ABSTRACT
The word circadian, derived from circa, about, and dies, day, is perhaps preferable to diurnal when referring to 24-h cycles, as it is intended to refer to the 24-h day and to include nocturnal as well as diurnal events. Moreover, these workers noted that this change was independent of the quantity of liquid taken and the volume of the urine output; they also noted that the day-night rhythm persisted when the food had been deprived of vitamin C for some time. A deficiency of vitamin C greatly elevated the plasma cortisol throughout the 24-h period and exaggerated the amplitude of the plasma cortisol changes, but did not alter the phase or the period of the cycle. Zuskin et al. observed that ascorbic acid supplementation reduces the airway constriction induced by inhalation of histamine in human adults. At that point frank scurvy develops and only traces of dehydroascorbic acid are to be found in the blood and tissues.
