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Can You Take 5-HTP and L-Phenylalanine Together?
May affect absorption
The short answer
L-Phenylalanine and 5-HTP are both large neutral amino acids competing for the LAT1 transporter at the blood-brain barrier. L-Phenylalanine may reduce 5-HTP brain uptake, decreasing serotonin synthesis from 5-HTP.
How to arrange timing
Separate L-Phenylalanine and 5-HTP by at least 2 hours for optimal brain uptake of each.
Reference
Reference noted for this combination: Fernstrom JD. Large neutral amino acids: dietary effects on brain neurochemistry and function. Amino Acids. 2013;45(3):419-430.
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.