Ascorbic acid and aging

Scurvy today is a rare disease affecting two different age groups. It occurs in formula-fed infants between the ages of 6 and 18 months whose diets have not been supplemented with added sources of ascorbic acid, and in men of middle or old age who are usually bachelors or widowers and who for more than a year have neglected fresh foods. It must be emphasized that in both of these age groups scurvy is only the predominating illness, and almost always there are other deficiencies or disease states. 

Yin, D. (1992) Lipofuscin-like fluorophores can result from reactions between oxidized ascorbic acid and glutamine. Carbonyl-protein cross-linking may represent a common reaction in oxygen radical and glycosylation-related ageing processes. Mech. Ageing Dev. 62 35-46. 

Yin, D. and Brunk, U.T. (1991) Oxidized ascorbic acid and reaction products between ascorbic and amino acids might constitute part of age pigments. Mech. Ageing Dev. 61 99-... 

Ascorbic acid in blood is transported by a reversible complex with serum albumin (Moloy et al., 1980). The main transport form of vitamin C seems to be the reduced molecule. The concentration of dehydroascorbic acid can, however, exceed that of ascorbic acid in vitamin C deficiency and certain diseases (Stone, 1977). The relation of ascorbic acid/dehydroascorbic acid in human plasma decreases also with age (Sasaki et al., 1983). Since the typical screening methods for the determination of vitamin C status in blood are not able to distinguish between the different circulating forms of vitamin C, it has to be clearly stated that the detailed interpretation of vitamin C status and its relation to certain disorders must reflect on both ascorbic acid and dehydroascorbic acid concentration in blood. 

Bates, C. J., and Cowen, T. D., 1988, Effects of age and dietary vitamin C on the contents of ascorbic acid and acid-soluble thiol in lens and aqueous humour of guinea pigs, Exp. Eye Res. 46 937-945. 

Advanced glycation end products attached to proteins (AGE proteins), which can be detected by their characteristic fluorescence, have been found to increase at an accelerated rate in diabetes and with increasing age (Monnier et al., 1984, 1986). However, the chemical and fluorescent characterization of these compounds remains imprecise or incomplete, and many products with similar fluorescent characteristics can be generated by ascorbic acid and unsaturated lipid, in vitro at least (Hunt and Wolff, 1990, 1992). 

An area of considerable interest is the antioxidant function of ascorbic acid. Ascorbic acid is probably the most effective and least toxic antioxidant present in the human body. Therefore, ascorbic acid may be important in protecting against oxidative stress-related diseases, including cancer, coronary heart disease, cataract formation, and aging. Chapters are devoted to these and other associations of ascorbic acid with disease. A related chapter is devoted to the radiation protective effect of ascorbic acid. One chapter is devoted entirely to the role of ascorbic acid in aging, while another chapter reviews the extensive epidemiological evidence for the relationship between ascorbic acid and chronic health risk. 

Extrinsic labeling has been used in several studies to assess apparent copper absorption inhumans. This includes studies to evaluate apparent copper absorption from plant- and animal-based diets [263, 264], and also the effect of ascorbic acid [265], age [146, 266, 267], copper intake [267-271], zinc intake [146], and iron supplementation [272] on copper absorption. By measuring urinary excretion of the tracer, copper retention has also been assessed from vitamin B6-defident diets [271], in pregnant women [263], in young men consuming a low copper diet [268], and for high copper intakes [270]. 

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