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DRI DIETARY REFERENCE INTAKES FOR Vitamin C, Vitamin E, Selenium, and Carotenoids
Clinical Effects of Inadequate Intake
Scurvy, the classic disease of severe vitamin C deficiency, is characterized by symptoms related to connective tissue defects. Scurvy usually occurs at a plasma concentration of less than 11 µmol/L (0.2 mg/dL). Clinical features of scurvy include follicular hyperkeratosis, petechiae, ecchymoses, coiled hairs, inflamed and bleeding gums, perifollicular hemorrhages, joint effusions, arthralgia, and impaired wound healing (Baker et al., 1971; Chazan and Mistilis, 1963; Levine et al., 1996b). Other symptoms include dyspnea, edema, Sjögren's syndrome (dry eyes and mouth), weakness, fatigue, and depression. In experimental subjects made vitamin C deficient but not frankly scorbutic, gingival inflammation (Leggott et al., 1986) and fatigue (Levine et al., 1996a) were among the most sensitive markers of deficiency. Vitamin C deficiency in infants may result in bone abnormalities such as impaired bone growth and disturbed ossification, hemorrhagic symptoms, and resultant anemia (Jacob, 1999).
Lack of ascorbate-related hydroxyproline and hydroxylysine formation needed for collagen cross-linking may explain many of the connective tissue and hemorrhagic manifestations of scurvy, however, the specific histologic defects have not been identified. Oxidative degradation of some blood coagulation factors due to low plasma ascorbate concentrations may contribute to hemorrhagic symptoms (Parkkinen et al., 1996).
Scurvy is rare in developed countries but is occasionally seen in individuals who consume few fruits and vegetables, peculiar or restricted diets, or in those who abuse alcohol or drugs. In the United States, low blood ascorbate concentrations are more prevalent in men, especially elderly men, than in women and are more prevalent in populations of lower socioeconomic status (LSRO/FASEB, 1989). Infantile scurvy is rarely seen, because human milk provides an adequate supply of vitamin C and infant formulas are fortified with the vitamin.
SELECTION OF INDICATORS FOR ESTIMATING THE REQUIREMENT FOR VITAMIN C
There is much support for the role of increased oxidative stress in the pathogenesis of cardiovascular disease (Jialal and Devaraj, 1996; Witztum and Steinberg, 1991). The most plausible and biologically