The Evidence Underpinning Sports Performance Products: a Systematic Assessment
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Downloaded from http://bmjopen.bmj.com/ on November 14, 2015 - Published by group.bmj.com Open Access Research The evidence underpinning sports performance products: a systematic assessment Carl Heneghan,1 Jeremy Howick,1 Braden O’Neill,1 Peter J Gill,1 Daniel S Lasserson,1 Deborah Cohen,2 Ruth Davis,1 Alison Ward,1 Adam Smith,2 Greg Jones,2 Matthew Thompson1 To cite: Heneghan C, Howick ABSTRACT ARTICLE SUMMARY J, O’Neill B, et al. The Background: To assess the extent and nature of evidence underpinning sports claims regarding improved sports performance made performance products: Article focus by advertisers for a broad range of sports-related - a systematic assessment. The marketing of sports products has become products, and the quality of the evidence on which BMJ Open 2012;2:e001702. a multibillion-dollar industry, but research in this doi:10.1136/ these claims are based. area has previously been labelled as methodo- bmjopen-2012-001702 Methods: The authors analysed magazine adverts and logically poor. associated websites of a broad range of sports - We aimed to assess the extent and nature of < Prepublication history and products. The authors searched for references claims regarding improved sports performance additional appendices for this supporting the performance and/or recovery claims of made by advertisers for a broad range of sports- paper are available online. To these products. The authors critically appraised the related products and the quality of the evidence view these files please visit methods in the retrieved references by assessing the the journal online (http://dx. on which these claims are based. level of evidence and the risk of bias. The authors also doi.org/10.1136/ Key messages bmjopen-2012-001702). collected information on the included participants, adverse events, study limitations, the primary outcome - The current evidence is not of sufficient quality to Received 19 June 2012 of interest and whether the intervention had been inform the public about the benefits and harms of Accepted 21 June 2012 retested. sports products. Results: The authors viewed 1035 web pages - There is a need to improve the quality and This final article is available and identified 431 performance-enhancing claims reporting of research, a move towards using for use under the terms of for 104 different products. The authors found 146 systematic review evidence to inform decisions. the Creative Commons Attribution Non-Commercial references that underpinned these claims. More Strength and limitations of this study 2.0 Licence; see than half (52.8%) of the websites that made - We attempted to identify a representative sample http://bmjopen.bmj.com performance claims did not provide any references, of products, but it is possible the products we and the authors were unable to perform critical analysed are at the worst end of the spectrum. appraisal for approximately half (72/146) of the - We did not give the manufacturers much time identified references. None of the references referred to respond to requests for information, given to systematic reviews (level 1 evidence). Of the more time a number may have provided more critically appraised studies, 84% were judged to be references. at high risk of bias. Randomisation was used in just over half of the studies (58.1%), allocation concealment was only clear in five (6.8%) studies; INTRODUCTION and blinding of the investigators, outcome assessors Exercise is important for improving overall or participants was only clearly reported as used in 1 20 (27.0%) studies. Only three of the 74 (2.7%) health across a variety of conditions. The studies were judged to be of high quality and at promotion of exercise is therefore an low risk of bias. important public health priority, particularly Conclusions: The current evidence is not of for the ‘economically and socially 2 sufficient quality to inform the public about the disadvantaged’. benefits and harms of sports products. There is a need Currently, the public are faced with a large 1Centre for Evidence-Based to improve the quality and reporting of research, Medicine, Department of number of adverts that make claims about Primary Care Health a move towards using systematic review evidence to enhanced performance and recovery for Sciences, University of inform decisions. a wide range of products, including drinks, Oxford, Oxford, UK supplements, clothing and footwear. Regula- 2 BMJ, London, UK tors require that marketing communications Correspondence to containing health claims must be supported Dr Carl Heneghan; by documentary evidence and ‘must not [email protected] mislead consumers by exaggerating the Heneghan C, Howick J, O’Neill B, et al. BMJ Open 2012;2:e001702. doi:10.1136/bmjopen-2012-001702 1 Downloaded from http://bmjopen.bmj.com/ on November 14, 2015 - Published by group.bmj.com The evidence underpinning sports performance products capability or performance of a product’.3 In spite of this, of all web pages viewed with the associated claims. To some adverts for sports drinks have previously been reduce errors, we directly cut and paste any claims and shown to mislead the public into incorrectly concluding searched the web pages for any references related to that the drinks contained no carbohydrates or additives.4 these claims. We compiled a database of all retrieved In addition, while some supplements have been shown references and then two reviewers (AS and GJ) emailed to potentially improve performance, many have no all manufacturers with the claims and the associated proven benefits and may cause serious side effects.5 The references asking them (1) to confirm whether our list marketing of sports products has become a multibillion- of claims and retrieved references was complete; (2) dollar industry,6 and the consumption of the so-called whether other data existed to support the claims; (3) if energy drinks is increasing year on year,7 but research in additional data were published, could they provide us this area has previously been labelled as methodologi- with the relevant references and (4) if the research was cally poor.8 unpublished, could they supply us with a copy of the The current confusion as to which products are actu- report. ally beneficial for sports performance is highlighted by the European Food Safety Authority decision to approve Data extraction certain products, such as carbohydrateeelectrolyte We extracted the following data (from both the magazine drinks to enhance water absorption during exercising and the websites) of included sports products into Micro- and maintain endurance performance, while not soft Excel: product category (ie, sports drinks, supple- approving a variety of other products; including L- ments, footwear, clothing or devices); website; number of carnitine, glutamine or typrosine, which claim to aid pages viewed; number and type of enhanced performance muscle recovery.9 We therefore aimed to assess the claim(s); references cited for the claims; qualifiers related extent and nature of claims regarding improved sports to the claim (eg, such as ‘should be used in conjunction performance made by advertisers for a broad range of with a healthy diet and training programme’) and whether sports-related products, and the quality of the evidence the product was endorsed/backed by a sports person or on which these claims are based. team. One reviewer (JH) acted as custodian of the data and checked all entries for consistency. METHODS Quality assessment In order to obtain a representative sample of adverts We obtained full-text copies of all cited references and applicable to the general population, we searched the assessed them using the Centre for Evidence-Based top 100 general magazines and the top 10 sport and Medicine (CEBM) Levels of Evidence.10 For treatment fitness magazines in the UK and the USA for the month benefits, the highest level of evidence for claim is of March 2012 according to the Magazine Audit Bureau a systematic review of randomised controlled trials or an of Circulations. This selection of magazines is distributed N-of-1 trial (level 1) followed by randomised trials to over 30 million customers in the UK alone. We (level 2) and non-randomised studies (level 3). The excluded magazines specifically aimed at body building. lowest level of evidence is mechanistic reasoning, which One reviewer (RD) examined each page of included includes expert opinion and animal studies (level 5). magazines to identify adverts. All adverts were then We assessed whether a study was appropriate for crit- assessed by second reviewers (AW, CH, MT and RD) as ical appraisal (recording the reasons if it was not either relevant to sports or not. A third round of reviews appropriate). Six reviewers (BON, CH, DSL, JH, MT and (CH and RD) assessed adverts that included specific PJG) then recorded the presence or absence of the performance-enhancing claims. following elements of critical appraisal: a clear hypoth- esis, control group, power calculation, randomisation, Inclusion and exclusion criteria allocation concealment, intention to treat, blinding We included oral sports drinks, oral supplements, foot- (investigator and/or subjects) and sports outcome wear and clothing or devices (such as wristbands). To be (subjective or objective) that demonstrates improved included, adverts had to make a claim related to sports performance or recovery. Extracted data were checked performance (defined as improvement in strength, independently by a second reviewer. One reviewer (CH) speed, endurance, etc) or enhanced recovery related to then assessed included studies using the Cochrane sports (eg, reduced muscle fatigue). We excluded method for risk of bias, assessing studies as high, unclear adverts related to purely weight loss, skin or beauty or at low risk of bias, which was checked by a second products, sports equipment (eg, bicycles) and classified reviewer (JH).11 Discrepancies were resolved by consul- adverts. We therefore only included adverts from the tation with other reviewers.