Feeling the Chill? Maybe it’s Time for Tyrosine

Thyroid & Adrenal

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It’s common to feel cold as we get older. One reason for that is because the blood vessels nearest to the surface of our skin can’t contract as easily as they used to.

But that extra sweater or blanket may not always be necessary. Individuals who often feel chilled may want to try supplementing with L-tyrosine instead.

This amino acid is used by the thyroid, along with iodine, to create the thyroid hormones necessary to keep our energy levels strong and give our metabolic “gas pedal” a healthy push. But in this clinical study, L-tyrosine also appeared to encourage the constrictions of blood vessels near the skin, an action called “cutaneous vasoconstriction” in older adults.

Abstract:

Lang JA, Krajek AC, Schwartz KS, Rand JE. Oral L-Tyrosine Supplementation Improves Core Temperature Maintenance in Older Adults. Med Sci Sports Exerc. 2020 Apr;52(4):928-934.

Introduction: During cold exposure, an increase in sympathetic nerve activity evokes vasoconstriction (VC) of cutaneous vessels to minimize heat loss. In older adults, this reflex VC response is impaired thereby increasing their susceptibility to excess heat loss and hypothermia. Because L-tyrosine, the amino acid substrate necessary for catecholamine production, has been shown to augment reflex VC in age skin, we hypothesize that oral ingestion of L-tyrosine will attenuate the decline in core temperature (Tc) during whole-body cooling in older adults.

Methods: In a randomized, double-blind design, nine young (25 ± 3 yr) and nine older (72 ± 8 yr) participants ingested either 150 mg·kg of L-tyrosine or placebo before commencing 90 min of whole-body cooling to decrease skin temperature to approximately 29.5°C. Esophageal temperature and forearm laser Doppler flux (LDF) were measured continuously throughout the protocol to provide an index of Tc and skin blood flow, respectively. The change in esophageal temperature (ΔTES) was the difference in temperature at the end of cooling subtracted from baseline. Cutaneous vascular conductance (CVC) was calculated as CVC = LDF/mean arterial pressure and expressed as a percent change from baseline (%ΔCVCBASELINE).

Results: Oral tyrosine ingestion augmented the cutaneous VC response to cooling in older adults (placebo, 14.4 ± 2.0; tyrosine, 32.7% ± 1.7% ΔCVCBASELINE; P < 0.05). Additionally, tyrosine improved Tc maintenance throughout cooling in older adults (placebo, -0.29 ± 0.07; tyrosine, -0.07 ± 0.07 ΔTES; P < 0.05). Both the cutaneous VC and Tc during cooling were similar between young and older adults supplemented with tyrosine (P > 0.05).

Conclusions: These results indicate that L-tyrosine supplementation improves Tc maintenance in response to acute cold exposure in an older population.