Beetroot is rich in nitrates and has been thought to enhance muscle blood flow or vascular dilation during exercise, but this has been proved wrong in a new study. But it did "de-stiffen" blood vessels under resting conditions, potentially easing the workload of the heart.
Endurance athletes have been known to consume the crimson supplement based on the belief that it may improve blood and oxygen flow in their muscles during training and competition and some strength and power athletes consume it in hopes that it can improve their ability to withstand muscle fatigue during repeated bouts of high intensity exercise.
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Researcher David Proctor of Penn State and his colleagues gave subjects either a placebo drink containing beetroot juice minus the nitrate or a relatively high dose of nitrate-rich beetroot juice and found that the latter did not enhance the natural rise in blood flow to the forearm muscles during graded hand-grip exercise.
Lead author Jin-Kwang Kim said that beetroot juice also had no effect on the dilation (widening) of the brachial artery in these volunteers.
Proctor added that although several studies have reported indirect evidence of improved muscle oxygenation during exercise after consuming nitrate-rich supplements such as beetroot juice, none of these studies directly measured blood flow to the contracting muscles and their study was the first to directly test this possibility in humans.
Proctor continued that the absence of any direct effect on forearm muscle blood flow or artery dilator function was not due to a lack of absorption of the supplement into the blood stream.
The study is published in the journal Applied Physiology, Nutrition, and Metabolism.