Glycine: A Sweet-Tasting Amino Acid with Broad-Ranging Health Benefits

BY SHAWN MANSKE, ND

Glycine is an amino acid derived from protein-rich foods such as meat, eggs, lentils, and dairy.¹ It’s considered a nonessential amino acid since the body can make glycine even if it doesn’t get enough from dietary sources. But the health benefits from getting adequate amounts of glycine – whether through diet or supplementation – are considerable.

As both a building block of protein and a signaling molecule, glycine plays fundamental metabolic and physiological roles in an array of health functions, including metabolic regulation, antioxidative reactions, and neurological function.² For patients, this translates to significant health benefits – specifically, glycine has been shown to:

• Prevent tissue injury
• Enhance antioxidant capacity
• Promote protein synthesis and wound healing
• Support immunity
• Reduce inflammation
• Address metabolic dysfunction (i.e., obesity, diabetes, cardiovascular disease)
• Improve sleep quality⁴

Glycine is also involved in modulating growth through the regulation of growth hormone (GH) synthesis, improving muscle tone, delaying muscular degeneration, promoting gut health, and protecting the intestine against the harmful effects of radiotherapy in cancer treatment.⁵ Recently, glycine was found to boost longevity in genetically heterogeneous mice. Existing evidence suggests that glycine prolongs life by mimicking methionine restriction and activating autophagy.⁶

Sweet Protein Synthesis

Glycine was first isolated in 1820 through the process of hydrolyzing gelatin by boiling it with sulfuric acid.⁷ Its name was derived from the Greek word “glykys” because of its sweet taste, which is similar to glucose.⁸

Glycine represents 11.5% of the total amino acid content in the human body. It makes up 20% of the total amino acid content in nitrogen; 80% of the body’s glycine supply is used for protein synthesis. Glycine is synthesized from choline, serine, hydroxyproline, and threonine through interorgan metabolism in which the kidneys and liver are primarily involved.⁹ The human body requires 2g of glycine per day, generally supplied through diet. 

Five Ways Glycine Supports Patient Health

#1 - Improving Sleep Quality

Glycine acts as a neurotransmitter, modulating neuronal activity. As an inhibitory neurotransmitter in the central nervous system, it plays an important role in the mechanism of pain transmission.¹⁰ By reducing subjective pain levels, this activity can allow people experiencing pain to get more restful and sustained sleep.

Supplementing with glycine before bed has been found to shorten the time to fall asleep, increase deep sleep stages, and decrease daytime drowsiness. This leads to improvements in subjective fatigue and feeling rested after awakening from sleep.¹¹ By enhancing sleep, glycine may also improve cognitive performance, stress resilience, and psychiatric disorders related to sleep disruption; its calming effects may support mental health overall.¹²

#2 - Supporting Mental Health

As mentioned above, reducing pain signaling can lead to improvements in one’s mood and well-being, as can improving one’s sleep. Remember, glycine also acts as an inhibitory neurotransmitter in the brain, helping modulate excitatory signaling that can come from excess sympathetic nervous system stimulation – a common experience in 

our modern, high-stimulus world. By modulating this signaling, glycine can support a more balanced mood and emotions. 

#3 - Immunomodulating and Anti-Inflammatory Activities

Inflammation is a significant function of our immunological defenses and is also involved in the pathology of metabolic disorders. Glycine has been shown to exert anti-inflammatory actions by reducing pro-inflammatory cytokines and increasing anti-inflammatory cytokines.¹³ By dampening inflammatory responses, glycine may mitigate chronic conditions like obesity, diabetes, and cardiovascular disease characterized by low-grade inflammation.¹⁴

#4 - As a Precursor to Glutathione

Glycine is a building block of glutathione (along with cysteine and glutamine), which plays a significant role in protecting cellular molecules from endogenous and exogenous reactive oxygen and nitrogen species by directly quenching these free radicals.¹⁵

Lower circulating levels of glycine have been reported in association with various cardiometabolic disorders, including obesity, type 2 diabetes (T2D), metabolic syndrome, non-alcoholic fatty liver disease (NAFLD), acute myocardial infarction, and coronary heart disease. Research has demonstrated that low glycine availability is a limiting factor for glutathione biosynthesis, which is restored by glycine supplementation, leading to lower oxidant damage in NAFLD and T2D.¹⁶

#5 - Promoting and Maintaining Gut Health 

Due to its anti-inflammatory and antioxidant properties, along with its ability to promote collagen synthesis and aid tissue repair, glycine may offer significant benefits to the intestinal tract.¹⁷ While preliminary, research has suggested that glycine may support the health of the gastrointestinal tract and the intestinal barrier by maintaining the thickness of the intestinal wall and the surface of the intestinal epithelium.¹⁸