Nitrate supplementation is an effective, evidence-based dietary strategy for enhancing sports performance. The effects of dietary nitrate seem to be mediated by the ability of oral bacteria to reduce nitrate to nitrite, thus increasing the levels of nitrite in circulation that may be further reduced to nitric oxide in the body. The gut microbiota has been recently implicated in sports performance by improving muscle function through the supply of certain metabolites. In this line, skeletal muscle can also serve as a reservoir of nitrate. Here we review the bacteria of the oral cavity involved in the reduction of nitrate to nitrite and the possible changes induced by nitrite and their effect on gastrointestinal balance and gut microbiota homeostasis. The potential role of gut bacteria in the reduction of nitrate to nitrite and as a supplier of the signaling molecule nitric oxide to the blood circulation and muscles has not been explored in any great detail.
Abstract from González-Soltero R, Bailén M, de Lucas B, et al.: Role of Oral and Gut Microbiota in Dietary Nitrate Metabolism and Its Impact on Sports Performance. Nutrients. 2020;12(12):3611.
Knowledge Transfer of Nikolaos Papaspanos (Thessaloniki)
The use of nitrate supplementation has a proven ergogenic effect in sports. In the oral cavity the nitrate (NO-3) is reduced to nitrite (NO-2) by anaerobic bacteria. Then in the stomach nitrite (NO-2) is reduced to NO which is bioactive in the tissues and blood. The remaining nitrate and nitrite are absorbed from the intestine into the circulation .
The higher concentration of NO in the blood causes vasodilation. The resulting increased blood flow to the muscles provides higher amounts of oxygen and enhances aerobic capacity .
Nitrate supplementation can also enhance anaerobic production of energy. Since phosphocreatine resynthesis is depended on aer-obic capacity, better aerobic capacity results in better phosphocreatine resynthesis, providing higher levels of energy substrate to the muscle. Furthermore, increased phosphocreatine resynthesis means lower concentrations of diphosphate (ADP) and inorganic phosphate (P) in the muscle. High concentrations of these two metabolites in the muscle are implicated in fatigue. Finally, NO-3 supplementation can promote the release of calcium from the sarcoplasmic reticulum in muscle cells and its subsequent reuptake, which increases the strength of muscle contraction . To summarize, nitrate supplementation enhances aerobic capacity and performance in high intensity exercise lasting 6–60 s .
The most common nitrate supplementation is beetroot juice. 500 ml of beetroot juice contain about 320 mg NO-3. Ergogenic effects of NO-3 can be achieved when 372–496 mg (6–8 mmol) of NO-3 are consumed in one dose, 90 min before a competition. However, highly trained athletes may need to supplement with a higher dose and for more than 1 day .
For the ergogenic effect of nitrate to be achieved, the appropriate oral microbiota must be provided. To reduce nitrate to nitrite, anaerobic nitrate-reducing bacteria, such as Prevotella, Veillonella and Haemophilus, must be present in the oral cavity ; otherwise, the supplementation has no use.
Conclusion for Clinical Practice
Intake of dietary nitrate can change the gut microbiota. Certain anaerobic gut bacteria can reduce nitrate to nitrite, thus generating NO which helps improve muscle performance. In another cooper-ation between the gut microbiota and muscle mass, certain bacteria produce short chain fatty acids (SCFA), with the most important being butyrate which participates in the Krebs cycle. Thus, it can be used as an energy substrate in the aerobic production of energy. Veillonella is one of the bacteria that can be found in both the oral cavity and the gut microbiota. Its presence in the gut microbiota also plays a significant role in enhancing sports performance, since it is responsible for transforming lactate – released from muscle into the intestine during physical activity – to propionate, another SCFA.
In conclusion, the oral/gut microbiota plays a significant role in the nitrate metabolism and thus in improving sports performance.
I hereby declare that there are no conflicts of interest with regards to this commentary.