Human requirements and needs. Vitamin C status: methods and findings.

Although vitamin C nutritional status in man may be determined on the basis of dietary intake findings and on clinical signs of a dietary deprivation, biochemical measurements represent the most objective approach. Without the availability of a functional biochemical procedure that relates to vitamin C status, information concerning inadequacies in this nutrient has been derived mainly from measuring ascorbate levels in serum (plasma), leukocytes, blood, and urine. The measurement of serum levels of ascorbic acid is the most commonly used and practical procedure for determining vitamin C nutritional status in individuals or population groups. Although leukocyte ascorbate levels provide information concerning the body stores of the vitamin, the measurement is technically more difficult to perform, and, hence, its use is largely confined to clinical situations as an aid in the diagnosis of scurvy. The clinical diagnosis of scurvy can be aided also by information on the urinary levels of ascorbic acid and the use of vitamin C loading or saturation tests. With recognized limitations, ascorbic acid can be measured in biological samples with the use of automated or manual colorimetric and fluorometric procedures. Nutrition surveys conducted in Canada and the United States have indicated vitamin C deficits among certain population groups.