Alteration of internal circadian phase relationships after morning versus evening carbohydrate-rich meals in humans.
The effects of a single morning and evening carbohydrate-rich meal for 3 consecutive days on circadian phase of core body temperature (CBT), heart rate, and salivary melatonin rhythms were compared under controlled constant routine conditions. In 10 healthy young men entrained to a natural light-dark cycle with regular sleep timing, CBT and heart rate were significantly elevated for approximately 8 h after the last evening carbohydrate-rich meal (EM), and nocturnal melatonin secretion (as measured by salivary melatonin and urinary 6-sulphatoxymelatonin levels) was reduced, compared to the morning carbohydrate-rich meal (MM) condition. Thus, circadian phase could not be measured until the following day due to this acute masking effect. The day after the last meal intervention, MM showed a significant advanced circadian phase position in CBT (+59+/-12 min) and heart rate (+43+/-18 min) compared to EM. However, dim-light melatonin onset was not significantly changed (+15+/-13 min). The results are discussed with respect to central (light-entrainable) and peripheral (food-entrainable) oscillators. Food may be a zeitgeber in humans for the food-entrainable peripheral oscillators, but melatonin data do not support such a conclusion for the light-entrainable oscillator in the suprachiasmatic nucleus.
Kräuchi
Kurt
K
Centre for Chronobiology, Psychiatric University Clinic, Basel, Switzerland. kurt.kraeuchi@pukbasel.ch
Cajochen
Christian
C
Werth
Esther
E
Wirz-Justice
Anna
A
D000328:Adult; D001831:Body Temperature; D001835:Body Weight; D002940:Circadian Rhythm; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004734:Energy Metabolism; D006339:Heart Rate; D006801:Humans; D008297:Male; D008550:Melatonin / Q000032:analysis; D013997:Time Factors
D004040:Dietary Carbohydrates; D008550:Melatonin