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How much vitamin C should you consume when you have a cold?
Last reviewed: 02.07.2025
Medical experts are confident that high doses of ascorbic acid for colds or viral infections help to overcome the disease faster. However, until now, no one knew the exact amount of vitamin for successfully fighting the disease.
The results of new research by scientists on this issue were published in the periodical Nutrients.
The success of treating a cold after taking ascorbic acid is dose-dependent: it is optimal if the amount of the drug taken is gradually increased to 6-8 g per day. By the way, this amount is 100 times higher than the recommended daily intake of vitamin C.
Scientists already have a lot of information about ascorbic acid for colds, since a huge part of the experiments was conducted on animals. Rodents were given vitamin C in various doses, after which the results were recorded. In the vast majority of cases, ascorbic acid helped to stop the development of a viral or microbial disease and quickly improve the condition of the body.
Taking into account the “universality” of the vitamin and its positive effect on immune defense, scientists from the Finnish University of Helsinki decided to conduct a study involving people - patients suffering from colds or acute respiratory viral infections.
How much vitamin C should you take to speed up the healing process without harming your body?
To answer this question, experts led by Professor Harry Hemilä analyzed data from two large-scale placebo studies.
The first experiment consisted of the following: two groups of volunteers were offered to take ascorbic acid in the amount of 3 g/day, the participants of the third group were offered to take 6 g of the vitamin per day, and the participants of the fourth group had to take a placebo. In patients of the third group, the disease was cured 17% faster, compared to the fourth group. In patients of the first two groups, the effectiveness was estimated at almost 9%.
Then a second experiment was conducted: several groups of participants took ascorbic acid in the amount of 4 and 8 g/day, or placebo, but only once - during the first day of a cold. Compared to placebo, 8 g of ascorbic acid was able to reduce the severity of the clinical picture by 19%. An amount such as 4 g was considered less effective - about two times.
Based on the results of the experiments, experts stated that there is a linear relationship between the amount of vitamin C consumed and the duration of the disease.
Professor Hemilä claims that 8 mg of the vitamin is not the maximum possible amount of the preparation. Probably, other experiments will be conducted a little later, using higher doses, for example, 15 mg/day and even more.
"The effectiveness of ascorbic acid in colds is undeniable. At the moment, we believe that it is entirely appropriate to take up to 8 g of the vitamin per day. At the same time, it is desirable that such treatment begin as early as possible," the professor concludes.
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