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Validating Vitamin C’s Role in the Prevention and Treatment of the Common Cold
October 5, 2009
Imagine for a moment that you are lying in bed; just having woke up from a night’s sleep. You’re throat is sore, you’re nose is a little runny, and your sinuses feel congested. Everyone knows the symptoms of the common cold: sneezing, coughing, runny nose, so within moments you conclude that you are getting sick, assuming that it is just a cold. This is not a bad assumption after all, since the common cold is the most common illness. In fact, more than one billion people in the United States are diagnosed with a cold each year (http://www.nlm.nih.gov/medlineplus/commoncold.html). According to researchers at the Mayo Clinic, the average adult is likely to have the cold two to four times a year, while children are generally slightly more susceptible to catching it (http://www.mayoclinic.com/print/common-cold).
According to Takkouche et al (2001), although the common cold is generally benign and acute, it is the cause of “approximately 30% of absenteeism from work in the United States” (page 38). The cause of the common cold is unknown. Since any one of 200 viruses can cause it, the manifestation of symptoms in each individual is slightly different. Although the cause of the common cold remains somewhat ambiguous, self-diagnosis and self-treatment of this illness is standard in American households.
Recalling back to my childhood, my mother would often recommend bed rest, Echinacea, some kind of cough syrup or decongestant, and she would always tell me to take extra vitamin C. This is not an uncommon suggestion. In fact, in a recent survey, “67% of the general public believes that taking vitamin C reduces cold symptoms” (Spiers, 2001, page 5). With that being said, millions of Americans overload their bodies with vitamin C with the hopes of reducing the duration of their annoying cold symptoms. Vitamin C can come from one’s diet, such as drinking lots of orange juice, or it can be supplemented via dietary supplements that contain very high doses of ascorbic acid. The image below shows the nutritional content of Airborne, a supplement that claims to boost and support your immune system with the goal of preventing illness.
As you can see, vitamin C is present in the greatest quantity proportional to the recommended daily value. The recommended dietary allowance (RDA) of vitamin C is 90 mg/day for adult males, and 75 mg/day for adult females (Naidu, 2003). Airborne contains 1,000 mg per dose, which is approximately 1,667% of the RDA! This proportionally high content of vitamin C in Airborne is not uncommon among the vast array of supplements that claim to offer help in protecting you from and fighting off illness. But where did this claim about vitamin C come from?
What is Vitamin C?
Vitamin C, also known as ascorbic acid, can be found in most fruits and green leafy vegetables. It is an essential vitamin to the health of humans. Its importance was discovered when sailors developed scurvy over long voyages across the sea. Since humans cannot synthesize vitamin C on their own, it must be supplemented through the food we eat (Naidu, 2003). When we ingest it in the food we eat (as a water soluble vitamin) it is absorbed. Importantly, vitamin C cannot be stored in the body like fat; it cannot be called upon for use at a later date. Thus, ascorbic acid must be regularly supplemented in our diets to maintain adequate levels.
With the abundance of fresh fruits and vegetables, and the vitamin-enriched content of many of the foods we eat today, health concerns that result from a lack of vitamin C in one’s diet have become quite rare.
What does Ascorbic Acid do for the Body?
Mechanisms by which it is Claimed to Prevent and Treat the Common Cold
Besides its ability to prevent scurvy, there is a lot of research that investigates other benefits of this vitamin. The most widely known health benefit of ascorbic acid is for the prevention and relief of the common cold. After his extensive research in the 1970s, Linus Pauling is considered to be the pioneer of the use of vitamin C for treating and preventing the common cold (Hemila, 1992). Pauling made a statistical analysis of four double-blind studies, and he showed that “mega-doses of vitamin C of 1-2 mg/day were efficacious in preventing colds and reducing their symptoms” (Spiers, 2001, page 4). Research indicates that vitamin C has been “shown to stimulate the immune system by enhancing T-cell proliferation in response to infection. These cells are capable of lysing infected targets by producing large quantities of cytokines and by helping B cells to synthesize immunoglobulin to control inflammation reactions This mechanism has been proposed for the enhanced immune response observed after administration of vitamin C during cold infections” (Naidu, 2003, page 4). But does vitamin C really help cure or prevent the common cold?
Ever since Pauling made his claims about the efficacy of vitamin C (and subsequently won a noble prize for it) almost 40 years ago, numerous follow up studies have been conducted to validate the role of ascorbic acid and the common cold. Spiers (2001, page 4) writes in his article that “the majority of these later clinical trials indicate that ascorbic acid supplementation in large doses has little, if any, effect on an individual’s likelihood of developing a common cold.” At low levels, at around 100 mg/day (right around the RDA) the majority of the ascorbic acid taken in will be absorbed. However, as the cells of the body become fully saturated with vitamin C, the efficiency of absorption greatly declines. Anything over and above 100 mg/day is essentially excreted unchanged in metabolites of urine (Naidu, 2003). In considering the mechanism by which vitamin C is absorbed in body, it is easy to see why extremely high doses of vitamin C seem to have no significant added health benefit.
Since there have been so many studies conducted that investigate the role of vitamin C in treating and preventing the common cold, the reviewed literature has been confined to articles written since the year 2000 to the present. Also, by refining the literature review to the most current studies, it is assumed that past research in this area will be considered and developed even further.
Sasazuki et al (2006) investigated the relationship between the common cold and vitamin C supplementation using a randomized controlled trial. Since there are inconsistent findings concerning the role of vitamin C in fighting and preventing infections, the researchers of this study sought to solidify the effects of vitamin C and human beings susceptibility to infection. They examined the incidence, duration, and severity of the common cold between low dose and high dose groups. The low dose group was given 50 mg/day—about half the RDA—while the high dose group was given 500 mg/day—about five times the RDA. The duration of this experiment is what makes this study of great importance. For five years, the researchers documented the incidence, duration, and severity of the common cold on a fairly large subset of the population in Japan. They found that “vitamin C was inversely related with common cold incidence […] while it had no effect on common cold duration or severity.” The incidence of the common cold was about 9.2% in the low-dose group compared to 3.2% in the high dose group. The relationship between cold duration and severity was shown to be statistically not significant between these two groups. While this study does show some positive results for the use of vitamin C for prevention of the cold only, there are some possible confounding factors that take away from their findings.
The low dose group was given a dosage of vitamin C below that of the RDA based on American standards. Not giving the participants in this group an adequate level of vitamin C may have contributed to their overall higher incidence of the cold. Also, factors such as physiological and psychological stress were not adequately accounted for. It has been shown that external stress factors obligate your body to utilize vitamin C at a greater levels; therefore, vitamin C must be supplemented more regularly or at higher doses. Since the participants in the low dose group were already receiving significantly low quantities of vitamin C, external stress may have caused depletion of the moderate levels of ascorbic acid in the body. Thus, it may have been the absence of adequate levels of vitamin C, rather than the presences of extremely large doses of this vitamin that increased cold incidence in the low dose group compared to the high dose group. While this particular study demonstrates an inverse relationship between incidence and levels of vitamin C, there are numerous other studies that disprove these findings. Sasazuki et al (2006) mentions one such study in their discussion, saying that “pooled analysis of six major intervention trials of normally nourished subjects in Western countries showed that the common cold incidence was not reduced in the vitamin C group, compared with the placebo group” (page 16).
Takkouche et al (2002) examined the protective effects of high doses of vitamin C and zinc on the development of the common cold. The study took place over the course of a year, and included over four thousand participants. Interestingly, vitamin C was not supplemented in this study, but rather the level of vitamin C was based on what the participants ate. According to the research questionnaire given to the subjects, the researchers discovered that “vitamin C intake in the study population [was] high; approximately 84% of women and 62% of men had intakes that were equal to or higher than the recommended dietary allowance of 70 to 90 mg per day respectively” (page 40). Knowing that doses of vitamin C that greatly exceed the RDA cannot be absorbed and utilized by the body explains why the researchers in this study did not supplement extra vitamin C in the diets of the participants. They found that neither vitamin C nor zinc intake was related to the incidence of the common cold. The study recognized that not finding a protective effect of vitamin C could be due to the fact that the amounts of ascorbic acid consumed in a normal diet are far below the doses used in studies that found a beneficial effect.
A review by Spiers (2001) presents a review of two journal articles in the Epidemiology journal. He reviews the Spanish study discussed above by Takkouche et al, as well as a Finnish study. Both of these studies were published in the same issue of Epidemiology, and both provide similar results. Rather than looking at supplementation, both studies examined the effect of dietary levels of vitamin C in the prevention and/or therapy of the common cold. There was a common finding: “dietary vitamin C has no effect on the risk of succumbing to the common cold” (page 4). While these results have already been discussed, Spiers presents an interesting perspective on the role of vitamin C and the common cold. He suggests that the placebo effect may be at work in the belief that vitamin C affects duration of a cold. Spiers postulates that it is not the symptoms themselves that are significantly affected by the vitamin C, but rather it is the subject’s perception of them that changes. Can the placebo effect really be the cause of the suspected immunological benefits of vitamin C? It is certainly a possibility. The inconsistencies in the data and results collected from various studies would be somewhat explained by the placebo effect, especially since a lot of the measurement tools used by the researchers were self-reported.
There is a general lack of consensus amongst the dozens of trials that have investigated the role of vitamin C, because the results often contradict. Despite all the promising findings on the level of individual studies, regular “meta-analyses of vitamin C trials, as well as other reviews, have failed to demonstrate any protective or curative effect on the common cold” (Takkouche et al, 2001, page 38).
The Supplement Industry: A Cause for Concern
Takkouche et al (2002) were wary of supplementing too much vitamin C, because a consistently large intake of vitamin C may cause adverse health effects in healthy people. The possibility of negative health outcomes should be a great cause for concern, especially since the vast majority of dietary supplements used for the treatment and prevention of the common cold contain mega doses of it.
Supplements—like Airborne considered above—that offer you proportionally high doses of vitamin C, do not offer proportionately higher health benefits. That is a common misconception! The belief that bigger is better, or that more is always beneficial, represents a general American philosophy (Devlin, 2009). This trend is observed in the use of pharmaceutical drugs as well. In comparison to other countries, the United States gives statistically higher doses of drugs than other developed nations despite any conclusive evidence that giving higher doses is necessarily more advantageous.
While The Food and Drug Administration (FDA) has stringent guidelines and regulations for pharmaceuticals drugs on the market, no such regulations exist for the dietary supplement industry.
The passing of the Dietary Supplement Health and Education Act of 1994, placed the manufacturer of the supplements responsible for ensuring the safety of their product before it is placed on the market. The FDA does hold the supplement industry to some standards, though they are not as stringent as those of the pharmaceutical industry. While the FDA does have the right to remove a dietary supplement from the market if it proves to be dangerous, the entire supplement industry remains largely unregulated (U.S. Food and Drug Administration). Manufactures of supplements are free to make unwarranted claims about efficacy that serve to trick consumers into purchasing their products (Devlin, 2009).
Americans not only waste their money when purchasing dietary supplements, such as Airborne, that cannot promise the results they preach , but also they may be putting themselves in danger. In the case of vitamin C, it has been shown that consistently high doses over a long period of time can cause minor health issues, like nausea, to more severe concerns of genetic damage (Brody, 1998). In her article, Brody claims that the type of vitamin C in supplements is slightly different than the naturally occurring vitamin C found in fruits and vegetables. The vitamin C in supplements is metabolized differently and has been shown to have damaging affects on DNA inside cells. Therefore, the dietary supplement industry must be cautious of marketing supplements with proportionately high doses of vitamin C, since it may be detrimental to consumer’s health. The lack of regulation on this industry presents a slippery slope: why isn’t the pharmaceutical industry held to the same relaxed standards as the supplement industry? Though vitamin C appears to be helpful—or at least not harmful—on first inspection, clearly there can be too much of a good thing.
Finally, it is important to note that despite all the research out there that supports the use of vitamin C in the prevention or treatment of the common cold, there is currently no major medical authority in the United States that recommends doing so (Spiers 2002). The goal of this investigation was to draw attention to the vast array of health claims in the media and on the web that are largely unwarranted. If this article achieves nothing else, I hope that it inspires a more inquisitive and skeptical attitude toward the health industry and its proponents.
Brody, J. E. (1998, April 9). Taking Too Much Vitamin C Can Be Dangerous, Study Finds. The New York Times. Retrieved from http://www.nytimes.com/1998/04/09/us/ taking-too-much-vitamin-c-can-be-dangerous-study-finds.html
Devlin, H. (September 10, 2009). Vitamin supplements are largely a waste of money, says professor. The New York Times. Retrieved from http://www.timesonline.co.uk/tol/life_
Dietary Supplements. (n.d.). U.S. Food and Drug Administration. Retrieved October 5, 2009, from http://www.fda.gov/Food/DietarySupplements/default.htm
Hemila, H. (1992, March). Vitamin C and the common cold. British Journal of Nutrition, (67), 3-16.
Naidu, K. A. (2003, August). Vitamin C in human health and disease is still a mystery? An overview. Nutrition Journal, 2(7), 1-10.
Sasazuki, S., Tsubono, Y., Okubo, S., Hayashi, M., & Tsugane, S. (2006, August). Effect of vitamin C on common cold: randomized controlled trial. European Journal of Clinical Nutrition, (60), 9-17.
Spiers, P. S. (2002, January). On the Prevention of the Common Cold: No Help from Vitamin C. Epidemiology, 13(1), 4-6.
Takkouche, B., Regueira-Mendez, C., Garcia-Closas, R., Figueiras, A., & Gestal-Otero, J. J. (2002, January). Intake of Vitamin C and Zinc and Risk of Common Cold: A Cohort Study. Epidemiology, 13(1), 38-44.
Vitamin Supplement Industry and You. (n.d.). Retrieved October 1, 2009, from Physician Select Vitamins website: http://www.psvitamins.com/vitaminsupplementsindustry_n_u.asp
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