New Reference Values for Vitamin C Intake

The German, Austrian, and Swiss nutrition societies are the editors of the ‘reference values for nutrient intake’. They have revised the reference values for the intake of vitamin C and published them in February 2015. The average vitamin C requirement in healthy adults is considered to be the vitamin C amount that compensates for the metabolic losses of vitamin C, and ensures a fasting ascorbate plasma level of 50 µmol/l. Based on the present data from studies with nonsmoking men, metabolic losses of 50 mg/day are assumed, as well as an absorption rate of 80% and an urinary excretion of 25% of the vitamin C intake. Taking this into account, the calculated average requirement in men is 91 mg/day. Considering a coefficient of variation of 10%, a reference value (recommended intake) of 110 mg/day for men is derived. The vitamin C requirement in women as well as in children and adolescents is extrapolated from the requirement in men and in relation to their body weight. This results in a recommended intake of about 95 mg/day for adult women. Because the requirement in pregnant and lactating women is increased, higher recommended intakes are derived for them, 105 mg/day for pregnant women from the fourth month on and 125 mg/day for lactating women, respectively. For boys and girls at the age of 1 to under 15 years, there are increasing recommended intake values from 20 to 85 mg/day. For male and female adolescents, at the age of 15 to under 19 years, the recommended intake is 105 and 90 mg, respectively. As smokers have higher metabolic losses and lower plasma levels of vitamin C than non-smokers (turnover is 40% higher), the reference value for vitamin C intake is set to 135 mg/day for female smokers and 155 mg/day for male smokers. For infants in their first year of life, the reference value (estimated value) is set to 20 mg vitamin C/day, based upon the lowest observed vitamin C intake for infants in the United Kingdom and the United States, that obviously meets the requirement in infants and that is 3 times higher than the amount necessary to prevent scurvy (7 mg/day).