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Plasma cortisol (A) and melatonin (B) levels of nine healthy male subjects (mean ± SEM). Lunch, dinner, evening snack, and breakfast are marked with dotted lines in respective order. Night-time (lights off at 10 p.m; lights on at 7 a.m) is marked with shaded region. Both cortisol and melatonin showed a normal circadian rhythm.
