Caffeine is arguably the most well researched ergogenic aid, while nitrate in the from beetroot juice is rapidly scaling the heights of the ergogenic ranks with a large number of studies showing significant performance benefits for endurance as well as strength/power-based sports. What’s more, the mechanisms by which each substance boosts performance are different. It’s make sense therefore to test whether combining the two together would result is greater effects than either alone. This is exactly what researchers from the UK did in the December issues of the 2013 ISRN Nutrition journal.
Researchers from The University of Nottingham and Loughborough University recruited a group of 14 healthy males with an average age of 22, who were all familiar with endurance exercise. The subjects were required to undertake 4 different testing sessions, namely: (1) placebo, (2) placebo + caffeine, (3) beetroot juice, and (4) beetroot juice + caffeine. These treatments were separated by a minimum of four days and subjects were required not to undertake any vigorous exercise the preceding day.
For those wondering what type of placebo the researchers used for beetroot juice, the company supplying the beetroot juice also provided a version of the juice completely devoid of nitrate content. This makes for a very effective placebo as taste, colour and consistency of the placebo is no different to normal beetroot shot.
Dosage wise, subjects were given 5mg/kg bodyweight of caffeine while the beetroot juice was administered in two separate 70ml shots (1st shot 2.5 hrs before & 2nd shot 1.25 hrs before) with each shot containing 4 mmol (i.e. 64mg) of nitrate to give a total of 128mg of nitrate pre-exercise. As for the exercise protocol, subjects has to complete an initial 30 minutes session on a stationary bike at 60% VO2max, which was followed by a time-to-exhaustion trial at 80% VO2max.
The researchers found that the beetroot and caffeine group experienced a 18% and 27% nonsignificant improvement in the time-to-exhaustion trial compared with the beetroot and placebo plus caffeine group respectively. The other significant finding was that only the beetroot and caffeine group experienced a significantly lower rating of perceived exertion (RPE) compared to the other groups. But a major limitation of the study was that although there was an overall trend towards improvement in the caffeine and beetroot group it was not statistically significant. One of the main reasons may be because of the study design that was used. Namely, the time-to-exhaustion trial. Studies have shown this particular test of performance has a large degree of interindividual variability. A preferred alternative protocol is the time trial, where participants are required to ride a given distance in as quick a time as possible. For example, studies have reported up to 27% versus <4% day-to-day variability for time to exhaustion and time trial protocols respectively.
Given the promising results, with the exception of its shortcomings, it is highly likely that similar studies will be conducted in the near future which attempt to address the flaws in this study. In the mean time, the odds are the average individual will get a good boost by having some beetroot juice alongside their coffee.
Larsen FJ et al. Dietary inorganic nitrate improves mitochondrial efficiency in humans. Cell Metabolism. 2011;13(2):149–159.
Handzlik MK & Gleeson M. Likely additive ergogenic effects of combined preexercise dietary nitrate and caffeine ingestion in trained cyclists. ISRN Nutrition. 2013:396581.