The Effect of L-Theanine Incorporated in a Functional Food Product (Mango Sorbet) on Physiological Responses in Healthy Males: A Pilot Randomised Controlled Trial

Abstract

Consumption of L-Theanine (L-THE) has been associated with a sensation of relaxation, as well as a reduction of stress. However, these physiological responses have yet to be elucidated in humans where L-THE is compared alongside food or as a functional ingredient within the food matrix. The aim of this study was to determine the physiological responses of a single intake of a potential functional food product (mango sorbet) containing L-THE (ms-L-THE; 200 mgw/w) in comparison to a flavour and colour-matched placebo (ms). Eighteen healthy male participants were recruited in this randomised, double-blind, placebo-controlled trial. The participants were required to consume ms-L-THE or placebo and their blood pressure (BP) (systolic and diastolic), heart rate (HR), and heart rate variability (HRV) were monitored continuously over 90 minutes. Eleven males (age 27.7 ± 10.8 years) completed the study. Changes in area under the curve for systolic and diastolic blood pressure and HRV over the 90 minute observation period indicated no differences between the three conditions (all p > 0.05) or within individual groups (all p > 0.05). The values for heart rate were also not different in the placebo group (p = 0.996) and treatment group (p = 0.066), while there was a difference seen at the baseline (p = 0.003). Based on the findings of this study, L-THE incorporated in a food matrix (mango sorbet) demonstrated no reduction in BP or HR and showed no significant parasympathetic interaction as determined by HRV high-frequency band and low-frequency/high-frequency ratio. Further studies should be focussed towards the comparison of pure L-THE and incorporation within the food matrix to warrant recommendations of L-THE alongside food consumption.

Effect of Green Tea Amino Acid L-Theanine on Physiological Responses: A Protocol for Clinical Trial

“…Changes in HRV will reflect the effects of L-THE on cardiac autonomic nervous system regulation, in particular relating to PNS activity (as indicated by changes in high frequency (HF) and low frequency (LF)). 1 This interaction between L-THE and HRV may potentially highlight the response to food consumption and its relationship with disease. 26 d. HR and HRV i.…”

“…Functional foods describe designed food items that have been shown to be health-enhancing; however, they contain bioactive non-'naturally occurring' compounds, with the aim of increasing product functionality. 1 This relatively new concept of health-promoting functional foods is a significant part of a growing global food trend that is becoming a secondary component of medical treatment. 1 Functional foods provide a potential opportunity to rely less on the use of pharmaceuticals, resulting in high demand for beverages and food products that include health-promoting active ingredients.…”

“…1 This relatively new concept of health-promoting functional foods is a significant part of a growing global food trend that is becoming a secondary component of medical treatment. 1 Functional foods provide a potential opportunity to rely less on the use of pharmaceuticals, resulting in high demand for beverages and food products that include health-promoting active ingredients. 2 The potential functional food additive L-Theanine (L-THE) is a green tea amino acid that has shown to increase relaxation, 3 decrease sleep disturbances 4 and decrease anxiety and the stress response 5 in its pure form in humans (healthy and non-healthy) via capsule intake.…”

“…It is specifically measured by changes between the highest points (R-R interval) of the heartbeat intervals observed on an electrocardiogram (QRS complex). 1 Due to its effect on the stress response, we hypothesize that L-THE will influence the physiological outcomes of the ANS, including but not limited to HR, HRV, BP and the HPA stress response via the salivary biomarker cortisol. 3,5,8 The consumption of L-THE has also been reported to have a profound effect on concentration and increasing alertness, which may improve the speed and accuracy of eye movements, and due to its effects on glutamatergic neurotransmission, may also alter neurophysiological responses in the retina.…”

Food Bioactives: Impact on Brain and Cardiometabolic Health—Findings from In Vitro to Human Studies

“…In consideration of this, and given the recent commercial availability of relatively pure L-THE, there is a strong potential for the development of functional food products that contain this amino acid as a bioactive ingredient. A study by Williams et al (2020) investigated the physiological responses, including heart rate (HR), heart rate variability (HRV) and BP in healthy males ( n = 11), following the acute ingestion of a functional food products (mango sorbet) containing 200 mg of pure L-THE [ 3 ]. In this double blind, placebo-controlled cross-over trial, the participants were required to consume the test food or placebo mango sorbet (color and flavor matched) after which their physiological responses were continuously monitored over a period of 90 min.…”