[Can the administration of large doses of vitamin C have a harmful effect?].

Vitamin C in its pure form or as a component of multivitamin and combined drugs belongs to the over-the-counter drugs that are available not only at the chemist's but in retail shops as well. Intensive promotion of the advantages of vitamin C as the compound that augments immunity to all sorts of infections, accelerates recovery, eliminates the symptoms of common cold and flu-like diseases, and contributes to general well-being, is of great importance to its intake in quantities far exceeding the recommended dietary allowance. Moreover, the subjects who simultaneously take several anti-common cold drugs are not aware of the fact that almost each of them contains ascorbic acid. Among numerous reports concerning positive effect of vitamin C as antioxidant and free radicals scavenger, there are also those pointing at its potentially pernicious effect. Vitamin C, especially in the doses exceeding daily recommended dietary allowance may result in oxalate crystallization, formation of advanced glycation end products and even exert prooxidant effect.