Twenty riders took on the Cape Epic, eight days and 567 km of South African mountain trails, and half of each team drank a ketone shot after every stage and before bed. Their bodies wore down at the same rate as their teammates' on a lookalike placebo

The Absa Cape Epic is a team race. Riders race in pairs and have to stay together, which makes it a neat place to run an experiment: two people on the same course, in the same heat, at the same pace, for eight days. In the 2025 edition that meant 567 km and 15,300 m of climbing in the Western Cape, with one stage reaching 43 °C.

A team from Stellenbosch University, KU Leuven and Hasselt University recruited ten pairs of trained riders who had entered the race. In each pair, one person was picked at random to drink Ketone-IQ, a commercial shot made of R-1,3-butanediol, and the other got a drink made to taste and feel the same with no active ingredient. Neither the riders nor the researchers knew who had which. Each rider took an 87.5 mL shot straight after every stage and another just before sleep. The paper was published on 9 October 2026 in the European Journal of Sport Science.

The idea comes from a solid line of lab research. The body makes ketones when food is short, and drinks that supply them raise blood levels without fasting. In earlier laboratory studies, a different and pricier product, a ketone ester, helped riders cope with deliberately brutal training blocks and protected their sleep after hard evening sessions. Butanediol is cheaper and tastes a little less harsh, but it is not a ketone itself: the liver has to convert it first, so blood levels rise more slowly and peak lower.

That is what happened here. Thirty to forty-five minutes after the post-stage shot, riders on the real drink averaged about 1.0 mmol/L of the main ketone in their blood, against about 0.4 on placebo, peaking near 1.5 by stage 6. The ester studies that found benefits reached 2 to 5 mmol/L.

Everything the researchers measured told the story of a hard race and nothing else. In both groups resting heart rate crept up by 4 to 7 beats a minute, and peak heart rate during stages fell by about 16 beats from the second stage on. Time spent in the easiest heart-rate zone went from about a quarter of the ride to three quarters, a sign of legs that would no longer go hard. Riders ate more as the week went on, around 60 g of carbohydrate an hour on the bike. By stage 6, reaction times had slowed by about 6.5%. REM sleep shrank late in the race. In none of these did the ketone riders differ from their teammates.

Two results look like effects at first glance and aren't. The ketone group reported feeling more mentally alert throughout, but they already felt that way before anyone drank anything. Their peak heart rates were lower across the race, but they fell at the same rate as the placebo group's. The authors flag both themselves, which is to their credit.

The authors suggest three reasons the drink did nothing: the ketone levels were too low, eight days is too short (the ester benefits in the lab took three weeks or more to appear), and fit riders racing at their own pace may simply have less to rescue than people pushed into overtraining on purpose. There was also real-world mess. Riders were told not to eat for 30 minutes after the post-stage shot, but most were soon into a recovery meal of around 92 g of carbohydrate and 45 g of protein, which may have blunted the rise.

Our reading: this is a small study, with 18 finishers, and the authors are right that it can't rule out a modest effect. But it is a properly blinded test of a product as people actually use it, in the conditions it is sold for, and the answer was no. It is also worth noticing who wrote it. One of the authors, Chiel Poffé of KU Leuven, led several of the laboratory studies that made ketone drinks look promising in the first place, and the drinks for this trial were supplied by the company that sells them. The paper reports a null result anyway. For a rider wondering where to spend money before a stage race, the evidence still points to the dull basics: enough carbohydrate on the bike, plenty of food and fluid afterwards, and sleep.