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Cited by 247Tryptophan and brain disordersFatty Acid Research and HealthRegulation of Appetite and Obesity

Effects of normal meals rich in carbohydrates or proteins on plasma tryptophan and tyrosine ratios

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Wurtman, Richard J, Wurtman, Judith J, Regan, Meredith M, McDermott, Janine M, Tsay, Rita H, Breu, Jeff J·2003·The American Journal of Clinical Nutrition
DOI 10.1093/ajcn/77.1.128
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Abstract

Background The delivery of circulating tryptophan to the brain and its conversion to serotonin vary directly with plasma concentrations of tryptophan and inversely with those of other large neutral amino acids (LNAAs). Although carbohydrate-rich, protein-free formula diets have been shown to elevate, and high-protein diets to depress, the tryptophan-LNAA ratio, few data are available about this ratio's responses to actual meals.Objective We determined whether carbohydrate-rich or protein-rich breakfasts, such as those Americans normally eat, produce substantial differences in the plasma tryptophan-LNAA ratio and in the corresponding ratio for tyrosine, the precursor of brain dopamine and norepinephrine.Design Nine overnight-fasted subjects consumed, 3-7 d apart, a carbohydrate-rich (69.9 g carbohydrate and 5.2 g protein) and a protein-rich (15.4 g carbohydrate and 46.8 g protein) breakfast. Blood samples collected at baseline and after 40, 80, 120, and 240 min were assayed for tryptophan, tyrosine, the 5 other LNAAs, and insulin.Results The carbohydrate-rich and protein-rich breakfasts had significantly different effects on both the plasma tryptophan-LNAA and tyrosine-LNAA ratios (each P < 0.01). Among the 8 subjects who consumed both breakfasts, the median difference for tryptophan:LNAA was 54% (range: 36-88%) and for tyrosine:LNAA was 28% (range: 10-64%). Insulin concentrations rose significantly after the carbohydrate but not after the protein meal.Conclusions High-carbohydrate and high-protein breakfasts similar to those Americans normally eat can cause substantial differences in the plasma tryptophan ratio and thus, probably, in brain tryptophan concentrations and serotonin synthesis. Such meals also change the plasma tyrosine ratio and may thereby modify catecholamine synthesis.

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  • Some studies used a placebo rich in carbohydrates, such as orange juice, which may have inadvertently affected brain uptake of tyrosine.

    “Furthermore, some studies used a placebo that was rich in carbohydrates (e.g., orange juice), which may have inadvertently affected brain uptake of tyrosine (Wurtman et al., 2003).”

    From Behavioral and cognitive effects of tyrosine intake in healthy human adults (2015) · cites this paper as Wurtman et al., 2003

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Authors
Wurtman, R. J., Wurtman, J. J., Regan, M. M., McDermott, J. M., Tsay, R. H., & Breu, J. J.
Affiliations
Massachusetts Institute of Technology (US)
Corresponding author
Wurtman, Richard J
ORCID
Regan, Meredith M
Venue
The American Journal of Clinical Nutrition
Publisher
Elsevier BV
Published
2003-01
Volume
77
Issue
1
Pages
128-132
ISSN
0002-9165 (ISSN-L)
DOI
10.1093/ajcn/77.1.128
OpenAlex
W2096665699
Cited by
247
References
34
Citations by year
2026: 9 · 2025: 11 · 2024: 19 · 2023: 22 · 2022: 22 · 2021: 34 · 2020: 9 · 2019: 6 · 2018: 6 · 2017: 13 · 2016: 8 · 2015: 5 · 2014: 11 · 2013: 6 · 2012: 7
FWCI
2.22
Type
journal article
Language
en
Open access
Licence
Locations
  • American Journal of Clinical Nutrition (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Institute of Mental Health (MH 28783)
  • National Center for Research Resources (M01 RR0008)
Topics
  • Life Sciences › Neuroscience › Biological Psychiatry › Tryptophan and brain disorders
  • Health Sciences › Nursing › Nutrition and Dietetics › Fatty Acid Research and Health
  • Life Sciences › Neuroscience › Endocrine and Autonomic Systems › Regulation of Appetite and Obesity
Keywords
tryptophan, tyrosine, large neutral amino acids, breakfast composition, high-carbohydrate diet, high-protein diet, serotonin synthesis, catecholamine synthesis, insulin response, plasma amino acids
MeSH terms
Adult, Amino Acids, Chromatography, High Pressure Liquid, Dietary Carbohydrates, Dietary Proteins, Female, Humans, Male, Tryptophan, Tyrosine

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