The next time you’re feeling the effects of sleep deprivation, consider adding L-glycine to your diet. A non-essential amino acid found predominantly in proteins, L-glycine is created in the body from another amino acid, serine. L-glycine has a variety of functions, such as protein production and as an inhibitory neurotransmitter in the spinal cord and brain. 

It is because of the amino acid’s inhibitory function that researchers at the Institute for Innovation and University of Miyazaki in Japan wanted to study the effects of L-glycine on insomnia symptoms by improving sleep quality. Researchers Makoto Bannai, Nobuhiro Kawai, Kaori Ono, Keiko Nakahara and Noboru Murakami report that insomnia affects about 30 per cent of the population.

Symptoms can include sleepiness, fatigue, inability to focus, memory deficits, and irritability, so finding an efficient treatment for insomnia is vital.

For the experiment, 10 healthy participants were recruited and baseline measures of sleeping patterns were recorded. In the randomized, crossover trial, the participants were given either three grams of L-glycine or a placebo half an hour before bedtime. Their sleep time was restricted to an average of 5.5 hours for three nights in a row. Their insomnia symptoms were evaluated using a visual analog scale, questionnaires, and various performance tests.

L-Glycine Effects on Sleep Quality

Researchers Bannai, Kawai, Ono, Nakahara and Murakami found that reaction time was significantly reduced for the L-glycine group when doing the psychomotor vigilance test. The amino acid group also tended to do better for the other forms of performance tests.

Self-reported symptoms of insomnia were improved only for the first day of sleep deprivation for the L-glycine group, but objective measures were improved up to the third day. The researchers also found that when compared to the placebo, the L-glycine participants had significantly less feelings of fatigue and improved sleep quality.

Based on findings from rat experiments, the researchers believe that the improvement in sleep quality stems from L-glycine’s ability to lower the body’s core temperature, which occurs naturally during sleep.