Impact of ketone salt containing supplement on cardiorespiratory and oxidative stress response in firefighters exercising in personal protective equipment

Background: Firefighters have the highest risk of on duty death due to cardiovascular disease which may be caused by excessive oxidative stress (OS). Animal studies have shown that ketone bodies may reduce OS; however, human trials are needed. Objectives: To examine the effects of a supplement containing ketone salts (KS) on blood OS and cardiorespiratory responses in firefighters exercising in personal protective equipment. Methods: Nine firefighters supplemented with KS or a calorie-and flavor-matched placebo (PLA) twice per day for 7 days in a randomized, crossover design. On the eighth day, firefighters arrived for testing after ≥ 8 hour fast and ingested the assigned supplement 35 minutes before performing the exercise task (35 minutes at 60% VO_2peak intensity) wearing personal protective equipment (i.e., turnout gear, self-contained breathing apparatus, air tank, gloves). Blood was sampled pre-and post-exercise (post periods: immediately, 30 minutes and 24 hours) and analyzed for markers of OS including red blood cell (RBC) levels of glutathione (GSH), oxidized glutathione, superoxide dismutase (SOD), as well as plasma levels of SOD, catalase, total antioxidant capacity, malondialdehyde, and glucose. Results: There was no treatment effect or treatment × time interaction (P > 0.05) for any of the markers of OS. However, the exercise protocol resulted in significant increases in RBC levels of SOD from pre-to immediately post-exercise and decreased RBC levels of GSH from pre-to 30 minutes post-exercise. Ingestion of KS resulted in a significant increase in ketone levels and reduction in heart rate during the exercise test. Conclusions: These findings suggest that 7 days of supplementation with a KS supplement does not impact markers of OS but reduces heart rate.