Is Glycine an Ergogenic Aid? by Jerry Brainum 11/26

 

 

Glycine is the smallest amino acid and arguably the sweetest. Its name comes from the Greek glykys, meaning “sweet,” and the powder tastes noticeably sugary. By contrast, arginine is famously bitter.  I once described it to a friend as tasting like dog vomit, and I stand by that.”Nutrition scientists sort amino acids into “essential” ones, which you must get from food, and “non-essential” ones, which your body can build on its own. Glycine falls into the second group, alongside arginine and glutamine. The body mainly makes it from serine and threonine, two other amino acids, and can also get it from choline, a nutrient found in foods like eggs and liver.

But “non-essential” doesn’t mean “unimportant.” Some researchers argue glycine is better described as conditionally essential: the body makes it, but perhaps not always in amounts sufficient for optimal growth and tissue repair. That case rests heavily on animal studies, where severe shortages have impaired growth and immune function. By contrast, a mild shortfall appears to cause no obvious harm.

Glycine’s most important job may be structural. It makes up roughly one-third of the amino acids in collagen, the protein that gives skin, tendons, ligaments, and cartilage strength and elasticity. Collagen production slows with age, which helps explain why skin thins and joints stiffen. This article asks whether giving the body more glycine can offset any of that, and whether it can make you a better athlete.

In the brain, glycine acts as an inhibitory neurotransmitter, a chemical messenger that makes nerve cells less likely to fire. That's likely why it’s studied for sleep and relaxation, though researchers are still working out how much oral glycine actually reaches the brain and changes its signaling.

In small trials, three grams of glycine before bed improved how well people said they slept. The sleep evidence is the strongest part of glycine’s case, but it’s modest. In small trials of people with mild sleep complaints, taking about three grams shortly before bed improved reported sleep quality and next-day alertness. That matters for athletes because sleep is when much of the body recovers. It is still a long way from showing that glycine makes anyone faster or stronger.

Glycine’s other reputed benefits are even less certain. Early trials have shown that a combination of glycine and N-acetylcysteine (NAC), an antioxidant precursor, improved markers of cellular energy production and oxidative stress in older adults. In rodents, glycine has protected the liver against alcohol-induced damage, and one line of animal research suggests it may soften the liver effects of high-dose oral anabolic steroids. Those are interesting leads, not proven human benefits, and . . .