Can You Take L-Threonine and L-Tryptophan Together?

May affect absorption

The short answer

L-Threonine and L-Tryptophan compete for intestinal amino acid transporters (System B0 and System ASC). High doses of threonine may reduce tryptophan absorption, potentially affecting serotonin synthesis.

How to arrange timing

Separate L-Threonine and L-Tryptophan by at least 1 hour for optimal absorption.

Reference

Reference noted for this combination: Bröer S. Amino acid transport across mammalian intestinal and renal epithelia. Physiol Rev. 2008;88(1):249-286.

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.