A questionnaire was distributed to 38 organisations in Dublin to obtain information about the extent to which Vitamin C is deliberately taken by the public in the form of fruit, or tablets containing ascorbic acid, the reasons for its consumption and the side-effects attributed to it, in relation to the basic dietary intake of Vitamin C. Of the 950 subjects in the sample, 60% significantly more of whom were female, deliberately took supplementary Vitamin C. Of the Vitamin C takers, 70% took a daily dose of 50 mg, 7% took 1000 mg or more; 28% took the supplementary dose all the time, 12% took it only when ill, in the form of tablets. Subjects with a dialy dietary intake of more than 75 mg were more likely to take supplementary Vitamin C. 36% of takers took Vitamin C for control of cold symptoms. Only 5% took it on medical advice. 8% of the subjects attributed side-effects to Vitamin C, sleepiness, soreness of the tongue and constipation being the most common, and equally common after fruit or tablets. Only 4% experienced abdominal symptoms. The results indicate that females who normally have higher tissue ascorbic acid levels, and those individuals who have higher basic dietary Vitamin C intakes, tend to supplement themselves to a greater degree with extra Vitamin C in the form of fruit or tablets. It appears that a proportion of the population has a higher physiological requirement of Vitamin C than other individuals who exist on the recommended dose.
l-dehydroascorbic acid can substitute l-ascorbic acid as dietary vitamin C source in guinea pigs