Everything You Should Know About Vitamin C
Most of us have heard of Vitamin C and associate it with foods such as oranges and other citrus fruits. In this blog post, we are going to dive into everything about Vitamin C. We will go over the basics, quality food sources, what happens if you don’t get enough, and how it affects iron absorption. And finally, we will answer a hot topic question – does taking Vitamin C help you recover from a cold or is it just a placebo?
Basics of Vitamin C
Vitamin C is one of many micronutrients that our bodies need to function. It is a water-soluble vitamin that we get from food. Many species can make Vitamin C on their own, but humans cannot and need to get it through dietary intake each day. This is because the gene responsible for an important enzyme (i-gulonolactone oxidase) in the synthesis of Vitamin C has evolved with mutations and has become non-functional in humans (1).
Vitamin C plays multiple important roles including the synthesis of collagen (an important protein in our bodies), neurotransmitter function and antioxidant function. Vitamin C paired with iron in the diet also increases the absorption of iron and can be an important pairing for those with iron deficiency. Food sources that are high in vitamin C include many fruits and vegetables including citrus fruit, kiwi, mango, broccoli, tomatoes, and peppers (1).
If we do not get enough vitamin C in our diet the clinical disease that results is called scurvy. Common symptoms of scurvy include impaired wound healing, gingivitis (inflammation of gums), petechiae (small red dots on skin), fatigue and lethargy (1). People with poor dietary intake are at an increased risk. Poor intake can be a result of many factors including poverty, limited access to fruits and vegetables, or food preferences.
The recommended daily amount (RDA) of Vitamin C is 75 mg for women and 90 mg for men (1,2). Studies have shown that the optimal level may be closer to 200 mg per day (1). Children have lower needs and pregnant and breastfeeding women have slightly higher needs than healthy adults. It is also recommended that those who smoke consume an extra 35 mg per day (1). To put all these numbers in perspective, 1 small orange (about tennis ball size) has roughly 50 mg of Vitamin C. In general, a variety of 5-9 servings of fruits and vegetables per day will provide 200 mg Vitamin C (1).
Vitamin C and the Immune System
Now onto the question that we have all been waiting to talk about. Just about everyone has heard at some point that taking a high dose of vitamin C, when sick, will help you recover faster. Some people even swear by it and take supplements at the first hint of a cold coming on. Many of us have also heard the other side that this does not actually work and is just a “placebo effect”. So, what is the truth? What does the science say?
In the 1970s, Linus Pauling published a theory that a daily 1000 mg dose of Vitamin C reduced the incidence of colds by 45%2. The response to this in the US was to market vitamin C as such and the sales of Vitamin C supplements almost doubled in a few years (2). Pauling’s theory was based off non-randomized controlled trials and some animal studies (2). This cast vitamin C supplementation into a long-standing controversy and is likely were much of today’s confusion stems from. Flash forward to the 2020’s and we may finally have an evidence-based answer.
In 2007, a large meta-analysis was conducted. If you are unfamiliar with meta-analyses, it is the process of looking at all studies that fit a defined criteria and statistically analyzing them to come to a conclusion of all the data. In this review, they only used studies that provided doses of 200 mg or more and those that had a control group (3). The review included 30 different studies and concluded that Vitamin C supplementation prior to a cold or during a cold did not reduce cold severity or duration (3). This is because although some trials found routine supplementation reduced cold severity and duration, none of the therapeutic or “real-life situation” trials found this to be true. They did find that there is some evidence for vitamin C supplementation use in individuals during short periods of severe exercise or in cold environments (3).
In 2018, another meta-analysis that reviewed eight systematic reviews including a total of 45 studies concluded that the consumption of Vitamin C does not prevent the incidence of colds (4). Most recently, in 2020, another review came out with an in-depth analysis. It too, states that in the general healthy population there is no evidence that vitamin C supplementation helps reduce colds (2). This review found that those under high physical stress such as those in the military and athletes with heavy exertion have showed some decreased incidence of colds with vitamin C supplementation (2). This article also dives into other disease states so if you are interested in learning more about Vitamin C in other specific situations, check it out here.
In summary, it has not been found that vitamin C supplementation helps reduce the incidence, duration, or severity of colds in the general population (2,3,4). There are specific subgroups that supplementation may be indicated for including high volume athletes and those in the military (2,3). If you are eating a well-balanced diet with fruits and vegetables, it is likely you are getting adequate Vitamin C. In conclusion, vitamin C supplements won’t help most people fight off or prevent colds and you should spend your money elsewhere.
Thanks for tuning in. Vitamin C you later.
References
1. Lykkesfeldt J, Michels AJ, Frei B. Vitamin C. Adv Nutr. 2014;5(1):16-18. Published 2014 Jan 1. doi:10.3945/an.113.005157
2. Cerullo G, Negro M, Parimbelli M, et al. The Long History of Vitamin C: From Prevention of the Common Cold to Potential Aid in the Treatment of COVID-19. Front Immunol. 2020;11:574029. Published 2020 Oct 28. doi:10.3389/fimmu.2020.574029
3. Douglas RM, Hemilä H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2007;(3):CD000980. Published 2007 Jul 18. doi:10.1002/14651858.CD000980.pub3
4. Gómez E, Quidel S, Bravo-Soto G, Ortigoza Á. Does vitamin C prevent the common cold?. ¿Previene la vitamina C el resfrío común?. Medwave. 2018;18(4):e7235. Published 2018 Aug 6. doi:10.5867/medwave.2018.04.7236
