We don’t typically hear a lot about ‘glycine for muscle.’ That’s probably because glycine is a dirt-cheap amino acid. Anything so abundant and easily obtainable is usually disregarded by the muscle supplement industry.
But glycine is good stuff. It’s a nonessential amino acid that appears to be anti-catabolic. That means it helps prevent muscle protein breakdown in the body. Glycine also appears to be an HGH secretagogue. This means it can stimulate the release of regenerative growth hormone from the pituitary gland.
Just these two benefits alone make ‘glycine for muscle’ a promising proposition for bodybuilding. Add to them the real possibility that glycine has anti-aging effects and you get a dietary supplement that might be underrated.
Glycine: The ‘flexible’ Amino Acid
As mentioned, l-glycine is a nonessential amino acid. That means it’s one of the 11 amino acids that are produced by the body; we don’t need to get it from dietary sources.
It’s also the smallest of the 20 amino acids and has a hydrogen atom as its side chain. This is unusual because all the other amino acids have a carbon atom as their respective side chains. Consequently, glycine is more conformationally flexible; it can conform more readily to different parts of protein structures. Perhaps it is this ‘elasticity’ that’s behind some of glycine’s unique benefits.
Because it’s so small, glycine can fit into both hydrophillic (watery) and hydrophobic (non-watery) cellular environments. Its size also allows it to attach easily to phosphate.
But let’s leave those details to the chemists and focus instead on what supplementation with this amino acid might do for muscle building and anti-aging.
Glycine for GH Release
In one study of 19 subjects, a dose of 6.75 grams of glycine on an empty stomach before bedtime was shown to cause a three-fold boost in growth hormone secretion. Keep in mind that about 50% of daily adult growth hormone output occurs in the first few hours of nightly sleep. Thus, a three-fold increase in this already high amount could be significant. It might provide noticeable benefits if it occurs consistently over time.
And just what are those benefits? 
Let’s start with the anabolic kind. Higher nighttime GH release can improve the body’s recuperation and repair of muscle tissue. This will likely have an indirect positive effect on muscle growth over time.
Many people mistakenly attribute their progress in the gym only to workout techniques. These individuals are often surprised to discover how much a recuperative nudge like higher consistent GH release can add to their progress.
This is why I’ve also designed my entire workout method for the best possible GH release.
But back to glycine: A 2007 study done on 11 subjects aged 30 – 57 demonstrated glycine’s sleep enhancing potential. The subjects took 3 grams before bedtime on one occasion while receiving a placebo on another. On the night they received the glycine, the subjects reported falling asleep faster and waking less often. They also reported feeling more clear-headed and alert the day following their night of sleep with glycine.
Deep, slow-wave sleep is when a good deal of compensatory muscle recuperation occurs. Consistently lengthening that stage of sleep is also one key to maximizing growth hormone release.
Glycine for Muscle: My Experience
As of this writing, my personal experience with glycine supplementation has been limited and measured, but positive. I’ve taken up to 7 grams on an empty stomach before nighttime sleep. This resulted in a noticeably deeper and more restful slumber on those nights.
Along with that, I noticed a clearer, calmer, and more in-control mood on the day following my night’s usage. This could be due to glycine’s role as an inhibitory neurotransmitter.
Could that add to the ‘glycine for muscle’ equation by reducing cortisol? It’s possible. Since cortisol is catabolic, this would make glycine a good anti-catabolic.
Regardless, I’ve been intermittent in my experimentation; choosing to use it only a few nights per week. That decision has been both mindful and intuitive. On the one hand, I’m wary of the possibility of down-regulating glycine receptors, thereby eventually creating the opposite effect from what I’m seeking.
But personal instinct has also been a factor. I naturally trend toward mild insomnia. With that, it only takes a couple nights of excessively deep sleep to have me overly-energized with wakefullness by the following night. Not a bad problem in some respects, but it quickly leads to inconsistent sleep patterns.
It might be surmised that consistent glycine usage would stop that, but I’m not betting on it for now.
Glycine for Muscle: Have you used it?
Whether you use glycine for muscle or other health reasons, only do so with full consultation of your medical doctor. Individual aminos in high dosages can act like drugs and sometimes react with prescription meds.
Human studies on glycine are scarce at this time. Therefore, I welcome any feedback from those who’ve used it, whether for muscle building, sports performance, or other reasons.
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