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Beetroot juice increases exercise endurance.

Bailey SJ et al. 2009. Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans. J App Physiol Aug 6 (Epub ahead of print).

According to this small study the nitrate content in beetroot juice may be responsible for reducing oxygen uptake to a surprising extent, making exercise less tiring. Nitric oxide (NO), synthesized in the body from l-arginine by NO synthases, plays a role in adaptation to physical exercise by modulating blood flow, muscular contraction and glucose uptake and in the control of cellular respiration. Other studies have shown that NO can be formed in vivo from the reduction of inorganic nitrate (N[O.sub.3.sup.-]) and nitrite ([N[O.sub.2.sup.-]). The diet constitutes a major source of nitrate and vegetables are particularly rich in this anion.

Hypothesising that dietary supplementation with inorganic nitrate in the form of beetroot juice would reduce the [O.sub.2] cost of sub maximal exercise and enhance the tolerance to high intensity exercise, the authors were amazed by the effects of beetroot juice on oxygen uptake as the effects could not have been achieved by any other known means, including training. In addition to the potential benefits for athletes, the researchers report that the findings could be relevant to elderly people or those with cardiovascular, respiratory or metabolic diseases.

Using a double blind placebo crossover design 8 men (aged between 19 and 38) consumed 500 mL per day of either organic beetroot juice (containing 11.2 +/0.6 mM of nitrate) or blackcurrant cordial (as placebo with negligible nitrate content) for six consecutive days and completed a series of 'step' moderate intensity and severe intensity exercise tests on the last 3 days.

On days 4-6 plasma (nitrite) was significantly greater following the beetroot juice consumption compared with placebo and systolic blood pressure was significantly reduced. During moderate exercise the nitrate supplementation reduced muscle fractional [O.sub.2] extraction. The gain of the increase in pulmonary V[O.sub.2] following the onset of moderate exercise was reduced by 19% in the beetroot group (V[O.sub.2] is the maximum volume of oxygen that the body can consume during intense whole body exercise).

During severe exercise the V[O.sub.2] slow component was reduced and the time to exhaustion was extended. It is unclear what the exact mechanism behind the apparent benefits is however the researchers suspect it could be a result of the nitrate turning into NO in the body reducing the oxygen cost of exercise.

Kim Hunter MNHAA

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Author:Hunter, Kim
Publication:Australian Journal of Medical Herbalism
Article Type:Report
Geographic Code:8AUST
Date:Sep 22, 2009
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