Effects of tryptophan-rich breakfast and light exposure during the daytime on melatonin secretion at night

Abstract

BackgroundThe 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.MethodsThirty 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.ResultsSaliva 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.ConclusionsThis 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.

Assessing Urinary Metabolomics in Giant Pandas Using Chromatography/Mass Spectrometry: Pregnancy-Related Changes in the Metabolome

“…5-HT is an important neurotransmitter in the central nervous system (37) that can be further converted to melatonin. Research illustrated that Trp-rich foods or intravenous Trp can promote melatonin secretion (38). Therefore, Trp is also a precursor of melatonin, making it a regulator of circadian rhythms.…”

Impact of a single, short morning bright light exposure on tryptophan pathways and visuo- and sensorimotor performance: a crossover study

“…Contrary to this, Chellappa et al [ 18 ] found strong correlations between faster reaction times and salivary melatonin concentrations. It was also recently shown [ 46 ] that a regimen comprising a trp-enriched diet in combination with BL exposure during the day promoted melatonin secretion at night.…”

Can tryptophan supplement intake at breakfast enhance melatonin secretion at night?

“…It is necessary to control the intakes of other nutrients in order to elucidate the effect of TRP intake in the morning on nocturnal melatonin secretion. For the same reason, although TRP intake did not significantly advance subjects’ circadian phases in the study by Fukushige et al [ 3 ], their results were not clear. Nakade et al [ 11 ] reported a positive correlation between the estimated amount of TRP intake at breakfast and Morningness-Eveningness Questionnaire (MEQ) score in children, suggesting that children consuming a higher amount of TRP at breakfast may have an earlier circadian acrophase.…”

“…Their study indicated that salivary melatonin secretion at 23:00 was increased by consumption of a TRP-rich breakfast with exposure to light of low color temperature during the night, compared with no intervention. Furthermore, a laboratory-based study by Fukushige et al [ 3 ] reported that melatonin secretion at night was significantly increased by consumption of a TRP-rich breakfast with daytime bright light exposure for 3 days, although the secretion was not significantly changed by consumption of a TRP-poor breakfast. Both field and laboratory-based studies indicated that melatonin secretion at night might be increased by TRP intake in the morning if there is exposure to bright light during the daytime.…”

“…This ratio depends on the contents of a meal; it is increased by intake of TRP-rich protein [ 7 ] and carbohydrates [ 8 – 10 ] and decreased by intake of LNAA-rich protein. In Fukushige et al’s study [ 3 ], the TRP/LNAA ratios of both TRP-rich and TRP-poor foods were very similar; therefore, it was difficult to conclude that the increase in melatonin secretion at night was due to the TRP-rich breakfast alone. It is necessary to control the intakes of other nutrients in order to elucidate the effect of TRP intake in the morning on nocturnal melatonin secretion.…”