A recent study discovered that consuming dietary nitrate, the active molecule found in beetroot juice led to a substantial improvement in muscle force during physical activity.
Although the benefits of dietary nitrate on exercise, including improved endurance and heightened high-intensity performance, are well documented, researchers still have much to uncover about the mechanisms behind this effect and how the body converts ingested nitrate into usable nitric oxide for cells.
In an effort to fill this knowledge gap, researchers from the University of Exeter and the National Institutes of Health in the US conducted a study in which they traced the distribution of nitrate ingested by ten healthy volunteers in saliva, blood, muscle, and urine. The volunteers then underwent a maximal leg exercise to determine where in the body the dietary nitrate was active, providing insights into its underlying mechanisms.
An hour after the nitrate was taken, participants were asked to perform 60 contractions of the quadriceps – the thigh muscle active while straightening the knee – at maximum intensity over five minutes on an exercise machine. The team found a significant increase in the nitrate levels in muscle. During the exercises, researchers found this nitrate boost caused an increase in muscle force of seven percent, compared to when the participants took a placebo.
Andy Jones, Professor of Applied Physiology at the University of Exeter, said: “Our research has already provided a large body of evidence on the performance-enhancing properties of dietary nitrate, commonly found in beetroot juice. Excitingly, this latest study provides the best evidence to date on the mechanisms behind why dietary nitrate improves human muscle performance.”
Previous studies had found an increase of nitrate in tissue and body fluid after ingesting labeled dietary nitrate. By using the tracer in the new study, researchers were able to accurately assess where nitrate is increased and active, and also shed new light on how the nitrate we consume is used to enhance exercise performance.
“This study provides the first direct evidence that muscle nitrate levels are important for exercise performance, presumably by acting as a source of nitric oxide,” said Dr. Barbora Piknova, research collaborator and staff scientist at the National Institute of Diabetes and Digestive and Kidney Diseases at the National Institutes of Health. “These results have significant implications not only for the exercise field but possibly for other medical areas such as those targeting neuromuscular and metabolic diseases related to nitric oxide deficiency.”
“15N-labeled dietary nitrate supplementation increases human skeletal muscle nitrate concentration and improves muscle torque production” by Stefan Kadach, Ji Won Park, Zdravko Stoyanov, Matthew I. Black, Anni Vanhatalo, Mark Burnley, Peter J. Walter, Hongyi Cai, Alan N. Schechter, Barbora Piknova and Andrew M. Jones, 6 January 2023, Acta Physiologica.
The research was conducted in collaboration with the University of Queensland, Australia, under the QUEX partnership with Exeter.