What does it do?
- Plasma levels of glycine decline post exercise, potentially due to increased utilisation. This suggests an increased need for glycine while collagen synthesis is elevated post exercise.5 It has been hypothesized that under circumstances of high demand such as a heavy training stimulus, dietary collagen may be of potential benefit.
- The addition of ascorbic acid and proline to cell culture growth media), results in an increased collagen content and improvement to mechanical properties6. This suggests both are important nutrients for the synthesis of collagen in connective tissue. However, whether intake beyond dietary sufficiency is required in vivo is yet to be determined.
- Although AAs derived from the consumption of diary protein (casein), including proline are incorporated into intramuscular connective tissue after a bout of resistance training, this does not result in a further increase of intramuscular connective tissue protein synthesis rates, compared to when a placebo is consumed. This may be due to the low glycine content of casein compared to collagen proteins.5
- Inflammation results in the disorganisation of collagen fibrils in the ECM, and has been proposed to lead to conditions such as tendinopathy.6 Glycine has been shown to inhibit inflammatory cell activation7, and therefore may be able to exert a beneficial effect in inflammatory conditions. The administration of glycine results in an improvement in the biochemical and biomechanical properties of an inflamed rat tendon8, and restores the anabolic response of muscle tissue to leucine under acute inflammatory conditions.9
- Plasma di and tri peptide amino acids of hydroxyproline available post the ingestion of collagen proteins appear to trigger a range of signalling responses in the human body. How this translates into functional outcomes of enhanced collagen synthesis or improved connective tissue health in vivo is still unclear.10