Nitric oxide and exercise: what is the deal?

Nitric oxide is a gas which is soluble in the human body, and scientists who studied and elucidated physiological role of nitric oxide were awarded a Nobel Prize in 1998. While nitric oxide is responsible for a variety of functions such as mediation of neurotransmitters in memory and learning, it has received a great deal of attention in exercise physiology. Some have suggested that nitric oxide could be ergogenic aid, or in other words, enhance athletic performance.

This notion is based on the fact that during exercise, nitric oxide modulates blood flow and the function of mitochondria, the energy producing organelles of the cell.  However, most studies that examined the role of nitric oxide on exercise performance are conflicting at best. Many used nitric oxide “cocktails” , meaning that what subjects were given contained not only nitric oxide but also other compounds such as vitamins, minerals, amino acids etc. This makes conclusions on the effect of nitric oxide somewhat foggy. If the effects on performance were observed, was the effect due to amino acids, vitamins or minerals  and other contents of the “cocktail” or nitric oxide per se?  Some have argued that the dose of nitric oxide also matters.  Yet when the amounts of nitric oxide present in commercially available nitric oxide supplementation were tested, they were found to be low.  It is for this reason that pharmaceutical grade products are often used in studies examining the effect of nitric oxide on exercise performance, products not freely available to the general public.

Still other studies have assessed how natural foods, such as beetroot juice, which are nitric oxide donors, affect performance.  Here again the findings were conflicting.  While some showed performance enhancement, others did not.  Some have argued that the reason for different findings across studies  rests in different methodologies, training status of the tested subjects, exercise protocols, duration of supplementation etc. More recently beetroot juice was suggested as an aid for acclimatization to high altitude. Some studies suggested that it may improve endothelial function and have favourable effects on blood pressure, while others proposed that it may have anti-thyroid properties.

So when it comes to nitric oxide, beetroot juice and athletic performance, the verdict is still out and more studies on nitric oxide and its effect on exercise performance are needed.

Nina Zisko, PhD student at CERG