Does Vitamin C Really Prevent the Common Cold?
With colder weather just around the corner, the threat of the infamous “cold season” may soon knock on the doors of the unsuspecting many this winter season. To reduce the odds of actually catching the common cold, the best medicine (yet again) seems to be preventative medicine. The ageless recommendation of increasing vitamin C intake to prevent the common cold is one that has been highly scrutinized by researchers.1 Does vitamin C actually prevent the common cold? The answer isn’t as straight-forward as all of us would have hoped; however, this is not necessarily because vitamin C was found to be unhelpful per se, but rather timing and dosage is everything and can make the difference. The question is, how so?
Why take Vitamin C in the first place?
First, a little bit of background on vitamin C may be helpful. Vitamin C, known chemically as ascorbic acid, is a water-soluble vitamin that our bodies cannot synthesize - meaning - we must obtain vitamin C from our diets or in supplements to prevent diseases that directly result from vitamin C deficiency such as scurvy. In reality, though, for most adults it doesn’t take much vitamin C (approximately 10 mg per day) to prevent a dreadful condition like scurvy.2 Therefore, most people are interested in how much extra vitamin C they should take to help enhance immunity, which is what vitamin C is typically associated with, particularly against the common cold. This is for good reason - Vitamin C plays an important role in our immunity because it can enhance our immune defenses, and it is a powerful antioxidant and plays a critical role in regenerating the master antioxidant: glutathione.
What does the evidence say on vitamin C?
Back to our original question: is vitamin C helpful in prevention, and how might timing and dosage make the difference?
Vitamin C is not a common nutrient deficiency, especially when compared to vitamin D or iron, for example, which makes it difficult to really know the impact of supplementing on a nutrient most people are already sufficient in. What isn’t known, and what has become a hallmark of a 2013 systematic review3 of research on the preventative nature of vitamin C, is whether or not regular intake may positively impact our bodies possibly preventing the common cold outright?
The short answer: no, it doesn’t prevent. But why? Because when it comes to the common cold, many things can influence how susceptible one is to contracting a common cold virus such as sleep quality4, workplace stress5, and personal and protective hygiene6. From a functional perspective, we also want to look into things such as diet & lifestyle, micronutrient status, and water intake to insure your body has the nutrition necessary to thrive. Sometimes, though, just plain being in the wrong place at the wrong time is enough opportunity to become exposed to a bug.
Vitamin C appears to shorten duration and severity
The aforementioned systematic review found that although vitamin C didn’t appear to prevent the common cold, with regular supplementation the severity and duration of the common cold was in fact reduced in children and adults. In children, the reduction in common cold was highest when 1-2g per day of vitamin C was taken (i.e., when we do catch a cold, we can be back to work, school, and play sooner).3 This find alone may be enough reason for all of us to supplement on vitamin C, starting yesterday!
Considering that vitamin C is a relatively cheap and safe supplement to take, and the fact that most people can tolerate the 1-2g per day dosage (especially if spread out in the day), we can determine for ourselves the impact of vitamin C on our bodies during this cold season. In time, perhaps more research will continue to elucidate whether regular supplementation is the only way to have a positive impact, or if therapeutic dosages of vitamin C may also be effective.
Common colds: Does Vitamin C keep you healthy? PubMed Health website. https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072728/. Updated October 5, 2017. Accessed December 5, 2017.
Vitamin C. Oregon State University Linus Pauling Micronutrient Information Center website. http://lpi.oregonstate.edu/mic/vitamins/vitamin-C. Updated January 1, 2014. Accessed December 6, 2017.
Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013 Jan 31;(1):CD000980. www.dx.doi.org/10.1002/14651858.CD000980.pub4 or https://www.ncbi.nlm.nih.gov/pubmed/23440782.
Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. Sleep Habits and Susceptibility to the Common Cold. Arch Intern Med. 2009 Jan 12; 169(1): 62–67. https://dx.doi.org/10.1001%2Farchinternmed.2008.505 or https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2629403/.
Park SG, Kim HC, Min JY, Hwang SH, Park YS, Min K
B. A prospective study of work stressors and the common cold. Occup Med (Lond). 2011 Jan;61(1):53-6. www.dx.doi.org/10.1093/occmed/kqq141 or https://www.ncbi.nlm.nih.gov/pubmed/20833997.
Common Colds: Protect Yourself and Others. Centers for Disease Control and Prevention website. https://www.cdc.gov/features/rhinoviruses/index.html. Updated February 6, 2017. Accessed December 6, 2017.