Beetroot Juice – How’d they think of that?!
The theory behind how beetroot juice enhances performance is a complex but interesting one. It’s been known for quite a while that nitric oxide (NO) in the blood is involved in the way that muscles produce energy. More NO in the blood during exercise appears to reduce the amount of oxygen it takes to produce energy, creating a type of “fuel efficiency” that could potentially improve exercise performance.
Early studies (see here and here) looked at trying to increase the amount of NO in blood by supplementing with the amino acid L-arginine, which is readily converted to NO in the blood. However this failed to produce the desired effect because the conversion of L-arginine only occurs in the presence of ample oxygen in the blood, which is not the case during exercise (because it’s being extracted to produce energy in the muscles).
More recently, however, it was discovered that blood nitrite (NO2-) could also be converted to nitric oxide, and does so during periods where blood oxygen levels were low. So the idea was to find a way to increase the level of nitrite in the blood.
Nitrite levels in the blood can be increased with direct supplementation of nitrite salts. But even tiny amounts of these increase the blood levels far too high, to a level that is toxic to humans (about as toxic as cyanide!). So scientists began looking at an indirect way to increase nitrite levels enough to produce more nitric oxide, but within a range that was safe.
To do this they realised that supplementing with nitrate (NO3-) could achieve this, because nitrate can be converted to nitrite. Interestingly, this conversion doesn’t occur in your blood, but actually takes place in your mouth – the bacteria that live in your mouth are capable of this conversion.
When you ingest nitrate initially, most of it is absorbed into the blood, but then secreted back into your mouth through the saliva glands. The bacteria then convert this to tiny amounts of nitrite, which is then re-absorbed into the blood, increasing the blood nitrite significantly, but safely.
Bring on the beets
This is where beetroot juice enters the picture. Of the naturally occurring food sources of nitrate, beetroot is one of the best and most palatable in the quantities needed to significantly increase blood nitrate (and therefore nitrite) levels. Hence the use of beetroot juice as a way of safely boosting blood nitrite was born.
About 300-500mL of beetroot juice provides the amount of nitrate needed for the average person to increase their blood nitrite, which occurs about 2-3 hours after drinking it. However just going out, buying your own beets and putting them in the food processor doesn’t guarantee you’ll get the benefit. The nitrate content of vegetables (including beetroot) varies significantly according to the soil it’s grown in, the time of year, the fertiliser used, and how soon after being picked the beets are juiced.
Therefore, to get a known quantity of nitrate, a few manufacturers (firstly in the UK and now in Australia) have sprung up, offering bottled beetroot juice with a known nitrate content.
Where’s the research at now?
The early studies of nitrate supplementation were published in 2007 (another followed in 2009) and followed the typical cycle I described in my last article. They were conducted in relatively untrained athletes, doing exercises that were easy to control in the lab but had little to do with actual sport.
Most also didn’t measure performance per se, instead measuring the body’s use of oxygen and showed the beetroot juice lowered the amount of oxygen required to do the same set amount of exercise. So it’s an inferred benefit, but not a measured enhancement of athletic performance by any means.
But these studies did spark the hype, publicity and commercial sales of the early beetroot juice products about three or four years ago.
Between 2009 and 2011 a few studies (here, here and here) were published that showed that nitrate supplementation (mostly from beetroot juice) improved the duration that someone could cycle at a constant intensity without having to stop. However it’s well known that these types of results don’t always translate into improved performance in a race situation (fixed distance, variable intensity not the other way around).
It wasn’t until 2011 that the first study was published that measured meaningful sporting performance with beetroot juice supplementation. In that study non-elite athletes took a single dose of beetroot juice three hours prior to both a 4km and 16km time trial. In both cases performance improved by around 2.7% compared to placebo (beetroot juice treated to remove the nitrate). The study showed that participants were able to maintain a higher power output for the same amount of oxygen consumed (or ride at the same power output while consuming less oxygen).
But 4km and 16km TTs are not a great indication of the ability of beetroot juice to improve performance in road cycling.
It wasn’t until last year that the first studies (here and here) were published looking at beetroot juice and cycling performance over longer distances. These studies also used elite level athletes for the first time. So far these studies have provided mixed results – while the average of all participants was not significantly better than placebo, some participants did improve with supplementation while others didn’t.
Those who did improve with beetroot juice were the ones where the supplementation increased their blood nitrite levels – but not everyone seemed to get that increase. Researchers speculate that this might be the case in highly trained athletes (say A-grade club and above) because they already have a high blood nitrite level without supplementation, possibly an adaptation to their training.
Many scientists are now concluding that a one-off dose of beetroot juice will not improve performance in highly trained athletes, and it may take much larger doses of nitrate (e.g. up to a week of drinking beetroot juice every day or using more potent forms of nitrate supplementation, such as sodium nitrate) to shift blood nitrite levels. However this is yet to be studied, so can only be viewed as theory or speculation.
It’s entirely possible that no amount of nitrate supplementation will improve performance in elite athletes, but until the research has reached its natural conclusion we won’t know whether beetroot juice is here to stay or a passing fad.
The products
There are a few brands of beetroot juice now available on the market in Australia. One of those brands, Beet It, is imported from the UK and was one of the first available here. It’s sold in selected health food stores. They make a beetroot and apple juice blend (you need to drink around 300-500mL to get the benefit of the nitrate), as well as “shots” of concentrated beetroot juice mixed with a touch of lemon juice. I first tried these with the search2retain team last year and the feedback on the taste wasn’t great – a bit like opening a can of beetroot and drinking the juice – only 500mL of it!
Throughout last year one of the search2retain guys stumbled across another product, Sunraysia Beetroot & Apple Juice, which is made here in Australia and sold in supermarkets for a lot less than the Beet It. This is probably because Sunraysia produced the drink with general health in mind (nitrates can also lower blood pressure), not as a sports specific product. Importantly, the riders rated the flavour much better and yet the nitrate level is about the same.
A new comer to the beetroot juice market is UpBeat, made in Western Australia. I haven’t tried this one so can’t comment on the taste, but it’s nitrate content is a little higher so you only need to drink 250mL to get the same amount of nitrate.
Summary
Beetroot juice may improve performance for some athletes in some situations, but exactly who and when is not yet clear from a research standpoint. But I’m sure that athletes who regularly measure and monitor their performance can decide for themselves whether it works or not.
For more elite athletes it’s likely that you’d need to use beetroot juice for several days in a row to get a meaningful boost in blood nitrite (and hence performance). But for the rest of us a single dose about 2-3 hours before exercise may just give you an extra percent or two.
Note: I’ve provided links to the abstracts of many of the research papers mentioned in this article. Please be aware though that the devil is usually in the detail with these types of studies, and so simply reading the brief results and the authors’ opinions in their conclusions often doesn’t give the full story. I could write another whole article using examples of where the abstract tells a very different story to the full text!
http://cyclingtips.com.au/2013/04/beetroot-juice-good-science-or-great-marketing-hype/
