Vitamin C: prospective functional markers for defining optimal nutritional status.
Most species of plants and animals synthesize ascorbic acid, but human subjects cannot, making vitamin C an essential component of our diet. Relationships between vitamin C intake and status, and between status and health are not yet clear. There is evidence, however, that higher intake of vitamin C is associated with lower risk of disease, supporting the concept that optimal intake is needed for optimal vitamin C status, and that both factors are required for optimal health. Vitamin C has low toxicity in healthy subjects, but a clear definition of optimal status and the dietary intake required to meet and maintain this status is needed before a change in the current recommended intake can be considered. Available evidence suggests that intake of 200 mg vitamin C/d saturates tissues and maintains fasting plasma levels above the proposed threshold (50 mumol/l) for minimum risk of CHD. However, the issue of whether or not these levels produce 'optimal vitamin C status' awaits the clear and accepted definition of the term. This definition in turn awaits the development of reliable functional markers capable of assessing the effects of varying levels of vitamin C nutriture. In the present paper the relationship between intake and body stores of vitamin C and the role of vitamin C in human health are reviewed briefly. The requirements of a reliable functional marker of human vitamin C status are defined, three classes of functional markers (molecular, biochemical and physiological) are described, and possible candidate markers are examined.
Benzie
I F
IF
Department of Nursing & Health Sciences, Hong Kong Polytechnic University, Kowloon, SAR, China. hsbenzie@polyu.edu.hk
D001205:Ascorbic Acid / Q000008:administration & dosage / Q000097:blood / Q000502:physiology; D015415:Biomarkers; D003327:Coronary Disease / Q000517:prevention & control; D006293:Health Promotion; D006801:Humans; D009751:Nutritional Requirements; D009752:Nutritional Status; D012016:Reference Values
D015415:Biomarkers; D001205:Ascorbic Acid