Limited agreement exists between rationale and practice in athletes' supplement use for maintenance of health: a retrospective study

Andrea Petróczi, Declan P Naughton, Jason Mazanov, Allison Holloway, Jerry Bingham

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. 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). 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). 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.