Ketones and bicarbonate for endurance performance? Original paper

Because ketones have the potential to spare the body’s glycogen reserves, exogenous ketones are sometimes used in endurance sports. They can cause mild acidosis, however, which may worsen performance. Can bicarbonate solve this problem?

In this randomized, controlled, crossover trial, 14 well-trained male cyclists completed four cycling sessions separated by 7-day washouts. Each session comprised a 60-minute warm-up (during which 60 grams of carbs were consumed), a 30-minute time trial, and an all-out sprint, without breaks. Before each session, the cyclists consumed one of four drinks:

• Ketones (50 grams) during the warm-up
• Bicarbonate (180 mg per kilogram of body weight, so 82 mg/lb) 1–2 hours before the warm-up
• Ketones + bicarbonate (KB)
• Placebo

The investigators controlled for dietary factors on the day of each session and the night before. They collected blood samples at various time points to assess blood ketone levels.

Ketones increased the blood pH, whereas bicarbonate decreased it. KB and placebo led to the same blood pH. Nevertheless, mean power output during the time trial was lower for ketones and KB than for bicarbonate and placebo, and this lower output was correlated with the higher blood ketones.

Time to exhaustion during the sprint was longer for bicarbonate and KB than for ketones alone or placebo.

The results of this trial suggest that bicarbonate use may improve sprint performance regardless of ketone use, whereas ketone use may reduce mean power regardless of bicarbonate use. Given that exogenous ketones either impair performance (as seen in this trial) or don’t affect it (as seen in another crossover trial,^[1]) it probably makes more sense to forgo them entirely.