Recommended Daily Amounts and Biochemical Roles—The Vitamin C, Carnitine, Fatigue Relationship

Nutritional thought has developed essentially in terms of deficiency diseases and their prevention. This approach has proved to be a useful analytical tool in revealing the biochemical role of certain essential dietary factors. Furthermore, the prevention of definable deficiency diseases offered a quantifiable, albeit negative, method of defining the recommended daily intake of a nutrient. But the amount of a nutrient necessary to prevent overt ill health is not necessarily to be equated with the amount consistent with the attainment of optimum health (itself a difficult-to-define state). This is particularly true if nutrients have adjuvant or supportive roles in addition to their functions as essential dietary factors. Even non-essential nutrients may be of definable nutritional significance. It is now generally accepted that dietary fibre and polyunsaturated fat are of probable dietary significance although no clearly definable deficiency disease can be attributed to their absence from the diet. Current thought is slowly forcing us to replace the traditional simplistic approach, structured around the prevention of deficiency diseases, by the concept of dietary optimisation. So too in the case of vitamin C (ascorbic acid): the current Recommended Daily Amount (RDA) for the UK is quite clearly based on the amount of the vitamin necessary to prevent the emergence of 'overt' clinical scurvy, as traditionally described: