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Figure 3 | Journal of Circadian Rhythms

Figure 3

From: A tryptophan-rich breakfast and exposure to light with low color temperature at night improve sleep and salivary melatonin level in Japanese students

Figure 3

Comparison of salivary melatonin concentration among the three groups. Group 1: no intervention; Group 2: Recommendation of high protein breakfast and exposure to sunlight; Group 3: Same as Group 2 plus the recommendation of exposure to low color temperature light emitted from an incandescent light bulb. A: Melatonin level in the saliva collected on the day just before the intervention (Kruskal Wallis test: χ2-value = 0.92, df = 2, p = 0.63); B: Melatonin in the saliva collected at the mid-point and on the day before the last day of the intervention (Bonferroni multiple comparison test: G1 versus G3, p = 0.018; G2 versus G3, p = 0.011).

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