Study reveals there is a 'striking lack of evidence' to back up claims made for trainers, drinks and supplements

Claims about how trainers, sports drinks and supplements will help grassroots or elite athletes train harder and achieve better times are usually based on no or flawed evidence, researchers have revealed.

Sportswear giants, such as Nike and Puma, and manufacturers of drinks, such as Powerade and Lucozade Sport, regularly insist their products confer advantages on users. But such claims are so difficult to verify because of a lack of reliable evidence to back them up that "it is virtually impossible for the public to make informed choices about the benefits and harms of advertised sports products, based on the available evidence", according to a study by a team from Oxford University and the British Medical Journal.

"There is a striking lack of evidence to support the vast majority of sports-related products that make claims related to enhanced performance or recovery, including drinks, supplements and footwear," conclude researchers led by Dr Carl Heneghan of Oxford's centre for evidence-based medicine.

Half the websites for such products provide no evidence for these claims and of those that do, half the evidence could not be critically appraised.

The findings, which will be broadcast in Thursday's Panorama on BBC One, suggest that many participants in sport may have been misled by marketing techniques and dubious claims and are wasting their money.

Makers of sports drinks have succeeded in persuading people that they need to drink them, rather than water, and forged links with leading sports bodies in a bid to gain the public's trust and normalise their use, according to a joint BMJ-BBC investigation.

Phrases such as "stay ahead of thirst", promotion of the "science of hydration" and advising sports enthusiasts to consume sports drinks before starting to exercise have helped create a global industry that forecasters Mintel estimated will be worth $1.6bn by 2016, they say.

Many such drinks, which are also popular with children, contain a lot of sugar. For example, a 500ml bottle of Powerade Ion4 contains 19.6g of sugar, while bottles of Lucozade Sport and Gatorade the same size contain 17.5g and 30g of sugar respectively, they found.

Drugs firm GlaxoSmithKline, who make Lucozade Sport, cited 174 studies to underline the merits of their drink, which they claim is "proven to enhance physical endurance" and is "specially formulated to help you get the most out of your sporting performance". But just three of the 174 studies were deemed of good enough standard by the researchers, leading them to note the "worrying" lack of reliable evidence.

The Oxford team did not find any reliable evidence that certain types of trainers help reduce the risk of sports injury. A recent American study, the largest of its kind undertaken, found no difference in injury risk between wearers of sports shoes designed to correct pronation and those in normal trainers.

But Professor John Brewer, head of sports science at the University of Bedfordshire, said that while those who exercised to keep fit may find that water is enough to quench their thirst, "those who compete intensively for long durations have been shown by numerous studies to improve their performance through the sensible consumption of sports drinks".

Dr Colin Cable, the pharmaceutical science information officer at the Royal Pharmaceutical Society, said that manufacturers of sports drinks must always support claims they make with proper evidence to help consumers. The alleged benefits of foods and dietary supplements must also be well-founded, he added.

"However, for the vast majority of sporting participants, it is questionable whether any form of supplementation will be necessary, as a healthy balanced diet will provide their body's requirements for protein, carbohydrate, vitamins and minerals," Cable added.