I saw many threads on here saying lysine reduces serotonin because it antgozies 5ht4. so I started taking it but it made me feel achy, tired, sleepy, jittery, dull and nervous. I tried different doses and 4 different brands, tried powder, capsules, caps. All same effect.
So I started researching pubmed and found the study: The depletion of tryptophan and serotonin in the brain of developing hyperphenylalaninemic rats is abolished by the additional administration of ly... - PubMed - NCBI
Now I understand why so many users on here had poor experiences with lysine long term. It made their immune system worse by keeping their tryptophan and serotonin high even when they try to deplete it. Antagonizing one receptor doesn't mean it decreases the level of the neurotransmitter. The few benefits one may get from lysine is probably just from its nitric oxide inhibition but the cons outweigh the pros.
The depletion of tryptophan and serotonin in the brain of developing hyperphenylalaninemic rats is abolished by the additional administration of lysine.
In suckling hyperphenylalaninemic (hyper-Phe) rats, all essential amino acids including tryptophan are depleted in the blood. The inadequate supply of Trp to the developing brain leads to a decline of Trp, of serotonin, and of 5-hydroxyindoleacetic acid. The exhaustion of amino acids in both blood and brain can be restored by administration of Lys. Even though Phe is still elevated in blood and brain, Trp, serotonin and 5-hydroxyindoleacetic acid, are no longer depleted in the brain. This observation contradicts the idea that the serotonin deficit in the developing hyper-Phe brain is caused by competitive uptake inhibition of tryptophan or by the interference of Phe metabolites with the formation of serotonin. Increased accumulation of all large neutral amino acids in peripheral tissues and an impeded intestinal amino acid transport in suckling hyper-Phe rats appear to be responsible for the deficient supply of other amino acids, including Trp, to the developing brain. The availability of Lys for developing extraintestinal tissues seems to be involved in the regulation of intestinal amino acid transport.
Some of my symptoms may have been caused by my consumption of black tea during the time I was taking lysine. I may have spoken too soon. Lysine has its benefits and side effects and it can both decrease and increase serotonin depending on many factors.