Abstract
The circadian adrenocortical rhythm has been established to be synchronized by feeding-fasting cycles more than light-dark cycles in rats. To elucidate roles of food intake in the formation of the rhythm in human subjects, the plasma level of cortisol was measured at circadian intervals in patients fed on an elementary diet intraduodenally. When the diet was given continuously throughout 24 hr for 2 weeks, the plasma cortisol level did not show any consistent rhythmic changes even under a normal light-dark schedule (lights on from 7 a. m. to 9 p. m.). When the diet was given from 7 a. m. to 11 p. m. every day, there was a clear circadian cortisol rhythm with a peak at 7 a. m., of which pattern was quite similar to that found in normal subjects fed orally.
It was concluded that food, more than light, is a potent synchronizer of the circadian adrenocortical rhythm in men, as in laboratory animals.
