Practical Issues in Evidence-Based Use of Performance Supplements: Supplement Interactions, Repeated Use and Individual Responses
Sports Med
Practical Issues in Evidence-Based Use of Performance Supplements: Supplement Interactions, Repeated Use and Individual Responses
Louise M. Burke 0 1 2
0 Mary MacKillop Institute for Health Research, Australian Catholic University , Melbourne, VIC , Australia
1 Sports Nutrition, Australian Institute of Sport , PO Box 176, Belconnen, ACT 2616 , Australia
2 Real-life Uses of Performance Supplements
Current sports nutrition guidelines recommend that athletes only take supplements following an evidencebased analysis of their value in supporting training outcomes or competition performance in their specific event. While there is sound evidence to support the use of a few performance supplements under specific scenarios (creatine, beta-alanine, bicarbonate, caffeine, nitrate/beetroot juice and, perhaps, phosphate), there is a lack of information around several issues needed to guide the practical use of these products in competitive sport. First, there is limited knowledge around the strategy of combining the intake of several products in events in which performance benefits are seen with each product in isolation. The range in findings from studies involving combined use of different combinations of two supplements makes it difficult to derive a general conclusion, with both the limitations of individual studies and the type of sporting event to which the supplements are applied influencing the potential for additive, neutral or counteractive outcomes. The repeated use of the same supplement in sports involving two or more events within a 24-h period is of additional interest, but has received even less attention. Finally, the potential for individual athletes to respond differently, in direction and magnitude, to the use of a supplement seems real, but is hard to distinguish from normal day to day variability in performance. Strategies that can be used in research or practice to identify whether individual differences are robust include repeat trials, and the collection of data on physiological or genetic mechanisms underpinning outcomes.
1 Introduction
According to surveys and the experience of most sports
nutrition professionals, there is a high prevalence of use of
sports foods and supplements among competitive athletes
[1]. While there are some concerns associated with such
observations, particularly around the indiscriminate use of
performance supplements [2], many expert groups now
take a pragmatic approach to the use of products and
protocols which have passed a risk:benefit analysis of being
safe, effective, and legal, while also being appropriate to
the athlete?s age and maturation in their sport [2, 3].
Indeed, a number of supplements have received plentiful
and insightful attention from sports scientists to produce
robust evidence of the scenarios in which they can enhance
sports performance. These include caffeine [4, 5], creatine
monohydrate [6, 7], bicarbonate [8, 9], beta-alanine
[10, 11], and beetroot juice/nitrate [12, 13].
While the evidence-base for the use of these products is
generally sound, it typically produces a recommended
protocol that is generic and isolated from other
performance strategies that the athlete may also be implementing.
Indeed, the laboratory situations in which most supplement
studies are conducted often fail to include many of the
important features associated with competitive sport.
Earlier work identified a range of characteristics which should
be included in investigations of strategies to enhance sports
performance to allow them to be more easily applied to
competitive athletes [14, 15]. These included using highly
trained participants to whom the results are intended to
apply, choosing performance protocols which mimic
reallife sport, and incorporating other nutritional strategies or
features according to the way they should be practiced in
the targeted sport or event. Such features have been
integrated into many recent investigations, including a number
of field studies in which the effect of a performance
supplement has been observed during simulated [16, 17] or
actual [18] sporting events.
Despite these advances, there are several real-life issues
related to the use of performance supplements that remain
relatively ignored. Poor interrogation of such issues makes
it difficult for athletes to undertake a thorough risk:benefit
analysis of their potential use of a supplement or to
implement a scenario-specific protocol for their product
use that is truly evidence-based. These issues included the
additive and interactive effects of combining the use of
several performance supplements for a single event,
considerations regarding the repeated use of a performance
supplement within a relatively brief period, and the notion
of individual responsiveness to supplement use. The aim of
this review is to examine our current state of knowledge
around these issues. It will focus on the performance
supplements which were previously identified as enjoying
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