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Nutrients 2017, 9(12), 1279; doi:10.3390/nu9121279

Dose-Dependent Effects of Oral Tyrosine Administration on Plasma Tyrosine Levels and Cognition in Aging

1
Wageningen University, Division of Human Nutrition, P.O. Box 8129, 6700 EV Wageningen, The Netherlands
2
Radboud University, Donders Institute for Brain, Cognition and Behaviour, Centre for Cognitive Neuroimaging, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
3
Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Department of Geriatric Medicine, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
4
Radboud Alzheimer Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
These authors contributed equally to this work.
*
Author to whom correspondence should be addressed.
Received: 15 September 2017 / Revised: 25 October 2017 / Accepted: 20 November 2017 / Published: 23 November 2017
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Abstract

The effects of tyrosine on plasma response and cognition in aging are unknown. We assessed the dose-dependent response to tyrosine administration in older adults in both plasma tyrosine concentrations and working memory performance. In this double blind randomized cross-over trial 17 older adults (aged 60–75 years) received a single administration of 100, 150, or 200 mg/kg body weight of tyrosine. For comparison, 17 young adults (aged 18–35 years) received a dose of 150 mg/kg body weight of tyrosine. Tyrosine plasma concentrations were determined before and 90, 120, 150, 180, 210, and 240 min after tyrosine intake. Working memory was assessed using the N-back task at 90 min after tyrosine administration. Older adults showed a dose-dependent increase in plasma tyrosine concentrations (p < 0.001), and the plasma response was higher than for young adults with the same dose (p < 0.001). Load-dependent working memory performance decreased with higher doses of tyrosine (p = 0.048), especially in older adults with greater dose-dependent plasma tyrosine responses (p = 0.035). Our results show an age-related increase in plasma tyrosine response, which was associated with a dose-dependent decline in cognitive functioning in older adults. View Full-Text
Keywords: tyrosine; dose-response; aging; working memory; plasma amino acids; catecholamines; dopamine tyrosine; dose-response; aging; working memory; plasma amino acids; catecholamines; dopamine
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MDPI and ACS Style

van de Rest, O.; Bloemendaal, M.; de Heus, R.; Aarts, E. Dose-Dependent Effects of Oral Tyrosine Administration on Plasma Tyrosine Levels and Cognition in Aging. Nutrients 2017, 9, 1279.

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