Why Are Gelatin And Glycine Recommended If Glycine Increases Serotonin Levels?


Nov 22, 2017


Thread starter
Apr 8, 2020


Nov 22, 2017

I don't know what is going on in that study, maybe somebody else can comment on it.

What I know is that on a physiological level, serotonin is produced from tryptophan.
Gelatin contains no tryptophan at all, therefore it can't lead to more serotonin.

Dietary glycine hasn't been as useful as gelatin itself for many people.


Aug 6, 2015


Nov 22, 2017
I believe Haidut has mentioned that brain serotonin is primarily driven by tryptophan intake/conversion to serotonin while peripheral serotonin is primarily driven by endotoxin/gut bacteria.

Interesting distinction


May 8, 2017
Oral administration of glycine increases extracellular serotonin but not dopamine in the prefrontal cortex of rats.
Bannai M1, Kawai N, Nagao K, Nakano S, Matsuzawa D, Shimizu E.
Author information

Glycine, one of the non-essential amino acids, has been reported to be effective in reducing negative symptoms of schizophrenia. Recently, we found that glycine improves subjective sleep quality in humans. The aim of this study was to investigate the effects of oral glycine administration on endogenous 5-hydroxytryptamine (5-HT) and dopamine in the prefrontal cortex (PFC) of living rats.

Microdialysis probes were inserted stereotaxically into the rat prefrontal cortex. Cortical levels of 5-HT and dopamine were measured following oral administration of 1 or 2 g/kg glycine, 2 g/kg d-serine, or 2 g/kg L-serine.

Both glycine and d-serine significantly increased extracellular 5-HT levels for 10 min, whereas dopamine levels remained unchanged. L-serine, in contrast, had no significant effects on 5-HT levels.

It is possible that the increase in 5-HT in response to glycine and d-serine was mediated by N-methyl-D-aspartate receptors. The transient increase in 5-HT in the PFC might be associated with the alleviation of negative symptoms in patients with schizophrenia and the amelioration of sleep quality in patients with insomnia.
NMDA activation (assuming) at 2g/kg rat weight with no other added nutrients could be stressful and is not really anything new.

What's interesting is L-serine didn't do this even though it can produce glycine and I've been wondering to what degree it might/not activate NMDA receptors (suggesting it's safe for sleep).
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