Limited agreement exists between rationale and practice in athletes' supplement use for maintenance of health: a retrospective study.
BACKGROUND
The widespread use of nutritional supplements among athletes is poorly understood. The prevalence of supplement intake and users' knowledge have been researched independently leading to useful, but disconnected, information on supplement use.


METHODS
The 'UK Sport 2005 Drug Free Survey' data (n = 874) were re-analysed using association [chi2] and 'strength of association' tests [phi], to discover observed incongruencies between self-reported supplement use and the underlying motives. Results are given for test pairs between 'motive for use' [doctor's advice, avoiding sickness, overcoming injuries and enhancement of diet] and each supplement used and these were categorized as strong (phi > .7), intermediate (7 < phi > .3) and weak (phi < .3).


RESULTS
The use of selected supplements varied widely as follows: multivitamin (72.7%), vitamin C (70.4%), echinacea (30.8%), iron (29.8%), magnesium (11.0%) and ginseng (8.3%). Associations with motive were found in 8 of the 10 test pairs which were expected from literature precedents, however only weak associations exist. Of these, four were associated with avoidance of sickness [iron (chi2 = 11.94, p < .001; phi = .15, p = .001), multivitamin (chi2 = 6.43, p < .001; phi = .11, p = .011), vitamin C (chi2 = 54.67, p < .001; phi = .32, p < .001) and echinacea (chi2 = 40.34, p < .001; phi = .28, p < .001)]. The remaining 4 associations were: no time to prepare meals with ginseng (chi2 = 7.64, p = .006; phi = .12, p = .006) and multivitamin (chi2 = 9.103, p = .003; phi = .13, p = .003); overcoming injuries with magnesium (chi2 = 6.99, p = .008; phi = .11, p = .008); doctors' advice and iron (chi2 = 35.00, p < .001; phi = .25, p = .001).


CONCLUSIONS
These results suggest a lack of understanding regarding supplements and health maintenance, except for vitamin C and echinacea. Furthermore, supplement use is apparently independent of physicians/dieticians' advice, except for iron. This may suggest a widespread circumvention of expert advice in the growing area of supplement use and therefore should be addressed to underscore potential health risks.
Petróczi
Andrea
A
School of Life Sciences, Faculty of Science, Kingston University, Penrhyn Road, Kingston upon Thames, Surrey KT1 2EE, UK. a.petroczi@kingston.ac.uk
Naughton
Declan P
DP
Mazanov
Jason
J
Holloway
Allison
A
Bingham
Jerry
J
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D054874:Athletic Performance; D003625:Data Collection; D019587:Dietary Supplements / Q000009:adverse effects / Q000706:statistics & numerical data*; D019317:Evidence-Based Medicine; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D008297:Male; D008903:Minerals / Q000008:administration & dosage*; D009747:Nutritional Physiological Phenomena; D009751:Nutritional Requirements; D012189:Retrospective Studies; D017678:Sex Distribution; D006113:United Kingdom; D014815:Vitamins / Q000008:administration & dosage*
D008903:Minerals; D014815:Vitamins