Synopsis

Source of validity: Scientific
Rating (out of 5): 2

L-glycine is an amino acid with several physiological roles, including serving as a building block for proteins, participating in neurotransmission, and being involved in the synthesis of compounds like creatine and glutathione. There is emerging scientific interest in glycine’s potential to support energy levels, primarily through its roles in mitochondrial function and sleep quality rather than direct energy production. Some human and animal studies suggest glycine supplementation may improve sleep quality and reduce fatigue, which can indirectly enhance perceived daytime energy. For example, a few small clinical trials have demonstrated that glycine taken before bedtime can improve subjective sleep quality and reduce feelings of fatigue in healthy adults. Additionally, glycine’s involvement in the synthesis of creatine—an important molecule for cellular energy in muscle—suggests a possible mechanism for supporting energy metabolism.

However, robust evidence directly linking glycine supplementation to increased energy levels or treatment of chronic fatigue is limited. Most studies are small-scale, short-term, and focus on sleep or cognitive function rather than direct measures of energy. There is no large-scale clinical evidence to strongly support glycine as a primary therapy for low energy. Thus, while there is some scientific rationale and preliminary evidence, it remains modest, warranting a rating of 2 out of 5.

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