NITRATES AND AEROBIC PERFORMANCE Nitrates are a proven performance enhancer, apparently via enhancing the effectiveness of nerve stimulation of skeletal muscle fibers. This effect provides 2 independent benefits: FIRST is an increase in efficiency, i.e. a decrease in the amount of oxygen used for a set level of exercise without an increase in blood lactate levels. This benefit has been demonstrated with diet changes alone (100-300 g of a nitrate-rich vegetable such as spinach or beetroot for 2 days) for both sub-maximal levels of exertion (ncbi.nlm.nih.gov/pubmed/17635415) as well as for maximal levels of exertion. (ncbi.nlm.nih.gov/pubmed/19913611) And, as expected, the same improvement in efficiency has been documented with the higher doses of nitrates used in experiments using acute and chronic supplements. SECOND is an improvement in overall exercise performance for continuous maximal exercise of 5–30 min. duration. (ncbi.nlm.nih.gov/pmc/articles/PMC4008816/). Specific examples: In one study with 6 days of supplementation ncbi.nlm.nih.gov/pubmed/22248502 - 10k time trial performance was improved slightly (953 vs. 965 seconds) - at a slight higher average power output 294 vs. 288 watts - and with a lower overall rate of oxygen consumption. In a second, assessing the benefits of acute use, nine club-level competitive male cyclists were given a single dose of 0.5 L of beetroot juice (containing ∼ 6.2 mmol of nitrate) 2.5 hours before a 4 and 16 km time trial. The 4-km performance improved by 2.8% and the 16.1-km performance by 2.7% (ncbi.nlm.nih.gov/pubmed/21471821). But as you might expect if the duration of effect is in the range of 30 minutes, there was no benefit found in a 50 mile time trial. (ncbi.nlm.nih.gov/pubmed/22526247) It is not the nitrate molecule itself that provides this benefit, but a metabolic end product, nitric oxide (NO). Nitrate is an inorganic anion particularly abundant in green leafy vegetables such as spinach, beetroot, rocket, or lettuce which is then converted into nitrite by bacteria in the oral cavity. The nitrite then enters the systemic circulation and is subsequently reduced to the active agent nitric oxide (NO) which is known to be an important “signaling molecule”, at the tissue level. Presumably NO is the agent that actually improves the nerve/muscle interaction. (ncbi.nlm.nih.gov/pubmed/24681572) How much beet juice (the form of nitrates used in most experimental studies)? 0.6 gm of nitrate (approximately 9.7 mmol) One study looking at maximal beneficial dosing demonstrated that exercise tolerance (measured as “time to task failure”) did not improve above 8.4 mmol of nitrate. ncbi.nlm.nih.gov/pubmed/23640589 It should be emphasized that 5–9 mmol of nitrate can readily be consumed within the normal diet and there is presently no evidence that additional nitrate intake produces greater benefits. (ncbi.nlm.nih.gov/pmc/articles/PMC4008816/) The beet supplement should be taken at least 2 – 2.5 hours before the event (if a single acute supplement is being used) or for 2 – 6 days if a chronic dietary change is the plan. And as of the moment, nitrates are not on the World Anti-Doping Agency’s (WADA) Prohibited List (usada.org/wp-content/uploads/wada-2015-prohibited-list-en.pdf) In summary, there is little to be lost, and for the elite athlete a definite gain from a trial of beet juice or a change to a high nitrate diet (spinach, beetroot, rocket). For those interested, a nice summary article can be found at ncbi.nlm.nih.gov/pmc/articles/PMC4008816/
Posted on: Wed, 31 Dec 2014 02:41:19 +0000
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