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Abstract Background Athletes are expected to consider multiple factors when making informed decision about nutritional supplement use. Besides rules, regulations and potential health hazards, the efficacy of different nutritional supplements in performance enhancement is a key issue. The aim of this paper was to find evidence for informed decision making by investigating the relationship between specific performance-related reasons for supplement use and the reported use of nutritional supplements. Methods The 'UK Sport 2005 Drug Free Survey' data (n = 874) were re-analysed using association [χ2] and 'strength of association' tests [ϕ] to show the proportion of informed choices and to unveil incongruencies between self-reported supplement use and the underlying motives. Results Participants (n = 520) reported supplement use in the pattern of: vitamin C (70.4%), creatine (36.1%), whey protein (30.6%), iron (29.8%), caffeine (23.8%), and ginseng (8.3%) for the following reasons: strength maintenance (38.1%), doctors' advice (24.2%), enhancing endurance (20.0%), ability to train longer (13.3%), and provided by the governing body (3.8%). Of thirty possible associations between the above supplements and reasons, 11 were predictable from literature precedents and only 8 were evidenced and these were not strong (ϕ < .7). The best associations were for the ability to train longer with creatine (reported by 73.9%, χ2 = 49.14, p < .001; ϕ = .307, p < .001), and maintaining strength with creatine (reported by 62.6%, χ2 = 97.08, p < .001; ϕ = .432, p < .001) and whey protein (reported by 56.1%, χ2 = 97.82, p < .001; ϕ = .434, p < .001). Conclusion This study provided a platform for assessing congruence between athletes' reasons for supplement use and their actual use. These results suggest that a lack of understanding exists in supplement use. There is an urgent need to provide accurate information which will help athletes make informed choices about the use of supplements.

Abstract 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 [χ2] and 'strength of association' tests [φ], 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 (φ > .7), intermediate (7 < φ > .3) and weak (φ < .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 (χ2 = 11.94, p < .001; φ = .15, p = .001), multivitamin (χ2 = 6.43, p < .001; φ = .11, p = .011), vitamin C (χ2 = 54.67, p < .001; φ = .32, p < .001) and echinacea (χ2 = 40.34, p < .001; φ = .28, p < .001)]. The remaining 4 associations were: no time to prepare meals with ginseng (χ2 = 7.64, p = .006; φ = .12, p = .006) and multivitamin (χ2 = 9.103, p = .003; φ = .13, p = .003); overcoming injuries with magnesium (χ2 = 6.99, p = .008; φ = .11, p = .008); doctors' advice and iron (χ2 = 35.00, p < .001; φ = .25, p = .001). Conclusion 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.