Collagen is the most abundant structural protein in the human body. From the skin to the tendons, including the joints and blood vessels: it is found in the extracellular matrix of the vast majority of our tissues.
Its main role is to maintain the integrity of those connective tissues, giving them strength, support and hydration. Thanks to these properties, collagen therefore contributes to good bone density and joint comfort, to wound healing, and to skin beauty.
What does this have to do with glycine ?
D’un point de vue moléculaire, le collagène est constituté de trois acides aminés majeurs : la proline, l’hydroxyproline et la glycine. Simple et petit, la glycine représente plus de 30% des acides aminés du collagène.
On the health supplement market, the two are often found side by side. But why consider a glycine supplement alone if collagen is already rich in that amino acid?
Let’s unpack what science says about the benefits of each, and about their potential complementarity.
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Collagen, a structural protein with many benefits
Improved skin quality
Some research conducted on people taking collagen supplements concluded that this supplementation could improve the appearance of the skin.
Collagen would mainly have an anti-aging effect, which explains its presence in many creams for mature skin. By providing additional support to the epidermis, the skin becomes smoother and firmer.
It also strengthens the skin’s protective barrier, thus preventing dehydration through evaporation. As a result, the skin appears plumper and more hydrated.
Collagen also plays a role in wound healing. Boosting its natural production could potentially promote the regeneration of skin tissue.
Less painful joints
Some scientific studies have already shown an improvement in joint comfort in athletes after 24 weeks of taking collagen supplements.
Similarly, there may be a relief of symptoms in people with osteoarthritis according to several studies.
Benefits of glycine supplementation
A lack of daily glycine intake
Glycine is one of the amino acids essential for collagen synthesis. It therefore ensures its proper functioning.
However, daily requirements appear insufficient according to the results of certain scientific research. Between a dietary intake estimated between 1.5 and 6 g of glycine, coupled with a natural synthesis from L-serine of 3 g per day, there would be a shortfall of about 10 g of glycine per day to meet the intake necessary for normal collagen production,
Increasing dietary intake via the intake of glycine supplements could in principle be a good strategy to increase healthy collagen production.
Improved sleep quality
Glycine supplementation is often recommended to improve sleep quality. Indeed, according to some studies, taking 3 g of glycine before going to bed reduces the feeling of fatigue the next day.
This would be due to the earlier onset of restorative sleep phases during the night. Other recent studies have also shown that taking collagen rich in glycine reduces the number of nighttime awakenings and improves cognitive function.
Anti-inflammatory effect
Glycine is considered an anti-inflammatory micronutrient, for which applications could be numerous.
Several scientific reviews have emerged in recent years and report promising results for its potential positive role in the prevention of inflammatory diseases.
Glycine supplementation has also shown interesting effects for alleviating neurological symptoms in people suffering from psychiatric disorders.
However, I believe that new studies on large-scale, healthy populations should be considered.
Glycine in athletes
Like collagen, glycine has a beneficial impact on joint health thanks to its protective anti-inflammatory effect on the joints.
Beyond effects similar to collagen supplementation, an increased intake of glycine promotes the normal synthesis of creatine. Creatine is an energy molecule essential for short, intense efforts such as weight training.
So, collagen or glycine?
Collagen, the first choice for joints
Are there similar benefits between taking collagen and taking glycine? Absolutely, since the former contains the latter, and the latter contributes to the synthesis of the former.
However, collagen supplementation also brings other components. Like hydroxyproline, which could provide additional benefits for the joints.
Glycine, a broader effect
En parallèle, la prise de glycine de façon plus concentrée pourrait répondre à vos besoins spécifiques, en participant activement à la synthèse de glutathion, un antioxydant, ou encore de créatine.
Between glycine and collagen: a matter of priority
There is no clear scientific answer about which supplement to choose. Taking one or the other essentially depends on your main goals, but also on your diet.
Il existe de la glycine entièrement végétale, alors que vous ne pourrez pas trouver de collagène vegan, par exemple. C’est pourquoi les personnes vegan se tournent vers la glycine.
Sources and scientific studies
Aguayo-Cerón KA et al., 2023, Glycine: The Smallest Anti-Inflammatory Micronutrient.
Miranda RB et al., 2021, Effects of hydrolyzed collagen supplementation on skin aging: a systematic review and meta-analysis.
Clark KL et al., 2008, 24-week study on the use of collagen hydrolysate as a dietary supplement in athletes with activity-related joint pain.
García-Coronado JM et al., 2019, Effect of collagen supplementation on osteoarthritis symptoms: a meta-analysis of randomized placebo-controlled trials.
Meléndez-Hevia et al., 2009, A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis.
Wataru YAMADERA et al., 2007, Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes
Razak MA et al., 2017, Multifarious Beneficial Effect of Nonessential Amino Acid, Glycine: A Review.
Soh J et al., 2024, The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review.
