Oral tyrosine supplementation improves exercise capacity in the heat

Abstract

Increased brain dopamine availability improves prolonged exercise tolerance in the heat. It is unclear whether supplementing the amino-acid precursor of dopamine increases exercise capacity in the heat. Eight healthy male volunteers [mean age 32 ± 11 (SD) years; body mass 75.3 ± 8.1 kg; peak oxygen uptake ([Formula: see text]) 3.5 ± 0.3 L min(-1)] performed two exercise trials separated by at least 7 days in a randomised, crossover design. Subjects consumed 500 mL of a flavoured sugar-free drink (PLA), or the same drink with 150 mg kg body mass(-1) tyrosine (TYR) in a double-blind manner 1 h before cycling to exhaustion at a constant exercise intensity equivalent to 68 ± 5% [Formula: see text] in 30°C and 60% relative humidity. Pre-exercise plasma tyrosine:large neutral amino acids increased 2.9-fold in TYR (P < 0.01), while there was no change in PLA (P > 0.05). Subjects cycled longer in TYR compared to PLA (80.3 ± 19.7 min vs. 69.2 ± 14.0 min; P < 0.01). Core temperature, mean weighted skin temperature, heart rate, ratings of perceived exertion and thermal sensation were similar in TYR and PLA during exercise and at exhaustion (P > 0.05) despite longer exercise time in TYR. The results show that acute tyrosine supplementation is associated with increased endurance capacity in the heat in moderately trained subjects. The results also suggest for the first time that the availability of tyrosine, a nutritional dopamine precursor, can influence the ability to subjectively tolerate prolonged submaximal constant-load exercise in the heat.

Oral branched-chain amino acid supplements that reduce brain serotonin during exercise in rats also lower brain catecholamines

“…Hence, TYR hydroxylase is much closer to substrate saturation than is TRP hydroxylase and precursorinduced increases in overall synthesis in the catecholamine pathway would be expected to be smaller than those in the 5HT pathway. This may account for the variable effects of TYR administration previously observed on physical performance and mental function in soldiers and athletes (Struder et al 1998;Lieberman 2003;Tumilty et al 2011;Watson et al 2012). However, since TYR hydroxylase is not fully saturated with substrate (Carlsson and Lindqvist 1978), the above considerations would also predict that reducing brain TYR concentrations might elicit a large reduction in catecholamine biosynthesis.…”

Spinach Effects (Amaranthus hybridus) on Spatial Memory

“…13 Tyrosine provides neuroprotective effect to acute stress by preventing the depletion of neurotransmitters in neurons. 14 Flavonoids can stop oxidative reactions inducing neuronal damage by inhibiting the activation of caspase-3 as its role as an anti-apoptosis. 15 Flavonoids synthesize acetylcholine and factors such as brainderived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the hippocampus and frontal cortex associated with spatial working memory improvement.…”

Nutra-ergonomics: influence of nutrition on physical employment standards and the health of workers

“…Military cadets who ingested 2 g of tyrosine a day for 6 days of a combat training course had enhanced memory and tracking tasks and reduced systolic blood pressure (Deijen et al 1999). However, the effect of tyrosine in the heat has produced mixed results, with some (Tumilty et al 2011) but not all (Tumilty et al 2014;Watson et al 2012) studies suggesting tyrosine availability may influence fatigue processes under hot conditions. Thus, in very challenging physical employment standards or prolonged work environments tyrosine supplementation may have application; however, there is no current evidence to suggest that tyrosine supplementation is beneficial under less extreme work conditions.…”