Relieving occupational fatigue by consumption of a beverage containing γ-amino butyric acid

Journal Title (Medline/Pubmed accepted abbreviation): J. Nutr. Sci. Vitaminol.
Year: 2011
Volume: 57
Page numbers: 9-15
doi (if applicable):

Summary of Background and Research Design

Background: With modern busy schedules, occupational fatigue is becoming very common. This can negatively affect work performance, as well as other areas of life such as physical performance in recreational sports. γ-Aminobutyric acid (GABA) is a compound endogenously produced from the amino acid glutamine in the brain. It has been found that GABA supplementation may be able to induce relaxation and reduce stress.

Hypothesis: GABA supplementation will improve performance on a mental task and reduce overall stress levels, as assessed by salivary stress markers

Subjects: 16 male and 14 female healthy Japanese people between 24-43 yrs old, avg. = 31.7 yrs. The subjects had no history of behavioral disorders, drug or alcohol abuse, diabetes, or other pre-existing medical conditions. The authors did not report if they inquired regarding the use of dietary supplements or medications in the subjects.

Experimental design: randomized, single-blind, placebo-controlled, cross-over design

Treatments: A 30 kcal, artificially sweetened beverage containing 0, 25, or 50 mg GABA.

Protocol: Participants were evaluated for chronic fatigue by using 3 different, validated methods:
  1. The Profile of Mood States (POMS) method that inquires about confusion, fatigue, vigor, depression, anger, and anxiety,
  2. A checklist for self-diagnosis of fatigue, and
  3. A Visual Analog Scale (VAS) questioning about level of fatigue, from 0 to 100.

According to at least one of these evaluations, those who met the criteria for fatigue during all 3 sessions were labeled as having “chronic fatigue on a daily basis”. Participants reported to the laboratory on 3 occasions within 3 wks. At each occasion they ingested a different beverage and completed a math test (the Uchida-Kraepelin Psychodiagnostic Test, UKT) that was designed to induce mental stress. Subjects completed the VAS before drinking the beverage, half way through the test, and at the completion of the test. The POMS questionnaire was completed before and after the test. Saliva was also acquired before, half way through, and at the end of the test to be assessed for salivary stress markers [chromogranin A (CgA) and cortisol]. It is unclear when the checklist for self-diagnosis was administered.

Summary of research findings
  • There were 9 subjects who were selected for having chronic fatigue on a daily basis.
  • Among those labeled with chronic fatigue (n = 9):
    • The high dose (50 mg) of GABA significantly elevated their mood (VAS scores increased) in both the second and first half of the test (p < 0.01).
    • GABA significantly attenuated the rise in salivary CgA and cortisol. Effects were seen with the 25 mg dose and were more pronounced with the 50 mg dose.
    • GABA reduced “localized discomfort”, drowsiness, lassitude, and inability to concentrate compared to the control group.
    • They performed significantly better on the math test with the GABA supplement than with the placebo. With 25 mg, p = 0.9557 but with 50 mg GABA, p = 0.0033.
  • Among those who did not suggest chronic fatigue, 50 mg GABA increased the ability to concentrate. No other reported symptoms were statistically significant.

Interpretation of findings/Key practice applications

Among people that have chronic fatigue, GABA significantly increases their ability to concentrate and perform on mental tasks. It also reduces stress biomarkers that are related to mental and physical fatigue. This may be because chronically fatigued individuals are deficient in GABA. Chronic fatigue is seen also in the sports community and it is likely that athletes who are regularly fatigued could benefit from GABA supplementation. Sleep, however, is probably the best remedy for fatigue and related ailments.


The authors did not expound on the results from the 21 people who were determined not to be “chronically fatigued”. It would be interesting to see if there are any benefits of GABA supplementation for those who are not feeling fatigued or those that are fatigued only on that day but not chronically.
                          This study measured performance on a mental test, not a physical test. Although the salivary biomarkers also detect physical stress, it would be interesting to directly measure physical performance with GABA supplementation.
NOTE: In Figure 2, the vertical scales are a bit misleading. It would have been clearer if the control, pre-test value had been assigned a value of 0 instead of 100.
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