title: Effects of tryptophan-rich breakfast and light exposure during the daytime on melatonin secretion at night.
abstract: BACKGROUND
  The purpose of the present study is to investigate effects of tryptophan intake and light exposure on melatonin secretion and sleep by modifying tryptophan ingestion at breakfast and light exposure during the daytime, and measuring sleep quality (by using actigraphy and the OSA sleep inventory) and melatonin secretion at night.
  
  
  METHODS
  Thirty three male University students (mean ± SD age: 22 ± 3.1 years) completed the experiments lasting 5 days and 4 nights. The subjects were randomly divided into four groups: Poor*Dim (n = 10), meaning a tryptophan-poor breakfast (55 mg/meal) in the morning and dim light environment (<50 lx) during the daytime; Rich*Dim (n = 7), tryptophan-rich breakfast (476 mg/meal) and dim light environment; Poor*Bright (n = 9), tryptophan-poor breakfast and bright light environment (>5,000 lx); and Rich*Bright (n = 7), tryptophan-rich breakfast and bright light.
  
  
  RESULTS
  Saliva melatonin concentrations on the fourth day were significantly lower than on the first day in the Poor*Dim group, whereas they were higher on the fourth day in the Rich*Bright group. Creatinine-adjusted melatonin in urine showed the same direction as saliva melatonin concentrations. These results indicate that the combination of a tryptophan-rich breakfast and bright light exposure during the daytime could promote melatonin secretion at night; further, the observations that the Rich*Bright group had higher melatonin concentrations than the Rich*Dim group, despite no significant differences being observed between the Poor*Dim and Rich*Dim groups nor the Poor*Bright and Rich*Bright groups, suggest that bright light exposure in the daytime is an important contributor to raised melatonin levels in the evening.
  
  
  CONCLUSIONS
  This study is the first to report the quantitative effects of changed tryptophan intake at breakfast combined with daytime light exposure on melatonin secretion and sleep quality. Evening saliva melatonin secretion changed significantly and indicated that a tryptophan-rich breakfast and bright light exposure during the daytime promoted melatonin secretion at this time.
authors.forename: Haruna
authors.initials: H
authors.lastname: Fukushige
authors.forename: Yumi
authors.initials: Y
authors.lastname: Fukuda
authors.forename: Mizuho
authors.initials: M
authors.lastname: Tanaka
authors.forename: Kaoru
authors.initials: K
authors.lastname: Inami
authors.forename: Kai
authors.initials: K
authors.lastname: Wada
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tsumura
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kondo
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Harada
authors.forename: Tomoko
authors.initials: T
authors.lastname: Wakamura
authors.affiliation: Department of Environmental Science, Fukuoka Women's University, 1-1-1, Kasumigaoka, Higashi-ku, Fukuoka 813-8529, Japan. morita@fwu.ac.jp.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Morita
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D062408:Breakfast; D002940:Circadian Rhythm / Q000502:physiology*; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000032:analysis*; D012463:Saliva / Q000737:chemistry; D014364:Tryptophan / Q000378:metabolism*; D055815:Young Adult
chemical_list: D014364:Tryptophan; D008550:Melatonin