Reference
Montenegro CF, Kwong DA, Minow ZA, Davis BA, Lozada CF, Casazza GA. Betalain-rich concentrate supplementation improves exercise performance and recovery in competitive triathletes. Appl Physiol Nutr Metab. 2017;42(2):166-172.
Design
Participants were supplemented with a beetroot concentrate for 6 days and then completed 2 double-blind, crossover, randomized exercise timed trials that started 7 days apart. The exercise trials consisted of 40 minutes of cycling (75±5% maximal oxygen consumption), followed by a timed 10-km run. Participants returned 24 hours later to complete a timed 5-km run to assess recovery.
Participants
Twenty-two (9 men and 13 women) triathletes (age 38±11 years) recruited from the University of California at Davis area; all participants exercised more than 5 hours a week, had completed a triathlon within the past year, and were nonsmokers in good health.
Study Medication and Dosage
For 6 days prior to each exercise trial, participants consumed either a betalain-rich concentrate (BRC) of beetroots (100 mg/d) or placebo. On the seventh day, participants received half their dose of BRC (50 mg) or placebo and then began a series of exercise trials 2 hours later. This beet concentrate was notable because it contained no sugars or nitrate.
Outcome Measures
Time to complete the 10-km and 5-km runs; serum creatine kinase; heart rate; and perceived exertion.
Key Findings
Participants ran the 10-km distance faster after taking the BRC than they did after taking placebo (49.5±8.9 vs 50.8±10.3 min; P=0.03). Despite running faster, their average heart rate and ratings of perceived exertion remained the same. Seventeen of the 22 participants ran the 5-km distance, which was run the day after the 10-km trial, faster after BRC (23.2±4.4 vs 23.9±4.7 min; P=0.003). Creatine kinase, a muscle damage marker, increased less (40.5±22.5 vs 49.7±21.5 U/L; P=0.02) from baseline after the 10-km run and subjective fatigue increased less (-0.05±6.1 vs. 3.23±6.1; P =0.05) from baseline to 24 hours after the 10-km run following BRC.
Practice Implications
In this study, beetroot improved 10-km run performance in competitive male and female triathletes. It also improved 5-km run performances 24 hours after the initial 10-km run, and the attenuated increase of creatine kinase and fatigue suggest an increase in recovery while taking beetroot. These findings support the use of beetroot for enhanced athletic performance.
Betalains have a wide range of biological activities with potential health benefits: they counter inflammation, protect the liver, and have anticancer and antioxidant activity.
Gretchen Casazza, the principle author of this study, had another but very similar study published barely 6 months earlier, which suggested similar benefits from beetroot supplementation. In the earlier study, 13 competitive runners (all male) completed the same double crossover supplementation protocol but with a slightly different and easier exercise routine. After the same 6-day routine of 100 mg per day of BRC, participants spent 30 minutes on a treadmill and then completed a 5-km time trial. While exercising at the same intensity, the runners had a 3% lower heart rate, a 15% lower rate of perceived exertion (RPE), and a 14% lower blood lactate concentration after taking BRC, compared to the control (P=0.05). Also compared to the control, 10 of the 13 runners had faster times in the 5-km time trial (23.0±4.2 vs 23.6±4.0 min) with lower RPE (P<0.05) after taking BRC. Lactate dehydrogenase, a marker of muscle damage, increased less from baseline to immediately and 30 minutes after the 5-km time trial after beetroot treatment, despite no differences in subjective measures of muscle soreness and fatigue.1
Suffice it to say that beetroot extract seems to be helpful for athletic performance. Given the earlier papers (one of which has been reviewed in this journal) on beet extracts and athletic performance, these current data come as no surprise. The surprise is that up until now the assumed mechanism of action of beets, which are high in nitrate, was related to the rapid conversion of nitrate to nitric acid. The beneficial effect of beets was thought to be due to the effects of a surge in nitric acid, but the beet concentrates used in both of these Casazza studies were nitrate-free. We need another explanation as to why beets help athletes.
Casazza suggests the benefit comes from betalains. The earlier of her 2 studies appears to be the first published that looked at betalains alone, without nitrates, and how they impact exercise performance. All prior studies had looked at beetroot juice that contained nitrates. Lansley’s 2011 study on competitive cyclists used juice that contained 6.2 mmol of nitrates,2 and Cermak’s 2012 study used juice with 8 mmol of nitrates.3 Again, because these 2 recent studies by Casazza used nitrate-free beet concentrate, we need to rethink our earlier assumptions.
Betalains, commonly used as food colorants, are the water-soluble pigments that give beets their vivid red color. Betalains have a wide range of biological activities with potential health benefits: they counter inflammation, protect the liver, and have anticancer and antioxidant activity.4 Betanin and betanidin, the main antioxidant components of betalains, inhibit lipid peroxidation and heme decomposition even at very low concentrations. Betalains are now considered a “new class” of dietary antioxidants.5
Studies show that pigments in betalains inhibit the growth of several different types of malignant tumors, including breast, liver, colon, and bladder cancers. Betalains fight cancer through effects on apoptosis—the process of programmed cell death built into all normal cells, but altered in cancer cells. Other potential mechanisms of action include negative effects on genes that promote cancer cell survival and genes that control blood vessel growth. The anticancer activity of betalains is enhanced by this multipronged attack on cancer cell growth.6
Given the evidence that betalains have a wide range of healthy effects in the body, it makes sense that betalains might be the active component of beets responsible for improved exercise performance.
In recent years, because of the nitric oxide theory, some have promoted beet juice extract as an herbal substitute for synthetic phosphodiesterase type 5 inhibitors such as sildenafil (aka Viagra). Research suggests that few if any herbs actually provide the promised chemical effects and that if these products have effect it is secondary to adulteration with active drugs.7 On the other hand, although we have yet to find publications on the subject, one might argue that the betalains alone, because they are potent antioxidants that lower reactive oxygen damage, may, like other plant polyphenols, protect against damage that leads to erectile dysfunction.8
