Requirements and Status Assessment

The minimum vitamin C requirement to prevent the development of scurvy has been found to be 10 mg/day (Hodges et al., 1971). This supply is not sufficient for the provision of acceptable reserves of the vitamin. The intake of 10 mg ascorbic acid per day reflects a plasma concentration of 7.6-14.1 p,mol/liter (0.13-0.24 mg/100 ml), a concentration that is far from tissue saturation. The renal clearance of ascorbic acid rises sharply at a point of 82 xmol/liter (1.4 mg/100 ml). An adequate plasma level of 44 p.mol/liter (0.75 mg/100 ml) can be maintained by a daily supply of 60-75 mg ascorbic acid. The daily amount of ascorbic acid, which is catabolized by the human body, can be calculated to be 60 mg based on a total body pool of ascorbic acid of approximately 1500 mg and a maximum turnover rate of 4%. These data are the scientific basis for the formulation of the above recommendations to meet the physiological needs. Table IV shows the recommended daily vitamin C intake for different population groups from the different societies that issue such recommendations. 

For the classification of ascorbic acid status as deficient, sufficient, or optimal, a relatively clear range of reference values exists. Table V shows the reference range for the definition of ascorbic acid status. Data derived from dietary records on the intake of ascorbic acid have to be handled carefully, since the concentrations in food show a wide range depending on several sources of variation (genotype, seasonal, food processing, etc.). Empirically estimated intake data are not always satisfactory 

Status Plasma Ijimol/liter (mg/dl) Body pool (mg) Mixed leukocytes nmol/lO cells (fjLg/lO cells) Mononuclear leukocytes nmol/108 cells ( jLg/108 cells) 

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Kretsch MJ, Sanberlich HE, Skala JH, and Johnson HL (1995) Vitamin B-6 requirement and status assessment young women fed a depletion diet followed by a plant- or animal-protein diet with graded amounts ofvitamin B-6. American Journal of Clinical Nutrition61,1091-1101. 

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