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Can You Take L-Isoleucine and L-Leucine Together?
May affect absorption
The short answer
L-Isoleucine and L-Leucine are both BCAAs that share the same intestinal (LAT) and blood-brain barrier (LAT1) transporters. When taken individually (not as a balanced BCAA blend), they compete for absorption, and leucine tends to dominate uptake.
How to arrange timing
When supplementing individual BCAAs rather than a balanced blend, separate L-Isoleucine and L-Leucine by at least 1 hour.
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.