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Can You Take L-Isoleucine and L-Tryptophan Together?
May affect absorption
The short answer
L-Isoleucine (a BCAA) and L-Tryptophan are both large neutral amino acids that compete for the LAT1 transporter at the blood-brain barrier. High-dose isoleucine reduces tryptophan brain uptake, potentially lowering serotonin synthesis.
How to arrange timing
Separate L-Isoleucine and L-Tryptophan by at least 2 hours to optimize tryptophan's brain uptake for serotonin production.
Reference
Reference noted for this combination: Fernstrom JD. Branched-chain amino acids and brain function. J Nutr. 2005;135(6 Suppl):1539S-1546S.
Important context
Whether supplements suit you together also depends on dose, product formulation, health conditions, and medication use. Ask a doctor or pharmacist first if you take medication, are pregnant or breastfeeding, or have a chronic condition.