Evening intake of alpha-lactalbumin increases plasma tryptophan availability and improves morning alertness and brain measures of attention

Background: Brain serotonin function is thought to promote sleep regulation and cognitive processes, whereas sleep abnormalities and subsequent behavioral decline are often attributed to deficient brain serotonin activity. Brain uptake of the serotonin precursor tryptophan is dependent on nutrients...

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Published in:	The American journal of clinical nutrition Vol. 81; no. 5; pp. 1026 - 1033
Main Authors:	Markus, C.R, Jonkman, L.M, Lammers, J.H.C.M, Deutz, N.E.P, Messer, M.H, Rigtering, N
Format:	Journal Article
Language:	English
Published:	Bethesda, MD American Society for Clinical Nutrition 01-05-2005 American Society for Clinical Nutrition, Inc
Subjects:	Adult amino acid metabolism Amino Acids - administration & dosage Amino Acids - pharmacology Analysis of Variance Biological and medical sciences brain Brain - drug effects Brain - metabolism cognition Cognition & reasoning Diet dietary protein dinner Double-Blind Method Electroencephalography Feeding. Feeding behavior Female Fundamental and applied biological sciences. Psychology Humans lactalbumin Lactalbumin - administration & dosage Lactalbumin - pharmacology Male nutrient availability nutrient utilization protein intake Proteins Psychomotor Performance - drug effects serotonin Sleep Sleep - drug effects sleeping metabolic rate Time Factors tryptophan Tryptophan - administration & dosage Tryptophan - blood Vertebrates: anatomy and physiology, studies on body, several organs or systems Availability Performance evaluation Human Evening Continuous α-lactalbumin Central nervous system Attention Tryptophan Sleep complaints Encephalon Blood plasma Sleep Lactalbumin Sleep wake cycle Performance continuous performance task event-related brain acivity
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Summary:	Background: Brain serotonin function is thought to promote sleep regulation and cognitive processes, whereas sleep abnormalities and subsequent behavioral decline are often attributed to deficient brain serotonin activity. Brain uptake of the serotonin precursor tryptophan is dependent on nutrients that influence the availability of tryptophan via a change in the ratio of plasma tryptophan to the sum of the other large neutral amino acids (Trp:LNAA). Objective: We tested whether evening consumption of alpha-lactalbumin protein with an enriched tryptophan content of 4.8 g/100 g increases plasma Trp:LNAA and improves alertness and performance on the morning after sleep, particularly in subjects with sleep complaints. Design: Healthy subjects with (n = 14) or without (n = 14) mild sleep complaints participated in a double-blind, placebo-controlled study. The subjects slept at the laboratory for 2 separate nights so that morning performance could be evaluated after an evening diet containing either tryptophan-rich alpha-lactalbumin or tryptophan-low placebo protein. Evening dietary changes in plasma Trp:LNAA were measured. Behavioral (reaction time and errors) and brain measures of attention were recorded during a continuous performance task. Results: Evening alpha-lactalbumin intake caused a 130% increase in Trp:LNAA before bedtime (P = 0.0001) and modestly but significantly reduced sleepiness (P = 0.013) and improved brain-sustained attention processes (P = 0.002) the following morning. Only in poor sleepers was this accompanied by improved behavioral performance (P = 0.05). Conclusion: Evening dietary increases in plasma tryptophan availability for uptake into the brain enhance sustained alertness early in the morning after an overnight sleep, most likely because of improved sleep.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	0002-9165 1938-3207
DOI:	10.1093/ajcn/81.5.1026