Abstract
Glutamine is a conditionally essential amino acid widely used in sports nutrition, especially because of its immunomodulatory role. Notwithstanding, glutamine plays several other biological functions, such as cell proliferation, energy production, glycogenesis, ammonia buffering, maintenance of the acid-base balance, among others. Thus, this amino acid began to be investigated in sports nutrition beyond its effect on the immune system, attributing to glutamine various properties, such as an anti-fatigue role. Considering that the ergogenic potential of this amino acid is still not completely known, this review aimed to address the main properties by which glutamine could delay fatigue, as well as the effects of glutamine supplementation, alone or associated with other nutrients, on fatigue markers and performance in the context of physical exercise. PubMed database was selected to examine the literature, using the keywords combination “glutamine” and “fatigue”. Fifty-five studies met the inclusion criteria and were evaluated in this integrative literature review. Most of the studies evaluated observed that glutamine supplementation improved some fatigue markers, such as increased glycogen synthesis and reduced ammonia accumulation, but this intervention did not increase physical performance. Thus, despite improving some fatigue parameters, glutamine supplementation seems to have limited effects on performance.
Highlights
Fatigue is defined as the inability to maintain power output and strength, impairing physical performance [1]
Since the mid-1980s and 1990s, the role of amino acids in the development of fatigue has been discussed [3,6,7,8,9], and evidence demonstrated that plasma glutamine concentrations and the glutamine/glutamate plasma ratio are reduced in athletes under chronic fatigue and overtraining syndrome, raising a question about the possible ergogenic effects of glutamine supplementation [10,11,12,13]
Nutrients 2019, 11, 863 considered as a direct stimulator of glycogen synthesis [7,16], (iii) this amino acid is the main non-toxic ammonia carrier, avoiding the accumulation of this metabolite [14], (iv) glutamine is linked to attenuation of muscle damage and is considered an indirect antioxidant via stimulation of glutathione synthesis [17,18], among others
Summary
Fatigue is defined as the inability to maintain power output and strength, impairing physical performance [1]. Nutrients 2019, 11, 863 considered as a direct stimulator of glycogen synthesis [7,16], (iii) this amino acid is the main non-toxic ammonia carrier, avoiding the accumulation of this metabolite [14], (iv) glutamine is linked to attenuation of muscle damage and is considered an indirect antioxidant via stimulation of glutathione synthesis [17,18], among others. Despite the potential of glutamine in attenuating some causes of fatigue, the effects of this amino acid supplementation on fatigue markers and physical performance have not been yet completely elucidated. The present article aims to review the main anti-fatigue properties of glutamine and the effects of this amino acid supplementation in this regard
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