Marine collagen may help to improve sleep quality thanks to its concentration of the amino acid glycine. Glycine acts as a neurotransmitter in the brain, increasing serotonin levels, which is known to promote feelings of calmness and helps to maintain a healthy circadian rhythm: a key factor in obtaining quality sleep (1). In a study of adults prone to insomnia, participants experienced a significant increase in sleep quality after consuming 3 grams of glycine before bed (1). The study suggests that glycine's positive effect on sleep quality can also be attributed to its ability to lower core body temperature, which helps to promote sleep (1).
References:
Haas, E (2006). Staying Healthy with Nutrition.
Bannai, M, Nobuhiro, K (2012). New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep.