The Olympics are now only a week away, and watching the world's top athletes in action may inspire less elite sports participants to look for ways in which they can boost their own performance. There is a large industry offering all kinds of products claiming to do just that: sports drinks and supplements, shoes and equipment. But what is the evidence for their benefits? According to a BBC television programme broadcast in the UK last night, which draws on an investigation conducted with the British Medical Journal (BMJ), the answer is 'not a lot'.
The investigation reveals new research carried out by the Oxford Centre for Evidence Based Medicine and the BMJ, and published in the online journal BMJ Open. It concludes that no sound evidence could be found to support claims made by some of sport's biggest brands and that it is "virtually impossible for the public to make informed choices about the benefits and harms of advertised sports products."
The findings are also highly critical of the methods used by the European Food Safety Authority (EFSA) to regulate these marketing claims. The overall message from investigation of the science behind the marketing hype for sports products is that we could be wasting our money in buying them.
A team at Oxford University tested the evidence behind 431 performance-enhancing claims in adverts for 104 different sports products including sports drinks, protein shakes and trainers.
If the evidence wasn't clear from the ads, they contacted the companies for more information. Some, like Puma, did not provide any evidence, while others like GlaxoSmithKline - makers of Lucozade Sport - provided 174 studies.
Yet only three (2.7%) of the studies the team was able to assess were judged to be of high quality and at low risk of bias. They say this absence of high-quality evidence is "worrying" and call for better research in this area to help inform decisions.
Many top sports scientists support this view. Professor Tim Noakes from the University of Cape Town says that while sports drinks may be helpful for elite athletes, the drinks companies rarely study ordinary gym goers. Many also contain high levels of sugar.
Dr Matthew Thompson from the Oxford team is also concerned about rising levels of obesity among children and young people. He says anything that suggests sports drinks are good for us "could completely counteract exercising more, playing football more, going to the gym more."
A BMJ press release says that sports drinks manufacturers are also telling us how to drink, with advice like "stay ahead of your thirst" when the evidence suggests it's best to drink when you're thirsty.
The Oxford team were also unable to find good quality evidence to support claims that special trainers reduce injury, although for decades the industry focus has been on creating specialised shoes which aim to reduce the risk of injury by cushioning against impact and controlling pronation - guidance which the NHS supports.
Sports injury expert, Professor Irene Davis of Harvard University argues that "there is no evidence for prescribing [tailored] footwear". This view is supported by evidence from a recent study by the US military - the biggest sports footwear study of its kind. Soldiers were divided into two groups - one of which was prescribed neutral shoes and the other received shoes tailored for their feet. "They found absolutely no difference between the groups in terms of injury patterns", says Professor Davis.
Benno Nigg, a leading expert in the biomechanics of running shoes who has worked with the major sports brands for over four decades, also told Panorama that his recent research confirms that "the most important predictors for injuries are distance, recovery time, intensity and those type of things." Shoes, he says, are "minor contributors."
Similarly, Carl Heneghan, who led the research team at Oxford University found "no evidence" to support claims that protein shakes or supplements boost performance and recovery any more so than eating a diet that's rich in protein and carbohydrates. Nutritionist, Professor Mike Lean describes protein shakes as "a rather expensive way of getting a bit of milk."
"These misleading messages filter down to everyday health advice by company-sponsored scientists who advise high-profile sports bodies," explains Deborah Cohen, BMJ Investigations Editor. "For instance, fear about the dangers of dehydration has become gospel and now influences what and how we drink when we exercise. It's a triumph of marketing over science."
The investigation concludes: "For now, the evidence we do have seems to be leading us to a rather common sense and affordable solution. Eat a well balanced diet, drink water, find some comfy shoes, and get out there and exercise regularly."
A suite of articles has been published by the BMJ - links to several are provided below. CAB Abstracts covers sports nutrition, and relevant content is highlighted in the Leisure Tourism Database, and Nutrition and Food Sciences Database. A few bibliographic records are given below.
Heneghan C, Howick J, O'Neill B, et al. The evidence underpinning sports performance products: a systematic assessment. BMJ Open 2012;2:e001702. doi:10.1136/bmjopen-2012-001702
The truth about sports drinks. BMJ 2012; 345 doi: 10.1136/bmj.e4737
Mythbusting sports and exercise products. BMJ 2012; 345 doi: 10.1136/bmj.e4848
Forty years of sports performance research and little insight gained. BMJ 2012; 345 doi: 10.1136/bmj.e4797
Energy-drink consumption in college students and associated factors. Attila, S.; Cakir, B.; Nutrition, 2011, 27, 3, pp 316-322, 22 ref.
Lactate, fructose and glucose oxidation profiles in sports drinks and the effect on exercise performance. John L. Azevedo, J.; Tietz, E.; Two-Feathers, T.; Paull, J.; Chapman, K.; PLos One, 2007, September, pp e927, 48 ref.
The knowledge and use of sports drinks in talented adolescent athletes. Burkhart, S. J.; Coad, J.; Proceedings of the Nutrition Society of New Zealand, 2008, 33, pp 85-90, 10 ref.
Dose response effects of a caffeine-containing energy drink on muscle performance: a repeated measures design. Coso, J. del; Salinero, J. J.; Gonzalez-Millan, C.; Abian-Vicen, J.; Perez-Gonzalez, B.; Journal of the International Society of Sports Nutrition, 2012, 9, 21, pp (8 May 2012), 52 ref.
Effects of a caffeine-containing energy drink on simulated soccer performance. Coso, J. del; Muñoz-Fernández, V. E.; Muñoz, G.; Fernández-Elías, V. E.; Ortega, J. F.; Hamouti, N.; Barbero, J. C.; Muñoz-Guerra, J.; PLoS ONE, 2012, 7, 2, pp e31380, 48 ref.