Facts You Did Not Know About Nitric Oxide
Nitric Oxide (NO) is a gaseous free radical found within the body that is synthesized from L-arganine and nitric oxide synthase (NOS). The NOS enzyme is found in multiple tissues and the NO formation is an oxygen dependent process. Due to its chemical properties, NO has the ability to rapidly diffuse through cells and into adjacent tissues, allowing it to be a potent auto-regulator of cerebral and coronary circulations in addition to pulmonary and systemic vascular resistance. One of the major actions that have been attributed to NO is its function as a potent vasodilator as well as its role in the “inhibition of proliferation of fibroblasts, vascular smooth muscle, platelet-induced vasoconstriction, platelet aggregation, and leukocyte adhesion”. Nitrate (NO3-) can be reduced to form nitrite (NO2-) by reductase enzymes and in acidic conditions. This conversion process takes places in several areas of the body. First, the dietary nitrate is ingested and absorbed rapidly, which is then secreted in bodily fluids such as saliva. As the nitrate in the saliva reaches the posterior surface of the tongue, bacterial flora metabolizes nitrate into nitrite, which, upon swallowing, acidic conditions within the stomach cause a rapid protonation of the nitrite. The pronated nitrite is then converted through a series of reactions to NO. After the completion of these reactions, the entire process results in the chemical production of NO in the upper intestine and in salivary glands. Nitrate not immediately converted in the oral cavity, is absorbed into the gastrointestinal tract and taken up by plasma in conjunction with more plasma nitrate being produced from total enzymatic body production of NO, which is then delivered back to the saliva to be converted by bacteria to nitrite.
Nitrate supplementation has been shown in healthy adults to significantly reduce VO2 levels on submaximal work rates while inversely producing a longer time to exhaustion along with no accumulation of lactate, indicating an increase in energy production efficiency. Similar studies have demonstrated an acute decrease in blood pressure, particularly in diastolic pressure post-exercise when subjects were supplemented with nitrates compared to a control on a low nitrate diet. In a short term study with COPD patients, subjects consumed either a nitrate-rich beetroot juice supplement (containing 6.77 mmol of nitrates), or a “nitrate-depleted beetroot juice (containing 0.002 mmol of nitrates) twice a day for 2.5 days with the final supplement being consumed approximately 3 hours before completing a cycling exercise test”. Between the two bouts of testing, a 30- minute rest period was instituted for recovery. After completion of the second bout of cycling, a “6-minute walk test was performed to assess functional capacity”.