Eight days. Hundreds of kilometres of punishing South African singletrack. Two doses of a premium ketone drink every day. And at the end of it, riders who drank Ketone IQ looked, felt and performed about the same as riders who drank a placebo.
That is the headline from a new double-blind trial in the European Journal of Sport Science, and it is a useful reality check for anyone considering ketone supplements for recovery.
What the researchers tested
Engelbrecht and colleagues followed 18 trained mountain bikers (10 teams) through the 2025 Absa Cape Epic, an 8-day multi-stage race. Riders were randomised to take either 87.5 mL of Ketone IQ, whose active ingredient is R-1,3-butanediol (BDO), or a placebo. They took it twice daily: once after each stage and once before sleep.
The team tracked a broad set of real-world markers:
- Heart rate, both during exercise and at rest
- Energy and carbohydrate intake
- Hydration
- Sleep metrics
- Cognitive performance, including reaction time
- Subjective stress and recovery
This was the point of the study. Most ketone research happens in controlled lab sessions. This one asked whether BDO helps when fatigue, sleep debt and fuelling pressure pile up over a week of racing.
The striking result: ketosis, but no payoff
The drink did what it promised on blood chemistry. BDO produced mild post-stage ketosis of about 1.0 mM β-hydroxybutyrate (BHB), starting from stage 1.
The benefits did not follow. Across the race, both groups showed the same signs of accumulating strain:
- Lower heart rate during exercise
- Higher resting heart rate
- Increased energy and carbohydrate intake
- Slower reaction time by stage 6
BDO did not change any of these patterns compared with placebo. The title of the paper states it plainly: post-exercise BDO did not improve markers of fatigue or recovery. The authors conclude that the modest ketosis was not effective under real-world racing conditions.
The pattern is the textbook picture of cumulative fatigue in stage racing, and the ketone drink did not bend it.
Butanediol is not the same as a ketone ester
This is the part buyers most often miss. "Ketone supplement" covers several different products.
The background literature the authors point to centres on ketone monoester (KME), which has been linked to better recovery and reduced physiological stress during endurance exercise. BDO is a different compound. It is a ketone precursor: the body has to convert it into BHB, rather than receiving a ketone directly. As a general rule, that conversion route tends to produce lower blood ketone levels than monoester drinks, and the roughly 1 mM seen here fits that picture.
The authors stress the point themselves, calling for "formulation-specific" evaluations. In plain terms, a null result for BDO does not prove that ketone esters fail, and a positive ester study does not prove BDO works. They are separate products with separate evidence.
What this means if you're thinking of buying
The study does not show that ketones are useless, but it does undercut the idea that Ketone IQ is a recovery shortcut for multi-day endurance efforts.
- Dose and timing tested: 87.5 mL twice daily, post-exercise and before sleep. That is the protocol that failed to move recovery markers here. Taking more, or at other times, was not tested.
- Who it might not be for: if your main goal is better recovery, sleep or next-day freshness across a stage race, this trial gives you no evidence of benefit.
- Where your money probably goes further: the riders in both groups were eating more carbohydrate and energy as the race went on. Nailing fuelling, sleep and hydration is a well-supported place to put effort and budget before a speculative supplement.
- Check the compound: if you are shopping, confirm whether a product is BDO or a ketone ester, and do not assume results transfer between them.
Limitations worth taking seriously
This was a small study, and the caveats matter.
- Sample size: 18 riders is small. A small trial can miss modest real effects, so "no difference detected" is not the same as "proven zero effect."
- Riders raced in teams: the 10 teams add real-world noise, such as differences in pacing, terrain exposure and individual stage demands, that a lab study would remove.
- One compound, one dose, one schedule: the findings apply to this BDO product, at this dose, in a post-exercise protocol. They say nothing about pre-exercise use or other formulations.
- Mild ketosis: blood BHB reached about 1.0 mM. Whether higher levels would change outcomes was not tested here.
The design is also a strength. Double-blind, placebo-controlled testing in an actual 8-day race is hard to do, and it is the kind of ecologically valid evidence that supplement marketing often lacks.
Bottom line
Ketone IQ raised ketones in Cape Epic riders, but it did not reduce strain, protect reaction time or improve recovery compared with placebo. For endurance athletes weighing a premium ketone drink, the evidence from this trial says to be sceptical about BDO for recovery. Larger studies, and direct comparisons with ketone esters, would give a fuller answer.
Source: Engelbrecht et al., "Post-Exercise R-1,3-Butanediol did not Improve Markers of Fatigue or Recovery During a Multi-Stage Mountain Bike Race," Eur J Sport Sci (2026). DOI: https://doi.org/10.1002/ejsc.70260. PubMed: PMID 42852530.
