Nitric oxide: facts and fiction
Nitric oxide (NO) supplements have become rather popular in recent years. In many places you will find that they are literally selling “nitric oxide”. But this is not possible because this molecule is a gas. So how do these food supplements work?
How nitric oxide food supplements work.
These are actually substances that promote the release of nitric oxide in the body. The main function of this gas is to dilate your blood vessels, thereby lowering your blood pressure. Nitric oxide also has antioxidant properties, decreasing the oxidation of LDL “bad cholesterol” vesicles, which lead to atherosclerosis. Nitric oxide plays such an important role in cardiovascular health that the Nobel Prize in Physiology or Medicine was awarded for its characterisation in 1998.
However, these supplements are generally marketed for the purpose of enhancing sporting performance. This makes sense, because dilating the blood vessels allows more blood to flow and makes it easier for oxygen and nutrients to reach the muscles. This also increases resistance to muscle fatigue and even reduces muscle recovery time.
Scientific studies of commercially available nitric oxide precursors have shown that L-citrulline has the highest efficacy because it is not degraded in the gut and generates L-arginine, the nitric oxide precursor. All other supplements have a major limitation: they are more prone to being converted into other compounds that do not perform the same function and are excreted from the body. However, nitric oxide is not a magic bullet; too much of this gas can be harmful to the body and it can go from having antioxidant properties to pro-oxidant properties, so it should be taken in moderation. For these reasons, the efficacy of these substances has been called into question in recent years.
Antioxidant substances also affect nitric oxide synthesis, although not in the same way as precursors. Antioxidants increase the activity of endothelial nitric oxide synthase (eNOS), the enzyme that produces nitric oxide in the muscle cells of blood vessels, while precursors generate the substrate for this enzyme. Thus, antioxidants restore eNOS activity when it is diminished (e.g. in old age, due to hypertension, high cholesterol, etc.).
Nitric oxide in pomegranates
Ellagitannins are a type of polyphenol with an antioxidant effect and they are found in many nuts and fruits. Punicalagins, the main ellagitannins in pomegranates, have been shown to be effective in improving both cardiovascular health and sporting performance. And with rather astonishing results.
Firstly, a 2014 study revealed that 200 mg of punicalagins per day almost completely restored endothelial function in hypercholesterolaemic pigs, from 50% to 90%. This effect is due to increased eNOS activity, which generates nitric oxide in our blood vessels. Given the similarities between the vascular systems of pigs and humans, these results would be very similar in humans.
Moreover, a study that was published in March 2019 showed the effectiveness of punicalagins in endurance sports. In this study, it was observed that it mainly affects the time when fatigue sets in, as it delays the onset of exhaustion. In an incremental exercise test on trained cyclists, it was shown to increase time to fatigue by 14%, even more than L-citrulline (12%).
Combining L-citrulline with ellagitannins.
A 2017 study showed that the concomitant intake of two juices, a citrulline-rich watermelon juice and an ellagitannin-rich pomegranate juice, increased the effects of both juices. The study showed that there were improvements in mean maximal strength, parameters related to the perception of effort and muscle soreness, and other biochemical markers involved in physical exercise. It is hypothesised that the synergistic effect of citrulline and ellagitannins is partly due to the antioxidant and anti-inflammatory properties of ellagitannins. Physical exercise produces a large amount of free radicals and has an inflammatory effect on muscles and tendons. The anti-inflammatory effect helps to reduce the feeling of muscle soreness after intense physical activity.
If you’re looking to improve your personal bests by enhancing your sporting performance with less effort and you want to feel less pain on recovery days, you may find it useful to include sources of citrulline and punicalagins in your diet.
