Lactate as fuel: what the evidence says

The claim that “lactate is a fuel” has moved from the fringes to the mainstream of metabolic science. But what exactly does the evidence support?

Lactate as an oxidisable substrate

Lactate can be oxidised for energy in tissues such as skeletal muscle, the heart and the brain. During exercise, a substantial fraction of the lactate produced is taken up and used rather than discarded.

What tracing studies suggest

Isotope-tracing work indicates that lactate is one of the most actively exchanged fuels in circulation, contributing carbon to central energy pathways across many tissues. This is a mechanistic argument for lactate’s role as a real energy source.

From mechanism to application

Demonstrating that lactate is a fuel at the cellular level does not automatically translate into a performance benefit when lactate is supplied externally. That step — from mechanism to applied outcome — is where the most important open questions lie, and where controlled human trials are needed.

A measured conclusion

Current research suggests lactate is a legitimate fuel. Whether and how exogenous lactate can be used to support performance is an emerging area with promising rationale and incomplete evidence.