Ketone ester drinks taken before exercise, along with carbohydrates, have recently been shown to improve performance in a 30 minute cycling time trial by 2.3%, which can be the difference between first place and last place. This study investigated the effects of a ketone salt on performance in a 4 minute cycling time trial.
Aside: Many are unaware that there are major differences between ketone salts and an ketone ester. Ketone salts contain BHB or AcAc joined by an ionic bond to a mineral such as sodium, potassium or calcium. This means that for every one part BHB or AcAc you also consume one part of the mineral, which can easily take you over the RDA (recommended daily allowance) for those ions. By contrast, a ketone ester contains BHB or AcAc joined to a ketone precursor by a chemical bond (called an ester bond). The ketone precursor is usually something that the body converts into ketones such as butanediol or glycerol. Unlike a ketone salt, this means a ketone ester can raise blood ketones without delivering any other substances.
Cyclists took either ketone salt or placebo both before and once during exercise. After the ketone salt drink, blood ketone levels reached 0.6 mM (which is the equivalent to about a day of fasting). They found that there was no difference in the 4 minute time trial performance between the ketone or placebo conditions. This may be because the exercise test was too short and intense to benefit from ketone supplements, or because blood ketone levels were too low to have a positive effect on performance. The authors concluded that before disregarding ketone salts, different doses and exercise tests should be investigated. However, multiple studies have shown that ketone salts aren't nearly as promising as a pure ketone ester drink.
Authored by Dr. Brianna Stubbs