Vitamin C remains a popular natural treatment for the common cold; however, this practice is often disparaged and widely discouraged on the Internet. A brief Internet search of various websites which make health information available to the public reveals that none of the experts are very enthusiastic about you taking vitamin C for a cold. WebMD, for instance, warns that while you may be, in their words, “tempted” to take vitamin C for a cold, the experts have found this has “little to no benefit.” The Mayo Clinic sagely advises that it won’t help you “for the most part.” On the other hand, Harvard Health Publishing concedes that it may be “marginally beneficial,” whilst Healthline puzzlingly asserts that there are no “reliable studies” proving that vitamin C is effective for colds before summarizing the results of a meta-analysis which found that vitamin C can reduce the length and severity of colds. The consensus seems to be that while it seems like there might be something to it, nobody actually recommends that you try it. This cagey, somewhat guarded conclusion stands in contrast to the one reached by mainstream media outlets, pop science websites, skeptic blogs, and most of the various other clutter that one finds strewn across the Internet, which is that taking vitamin C for a cold is an utter myth, yet another bogus alternative health practice which has been thoroughly debunked by modern science. So why do so many people continue to insist that vitamin C helps them get over a cold, and why has the idea become so controversial?
The first inkling that vitamin C might be beneficial to the immune system came shortly after it was (re)discovered to be the cure for scurvy, or in other words the 1930s. It had long been known that most people who developed scurvy did not die of scurvy itself, but of pneumonia. It had also long been observed that both children and adults with scurvy were excessively prone to upper respiratory infections (Hess, 1932). It was even known that epidemic pneumonia in populations suffering from scurvy could be cured with foods that were high in vitamin C (Robertson, 1934). So since the very beginning, it was known that whatever causes scurvy also seems to cause upper respiratory infections and that you can treat such infections with the same agent that you would use to treat scurvy. As vitamin C began to be studied in greater depth, it was discovered that immune cells store large quantities of vitamin C, probably to quench free radicals generated while fighting an infection, and that during an infection these stores are rapidly depleted. Early animal studies showed vitamin C to have a clear benefit against a variety of infections (Hemila, 2017), and a few early human studies seemed to confirm this, such as a British study which found that colds last twice as long when people are deprived of vitamin C (Bartley et al., 1953). So it seems inexplicable that so many health websites would still discourage you from taking vitamin C for a cold, especially given that as a supplement it is remarkably safe and generally inexpensive. This is because despite the inherent logic and early evidence, the results of randomized controlled therapeutic trials have been frustratingly mixed, and science always errs on the side of not using natural medicine. But it still leads one to wonder, why? If scientific evidence should be taken as the gold standard of truth, why does it so often contradict itself, and which side should you believe?
With the exception of some of the more polemical skeptic blogs, most serious sources will by now reluctantly begrudge that vitamin C does show, at least in some cases, a clear benefit for preventing colds, but most of them will tell you that this is only really true for people who engage in strenuous exercise (i.e., very few people overall). This is largely due to an influential 2013 Cochrane review. This review calculated that while taking vitamin C resulted in a paltry 0.98 absolute risk reduction among the general population (basically no effect), there was an appreciable 0.48 absolute risk reduction among “marathon runners, skiers, and soldiers in subarctic exercise” (Hemila and Chalker, 2013). In other words, taking vitamin C may halve your chance of getting a cold, but only if you are a warrior training in the arctic or someone who likes to run marathons (or a skier – but we’ll come back to that later). This is what led WebMD to conclude that while generally ineffective, vitamin C may prevent colds in those who are, as they put it, “in extremely good physical condition.” First of all, this is missing the point – it would seem to work best in people who are subjected to extremely stressful conditions, which are known to deplete the body’s vitamin C levels, not simply for people who are already in a state of extremely good physical condition. And what about those presumably very fit and athletic alpine skiers, whom the Cochrane review saw fit to exclude from the general populace and lump in together with arctic soldiers and marathon runners?
That study was performed in 1961 and involved 279 participants who were given one gram of vitamin C or placebo daily for seven days. The vitamin C group experienced less than half as many days of training lost to illness and reported less than half as many cold symptoms overall (Ritzel, 1961). Because these subjects were alpine skiers, this result has been used to further support the limited conclusion that while vitamin C may be effective, this is only true for strenuous athletes, you know, like Olympic skiers training at the highest level in a harsh environment. But what makes this all so spurious is that the 279 “alpine skiers” in this study were, in fact, schoolchildren attending a weeklong camp at a Swiss ski resort! But yes, for the purposes of this review, let’s lump these schoolchildren together with marathon runners and soldiers training in subarctic conditions to conclude that vitamin C is useless to regular people and will only prevent colds if you’re exceptionally fit or training in extremely harsh conditions (like those of a Swiss chalet, for instance). This type of disingenuous obscuration is just one example of how even respectable scientific reviews can attempt to conceal the true benefits of natural therapies or addend them with absurd qualifiers that would make them seem useless to the average person.
Wikipedia® has an entire entry devoted to vitamin C and the common cold, in which after parroting the notion that vitamin C is only of benefit during periods of extreme physical stress (as may be experienced while sipping hot cocoa after learning to zigzag down a steep slope), it claims that there “is no effect” to taking large doses of vitamin C to treat the common cold. But the article which Wikipedia cites to support this claim is a meta-analysis which did not conclude that there was no effect, as Wikipedia dishonestly states, but concluded rather that there was “no consistent effect” (emphasis mine). This does not mean there was no effect – it means some of the studies in the meta-analysis did show an effect, while other studies did not; hence, the effect shown was not consistent. As it happens, this particular study cited by Wikipedia is the very same Cochrane review which asserted that elementary schoolchildren being taught to ski in Switzerland are generally held to the same rigorous physical standards as soldiers preparing for arctic warfare. They must turn out some great skiers! The review was forced to conclude that there was “no consistent effect” because there were, in fact, several studies included which showed that there was an effect, including some from an earlier meta-analysis that arrived at the opposite conclusion.
The very first meta-analysis of vitamin C for treating colds, long preceding this Cochrane review, was conducted by the infamous Nobel laureate Linus Pauling in 1971. It involved the four then-extant, randomized, placebo-controlled trials using high-dose vitamin C to treat the common cold, and it concluded (with a p-value <0.00003, or basically beyond a shadow of a doubt) that vitamin C was an effective treatment for the common cold. Following this, he published a book with claims to that effect, and interest in vitamin C as a treatment for the common cold surged, with many new studies subsequently emerging. Then, in 1975, three new meta-analyses were published, all suspiciously within months of each other, which arrived at the very opposite conclusion. As a result, the idea was largely abandoned by the mainstream medical community. These three meta-analyses, which were published all at once and together effectively ended all interest in treating colds with vitamin C, did so despite being heavily criticized at the time and have since been proven to contain, as the author of one review put it, “serious inaccuracies and shortcomings” (Hemila, 1996).
Why does there always seem to be so much confusion and conflicting results from science as regards holistic therapies, and why is mainstream science so quick to discard natural therapies even after clear evidence emerges to prove them? Historically, there has at times been used a general method to discredit alternative therapies by the mainstream scientific community. Basically, the formula goes like this:
- Deny the natural therapy works, until a randomized controlled trial (RCT) comes out finally proving that it does.
- After this RCT comes out, conduct more RCTs in order to “confirm” the results of the first one, but this time use a much lower and largely ineffective dose than did the original study.
- Claim that the evidence is mixed; call for large-scale meta-analysis.
- Conclude from the large-scale meta-analysis that there seems to be “no consistent effect.”
- Decry the natural therapy as not being evidence-based; ridicule anyone who says otherwise.
This is why, despite the fact that many early studies clearly showed vitamin C to be an effective treatment for colds, health websites intended for lay people and media outlets (many of which are paid for by ads from pharmaceutical companies) all continue to assert that this is not actually the case. The fact that the studies which do show a benefit are always older than the subsequent studies used to dilute and discredit them only makes the above formula more effective, as it will naturally be assumed that the older studies were somehow primitive and flawed while the newer, “more advanced” studies are more likely to be the accurate ones. However, we must be aware that whenever scientific research proves that a natural therapy works, a potential exists for conventional medicine to dilute the result with poor-quality studies, draw conclusions using ambivalent language that the media can easily misinterpret, or use spurious meta-analysis techniques to hide the true effect. The truth would seem to be this: your immune system needs vitamin C, lack of vitamin C causes upper respiratory infections, most sources of stress increase the body’s demand for vitamin C, getting sick increases the body’s demand for vitamin C, that up until it became popular for regular people to do so all the research was showing that vitamin C could prevent or reduce the severity and duration of the common cold … but the current scientific consensus maintains that this benefit only applies to people under conditions of extreme physical stress, like children attending a holiday camp at a Swiss ski resort.
Hess A.F. Diet, nutrition and infection. N. Engl. J. Med. 1932;207:637–648. doi: 10.1056/NEJM193210132071501.
Robertson E.C. The vitamins and resistance to infection: Vitamin C. Medicine. 1934;13:190–206. doi: 10.1097/00005792-193405000-00001.
Hemila H. Vitamin C and Infections. Nutrients. 2017;9(4):E339. doi: 10.3390/nu9040339
Bartley W., Krebs H.A., O’Brien J.R.P. Vitamin C Requirement of Human Adults. Her Majesty’s Stationery Office (HMSO); London, UK: 1953. A Report by the Vitamin C Subcommittee of the Accessory Food Factors Committee.
Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. The Cochrane Database of Systematic Reviews. 2013;1:CD000980. doi: 10.1002/14651858.CD000980.pub4.
Ritzel G. Critical evaluation of Vitamin C as a prophylactic and therapeutic agent in colds. Helv. Med. Acta. 1961 Jan;28:63-8. Accessed online at http://www.mv.helsinki.fi/home/hemila/T3.pdf
Hemila H. Vitamin C supplementation and common cold symptoms: problems with inaccurate reviews. Nutrition. 1996;12(11-12):804-9.
Ian Spohn, ND, is a naturopathic doctor who enjoys challenging the dogmas of both conventional and alternative medicine. He is a passionate supporter of the paleo diet and classical homeopathy.
Any homeopathic claims are based on traditional homeopathic practice, not accepted medical evidence. Not FDA evaluated.
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.