold, began to espouse the wonders of Oil of Oregano — which, he assured me, was the best immune booster on the market.  He always takes it at the first sign of cold, and he never gets sick.   I knew from the detailed review Scott did over at Science Based Pharmacy that Oil of Oregano was “all anecdotes, no science”, so I smiled politely, thanked him for his advice, and finally finished what I’d intended to do when I read the Crislip article.

Turns out the fact-checking on this wasn’t all that hard – I had to look no further than Harvard Medical School’s 2010 publication, The Truth About Your Immune System: What You Need to Know, from which the title quote is taken.  Concise and readable without shying away from the technical details, the report provides a comprehensive overview for the layperson of what the evidence says — and doesn’t say — about how the immune system works and what you can do to improve its function.

Enticing, But Elusive

The report is unequivocal about the current state of the science: simply put, there is no known way to boost one’s immune system other than vaccination.  While admitting that there is indeed tantalizing research positing a connection between immune function and various aspects of diet and lifestyle, all of it is preliminary and researchers don’t yet know enough about “the intricacies and interconnectedness of the immune response” to recommend anything more than general healthy-living strategies.  Taking aim specifically at marketers that claim otherwise, the report states:

Many products on store shelves claim to boost or support immunity.  But the concept of boosting immunity actually makes little sense scientifically.  In fact, boosting your immune response is not necessarily a good thing.  A hyperactive immune response underlies a number of major diseases, including diabetes, rheumatoid arthritis, and lupus.  It is also responsible for allergic reactions to ordinary nontoxic substances.

Even if it were a good thing, attempting to boost the cells of the immune system is especially complicated because there are so many different kinds of cells in the immune system that respond to so many different microbes in so many ways.  Which cells should you boost, and to what number?  So far, scientists don’t’ know the answer.

The report then goes on to take a close look at the evidence on a wide array of putative immune boosters.  Here’s what it has to say:

  • On Vitamins: “So far, there is no evidence that taking extra amounts of any vitamin will boost the immune response or protect against infection in any way.”
  • On Diet: “There are still relatively few studies of the effects of nutrition on the immune system of humans, and even fewer studies that tie the effects of nutrition directly to the ability to fight off infectious disease.”
  • On Exercise: “a direct beneficial link hasn’t been established”
  • On Probiotics & Prebiotics: “a direct connection between taking these products and improving immune function has not yet been made scientifically.  In fact, changing the balance of bacteria already long established in the human gut may not even be possible.”
  • On Herbs & Supplements: “Although a few preparations have been found to alter some components of the immune function, thus far there is no evidence that they actually bolster immunity to the point where they protect against infection and disease….Scientists don’t know, for example, whether an herb that seems to raise the levels of antibodies in the blood is actually doing anything beneficial for the overall immunity.”    Similar conclusions are made for the supplements they cover specifically in the report — Astragalus, Echinacea, Ginseng, Licorice Root, and Umckaloabo.

So what’s a body to do?  With the claims of marketers (and newscasters) in tatters, the report lists six steps you can take to help your immune system.  It’s instructive that five of them – good hygiene, food safety, clean water, insect repellent, and safe sex – are about avoiding pathogens entering your body in the first place, rather than improving your body’s response.  The sixth of course is vaccination, still the only known way to make your immune system work better.

Which leaves the cold sufferer reduced to the old standbys – rest, liquids, and the comforting knowledge that it will all be over soon.  For as an Egyptian physician I once knew told me, “In my country, they say that without treatment a cold will last for seven days.  With treatment — a week.”

Photo courtesy of William Brawley under Creative Commons.

27 Responses to “Coughs, colds, and the “appealing but mistaken concept of boosting the immune system””

  1. Blondin says:

    Thank you for this article – a very important message nicely encapsulated.

    Isn’t it ironic that there are so many purveyors of “natural healing” products who would have you believe that you need their help to improve your body’s (already quite robust) natural ability to protect and heal itself.

  2. Thomas Doubts says:

    S’funny how people equate lack of symptoms with a strong immune system. Last week, as she snuffled, sneezed and leaked mucous, a colleague lamented her “terrible immune system” for not working properly. When I pointed out that the cold symptoms she was experiencing showed that her immune system was hard at work, she seemed confused by this. Ho-hum, Mark’s tagline from Quackcast appears to hold water: everyone needs more Mark Crislip…

    • Erik Davis says:

      It’s a complicated area, and I think most people are simply uninformed — I certainly was until I spent the time researching it. The concept is not at all implausible, and it’s become one of those things that’s repeated constantly and casually from so many sources without question that it’s hard to see. But it occurred to me that if more attention was given to the flaws in the basic concept of immune boosting, it might cause more people’s warning bells to go off when specific products claim to do it.

  3. Composer99 says:

    The conceptual error involved in believing in ‘boosting’ an otherwise acceptable immune system is hinted at in the Harvard report.

    Sure, you can boost your immune system. If you want to have one of these.

    (I felt more or less safe in linking to Wikipedia since 17 out of 24 references had PMIDs (whew!) and most of the rest were links to other medical journal articles/CDC documents. Surprisingly there was a reference to an episode of House.)

  4. Kyle says:

    I’m glad that you remembered to include oil of oregano. It seems to be the new snake oil of choice in my neck of the woods. Frankly, I can’t stand the smell of the stuff, but then again, that may be why people think it works? Just a new spin on the old “If it tastes bad, it must be good for you”?

  5. Undoubtedly, the best immune boosters will be the all natural products that have been used by the Chinese or Native Americans for hundreds or even thousands of years. Especially the ones that have quantum effects, exist outside of the current scientific paradigm, are scientifically proven, but scientists don’t want us to know about.

    Did I miss anything?

    • gmcevoy says:

      “but scientists don’t want us to know about” because they’re Big Pharma shills.

      Next time I’m at the Outlaw’s cottage near Pugwash, I’ll wave.

  6. crf says:

    People might like to read these posts by Yoni Freedhoff on companies’ “badvertizing” the immune-boosting prowess of their wares.

    The Canadian Medical Association sells Echinacea for pediatric flu prevention!
    Badvertising: Mott’s Fruitsations miracle sauce
    Antioxidant Immune Protecting Grape Juice

  7. Skeptical of your skepticism says:

    “Boosting your immune system” is a vulgar phrase that may not accurately reflect the action undertaken. That you chose to focus on this specific phrasing in order to build up a straw man indicates to me that you are biased in your approach of the subject.
    First, one would need to know what the optimal level of an immune system is. Then, one would evaluate if an individual’s immune system is at a less than optimal level. If that is found to be the case, Vitamin C or Vitamin D or other “treatments” might “boost” the immune system back up to a normal level, by alleviating a deficiency.
    Or maybe you’re skeptical of Vitamin Cs ability to treat scurvy, as well…
    Similarly, Oil of Oregano might free up the immune system to fight the cold infection by killing other microbes and bacteria that may be around. Or, you could go ahead and be skeptical of carvacrol’s antiseptic and antimicrobial properties.

    Truth is, I just stumbled across this site, and you sound like a bunch of shills. You’re not skeptical of any pharmaceutical or orthodox treatment, even those that are recalled, discontinued or admitted to having been dangerous.

    So, go ahead and ridicule your co-worker and all those who would be curious to find out more about treatments, nature and how we fit in. You’ve shown them all! By linking to a “detailed review” that details all the things not known, you’ve shown them that we know oregano doesn’t work! Brilliant!

    • Erik Davis says:

      I didn’t ridicule my coworker — in fact, I think I said I did the exact opposite. As for why I chose to look at immune boosting as a concept, I think I also explain that in the article — it’s because that’s what marketers of these products claim they do. I didn’t just pick it out of thin air as a way of mounting a gratuitous attack as you suggest — this is what they say, so this is what I addressed.

      And you’re right, Oil of Oregano might “free up the immune system to fight cold infection by killing other microbes and bacteria that may be around”. Or it might not, and right now there’s no actual evidence to support your contention. Until there is, I’m personally not going to put much stock in it. Show me a replicated, well-powered randomized controlled trial that shows an effect and I’ll gladly change my mind.

      And that’s because, far from being a pharma shill, I couldn’t care less whether it’s produced by Glaxo or picked off a tree in your backyard…if it actually works. As evidence, I’ll point you to the part in the article (which I’m increasingly thinking you might not have actually read) where I talk about the children’s OTC cough and cold remedies that have been removed from the market.

      • Same guy says:

        Fine, you “talk about” the children’s medicines that were removed from the market. Did you write an article questioning their efficacy beforehand? Or did you support them back then, based on well-powered randomized controlled trials that showed an effect? What about Vioxx? How many skeptical articles did you write about that, before they recalled it? I’m guessing none, because it had been “rigurously studied” before being approved for distribution. Right?

        One more question: did the natives have double-blind controlled studies that showed the efficacy of Vitamin C against scurvy? I’m not sure they did. And yet, it worked! But I’m guessing that if you had been part of Columbus’ crew, you would have rejected such primitive, superstitious treatment with no actual evidence to support the contention.
        Bottom line, if something works, it does so even without FDA approval. The studies don’t give a product its efficacy, they just (re)discover it. Hence, lack of studies, which can be attributed to economical or other reasons, don’t negate a products efficacy either.
        When studies do appear that show the immune-system supporting properties of allicin, you jump on the bandwagon, but my great-grandmother didn’t need any four-eyed scientist to tell her that garlic helped her avoid colds.
        I guess it comes down to personality. Some people will try, experiment alternative, plant-based, potential treatments, while others will wait to be spoon-fed the official view as to what works. I find the latter more cowardly, and it may be why some of those people will put down plant-based medicine every chance they get, to make themselves feel better. :P

      • Same guy says:

        Also, a word about the “immune-boosting concept”. Yes, that is the verbiage the marketers of these products use. But is it the point they’re trying to get across?
        When YOU hear immune-boosting, you think of a hyper-active immune system. That it was boosted from an optimal level to a dangerous, enhanced level.
        Is that really the point THEY’RE trying to get across with their aurally pleasing soundbyte? Maybe, when THEY talk about “boosting your immune system”, they mean that the modern diet and lifestyle leaves the immune system of average people working at a reduced level. “Boosting it” could, in this context, mean bringing it back up to a normal operation level. To support, not “improve” your body’s (already quite robust) natural ability to protect and heal itself, as Blondin puts it in the first message.

        So, if you’re attacking their language skills, the words they use, and avoid challenging the point they’re trying to get across, you’re just building up a straw man argument, really.

        Anyway, I hope you’re not offended. I see myself as a pretty adept critical thinker and I always appreciate debating with smart individuals.

      • Erik Davis says:

        Same guy: Certainly not offended, and I agree that Vioxx is an instructive case study, though perhaps for different reasons. Consider this: like all prescription pharmaceuticals, Vioxx underwent years of research, followed by phased trials, followed by independent government review of the research and trial results, ultimately leading to approval. And after all of that, there was still a significant adverse effect that wasn’t caught by the process — an effect that was only caught because clinical trials continued after approval. Without that kind of research, the increase in heart attacks would probably have faded into the background noise, and it’s extremely unlikely anecdotal evidence alone would have caught it.

        For better or worse, we’ve decided as a society to outsource our pharmaceutical development to private enterprise. Those organizations will sometimes fail to exercise appropriate judgment when weighing risk vs. return, and occasionally they’ll do a lot worse than that. But the point here is that the more bad faith you attribute to Merck in the Vioxx example, the better the story becomes for the science and approvals process themselves — something must be very right if they could overcome the kind of deliberate deception I’ve seen attributed to Merck by some of their critics.

        Compare all of that to the natural health industry, which has none of that research and none of that oversight. How are dangerous natural remedies spotted and removed from the market? After all, natural doesn’t mean safe — there are lots of poisons in the natural world, and any pharmacologically active agent, natural or synthetic, is going to have a risk profile. Given the choice between a well studied synthetic pharmaceutical and an unstudied natural one, I’ll choose the one with the better data trail any day. Both methods will be wrong some of the time as Vioxx proves, but the latter will be wrong a lot less often. We didn’t always have the luxury to make this choice, as your scurvy example illustrates, but we do today.

        I think Vitamin C for scurvy is also a really instructive case study, incidentally, because it’s one where the anecdotal evidence is validated by clinical trials. There are lots of others — indeed, a good chunk of modern medicine has been the result of testing traditional remedies with better methods, and proving that some do in fact work. Yet, if I’m reading you right, you seem to jump from those specific examples to a a general principle that anecdotal evidence / traditional remedies are better than scientific evidence / clinically-proven remedies — and that’s simply not the case. There are lots of traditional remedies that have been tested by researchers and shown pretty clearly to either do nothing or have an unacceptable safety profile.

        Which is not to say your grandmother shouldn’t eat garlic — I eat lots of it — just that she shouldn’t choose the Shrimp Scampi over the flu shot. While it’s theoretically possible that garlic provides some protection, there’s zero scientific evidence to support it, and I wouldn’t trust an “argument from antiquity” against catching and spreading influenza. Compared to a proven vaccine with 60 years of data behind it — well, there is no comparison.

  8. Thomas Doubts says:

    Good article Erik, and a healthy discussion. Just for the sake of accuracy though, scurvy is caused by a deficiency of Vitamin C. It is neither microbial nor virological, and so falls outside the immune response. As support for the “Vit C dosing boosts the immune system” argument, it fails.

  9. Same guy says:


    I didn’t want you to think that I disappeared. I appreciate you taking the time to answer my messages and I now understand better where you’re coming from.
    The main reason I protested against part of the article is because it seemed to imply that lack of proof of an effect constitutes proof of a lack of an effect. That constitutes a logical fallacy, especially when research was admitted to be lacking. But most of this was in the linked page, not the main article.


  10. Same guy says:

    Kim Hebert, we should absolutely attempt to verify your claim before dismissing it. Fortunately, that has been done, as throughout history, mankind has attempted to keep tigers away with the use of rocks. Their evidence is merely anecdotal, but still, it seems to point towards the fact that most rocks, in the state they are usually found in nature, do not usually possess the property of keeping tigers away.
    However, those same rocks can potentially be imparted with the property of driving tigers away, were enough force applied to each rock and multiple rocks used in a cumulated effort.
    If I was to go to another planet where I lacked the accumulated knowledge of thousands of years of history, I might find the need to inquire about the properties of certain rocks, plants or minerals to keep away some local pests I might potentially encounter.


  1. [...] Skeptic North’s Erik Davis looked at the evidence for some of the most popular cold remedies in a recent post, and the results aren’t great. “[S]imply put, there is no known way to boost one’s immune system other than vaccination.” [...]

  2. [...] Davis at Skeptic North posted this excellent review of “immune boosting” supplements and the medical journals that have weighed in on them. [...]

  3. [...] I should mention that I found both of these links on Skeptic North’s article, Coughs, colds and the “appealing but mistaken concept of boosting the immune system” [...]

  4. [...] too coherent, and no one has been compared to Hitler. But it’s not a straw man either (look here, here, and here for recent examples), merely a distillation of an argument I’ve seen made [...]

  5. [...] Hostile Bid For Illumina Ups Stakes In DNA Tech Race (this could be a disaster for Illumina) Coughs, colds, and the “appealing but mistaken concept of boosting the immune system” Science And The State Of The [...]

  • Erik Davis

    Erik is a technology professional based in Toronto, focused on the intersection of the internet and the traditional media and telecommunications sectors. A reluctant blogger, he was inspired by the great work Skeptic North has done to combat misinformation and shoddy science reporting in the Canadian media, and in the public at large. Erik has a particular interest in critical reasoning, and in understanding why there’s so little of it in the public discourse. You can follow Erik's occasional 140 character musings @erikjdavis