Welcome to our nutrition blog by Dr James Morton, Senior Sports Nutritionist for Science in Sport (SiS), where he will be giving advice on nutrition, dispelling fuelling myths and offering his tips every month. If you have a sports nutrition question or area you'd like to see covered in the blog, email firstname.lastname@example.org.
James has led and collaborated in over 40 research papers and publications and is also Senior Lecturer in Exercise Metabolism & Nutrition at Liverpool John Moores University (LJMU).
Nitric oxide is one of the body’s main signaling molecules where it helps to regulate many physiological processes such as blood flow, muscle glucose uptake and even oxygen consumption by our muscles. It was traditionally thought that the production of nitric oxide was made by the enzyme nitric oxide synthase and that its production could not be influenced by dietary means. However, emerging research over the last 5 years has suggested that increasing dietary nitrate intake can lead to increased nitric oxide production, which can subsequently lead to improved exercise performance.
Nitrates are especially high in green leafy vegetables such as beetroot, lettuce, spinach and celery, for example, though the exact content can vary considerably based on soil conditions and time of year etc. As a means to provide a constant dose of nitrate, most researchers have focused on the use of beetroot juice to elevate the amount of nitrate available. When nitrate is ingested, it is converted to nitrite by bacteria in the mouth and subsequently converted to nitric oxide in the stomach so that it now available for use by our muscles. The beetroot juice studies, mostly led by Prof Andy Jones, have typically employed a loading dose of 0.5 L of beetroot juice per day for the 5 days prior to your event. When undertaking this protocol, data are now accumulating to suggest improved physiology athletic performance in a variety of sports.
The most notable effect initially was that loading with nitrate reduces the amount of oxygen required to exercise at a given power output or running speed. Effectively, this means that our muscles become more efficient and that the exercise is less metabolically demanding than normal. This reduction in oxygen consumption has been repeatedly observed during cycling, walking and running exercise. Importantly, the improved physiology was not observed after consumption of beetroot juice that had the nitrate content removed (i.e. a placebo solution) thus confirming that it is the nitrate per se that is the magic ingredient and not the beetroot juice.
In addition to the effects of nitrate on oxygen consumption, many researchers have also observed that this translates to improved exercise performance. Indeed, individuals can exercise for significantly longer (usually in the magnitude of 15-20% longer) when exercising at a given intensity after a period of nitrate supplementation. It is of course worth noting that exercise capacity tests (i.e. exercising until the point of exhaustion) are not immediately representative of real world conditions where the goal is to go as fast as possible. Nevertheless, these studies have since been supplemented by more recent research confirming that nitrate supplementation can improve race time by approximately 3%. Effectively, nitrate supplementation increases power output for a given level of oxygen consumption thus improving our muscular efficiency. The performance boosting effects of nitrate appear to be particularly effective for exercise lasting <60 minutes and further research is required to evaluate if nitrate can improve race time during longer endurance events. For runners, in particular, nitrate loading would therefore appear beneficial for 5 and 10 km events as well as half-marathon type distances.
Given that nitrate is the performance boosting ingredient and not the beetroot juice per se, athletes are searching for new ways to increase nitrate in their diets especially considering that many individuals do not like beetroot juice for taste reasons. In this regard, Science in Sport have developed the world’s first nitrate gel, SiS GO + Nitrates, that contains a standardized dose of nitrate. Two gels per day is equivalent to the 0.5 L dose of beetroot juice and feedback from athletes suggest it is a more palatable approach to nitrate loading.
The nitrate story is clearly just at the beginning and is likely to continue to dominate sports nutrition research for many years to come. With continued research, perhaps nitrate loading will one day become just as important as carbohydrate loading.
Check out the first Nutrition clinic on marathon fuelling to help on those longer runs.
For more info on the products that Dr James works on, check out the SiS GO+ Nitrates.