We all know that having a cold can feel terrible, and sometimes we are willing to try just about anything to feel better. Decongestants and cough syrup? Yes, please! Chicken noodle soup? Sure, why not! But what about vitamin C supplements? Can they actually help you get over a cold?
Taking vitamin C supplements was first touted as a cold remedy in 1970 when Linus Pauling, a famous Nobel Prize-winning chemist, published a book about it. Since then, researchers have run many clinical trials to test Pauling’s claims and figure out how well, if at all, vitamin C works in preventing and treating colds. Many of these trials have come to opposite conclusions. So, can vitamin C help you take on the common cold? Turns out, that depends on how much vitamin C you take, what aspect of a cold you are looking at, and on you.
What do studies say about taking vitamin C to shorten a cold?
Looking at multiple large studies, most show that large doses of vitamin C do shorten colds, but probably not by as much as you want. A high-quality meta-analysis, which examined multiple studies, found that 1,000 mg vitamin C or more per day shortened colds by 0.93 days on average.1Hemilä H. and E. Chalker. Commentary: The Long History of Vitamin C: From Prevention of the Common Cold to Potential Aid in the Treatment of COVID-19. Front Immunol, 2021. 12. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8047412/ While shortening your cold by a day may not seem like much, vitamin C does seem to make cold symptoms milder as well, which can help you feel less bad while sick and maybe allow you to continue your daily activities.2Hemilä, H. Vitamin C supplementation and common cold symptoms: problems with inaccurate reviews. Nutrition, 1996. 12(11-12). https://pubmed.ncbi.nlm.nih.gov/8974108/3Pitt, H. A. and A. M. Costrini. Vitamin C prophylaxis in marine recruits. JAMA, 1979. 241(9). https://pubmed.ncbi.nlm.nih.gov/368370/4Ludvigsson, J., L. O. Hansson, and G. Tibbling. Vitamin C as a preventive medicine against common colds in children. Scand J Infect Dis, 1977. 9(2). https://pubmed.ncbi.nlm.nih.gov/897573/5Anderson, T. W., D. B. Reid, and G. H. Beaton. Vitamin C and the common cold: a double-blind trial. Can Med Assoc J, 1972. 107(6). https://pubmed.ncbi.nlm.nih.gov/5057006/6Van Straten, M. and P. Josling. Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled survey. Adv Ther, 2002. 19(3). https://pubmed.ncbi.nlm.nih.gov/12201356/7Sabiston, B. H. and M. W. Radomski. Health problems and vitamin C in Canadian northern military operations. 1974. https://www.epistemonikos.org/en/documents/7d1395866e7f578d164ccc35af221804174b26e7
For example, one of the largest good-quality studies found that people taking a high dose of vitamin C while sick were less likely to take time off work or be confined to their home.5Anderson, T. W., D. B. Reid, and G. H. Beaton. Vitamin C and the common cold: a double-blind trial. Can Med Assoc J, 1972. 107(6). https://pubmed.ncbi.nlm.nih.gov/5057006/ Furthermore, when people did need to take off work or stay home because of a cold, taking vitamin C seemed to reduce their down time, allowing them to return to work or their normal activities sooner. While vitamin C did not lessen nose and throat symptoms, it did protect against more general cold symptoms like tiredness, chills, and fever, which is likely why fewer people taking vitamin C felt the need to stay home or take off work when sick.
So, while taking vitamin C today will not magically restore you to perfect health tomorrow, taking it daily (≥1,000 mg/day) from the time you first feel sick until you feel better may make your symptoms milder and shorten your cold a little bit.
What about preventing colds? If I take vitamin C supplements every day, am I less likely to catch a cold?
If we look at just large studies of high-dose vitamin C (≥1,000 mg/day), most agree that vitamin C does not lower most people’s chances of catching a cold, at least in Western populations.8Hemilä, H. Do vitamins C and E affect respiratory infections? 2006. https://researchportal.helsinki.fi/en/publications/do-vitamins-c-and-e-affect-respiratory-infections While this may be disappointing, there do seem to be some exceptions.
Most people are not deficient in vitamin C since most people eat fruits and vegetables. However, there is some research showing that vitamin C supplements (1,000 mg/day) can prevent colds in young men who consume 60 mg vitamin C or less per day, which is less than the amount of vitamin C found in a single orange.9Johnston, C. S., G. M. Barkyoumb, and S. S. Schumacher. Vitamin C supplementation slightly improves physical activity levels and reduces cold incidence in men with marginal vitamin C status: a randomized controlled trial. Nutrients, 2014. 6(7). https://pubmed.ncbi.nlm.nih.gov/25010554/ Vitamin C supplements also shortened colds in this population by 59%. Vitamin C may help other groups of people who are vitamin C deficient as well, since vitamin C deficiency is associated with higher risk of infections.10Hemilä, H. Vitamin C and Infections. Nutrients, 2017. 9(4). https://pubmed.ncbi.nlm.nih.gov/28353648/
Interestingly, many studies show that vitamin C supplementation can also prevent colds in people who are very active.11Hemilä, H. Vitamin C and common cold incidence: a review of studies with subjects under heavy physical stress. Int J Sports Med, 1996. 17(5). https://pubmed.ncbi.nlm.nih.gov/8858411/ This includes marathon and ultramarathon runners taking 500-1,000 mg/day,12Peters, E. M. et al. Vitamin C supplementation reduces the incidence of postrace symptoms of upper-respiratory-tract infection in ultramarathon runners. Am J Clin Nutr, 1993. 57(2). https://pubmed.ncbi.nlm.nih.gov/8185726/13Peters, E. M. et al. Vitamin C as effective as combinations of anti-oxidant nutrients in reducing symptoms of upper respiratory tract infection in ultramarathon runners. Sports Medicine, 1996. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiQt42qsvH3AhUiZN8KHQ3NAXsQFnoECBUQAQ&url=https%3A%2F%2Fwww.mv.helsinki.fi%2Fhome%2Fhemila%2FCC%2FPeters_1996_ch.pdf&usg=AOvVaw075GRv6DaBFnKmGv6Loy1714Himmelstein, S. A. The effect of vitamin C supplementation on incidence of upper respiratory tract infections in marathon runners. 1998. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjIgYazs_H3AhVLU98KHXQkDZ4QFnoECAgQAQ&url=https%3A%2F%2Fwww.mv.helsinki.fi%2Fhome%2Fhemila%2FCC%2FHimmelstein_1996.pdf&usg=AOvVaw0-HoLopPANfG96ythT3LHj soldiers taking 1,000-6,000 mg/day,15Kim, T. K., H. R. Lim, and J. S. Byun. Vitamin C supplementation reduces the odds of developing a common cold in Republic of Korea Army recruits: randomised controlled trial. BMJ Mil Health, 2022. 168(2). https://pubmed.ncbi.nlm.nih.gov/32139409/7Sabiston, B. H. and M. W. Radomski. Health problems and vitamin C in Canadian northern military operations. 1974. https://www.epistemonikos.org/en/documents/7d1395866e7f578d164ccc35af221804174b26e7 and skiers taking 1,000 mg/day.16Ritzel, G. Critical evaluation of vitamin C as a prophylactic and therapeutic agent in colds. Helv Med Acta, 1961. 28. https://pubmed.ncbi.nlm.nih.gov/13741912/ There are likely other physically active groups of people that could likewise benefit from vitamin C, but they have not been studied yet.
A lot more studies are needed to figure out if there are other groups of people who can prevent colds by taking vitamin C. That said, vitamin C does not seem to prevent colds for most of us.
So, should I take vitamin C supplements if I’m worried about a cold?
If you are worried about catching a cold, taking vitamin C supplements will most likely not help you unless you are under a lot of physical stress or are vitamin C deficient. However, if you think vitamin C may help you, taking up to 2,000 mg/day is considered safe for most adults (having more than this can sometimes cause side effects like diarrhea, nausea, and kidney stones). If you have a cold, there is a good chance that taking 1,000-2,000 mg vitamin C each day you are sick, starting from the time you first start feeling sick, could help you feel a bit better and get over your cold a little faster.