An impressive perk of powerful ingredients like Peptan® is that they go far beyond a single offering. Peptan® collagen is the hero of our products for its overwhelming beauty-enhancing power, but its spill-over health benefits make it a no-brainer daily supplement. One of these is: better sleep. Here's how it works.

Collagen and glycine

Collagen is rich in the amino acid, glycine. In particular, glycine helps the body make serotonin, a hormone and neurotransmitter that has significant effects on sleep and mood. It also influences key receptors in the brain that affect learning and memory. 

Studies show that higher levels of this amino acid may:

  • Help you fall asleep more quickly
  • Increase your sleep efficiency
  • Reduce symptoms of insomnia
  • Improve sleep quality and promote deeper more restful sleep
  • Help you regulate sleep cycles after disruption

The evidence

Now, let's go into a few details of how this magic happens with a number of scientific studies.

Body temperature:

A recent study1 of the effects of glycine as a supplement showed it triggered a drop in body temperature and at the same time helped people both fall asleep more quickly and spend more time in REM sleep. Other research2 has shown supplemental glycine may help you move more quickly into deep, slow-wave sleep.

So, how does it drop the body's temperature and how does that improve sleep? Well, glycine works to increase blood flow to the body’s extremities, which reduces core body temperature. The body’s fluctuating temperature affects sleep-wake cycles, and your ability to initially fall asleep. A slight drop in body temp is a key part of the body’s physical progression into sleep. 


Glycine increases serotonin levels, which have a complex relationship with sleep. Among other things, serotonin is required to make the sleep hormone melatonin. In people who have difficulty sleeping or sleep disorders such as insomnia and sleep apnea, increasing serotonin levels can help restore healthy sleep patterns, and encourage deeper, more restful and refreshing sleep. Research shows3 oral glycine elevates serotonin, reduces symptoms of insomnia, and improves sleep quality. Other studies4 suggest it may help you bounce back to healthy sleep cycles after a period of disrupted sleep.

Cognitive function and memory enhancement:

Glycine is active in the hippocampus, an area of the brain important for memory and learning. In supplement form, glycine appears to deliver benefits for daytime cognitive function. In the same study that showed supplemental glycine made it easier to fall asleep and get to slow-wave sleep, scientists also found people scored higher on daytime cognition tests. And supplemental glycine has been shown to improve both memory and attention in young adults5.

Decreasing fatigue:

While glycine doesn’t actually decrease fatigue, its effects in normalising your sleep patterns and in making sleep more effective help reduce patterns of fatigue. It also helps you feel more rested on less sleep since your sleep is more effective. In a study published by the Sleep and Biological Rhythms Society6, researchers found that glycine produced improved feelings of clear-headedness and liveliness after consuming glycine before bedtime. In another study7, volunteers were evaluated after three nights of sleep deprivation. The participants in the study had their sleep reduced by nearly 2 hours per night for 3 consecutive nights. Those who were given glycine before had significantly less fatigue, less daytime sleepiness, and higher daytime performance than those who ingested a placebo.

Low amino acid levels and fatigue

Significantly depleted amino acid levels have been associated with long-term fatigue. In a study8, provision of an amino acid supplement (containing glycine amongst other amino acids) for 30 days resulted in significant improvements in reported fatigue and sleep for 81% of the trial cohort with all females reporting improvements in fatigue. It was concluded that people suffering fatigue would be likely to experience significant benefits from amino acid supplementation.

Glycine and mental illness

Glycine helps treat mental illness. Researchers have seen positive effects in glycine treating obsessive-compulsive disorder, body dysmorphic disorder, and in reducing symptoms of schizophrenia. It may also help reduce the effects of depression, especially if you have low glycine levels. Depression is associated with low glycine blood levels as well as high taurine levels.


  1. Kawai, N., et al. (2015). The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Neuropsychopharmacology, vol. 40, pp 1405 – 1416.
  2. Yamadera, W., et al. (2007). Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep and Biological Rhythms, vol. 5, pp 126 – 131.
  3. Bannai, M., et al. (2011). Oral administration of glycine increases extracellular serotonin but not dopamine in the prefrontal cortex of rats. Psychiatry and Clinical Neurosciences, vol. 65, pp 142 – 149.
  4. Pharmacokinetics and cerebral distribution of glycine administered to rats. Amino Acids, vol. 42, iss. 6, pp 2129 – 2137.
  5. File, S., et al. (1999). Beneficial effects of glycine (bioglycin) on memory and attention in young and middle-aged adults. Journal of Clinical Psychopharmacology, vol. 19, iss. 6, pp 506 – 512.
  6. Inagawa, K., et al. (2006). Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep and Biological Rhythms Society, vol. 4, iss. 1, pp 75 – 77.
  7. Bannai, M., et al. (2012). The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Frontiers in Neurology, vol. 3, iss. 61.
  8. Dunstan, R., H., et al. (2017). Diverse characteristics of the urinary excretion of amino acids in humans and the use of amino acid supplementation to reduce fatigue and sub-health in adults. Nutrition Journal, iss. 16:19.