Can Beet Juice Lengthen Your Workouts?
A new study published in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology reveals that regular consumption of beet juice has positive cardiovascular effects during exercise and leads to increased endurance.
For the study, healthy males drank beet juice for 15 days. They experienced lower blood pressure and more dilated blood vessels at rest and during exercise. With the beet juice consumption, their blood vessels also dilated more easily and the heart consumed less oxygen during exercise.
The findings suggest that beet juice can be used as a dietary nutraceutical supplement to enhance oxygen delivery to the muscles and reduce the work the heat does during exercise. The researchers added that exercise can be performed at a given workload for a longer period of time before the onset of fatigue.
Beet Juice Benefits And Theories
In January 2015, a study in the journal Applied Physiology, Nutrition and Metabolism reported that those who drink beet juice before exercising to increase blood flow and improve performance might be surprised by the results. The study conducted at Penn States Noll Laboratory revealed that while beet juice rich in nitrates did not enhance muscle blood flow or vascular dilation during exercise, it did de-stiffen blood vessels under resting conditions, which potentially eased the workload of the heart.
Nitrates found in highest concentrations in leafy green vegetables such as spinach and beetroot - are converted naturally in the body to nitric oxide, a molecule that relaxes and widens blood vessels and affects how efficiently cells use oxygen. For the study, participants were given either a placebo drink containing beet juice without the nitrate or a relatively high dose of nitrate-rich beet-root juice. They discovered that the latter did not enhance the natural rise in blood flow to the forearm muscles during graded handgrip exercise.
They also observed a direct correlation between nitrite levels in the blood and the slowing of participants arterial pulsation velocity and indication that the supplement had a biological artery de-stiffening effect.
"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," said David Proctor, professor of kinesiology and physiology at Penn State University. Our study was the first to directly test this possibility in humans. 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. Measurements of the breakdown product of the nitrate in the participants' blood indicated that these participants absorbed the nitrate from the drink and converted it to nitrite, the precursor to nitric oxide. However, there are circumstances unique to our experimental design that should be considered, as with any study, before drawing any broad conclusions.
We speculate that the null effects on muscle blood flow observed in this first study resulted from two factors, Proctor added. Subjects were young individuals with blood pressure and cholesterol levels in the 'very healthy' range. Therefore, the lack of improvement in muscle blood flow and vessel function following nitrate supplementation could result from the fact that these subjects had well-preserved vascular endothelial function to begin with. A second contributor could be the relatively small range of forearm exercise intensities we examined in this study. It is possible that any blood flow enhancing effect of dietary nitrate will only be apparent during higher intensity and fatiguing work intensities; conditions within the muscle that favor the conversion of nitrite to nitric oxide.