Exogenous lactate
Evidence: weak
Lactate is genuinely a fuel and a signal inside the body, but taking it by mouth as a supplement has not improved performance in the controlled trials to date, and it reliably upsets the gut. Plausible mechanism, no delivered benefit.
Not medical advice
This is a general knowledge base, not medical or dietary advice. If you are injured, unwell or weighing up a supplement or a change to your diet, speak to a doctor, physiotherapist or registered dietitian who knows your situation.
Keep it in proportion
The basics are where the real gains are: consistent volume, sleep and adequate fuelling. Weigh anything below honestly, and do not let a marginal or over-marketed aid pull attention from the things that actually move the needle.
Interest in lactate drinks and gels follows from a genuine correction in the science. Lactate is not a waste product but a fuel the body produces, moves between tissues and burns, and a signal that helps drive adaptation, which is the lactate shuttle. The marketing leap is from “lactate is a fuel” to “swallowing lactate helps,” and those are separate claims that need separate evidence.
The rationale
Because working muscle, the heart and the brain all oxidise lactate, and the liver uses it to make glucose, a dose taken before or during exercise could in principle add a fuel that spares glycogen and buffers less than expected because it is consumed as it is used. That is the mechanistic case, and it rests on solid shuttle physiology.
The key evidence
Delivery is where the case weakens. In a randomised, double-blind crossover trial, 16 trained cyclists took 120 mg·kg⁻¹ of calcium lactate 70 minutes before a two-hour protocol of repeated 1 km and 4 km time trials. Lactate raised blood bicarbonate and shifted acid-base balance in the expected direction, and it lowered perceived exertion, yet it produced no improvement in time-trial performance, and gastrointestinal symptoms (cramps, flatulence, belching, bowel urgency) rose significantly (Bordoli et al. 2024). The metabolic and perceptual signals moved without the performance following, and the gut paid for it.
The authors suggest the dose may have been too small and call for work on other lactate forms and dosing, so the ergogenic question is open rather than closed. It sits in the same place as ketone esters: a coherent mechanism, an expensive and novel product, and no demonstrated race-day benefit once independent trials look for one.
The verdict
For a distance runner, exogenous lactate is not a supplement to reach for. The physiology it borrows is real, but no controlled trial has yet turned it into a faster race, the gut tolerance is poor, and the lever that actually decides fuelling remains carbohydrate at high intake rates. It is worth knowing about as an emerging idea and as a good test of the difference between a mechanism and a proven effect, which is what evaluating supplements is for. Emerging, not proven.