The latest trial, published last month in the British Medical Journal’s military edition, was conducted by South Korea’s army. The Republic of Korea (ROK) military has a high incidence of respiratory diseases at training centres. So they decided to test the effects of giving 6g a day versus a placebo for 30 days. 695 soldiers got the vitamin C, and 749 got the placebo. They didn’t know what they were taking. In those taking vitamin C has 20% less colds, according to their medical records1. So, for those receiving military training, vitamin C does reduce the risk of getting a cold.
In 2017, Harri Hemilä reviewed all studies on vitamin C, paying particular attention to the dose. Overall, he found that while there were not a lesser number of colds if you combined all studies ”vitamin C has prevented colds in British men”2. Four trials found that vitamin C decreased the incidence of colds by 30%, and in another set of four trials, the proportion of men who had recurrent common cold infections during the study decreased by a mean of 46%. That’s almost a halving in number of colds. Vitamin C also halved the incidence of colds in five randomised controlled trials during which the participants were under heavy short-term physical activity.
A more recent small study in the US reported a 45% decrease in number of colds through supplementation in those with low vitamin C levels3. Then, two other studies reported that 16% and 17% more children taking vitamin C versus placebo didn’t succumb to infection4. If you put this the other way around, one in six children taking vitamin C didn’t get a cold. So, if your are a British man, a child, exercise regularly or have low vitamin C levels, eg don't eat much fruit and veg, then you can expect to, not only get shorter and less severe colds, but to get less overall.
All references to the studies are in my new book, FLU FIGHTERS - out 30 April. Read more about teh book and ordering details at www.flufighters.net.
1. T Kim et al, ‘Vitamin C supplementation reduces the odds of developing a common cold in Republic of Korea Army recruits: randomised controlled trial’ BMJ Mil Health (2020), Mar 5, (Epub ahead of print)
2. H Hemilä, ‘Vitamin C intake and susceptibility to the common cold.’ British Journal of Nutrition, (1997), 77:59-72.; see also C Bates et al, ‘Vitamin C intake and susceptibility to the common cold: Invited comments and Reply.’ British Journal of Nutrition, (1997), 78:857-66; see also H Hemilä, ‘Vitamin C and common cold incidence: A review of studies with subjects under heavy physical stress.’, International Journal for Sports Medicine, (1996), 17:379-83.
3. C Johnston, ‘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):2572-83.
4. J Coulehan et al, ‘Vitamin C prophylaxis in a boarding school.’ New England Journal of Medicine, (1974), 290(1):6-10.; see also M Van Straten and P Josling, ‘Preventing the common cold with a vitamin C supplement: a double-blind, placebo-controlled survey.’ Advances in Therapy, (2002), 19(3):151-9.