According to the 2001–2002 National Health and Nutrition Examination Survey (NHANES), mean intakes of vitamin C are 105.2 mg/day for adult males and 83.6 mg/day for adult females, meeting the currently established RDA for most nonsmoking adults [18]. Mean intakes for children and adolescents aged 1-18 years range from 75.6 mg/day to 100 mg/day, also meeting the RDA for these age groups [18]. Although the 2001–2002 NHANES analysis did not include data for breastfed infants and toddlers, breastmilk is considered an adequate source of vitamin C [8,13]. Use of vitamin C-containing supplements is also relatively common, adding to the total vitamin C intake from food and beverages. NHANES data from 1999–2000 indicate that approximately 35% of adults take multivitamin supplements (which typically contain vitamin C) and 12% take a separate vitamin C supplement [19]. According to 1999–2002 NHANES data, approximately 29% of children take some form of dietary supplement that contains vitamin C [20].
Vitamin C status is typically assessed by measuring plasma vitamin C levels [4,13]. Other measures, such as leukocyte vitamin C concentration, could be more accurate indicators of tissue vitamin C levels, but they are more difficult to assess and the results are not always reliable [4,9,13].