The efficacy of GABA supplementation is partly measured by heart-rate variability (HRV), which is determined by the fluctuation in inter-beat intervals controlled by the sympathetic and parasympathetic branches of the autonomic nervous system.
“Sedentary individuals characterized by low physical fitness often manifest autonomic imbalances typified by augmented sympathetic and attenuated parasympathetic activity at rest,” the team of Brazilian researchers wrote in the Journal of Dietary Supplements.
“Within this investigation, volunteers previously sedentary underwent a structured training regimen, wherein the GABA-supplemented group demonstrated promising findings with marked improvements in HRV. These favorable GABA-associated effects on HRV potentially stem from dual avenues: direct HRV enhancements and secondary improvements in emotional and sleep parameters, subsequently influencing HRV.”
The findings suggest that the elevation of HRV fostered the nervous system's "rest and digest" parasympathetic predominance over "fight or flight" sympathetic excitation, presenting GABA supplementation "as a promising avenue for augmenting both cardiovascular and emotional well-being among individuals actively participating in physical exercise.”
GABA and the brain
GABA is a neurotransmitter implicated in stress, anxiety, sleep-related disorders, and heart rate reactions and HRV, the latter serving as a cost-effective, noninvasive metric to determine cardiovascular health, the researchers noted.
“Modulated by the sympathetic and parasympathetic branches of the autonomic nervous system, [GABA] offers insights into cardiac autonomic control and cardiovascular wellbeing,” they wrote.
Beyond physical determinants of health, GABA can also improve cognitive measures. A 2020 study showed that 12 weeks of GABA supplementation at 100 mg per day improved test scores for visuospatial/construction faculty and memory, which also improved when the dose doubled to 200 mg.
Another study found that higher doses of GABA can have activating effects in the brain, which is a significant finding considering GABA is reported to not pass the blood-brain barrier.
Study details
The randomized, double-blind, placebo-controlled clinical study included 30 sedentary women over the age of 18 who were overweight or obese. Their BMIs equaled or exceeded 25, and these women did not include regular physical activity exceeding 150 minutes in their weekly routines.
The participants were randomly assigned to one of two cohorts: the experimental group that received 200 mg of GABA once daily for a total of 90 supplementation doses, and the placebo group. GABA capsules were provided by Official Farma, Santo André, Brazil. The volunteers were told to take one capsule nightly, 30 minutes before bedtime.
Over 90 days, each group participated in physical exercise while receiving supplementation. Training included three weekly 50-minute sessions comprised of an initial 20-minute high-intensity interval aerobic exercise, followed by a 20-minute resistance muscle strength session and a 10-minute wind-down period of flexibility and joint mobility exercises.
“These findings suggest that GABA supplementation might bolster parasympathetic predominance, implying a beneficial autonomic regulatory impact, particularly post-training, when vagal influence tends to recede,” the researchers wrote.
Additionally, participants were assessed at three points: baseline, halfway though the experiment and at the completion of the study. During that time, researchers measured sleep efficiency and emotional response.
Depression, anxiety and stress were measured through a 21 item self-assessment tool, and a life events scale was used to determine the influence of life events over a year. The sleep index questionnaire had 19 self-rated questions and five questions that were answered by either bedmates or roommates. Questions determined sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, whether sleep medication were used or daytime dysfunction.
Those receiving GABA supplementation showed significant improvements in sleep efficiency, emotional responsiveness and mitigating depression, the researchers concluded.
Source: Journal of Dietary Supplements
doi: 10.1080/19390211.2024.2308262
“GABA Supplementation, Increased Heart-Rate Variability, Emotional Response, Sleep Efficiency and Reduced Depression in Sedentary Overweight Women Undergoing Physical Exercise: Placebo-Controlled, Randomized Clinical Trial”
Authors: Aparecida Patricia Guimarães et al.