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Vitamin C does work for colds - but UK authorities didn't report it
by Patrick HolfordA new review of vitamin C evidence concludes that doses of vitamin C above 1 gram decreases cold severity and doses of at least 6 grams, ideally 8 grams, during a cold reduced duration considerably, halving recovery time if you take 8 grams. [1] A previous UK placebo-controlled trial illustrates the meaningful clinical difference between the number of colds, cold duration and severity. [2] This trial comprised 168 volunteers who were randomized to receive a placebo or vitamin C (2 x 500 mg daily) over a 60-day winter period. The vitamin C group had fewer colds (37 vs 50, P = 0.05), and even fewer virally challenged 'cold' days (85 vs 178, P=0.03) and a shorter duration of severe symptom days (1.8 vs 3.1 days, P = 0.03). The number of participants who had two colds during the trial was significantly reduced (2/84 on vitamin C vs 16/84 in the placebo group; P = 0.04). In summary, cold symptoms have been shown to be less severe and resolve more quickly with oral vitamin C with a dose-dependent effect. Higher doses, such as 1 gram per hour, which Dr Linus Pauling first recommended to achieve the same blood level of vitamin C of animals who make during the viral infection, may be more effective but no trials have been done at that level. Pharmacokinetic studies in healthy volunteers support a 200 mg daily dose to produce a plasma level of circa 70 to 90 µmol/l. [3] Higher intakes of vitamin C are, however, likely to be needed during viral infections with 2-3 g maintaining normal plasma levels between 60 and 80 µmol/l, [4] taken every 2 to 4 hours, as viral infection depletes vitamin C. A similar finding occurred in covid-19 patients for whom plasma concentrations of vitamin C in most of these patients were reported to be very low with 70-80% of the patients having hypovitaminosis C (plasma concentration < 23 µmol/L). [5,6] Whether higher plasma levels higher than 60 to 80µmol/L have additional benefit is yet to be determined but would be consistent with the results of clinical trials. Professor of Public Health, Dr. Harri Hemila from the University if Helsinki, who authored this review has also reanalyzed the seminal Sheffield Study in the UK, back in the 1940's. [7] In the study 10 participants were "deprived" and not given vitamin C supplements, 7 participants were administered 10 mg/day vitamin C as a supplement, and 3 participants were administered 70 mg/day. Colds lasted on average 6 days during vitamin C deprivation, compared with 3 days on the 10-70 mg/day dosage. Thus, deprivation nearly doubled the duration of colds. Jowett concluded that "such evidence as there is, however, definitely confirms the hypothesis that the absence of vitamin C tended to cause colds to last longer". The reanalysed results show that vitamin C deprivation increased the duration of colds on average by 77% (P = 0.014). Vitamin C deprivation decreased the recovery rate from colds by 60% (P = 0.008) and extended the duration of 1 day colds by 2.2 days. (95% CI 1.0 to 5.4 days). "The finding that vitamin C deprivation extended the duration of colds was not reported in the summaries of the trial published in the Lancet (1948) and in the Proceedings of the Nutrition Society (1953). In addition, this finding is also not mentioned in the current UK recommendations for vitamin C. As a consequence, readers have not been fully informed about the common cold results of the Sheffield trial for several decades." Says Professor Hemila. The Lancet was the UK's leading medical journal at that time. References1. Hemilä H, Chalker E (2025) Vitamin C for the common cold and pneumonia. Pol Arch Intern Med. 2025:Jan 13:16926. https://doi.org/10.20452/pamw.16926 2. Van Straten M, Josling P (2002) Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled survey. Adv Ther. 19:151-159. https://pubmed.ncbi.nlm.nih.gov/12201356 https://www.researchgate.net/profile/Peter-Josling/publication/11187865 3. Levine M, Conry-Cantilena C, Wang Y, et al. (1996) Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. PNAS USA, 93:3704-3709. https://pubmed.ncbi.nlm.nih.gov/8623000; see also Levine M, Wang Y, Padayatty SJ, Morrow J (2001) A new recommended dietary allowance of vitamin C for healthy young women. PNAS USA, 98:9842-9846. https://pubmed.ncbi.nlm.nih.gov/11504949 4. de Grooth HJ, Manubulu-Choo WP, Zandvliet AS, et al. (2018) Vitamin-C pharmacokinetics in critically ill patients: a randomized trial of four intravenous regimens. Chest, 153:1368-1377. https://pubmed.ncbi.nlm.nih.gov/29522710; see also Hume R, Weyers E (1973) Changes in leucocyte ascorbic acid during the common cold. Scott Med J. 18:3-7. https://journals.sagepub.com/doi/abs/10.1177/003693307301800102 5. Arvinte C, Singh M, Marik PE (2020) Serum Levels of Vitamin C and Vitamin D in a Cohort of Critically Ill COVID-19 Patients of a North American Community Hospital Intensive Care Unit in May 2020: A Pilot Study. Med Drug Discov.8:100064. https://doi.org/10.1016/j.medidd.2020.100064 6. Tomasa-Irriguible TM, Bielsa-Berrocal L (2021) COVID-19: Up to 82% critically ill patients had low Vitamin C values. Nutr J. 20:66. https://doi.org/10.1186/s12937-021-00727-z. 7. Hemilä H (2025) Effect of vitamin C deprivation on the duration of colds in the Sheffield study (1953): a statistical analysis. Zenodo. Jan 22, 2025 online. https://doi.org/10.5281/zenodo.14717361 Orthomolecular MedicineOrthomolecular medicine uses safe, effective nutritional therapy to fight illness. 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