Ketones and Athletic Performance
by Doug Stewart
A couple of weeks ago, I shared an article that provided a summary of the current best practice around carbohydrate consumption for endurance athletes. You can find the newsletter here.
Looking further into nutrition for endurance, a recently published paper, Exogenous Ketone Supplements in Athletic Contexts: Past, Present, and Future, explores the use of ketones by reviewing the current published research on this topic.
The USADA website describes Ketones as:
Ketones, or “ketone bodies,” are molecules produced in the liver when the body metabolizes fat. These molecules are produced in response to starvation, prolonged strenuous exercise, and carbohydrate-restricted diets like the “ketogenic diet.” In the absence of carbohydrates (sugars) the body can use ketones as an energy source.
The theory is, then, that taking supplementary ketones can help endurance performance by making more available to be used for energy. This has resulted in commercially available ketone esters and salts being developed and to some extent limited adoption by endurance athletes.
The current paper explains that the research and use by athletes has primarily focused on increasing ketone availability in the body. This can potentially occur within minutes of ingestion. So if an athlete needs energy quickly, the theory is that ketones may provide a solution. Moreover, elevated levels can be sustained for several hours, depending on the volume and type of ketones consumed. However, levels and absorption speed are influenced by many factors, including whether the athlete is resting or exercising, is fasted or has eaten, and gender.
Additionally, across the existing research, there are different types of procedures, types of ketones used and amounts taken by the athletes.
Taking all that into account, the current paper does a great job of highlighting two areas that are likely important for athletes – potential GI issues and performance improvements.
With respect to GI issues, they discuss multiple studies that have shown increased rates of GI complaints when ketones are taken at rest – with flatulence, cramping, belching and nausea some of the symptoms listed. Moreover, when compared to control groups, the research investigating ketone ingestion when exercising also found, in some cases, higher rates of GI issues.
However, GI symptoms may be dependent on the size of the doses taken, as smaller doses do not appear to have these negative effects. They also dependent on the types of ketones taken.
Looking at the impact on athletic performance, the authors conclude:
While there are mechanistic bases for potential beneficial effects of exogenous ketone supplements in various athletic contexts, most studies to date have failed to observe benefits to performance or recovery.
Therefore, it appears that there is limited benefit, and potentially increased risk of GI issues, if taking exogenous ketones at this time for endurance athletes.
References:
Evans, M., McClure, T.S., Koutnik, A.P. et al. Exogenous Ketone Supplements in Athletic Contexts: Past, Present, and Future. Sports Med (2022). https://doi.org/10.1007/s40279-022-01756-2
United States Anti Doping Agency Website: https://www.usada.org/spirit-of-sport/education/ketones-frequently-asked-questions/