Skeptical Raptor's Blog hunting pseudoscience in the internet jungle

Supplements to treat the common cold–myth vs science


cold-cureIt’s getting colder outside, and if you go into any pharmacy, grocery store, chemist, or superstore, you will find literally a dozen or more homeopathic, herbal, or other unproven lotions and potions to prevent or treat the common cold, or rhinovirus. These supplements are a significant part of the annual US$108 billion dollar supplement/nutraceutical industry. 

These alternative medicine (so named because there is no scientific evidence supporting their efficacy, let alone safety) products make claims that are so wonderful, many people take them. Then they themselves tell their friends how fast they got rid of their cold. Or that their cold wasn’t as bad after taking the supplement.

The problem is that determine the length and severity of the course of the common cold is entirely subjective. Since the disease is rather mild with few serious complications, it’s hard to determine when it exactly stopped and started, and how bad it was.  The common cold tends to resolve itself without external help, but there really isn’t much you can do to make your immune system attack that cold faster.

 

Below are some of the most common and well-known cold treatments (there isn’t enough time to review them all), along with what real science says about them in high quality systematic reviews in Cochrane reviews and other high impact medical journals:

Echinacea. Here’s a systematic review in the Cochrane Reviews that concluded: “Beneficial effects of other Echinacea preparations, and Echinacea used for preventative purposes might exist but have not been shown in independently replicated, rigorous RCTs (randomized controlled trials.” Here’s a study in the very high-impact in the New England Journal of Medicine that concluded: “The results of this study indicate that extracts of E. angustifolia root, either alone or in combination, do not have clinically significant effects on infection with a rhinovirus or on the clinical illness that results from it.” So no clinical evidence has been found to support use of the herb in preventing or treating the common cold. 

Amusingly, Echinacea’s modern-day use as a cold remedy dates to the 1960′s when a Swiss herbal supplement maker who, during a trip to South Dakota in the 1960s, was erroneously told echinacea was used for cold prevention by Native American tribes who lived in the area. In other words, its current use wasn’t even based on a myth or some legend, but on a mistake.

Vitamin C. According to a systematic review in the Cochrane Reviews“The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified.” Admittedly, the did find some evidence, never in the form of a double blind or randomized clinical trial, that vitamin C may reduce the length of a cold. Given the low cost of vitamin C, it probably does no harm to try it, but there is absolutely no evidence that it has a prophylactic effect nor will it reduce the severity of the cold. Downing a handful of vitamin C every day probably will do nothing for you.

duck-quackOscillococcinum is a homeopathic preparation which derived from duck liver and heart, diluted to 200C, which means 200 1:100 dilutions–this means there is one molecule of duck guts for every 10^55 cubic light years of water. In other words, the odds are there isn’t a single molecule of duck guts in any oscillococinum pill you swallow. And there isn’t any logical explanation of any possible mechanism that would allow one to conclude that duck offal has an effect on viruses. Based on this ridiculous figurative and literal quackery (get it), one would not be surprised by a Cochrane systematic review that concludes, “There is insufficient good evidence to enable robust conclusions to be made about Oscillococcinum(®) in the prevention or treatment of influenza and influenza-like illness.” And given the lack of plausible physiological effects, don’t expect good evidence to appear out of nowhere.

Garlic. According to another systematic review from Cochrane, “there is insufficient clinical trial evidence regarding the effects of garlic in preventing or treating the common cold. A single trial suggested that garlic may prevent occurrences of the common cold but more studies are needed to validate this finding. Claims of effectiveness appear to rely largely on poor-quality evidence.” Please don’t fall for the Argument from Ignorance logical fallacy, that is, since we can’t prove that garlic doesn’t work, that it could work. Those who are making the claim for garlic’s efficacy need to provide evidence, and according to this systemic review, they haven’t.

Zinc.  The evidence about zinc and colds are a bit more nuanced. In the opinion of a recent Cochrane review, “Zinc administered within 24 hours of onset of symptoms reduces the duration of common cold symptoms in healthy people but some caution is needed due to the heterogeneity of the data.Regarding prophylactic zinc supplementation, currently no firm recommendation can be made because of insufficient data. Although I have stated many times that Cochrane reviews can be an “authority” in science based medicine, I have found that sometimes they make ridiculous conclusions based on weak evidence. As I always recommend, you need to review the data, and in this case, they used only 5 small studies to come to the positive parts of the recommendation. And that’s just not a very good systematic review. A review of Cochrane’s review (yes that happens) stated that “we are concerned that the potential threats of such biases in the review have not been considered carefully enough. We therefore feel that readers should be cautious in their interpretation of the evidence presented in owing to the possible threat of reporting and publication biases on the results of their Cochrane review.”

Since the evidence seems to be somewhat equivocal, it would appear that taking zinc for the cold couldn’t hurt.  However, “the FDA has received more than 130 reports of loss of sense of smell associated with the use of these three Zicam products. In these reports, many people who experienced a loss of smell said the condition occurred with the first dose; others reported a loss of the sense of smell after multiple uses of the products. In other words, zinc has debatable efficacy, yet may destroy your sense of smell.  That’s a bad benefit to risk ratio, especially since your sense of smell is critical for everything from determining if your food has gone bad to being warned of a natural gas leak. Given the very real and very dangerous risks, why would anyone take a potion that has limited evidence of efficacy?

Chinese medicinal herbs. Once again, let’s turn to a summary from Cochrane: “The risk of bias was so high that the evidence did not support using any Chinese herbal preparation(s) for the common cold. Well-designed clinical trials are required.” 

So, we can conclude what? Well, of the best-known alternative medicine treatments for the common cold, none have anything more than very weak evidence in support, and even that evidence is based on some badly biased studies. Furthermore, the one thing that might work, zinc (and that evidence is also extremely weak and unrepeated) might have some serious risks to its use.

Airborne. This is a dietary supplement that contains herbal extractsamino acidsantioxidantselectrolytes, synthetic vitamins, and other ingredients that is heavily marketed as supporting the immune system against colds and other diseases. As I’ve written, “supporting the immune system” is just not possible, except in very rare cases of chronic illnesses or medical treatments that might suppress the immune system. The immune system is very powerful and extraordinarily complex, and there simply isn’t a quick and easy way to make it work better (other than vaccinations, of course). Furthermore, the US Federal Trade Commission, fined the manufacturer of Airborne (note: the current US government shutdown may make this link dead temporarily) for US$7 million stating that “there is no competent and reliable scientific evidence to support the claims made by the defendants that Airborne tablets can prevent or reduce the risk of colds, sickness, or infection; protect against or help fight germs; reduce the severity or duration of a cold; and protect against colds, sickness, or infection in crowded places such as airplanes, offices, or schools.” 

So what do you do about colds? Really, the CDC makes the best recommendations for treating the common cold:

  • Get plenty of rest
  • Drink plenty of fluids
  • Use a clean humidifierExternal Web Site Icon or cool mist vaporizer
  • Avoid smoking, second-hand smoke, and other pollutants (airborne chemicals or irritants)
  • Take acetaminophen, ibuprofen or naproxen to relieve pain or fever (read about what is safe to give your child)

So, don’t waste your money on the alternative medicine nonsense!

Key citations:

 

Comments (3)
Powered by WordPress 3.9.1
Don't forget to subscribe to this blog through any the services in the right sidebar.