An honest look at carbohydrates and the new exogenous lactate boom
In short
As things stand today there is no consistent evidence that exogenous lactate taken orally improves endurance performance. The mechanism — the lactate shuttle — is solid science and is not in dispute. What is not demonstrated is that taking it during exercise translates into more performance, and several studies document more digestive discomfort, not less. The strategy with the most evidence behind it is still well-combined carbohydrate.
- Exogenous carbohydrate is among the best documented in exercise physiology. It delays fatigue and maintains performance in long efforts. That is not a matter of opinion.
- The limit is not maltodextrin, it is using a single source. The SGLT1 transporter saturates at around 1 to 1.2 g/min; combining it with fructose, which uses GLUT5, opens a second absorption route in parallel.
- Multiple transportable carbohydrates are one of the best established pillars of modern sports nutrition, from Jeukendrup and Currell (2008) through to a 2022 study at 120 g/h in high-level cyclists.
- The evidence on oral lactate is mixed. Trials with 120-400 mg/kg find no significant improvements in endurance time trials, and a 2024 paper found that oral sodium lactate did not increase blood lactate and did produce moderate-to-severe gastrointestinal effects.
- A professional team trying it is not the same as "it is proven to work". They use it selectively, not as the basis of their nutrition, which fits with a phase of experimentation.
- Even lactate products rest on a base of multiple transportable carbohydrates, typically between 40 and 90 g of carbohydrate for every 5-10 g of lactate. Lactate is, for now, the experimental addition on top of that base, not a substitute.
Introduction
Over the past few months a current has appeared, still a minority one but growing, of athletes who distrust maltodextrin as an ingredient in their sports nutrition. In parallel, exogenous lactate has arrived with considerable media force: new gels and drink mixes that supply lactate alongside carbohydrate, and which have even been seen in the professional peloton this summer.
We think it is good news that the science of fueling keeps moving forward. But we also believe that two things being mixed together on social media and in the popular conversation need separating: the physiological mechanism, (interesting and in some cases real), and the evidence that this mechanism translates into more performance in practice, (still limited, depending on the ingredient). We are going to walk through the complete map of fuel during exercise, from what is already solidly demonstrated to what is at the research stage.
1. The starting point: why carbohydrate is still the base
During moderate-to-high intensity exercise, carbohydrate is the main energy substrate. Glycogen stores are limited, so supplying carbohydrate from outside, ("exogenous" carbohydrate), delays fatigue and maintains performance in long efforts. This is not a matter of opinion: it is among the best documented in exercise physiology.
The historical problem was a different one: the gut has an absorption limit for one single type of glucose transporter, (SGLT1), sitting at around 1 to 1.2 g/min. Going past that figure using only glucose or maltodextrin can cause discomfort, because unabsorbed sugar is left fermenting in the gut. This is where maltodextrin's bad reputation was born, unfairly, and we discuss it in detail in a separate article, because it deserves a space of its own.
The solution exercise physiology has demonstrated over the last two decades is not to "remove maltodextrin", but to combine it with fructose, which uses a different transporter (GLUT5). Using two absorption routes in parallel achieves greater total oxidation of exogenous carbohydrate and a lower probability of gastrointestinal discomfort than using a single source at high doses. This finding, known as multiple transportable carbohydrates, is one of the best established pillars of modern sports nutrition, with studies going back to Jeukendrup and Currell (2008) that have continued to be confirmed to this day. A 2022 study in high-level cyclists showed that combining fructose and maltodextrin at a 0.8:1 ratio at 120 g/h increased exogenous carbohydrate oxidation compared with protocols containing less fructose, without worsening digestive tolerance.
In short: the base of endurance performance is still well-combined carbohydrate. It is not an outdated formula that we need to look for alternatives to; it is, as things stand, the strategy with the most evidence behind it of all those that exist.
2. The new piece of the map: exogenous lactate
For some years now lactate has been reclaiming its place as a legitimate energy substrate thanks to the work of Professor George A. Brooks and his theory of the lactate shuttle: lactate is not just a waste product of intense exercise, but can be transported and oxidised as fuel by the heart, the brain and the muscle. This is solid science and is not in dispute.
What is in dispute — and this is where it pays to be precise — is whether taking lactate orally during exercise improves performance in practice. The current evidence is mixed:
- Several controlled trials with doses of 120-400 mg/kg of oral lactate have found no significant improvements in performance in endurance time trials.
- A 2024 study (McCarthy et al., Journal of Applied Physiology) found that oral ingestion of sodium lactate did not increase blood lactate concentration and was accompanied by moderate-to-severe gastrointestinal effects.
- Other papers do find modest benefits, but almost exclusively in very short efforts of extremely high intensity, (close to VO2max), not in the prolonged endurance context where most of these products are being sold.
- It is true that this summer we have seen top-level professional cycling teams testing exogenous lactate products in competition, with researchers of serious standing behind them. But it pays not to confuse, "they are using it", with, "it is proven to work": the specialist press coverage itself has been clear that its real impact on performance, "remains a mystery", and that any progression by a rider during that period cannot be attributed to a single product, given the number of variables involved in the performance of an elite athlete. What is more, those same teams use it selectively, not as the basis of their nutrition, which fits better with a phase of experimentation than with a closed validation.
- Even the most advanced lactate products that have reached the market still rest mostly on the same base of multiple transportable carbohydrates described above, (typically between 40 and 90 g of carbohydrate for every 5-10 g of lactate). That is, lactate is, for now, the experimental addition on top of an already validated carbohydrate base, not a substitute for that base.
- It is not only that evidence in favour is lacking: there are also expert voices questioning the mechanism itself. Professor of Physiology Jesús Rodríguez Huertas (University of Granada), who specialises in the mitochondrial bioenergetics of exercise, has publicly argued that lactate supplied from outside could compete with the mechanisms the muscle itself uses naturally to manage its own lactate during effort, even going as far as interfering with mitochondrial function. In his assessment, commercial lactate products have been launched onto the market without serious clinical trials in people to support their efficacy. It is worth qualifying that this position comes in large part from his own group's research and that he himself acknowledges that human trials are still lacking; it is not the final word, but it is an additional reason not to take for granted that exogenous lactate offers any real advantage.
We are not saying that exogenous lactate has no future: the lactate shuttle mechanism is real and research continues, and it is healthy that the sector should keep exploring. What we are saying is that, as things stand today, not only is there a lack of consistent evidence that it improves endurance performance compared with what we already know works, but there are also serious physiological arguments that invite caution, and in several studies it produces more digestive discomfort, not less.
3. Quick comparison
| Multiple transportable carbohydrates (glucose/maltodextrin + fructose) | Oral exogenous lactate | |
|---|---|---|
| Mechanism | Well established: two absorption routes, greater exogenous oxidation | Plausible, (lactate shuttle), but its efficacy by the oral route still under study |
| Performance evidence | Solid and replicated in long-duration endurance | Limited, mixed, mostly in short efforts of very high intensity |
| Digestive tolerance | Good if sources are combined | Variable; some studies document moderate-to-severe discomfort |
| Track record | Decades of use and validation in elite and amateur sport | Very recent, first commercial products at the testing stage |
4. The Novafit approach
At Novafit we do not chase trends: we apply what the evidence consistently supports, with room to keep evolving if the science of lactate ends up being confirmed in the future. But our essence does not stop there: it is not only about formulating with what science supports, but about doing it in perfect harmony with natural fruit pulp and 100% artisanal production, which our own team carries out in our workshop. That is why our gels combine 5 carbohydrate sources (Golden Sugar, corn glucose syrup, fructose syrup, maltodextrin and Palatinose), in a glucose:fructose ratio of 1:0.8, exactly the kind of combination the scientific literature identifies as optimal for maximising exogenous oxidation and minimising digestive discomfort. We add 30% real fruit pulp, sodium in citrate form and magnesium in bisglycinate form, both chosen for their better digestive tolerance and bioavailability compared with the more common forms on the market, (sodium chloride and magnesium oxide or citrate), produced artisanally, gluten free, lactose free and suitable for vegans: a distinctive approach within the sector, where the ultra-technical lives alongside the natural and the handmade.
If you want to understand in detail why maltodextrin has a bad reputation it does not deserve, we go through it point by point in our article:
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Frequently asked questions
Do lactate gels work?
As things stand today there is no consistent evidence that they improve endurance performance. The underlying mechanism, the lactate shuttle, is solid science, but several controlled trials with doses of 120-400 mg/kg of oral lactate have found no significant improvements in endurance time trials. The modest benefits that are documented appear almost exclusively in very short efforts of extremely high intensity, close to VO2max, which is not the context in which most of these products are sold.
What is the lactate shuttle?
It is Professor George A. Brooks's theory, according to which lactate is not just a waste product of intense exercise, but can be transported and oxidised as fuel by the heart, the brain and the muscle. That part is solid science and is not in dispute. What is in dispute is whether taking lactate orally during exercise translates into more performance in practice.
Do lactate gels upset your stomach?
Tolerance is variable and there are studies documenting moderate-to-severe discomfort. A 2024 paper (McCarthy et al., Journal of Applied Physiology) found that oral ingestion of sodium lactate did not increase blood lactate concentration and was accompanied by moderate-to-severe gastrointestinal effects. In several studies exogenous lactate produces more digestive discomfort, not less.
If professional teams use it, does that not mean it works?
Not necessarily. This summer top-level teams have been seen testing exogenous lactate products in competition, with researchers of serious standing behind them, but it pays not to confuse "they are using it" with "it is proven to work". The specialist press coverage has been clear that its real impact on performance remains a mystery, and no progression by a rider can be attributed to a single product given the number of variables involved. What is more, those same teams use it selectively, not as the basis of their nutrition.
How much lactate is in a lactate gel, and does it replace carbohydrate?
It does not replace it. Even the most advanced lactate products on the market still rest mostly on a base of multiple transportable carbohydrates, typically between 40 and 90 g of carbohydrate for every 5-10 g of lactate. Lactate is, for now, the experimental addition on top of an already validated carbohydrate base.
Why are maltodextrin and fructose combined?
Because they use different intestinal transporters. Glucose and maltodextrin are absorbed by SGLT1, which saturates at around 1 to 1.2 g/min; fructose uses GLUT5. Opening two absorption routes in parallel achieves greater total oxidation of exogenous carbohydrate and a lower probability of gastrointestinal discomfort than using a single source at high doses. This is what is known as multiple transportable carbohydrates.
How much carbohydrate per hour can you absorb?
With a single source the ceiling is around 1 to 1.2 g/min, the limit of the SGLT1 transporter. Combining sources takes you well above that: a 2022 study in high-level cyclists showed that a fructose:maltodextrin ratio of 0.8:1 at 120 g/h increased exogenous carbohydrate oxidation compared with protocols containing less fructose, without worsening digestive tolerance.
Does exogenous lactate have a future?
It may. The lactate shuttle mechanism is real, research continues and it is healthy that the sector should keep exploring. What we are saying is that today not only is there a lack of consistent evidence that it improves endurance performance compared with what we already know works, but there are also serious physiological arguments that invite caution.
References
- Jeukendrup, A. E. & Currell, K. (2008). Superior endurance performance with ingestion of multiple transportable carbohydrates. Medicine & Science in Sports & Exercise, 40(2), 275-281.
- Podlogar, T., Bokal, Š., Cirnski, S. & Wallis, G. A. (2022). Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g/h vs 90 g/h. European Journal of Applied Physiology.
- Rowlands, D. S. et al. Fructose-glucose composite carbohydrates and endurance performance: critical review and future perspectives.
- McCarthy, S. F., Bornath, D. P. D., Tucker, J. A. L. & Hazell, T. J. (2024). Oral sodium lactate ingestion does not increase blood lactate concentrations and is accompanied by moderate-to-severe gastrointestinal side effects. Journal of Applied Physiology, 137(5), 1279-1284.
- Brooks, G. A. The lactate shuttle during exercise and recovery. Medicine & Science in Sports & Exercise (1986).
- Specialist professional cycling coverage on the use of exogenous lactate in competition, summer 2026.
- Rodríguez Huertas, J. Statements on the efficacy and mechanisms of exogenous lactate in sport. University of Granada, July 2026.
Article produced by the Novafit technical team.
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