BEETROOT JUICE SUPPLEMENTATION
AND EXERCISE
DEBRA WEIN, MS, RD, LDN, NSCA-CPT,*D, AND KELLY MURPHY, RD, LDN
W
e all remember the dreaded words at dinnertime “finish
your beets.” Nowadays, research on the benefits of
beetroot juice has athletes clamoring for the same
deep red vegetable that had us wishing we had a dog under
the table as children. This article will address possible benefits,
proposed mechanisms, dosage, and frequency of this potential
ergogenic aid.
Beets, a rich source of antioxidants and nitrates, may serve to
improve blood pressure and blood flow throughout the body,
including the muscles, brain, and heart (1). Humans regularly
consume nitrates from sources such as beets, lettuce, celery,
and spinach (see Table 1 for additional sources). In the body,
these nitrates are absorbed in small amounts in the mouth but
primarily in the stomach, where they are quickly converted to
nitric oxide (NO) (1).
THE ROLE OF NITRIC OXIDE
Increasing NO can be beneficial for individuals due to its role in
regulating blood flow, neurotransmission, immune function, blood
sugar regulation, calcium regulation, and muscle contraction (7).
Potentially, there could be additional benefits for athletes as it
may help to increase oxygen in contracting muscles, decrease
adenosine triphosphate (ATP) cost during exercise, increase
tolerance to long-term high-intensity exercise, and time to
exhaustion (1,2).
When engaging in moderate-intensity exercise, the lungs take in
oxygen at a rate that is very similar to the uptake of oxygen into
skeletal muscles (1). Oxygen intake into both lungs and muscles
increases exponentially with exercise (1). When exercise intensity
increases to a certain level, the uptake of oxygen into the lungs
causes a shift in the energy system utilized, and therefore creates
an increased oxygen cost on the muscles (1). In other words, when
an individual cannot breathe in as much oxygen during exercise,
the muscles have to work through a different energy system to
continue performing the same function.
Several studies have shown increased exercise performance or
a decreased time to exhaustion when participants were given
beetroot juice supplements prior to exercise (1,2,4,6,7). In one
study, researchers tested active males on three different
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occasions and found that there was no increase in oxygen
intake by the lungs in those individuals consuming the beetroot
juice. However, the researchers did find that the amount of
hemoglobin (which carries oxygen in the blood) in the muscle
was higher during exercise in those who consumed the beetroot
juice. In addition, the beetroot juice group had increased oxygen
delivered to the muscle, which allowed for increased exercise until
exhaustion (6).
TIMING AND DOSAGE
Recently, researchers looked into the timing, concentrations,
and frequency of consumption of the juice needed to promote
performance improvements.
Some studies have looked at the best amount of beetroot juice
to consume. One study compared 4 mmol, 8 mmol, and 16 mmol
nitrate concentrated beetroot juice to determine if a greater
benefit existed from consuming a more concentrated amount.
Athletes were tested on four separate occasions during a threeweek period. Each participant consumed the beetroot juice 2.5
hr before performing a moderate- or high-intensity exercise
(which lasted approximately five minutes) and found that all
concentrations increased nitrite concentration and oxygen delivery
in the blood (7). Additionally, the participants who consumed 8
mmol and 16 mmol concentrations improved time to failure of
exercise. The 16 mmol concentrated beetroot juice group improved
time to exhaustion by 12%, whereas the 8 mmol concentration
group improved results by 14%. The results show that individuals
who consumed 8 mmol concentrations actually improved the most
in time to failure of exercise (7).
In other studies, researchers compared consumption between
2 – 3 hr prior to exercise and found the beetroot juice had
beneficial effects on exercise 2 – 2.5 hr after drinking it (1,2,4,5,7).
One such study provided 20 trained athletes with 140 mL of
beetroot juice of 8.7 mmol concentration, 2.5 hr before performing
a one-hour cycling time trial. Although the results found highe