Tart cherry juice seemed to be the drink of choice at the Tour de France this summer. Riders taking on the race, which took place over three weeks in July, were spotted gulping down the supplement at the finish each day.
Elsewhere, footballers and tennis players have been seen swigging pickle juice, while athletes in other events have been consuming baking soda gels. These are just the latest sports supplements to gain widespread attention – there are many more exotic options already available. But what are they actually doing for athletes?
What supplements actually work?
Supplements are widely used by athletes at all levels and can be consumed for several reasons. Professional athletes may take them to obtain a high dose of a particular nutrient in concentrated form and help meet the high-energy needs of an endurance event.
Creatine, for example. It’s a compound produced in the body and found in protein-rich food such as meat. It can act as a quick source of energy for muscles, and some research recommends that people who exercise consume up to 20g of creatine per day to maintain their body's stores of the compound. But that would mean eating 4kg (8lbs) of steak.
“[Creatine] needs to be used as a supplement in that regard because it would be very uncomfortable to eat that amount of meat,” says Dr Stephen Bailey, a leading expert on exercise physiology from Loughborough University in the UK.
Supplements also have the potential to enhance performance. Bailey thinks that athletes should prioritise eating a nutrient-rich diet, fine-tuning how much water they drink and perfecting their training to obtain the best results. But supplements could provide an additional boost once those are all taken care of.
“In elite sport, the margins between success and failure are very small,” he says. “So if you’ve done everything else well and you’re looking for that very small incremental improvement, then [supplements] might be able to give you a meaningful performance outcome.”
Ketone drinks, for example, have become popular among elite endurance athletes looking to gain a competitive advantage. When the body turns fat into energy during prolonged exercise, molecules called ketones are produced that can be used as a source of fuel for muscles and the brain. They’re an alternative to glucose, the body’s main source of energy.
“Ketones are there to top up glucose levels,” says Prof Keiran Clarke, a biochemist at the University of Oxford.
Clarke and her colleagues invented a ketone drink that was shown to help professional cyclists ride 400m (1,300ft) further over half an hour, on average, compared to those who consumed energy drinks containing carbohydrates or fat.
Ketones can also provide a cognitive boost, which Clarke thinks is more significant. At the Tour de France, for example, riders may start to lose their ability to think strategically when their glucose levels are low at the end of the day.
“That’s where [ketone drinks] really help,” says Clarke.
Sports supplements can also help with recovery after a competition. It’s likely to be the main benefit of tart cherry juice since it has anti-inflammatory properties.
“It’s a fairly successful way to try and manage inflammation post-exercise,” says Bailey. “That might then lower soreness.”
The problems
The big problem with sports supplements, however, is identifying which ones are effective. The market is flooded with them and while all claim to have benefits, many haven’t been rigorously tested.
“There’s a lot of money in the dietary supplement business,” says Floris Wardenaar, an associate professor in sports nutrition at Arizona State University in the US. “It’s really easy to start your own supplement business: basically anyone, without any knowledge, can create something.”
Even in cases where a supplement has been studied, it might have been tested on muscle cells in the lab, but not when ingested by humans.
In a consensus statement issued by the International Olympic Committee (IOC) in 2018, just five supplements (caffeine, creatine, nitrate, beta alanine and sodium bicarbonate) were backed for athletic use. They were the only supplements supported by significant evidence showing performance improvements in specific scenarios.
Besides their concerns over their efficacy, contamination is also an issue. In the UK, supplements are regulated as food, but it can still be hard to control what’s in them (in the US, they’re not regulated as tightly).
Nevertheless, it’s not impossible for impurities to be introduced during the manufacturing process, and analyses of supplements have found banned substances, such as anabolic steroids, in 14–15 per cent of samples tested.
Athletes typically take several supplements, many of which may be contaminated, making the issue even more complex. Wardenaar says that small amounts of banned substances in different products could add up and, in theory, cause a positive doping test. A result that could see the athlete banned from competition.
“Going to a third-party testing organisation is the route to go to make sure a supplement has the substances [an athlete] is looking for, as listed on the label,” he says.
The changing landscape
Whether certain substances in sports supplements should be prohibited can also be a grey area. The World Anti-Doping Agency (WADA), an international independent agency that aims to prevent doping in sports, bans substances that satisfy two out of three of the following criteria:
- If they enhance sports performance
- If they represent an actual health risk to an athlete
- If they violate the spirit of sport
The list is reviewed annually to address substances that have come to prominence and may have the potential to be misused.
Caffeine, for example, used to be on WADA’s prohibited list. But in 2004, its use was permitted again for a number of reasons, including that the performance boost was considered to be minor and the fact that it’s so widely present in foods and drinks that it’s hard to control.
What’s more, determining how a supplement might affect an athlete isn’t always straightforward since the effect can vary between individuals. Some people will be set for the day after one cup of coffee, for example; others will need two or three.
Complicating matters further, according to Bailey, is the fact that the personalisation of supplements is becoming more widespread. Genetic testing technologies are being used to examine how an athlete’s genes may affect their response to nutrients or other food components, for example.
Gender is also influencing supplement recommendations now. Different amounts of carbohydrates and protein are now recommended for male and female athletes, for example. There are also questions around whether women might need different supplements at different times in their menstrual cycle or whether the effect of the contraceptive pill should be considered.
As new formulations of different supplements continue to hit the market, athletes may also be able to get a better boost. Bailey says that sodium bicarbonate supplements (baking soda, basically) have been a popular choice to neutralise fatigue-causing lactic acid produced during high-intensity exercise. However, they can also cause stomach problems such as nausea and diarrhoea. Many companies have created hydrogels that release baking soda further along the gastrointestinal tract to alleviate this.
“There are constantly new approaches in terms of food technology,” says Bailey. “Sodium bicarbonate is very topical at the moment in elite cycling, so more work needs to be done to help us understand that scenario.”
