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Citation: Newbury, J.W.; Sparks, S.A.;
Cole, M.; Kelly, A.L.; Gough, L.A.
Nutritional Supplement Use in a UK
High-Performance Swimming Club.
Nutrients 2023,15, 3306. https://
doi.org/10.3390/nu15153306
Academic Editor: Matthew Barnes
Received: 5 July 2023
Revised: 19 July 2023
Accepted: 24 July 2023
Published: 26 July 2023
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nutrients
Article
Nutritional Supplement Use in a UK High-Performance
Swimming Club
Josh W. Newbury 1, S. Andy Sparks 2, Matthew Cole 1, Adam L. Kelly 1and Lewis A. Gough 1,*
1Research Centre for Life and Sport Science (CLaSS), School of Health Sciences, Birmingham City University,
Birmingham B9 3TN, UK; josh.newbury@mail.bcu.ac.uk (J.W.N.); matthew.cole@bcu.ac.uk (M.C.);
adam.kelly@bcu.ac.uk (A.L.K.)
2Sport Nutrition and Performance Research Group, Department of Sport and Physical Activity,
Edge Hill University, Ormskirk L39 4QP, UK; sparksa@edgehill.ac.uk
*Correspondence: lewis.gough@bcu.ac.uk
Abstract:
The aim of this study was to observe the nutritional supplement practices of highly trained
swimmers on a national talent pathway, since it is often reported that swimmers engage in widespread
supplement use at the elite level. Thus, this study employed a validated supplement intake question-
naire with forty-four swimmers from a high-performance swimming club, which had three distinct
talent stages: development (aged 11–14 years, n= 20), age-group (aged
13–17 years
,
n= 13),
and
national level (aged
≥
16 years, n= 11). Ninety-eight percent of the interviewed swimmers reported
using at least one supplement, with performance (34%) and recovery (19%) cited as the primary
reasons. National swimmers used more total supplements (8.1
±
3.4 supplements) compared to age-
group (4.8
±
2.0 supplements, p= 0.003, g= 1.17) and development (
3.9 ±1.7 supplements
,
p< 0.001
,
g= 1.69) swimmers, mostly because of a greater intake of ergogenic aids (
2.4 ±1.4 supplements
vs.
age-group: 0.5
±
0.5 supplements, p< 0.001, g= 1.12; vs. development: 0.1
±
0.2 supplements,
p< 0.001
,g= 1.81). Parents/guardians were the primary supplement informants of development
swimmers (74%, p< 0.001, V= 0.50), whereas performance nutritionists informed ~50% of sup-
plements used by age-group and national swimmers (p< 0.001, V= 0.51). Based on these results,
supplement education and greater focus on basic sport nutrition practices may be required for
parents/guardians at the development level. Moreover, further research is needed to support the
high number of ergogenic aids used by national swimmers, with the efficacy of these supplements
currently equivocal in the applied setting.
Keywords: supplements; sport nutrition; ergogenic aids; swimming; adolescent athletes
1. Introduction
The International Olympic Committee (IOC) define nutritional supplements as foods,
food components, nutrients, or non-food compounds that are purposely ingested in addi-
tion to the habitual diet to achieve a specific health and/or performance outcome [
1
]. This
broad definition describes a wide variety of commercially available supplements. Therefore,
Garthe and Maughan [
2
] recommend the following subcategories: (a) ‘sports supplements’
that provide convenient sources of energy and macronutrients for when whole food sources
are impractical (e.g., sports drinks, whey protein); (b) ‘medical supplements’ that can be
used to treat and/or avoid clinical issues (e.g., iron, vitamin D
3
); and (c) ‘ergogenic aids’
that have potential to improve exercise performance (e.g., caffeine, creatine monohydrate).
There are also other supplements described as ‘herbal’, ‘botanical’, or ‘functional’ that
are claimed to optimise health; however, the safety and efficacy of such supplements is
questionable for athletes given that their production methods and active ingredients are
often unclear [
3
]. Nonetheless, supplements from each of these categories offer practical
benefits that are attractive to athletes, resulting in widespread use across sports at the
elite [4], junior [5], and recreational levels [6].
Nutrients 2023,15, 3306. https://doi.org/10.3390/nu15153306 https://www.mdpi.com/journal/nutrients
Nutrients 2023,15, 3306 2 of 13
Supplement use generally increases with age and training status, but the total number
and type of supplements that are consumed may also be influenced by a sport’s cultural
norms [
1
]. In Olympic athletes, for example, swimmers are often placed among the highest
supplement users, with 56% of swimmers reporting using supplements at the Atlanta 1996
Games, which increased to 69% of swimmers at Sydney 2000 [
7
,
8
], although, this only
consisted of vitamins, minerals, and amino acids; therefore, limited information on sports
supplements was provided [
1
]. Indeed, later reports showed that 97–99% of Australian
swimmers used nutritional supplements prior to the 1998 and 2009 World Aquatic Champi-
onships [
4
,
9
], albeit with an increase in the total number (mean increase: +3.3 supplements)
and types of supplements (sports: +1.8 supplements, ergogenic: +1.2 supplements) being
consumed across the 11-year window [
10
]. Along with more supplements now being
available to swimmers, there is also an increased dissemination of supplement information
(or misinformation) occurring via the internet, which appears to inform most supplement
practices made by swimmers and their coaches, rather than seeking advice from qualified
nutritionists [
11
,
12
]. Consequently, large supplement intakes may not be restricted to elite
competitors, with national and international swimmers in Spain both reporting an equally
prevalent consumption rate (~87%); including little differences in the total number and
types of supplements being reported [
12
]. Given that adolescents make up a large propor-
tion of competitors at the national level in swimming, this suggests that supplement use is
as similarly widespread in adolescents as it is with adults, though with younger cohorts
receiving less guidance on safe practices [
13
]. However, little information is available with
this cohort, especially within a high-performance UK landscape. As a result, identifying
the current practices of adolescent swimmers may assist with swimmers becoming safe
users of supplements as adults and improve their performance as at this stage.
The supplement use of adolescent swimmers is currently difficult to determine as this
population’s intakes have either been investigated alongside other sports [
11
,
13
] or have
been overlooked in dietary investigations [
14
–
16
]. However, studies that have attempted
to document the supplement beliefs and behaviours of highly trained young athletes
reported that 35–100% regularly consume nutritional supplements, with the most common
reasons being to improve performance (20–65%), enhance recovery (33–40%), and support
health (23–56%) [
5
,
11
,
13
,
17
,
18
]. Such widespread supplement use can be justified at this
age since a ‘food first, but not always food only’ approach to nutrition is optimal for the
health and performance of highly trained athletes, even in adolescents where the intake of
whole foods around training and competitions can be impractical [
19
]. Though, what is
more dubious is the intake of ergogenic aids as the possibility of marginal performance
benefits in this cohort is likely outweighed by the chance of adverse side-effects and/or
inadvertent doping [
20
,
21
]. Nonetheless, 57–72% of adolescents believe performance-
enhancing supplements to be important for sporting success, continuing to use them
despite knowing the inherent risks and being unclear on correct dosing protocols [
5
,
11
,
13
],
which might be because supplement knowledge is often obtained from coaches and family
members, as opposed to qualified nutrition practitioners [
5
,
11
–
13
,
18
,
19
]. These potential
outcomes can provide evidence for monitoring and intervention strategies for supplement
education that sport scientists/nutritionists can employ when working with swimmers. As
a result, this might improve the athletes’ relationship with supplement usage and, therefore,
increase safe practices and remove some potential negative consequences of supplement
usage (e.g., inadvertent doping).
The aim of this study was therefore to observe the current supplement practices at three
distinct talent stages within a UK-based high-performance swimming club: development
phase (aged 11–14 years); national age-group level (aged 13–17 years); and experienced
national competitors (aged ≥16 years).
Nutrients 2023,15, 3306 3 of 13
2. Materials and Methods
2.1. Participants
A total of 44 swimmers across three talent stages voluntarily participated in this study
(Table 1). The first talent stage (development) consisted of 20 swimmers who were all
on a development pathway with the investigated swimming club. All swimmers in this
group were aged 11–14 years and all competed at the regional level, with ten swimmers
also being nationally ranked in the top 10 swimmers in their respective age groups for at
least one event. The second talent stage (age-group) consisted of 13 swimmers who were
all nationally competitive in age-group swimming categories (aged 13–17 years) but were
not yet at the performance level to consistently qualify for national competitions. Seven
of this group were nationally ranked in the top 10 swimmers for their specialist event,
whereas one had recently been selected to represent their nation at the junior level. The final
talent stage (national) consisted of 11 swimmers who all consistently qualified for national
swimming competitions. All members of this group were aged
≥
16 years, including three
national medallists and five swimmers who had represented their respected nations at
junior international competitions. An a priori power calculation with input parameters of
α
= 0.05 and ß = 0.80 determined this sample size appropriate for detecting medium effect
sizes (0.50) in one-way analysis of variance tests (three groups, one measure) with a power
of 80% (G*Power, v.3.1.9.4, Universität Düsseldorf, Germany) [22].
Table 1. Participant competitive status and training characteristics.
Measure National
(n= 11)
Age-Group
(n= 13)
Development
(n= 20)
Males
(n= 21)
Females
(n= 23)
Combined
(n= 44)
Age (years) 20 ±2 15 ±1 13 ±1 16 ±3 15 ±3 15 ±3
Years competitive 9±2 *#5±1 * 3 ±1 5 ±3 5 ±3 5 ±3
Weekly training sessions 6.9 ±1.2 * 6.2 ±0.8 * 5.7 ±0.5 6.0 ±0.7 6.3 ±1.1 6.2 ±0.9
Weekly training hours 17.6 ±3.2 * 15.8 ±2.4 * 12.3 ±1.2 14.4 ±2.3 14.9 ±3.8 14.6 ±3.1
WA points 698 ±59 *#622 ±67 * 483 ±69 555 ±123 598 ±99 578 ±112
World Aquatic (WA) points awarded for swimmers’ fastest long-course (50 m) swimming performance in 2022.
Training hours include both pool and land activities undertaken at the swimming club. * Greater compared to
development (p< 0.05).
#
Greater compared to age-group (p< 0.05). Statistical comparisons are described in
Section 3.1.
2.2. Experimental Procedures
A descriptive and cross-sectional design was used to observe supplement practices.
Each swimmer underwent a short interview (10–15 min) with the lead researcher based on
the questions adapted from a validated supplement intake questionnaire [
20
], which had
recently been used to observe supplement use in both competitive pool [
12
] and open water
disciplines [
23
]. The interview method was used as opposed to an electronic questionnaire
due to its logistical ease in adolescent swimmers, as it enabled the researcher to instantly
clarify questions and/or ask for further information if answers were unclear. In addition,
the researcher also provided a comprehensive list of supplements and was able to explain
each one in further detail to facilitate supplement recall. Some adolescents also did not
have access to their own mobile devices. Therefore, this method enabled swimmers to
answer questions honestly without being influenced by parents/guardians or coaches. The
questions that were asked were as follows: (a) what supplements are consumed; (b) why is
that supplement consumed; (c) where was the information for that supplement sourced;
(d) how frequently is that supplement consumed; and (e) where was the supplement
purchased? Swimmers were asked to detail the supplements they consumed in the last
12 months as per previous research [4,12].
Nutrients 2023,15, 3306 4 of 13
Most swimmers and their parents/guardians received sport nutrition support prior
to this study, which was embedded into the training schedule by the high-performance
swimming club. National swimmers received individual support via nutrition consulta-
tions, body composition analysis, competition planning, and advice regarding ergogenic
supplementation. Both national and age-group swimmers received classroom-based group
education workshops, i.e., [
24
], were given regular nutritional prompts via mobile group
communication (WhatsApp, Menlo Park, CA, USA), and had access to electronic PDF
and presentation resources (Google Drive, Mountain View, CA, USA). The nutritionist
did not directly engage with development swimmers, but parents/guardians of all three
groups received access to online resources and could communicate with the nutritionist
via mobile group communication. The level and frequency of individual support pro-
vided to swimmers and parents/guardians were determined by their engagement with
the provisions.
2.3. Data Groups for Analysis
Supplement intakes were compared by talent stage (national vs. age-group vs. de-
velopment) rather than participant age due to the differing levels of nutrition support
they received. For each individual question, the following categories were applied for
data analysis based on the swimmers’ responses. Supplement type: sports supplements;
ergogenic aids; and health supplements, whereby ‘health’ supplements included vitamins,
minerals, medical, and herbal supplements. Reasons for use: increase performance (includ-
ing ‘increasing energy levels for racing’); enhance recovery; general health; convenient
source of nutrients; muscle growth; immune support (avoiding or reducing length of ill-
nesses); hydration; sleep support; and unsure. Information source: performance nutritionist;
swim coach; other coach (i.e., physiotherapist, personal trainer); teammate; medical doctor;
parent/guardian; friends and siblings; media (i.e., internet, social media role models);
and national governing bodies (i.e., recommended at a development camp, provided by
supplement partners). Supplement frequency: daily; regularly (1–4 days
·
week
−1
); and occa-
sionally (i.e., at competitions only). Supplement source: grocery stores; general stores online
(e.g., Amazon); online sport nutrition outlets; health and wellness stores; pharmacies; and
supplied directly from a performance nutritionist or a parent/guardian.
2.4. Statistical Analysis
All quantitative data (i.e., total supplements, participant characteristics) are presented
as mean
±
standard deviation, whereas the frequency of the qualitative responses (i.e.,
individual supplements, information sources, reasons for use) are reported as percentages.
Prior to statistical analyses, all data were checked for normality and homogeneity of
variance using the Shapiro–Wilk and Levene tests, respectively. Based on the data in this
study violating normality and sphericity, non-parametric tests were utilised. Kruskal–
Wallis tests were used to analyse group level differences between talent stages (national,
age-group, development), whereas Mann–Whitney Utests were used to analyse sex-
based differences. Hedge’s gbias-corrected effect sizes were calculated and reported for
pairwise comparisons, based on there being
≤
20 participants in each talent group [
25
].
These effect sizes were interpreted as ‘small’ (0.20–0.49), ‘moderate’ (0.50–0.79), and ‘large’
(
≥
0.80) [
26
]. Pearson’s Chi-Square (
χ2
) tests were used to determine differences in frequency
distributions between groups. Cramer ’s V effect sizes were calculated for comparisons
between frequency distributions, which were interpreted as ‘weak’ (0.05–0.09), ‘moderate’
(0.10–0.14), ‘strong’ (0.15–0.24), and ‘very strong’ (
≥
0.25) [
27
]. Statistical significance was
set at p< 0.05, and all statistical analyses were performed using the Statistical Package for
Social Sciences (v.28, IBM Statistics, Chicago, IL, USA).
Nutrients 2023,15, 3306 5 of 13
3. Results
3.1. Participants
There were incremental increases in age (p< 0.001) and years competitive (p< 0.001)
between the training phases (Table 1), such that national swimmers were older and more
experienced than age-group swimmers (p< 0.001, g= 3.14; and p< 0.001, g= 1.73, respec-
tively), and age-group swimmers were older and more experienced than development
swimmers (p< 0.001, g= 1.95; and p< 0.001 g=1.73, respectively). Moreover, the swim-
mers’ mean WA points were also increased at each talent stage (p< 0.001), with national
swimmers being higher performers compared to age-group swimmers (p= 0.010, g= 1.14),
and age-group swimmers being higher performers than development swimmers (p< 0.001,
g= 1.99). An increased number of weekly training sessions (p= 0.008) and training hours
(p< 0.001) was also observed, but only between swimmers of development and age-group
levels (p= 0.005, g= 1.44; and p< 0.001, g= 1.94, respectively). There were no sex-based
differences in any participant characteristics (all p> 0.05).
3.2. Supplement Type and Prevalence
Ninety-eight percent (43 of 44) of swimmers reported using at least one nutritional
supplement. These supplement intakes differed between talent stages (p< 0.001, Table 2),
such that national swimmers reported using a greater number of individual supplements
compared to both age-group (p= 0.003, g= 1.17) and development swimmers (p< 0.001,
g= 1.69
). No difference in total supplement intake was observed between development
and age-group swimmers (p= 0.169, g= 0.35).
Group differences in the consumption of ergogenic aids (p< 0.001) and health sup-
plements (p= 0.011) were also identified; however, all three talent stages reported using
a similar number of sports supplements (p= 0.982; Table 2). With regards to ergogenic
aids, a higher proportion of national swimmers declared the consumption of beta-alanine
(p= 0.002,
V= 0.54); caffeine anhydrous
(p< 0.001,
V= 0.68); caffeine drinks and gels
(
p= 0.008,
V= 0.47); creatine monohydrate (p< 0.001, V= 0.62); and sodium bicarbon-
ate (
p= 0.001,
V= 0.55) compared to development swimmers. This resulted in national
swimmers reporting more ergogenic aids compared to age-group swimmers (p< 0.001,
g= 1.81), whereas age-group swimmers also reported consuming more ergogenic aids
compared to development swimmers (p= 0.005, g= 1.12). An increased intake of health
supplements also occurred in national swimmers compared to both age-group (p= 0.032,
g= 0.79) and development levels (p= 0.003, g= 1.27). This occurred due to an increased
proportion of national swimmers declaring the use of magnesium (p= 0.043, V= 0.38),
omega-3 fatty acids (p= 0.003, V= 0.51), vitamin D3(p= 0.016, V= 0.44), and zinc supple-
ments
(p< 0.001,
V= 0.62). No difference in health supplement use was found between
age-group and development swimmers (p= 0.621, g= 0.26). Despite a similar number of
sports supplements being reported between groups, a larger distribution of sports drinks
was identified in development swimmers (p< 0.001, V= 0.59), whereas protein powders
were more frequently reported by national swimmers (p= 0.003, V= 0.51).
Male and female swimmers both reported using a similar total number of supplements
(p= 0.085, g= 0.45), including a similar number of ergogenic (p= 0.484, g= 0.07) and health
supplements (p= 0.103, g= 0.44; Table 2). A greater proportion of males did, however,
report using multivitamin supplements (p= 0.007, V= 0.41). Male swimmers also reported
using more sports supplements compared to females (p= 0.021, g= 0.76), with a greater
proportion of males consuming protein-enhanced foods (p= 0.036, V= 0.32). In contrast, a
greater proportion of females reported ingesting caffeine anhydrous (p= 0.034, V= 0.32),
whereas males used a wider variety of ergogenic supplements.
Nutrients 2023,15, 3306 6 of 13
Table 2.
Total number and prevalence of nutritional supplements reportedly used by three training
tiers within a UK-based, high-performance swimming club.
Category/Individual
Supplements
Overall
(n= 44)
National
(n= 11)
Age-Group
(n= 13)
Development
(n= 20)
Males
(n= 21)
Females
(n= 23)
Total (supplements) 5.2 ±2.9 8.1 ±3.4 ab 4.8 ±2.0 3.9 ±1.7 5.9 ±2.7 4.6 ±2.9
Sports (supplements) 2.5 ±1.0 *#2.7 ±1.7 2.6 ±0.7 2.6 ±0.9 2.9 ±0.8 †2.2 ±1.0
Dextrose/maltodextrin (%) 0 0 0 5 0 4
Electrolytes (%) 18 18 38 5 29 9
Liquid meals (%) 9 18 0 10 0 17 ‡
Protein bars (%) 43 36 54 40 57 30
Protein-enhanced food (%) 45 45 46 45 62 ‡30
Protein powder (%) †45 82 54 20 52 39
Sports bars (%) 2 0 0 5 0 4
Sports drinks (%) †68 27 62 95 67 70
Sports gels (%) 18 9 8 30 19 17
Ergogenic (supplements) 0.8 ±1.4 2.4 ±1.4 ab 0.5 ±0.5 b0.1 ±0.2 0.8 ±1.7 0.9 ±1.2
Beetroot juice (%) 5 9 8 0 10 0
Beta-alanine (%) †14 45 8 0 14 13
Caffeine anhydrous (%) †30 82 23 5 14 43 ‡
Caffeine drinks/gels (%) †9 36 0 0 10 9
Citrulline malate (%) 2 9 0 0 5 0
Creatine monohydrate (%) †16 55 8 0 19 13
Sodium bicarbonate (%) †9 36 0 0 10 9
Health (supplements) 1.8 ±1.6 * 3.0 ±1.3 ab 1.7 ±1.8 1.3 ±1.3 2.2 ±1.4 1.5 ±1.7
Ginger (%) 2 0 8 0 5 0
Iron (%) 20 27 15 20 24 17
Magnesium (%) †5 18 0 0 10 0
Melatonin (%) 2 9 0 0 0 4
Multi-vitamin (%) 41 36 31 50 62 ‡22
Omega-3 fatty acids (%) †20 55 0 15 19 22
Probiotics (%) 20 9 38 15 24 17
Vitamin C (%) 18 27 31 5 24 13
Vitamin D3(%) †39 73 38 20 38 39
Zinc (%) †11 45 0 0 10 13
* Greater intake compared to health supplements (p< 0.05);
#
greater intake compared to ergogenic aids (
p< 0.05
);
a
greater intake compared to age-group swimmers (p< 0.05);
b
greater intake compared to development swimmers
(p< 0.05);
†
= percentage difference between talent stages (p< 0.05);
‡
= percentage difference between sexes
(p< 0.05).
3.3. Reasons for Supplement Use
All three talent stages cited similar reasons for their supplement use (all p> 0.05,
V< 0.15)
, with ‘performance’ (34
±
7%) and ‘recovery’ (19
±
7%) being the largest motiva-
tors (Figure 1A). Other popular reasons for supplement consumption were for ‘convenient
nutrient sources’ (13
±
3%) and for ‘general health’ (12
±
2%). Out of all supplements
used, swimmers stated that they were ‘unsure’ why they consumed 18
±
5% of their total
supplements. The reasons for supplement use differed between sexes, such that female
swimmers consumed more supplements for ‘performance’ (p= 0.003, V= 0.20), whereas
male swimmers consumed more supplements for ‘muscle growth’ (p= 0.007, V= 0.18)
(Figure 1B). No other sex-based differences occurred (all p> 0.05, V< 0.10).
Nutrients 2023,15, 3306 7 of 13
Nutrients 2023, 15, x FOR PEER REVIEW 7 of 13
Figure 1. Reasons for nutritional supplement use reported by swimmers in accordance with (A)
their stage on the national talent pathway; and (B) their sex. * Proportional dierence between
groups (p < 0.05).
3.4. Information Sources
Seventy-ve percent of all reported supplements were informed by a parent/guard-
ian or a performance nutritionist, though this distribution was not equal across groups
(Table 3). Development swimmers were most reliant on parent/guardian information,
whose inuence was less present in national swimmers (p < 0.001, V = 0.50). In contrast,
national and age-group swimmers both reported a performance nutritionist as the most
inuential supplement advisor, compared to no swimmers at the development level (p <
0.001, V = 0.51). Additionally, a greater proportion of national swimmers reported gaining
supplement information from their swimming coach compared to the other training
stages (p = 0.007, V = 0.21), whereas the development group sourced more information
from the media (p = 0.012, V = 0.20). A sex-based dierence was also found, whereby a
greater proportion of female swimmers sourced their supplement information from a per-
formance nutritionist (p < 0.001, V = 0.29), compared to males who sourced more infor-
mation from a parent/guardian (p = 0.010, V = 0.17) and other coaches (p = 0.050, V = 0.13).
Figure 1.
Reasons for nutritional supplement use reported by swimmers in accordance with (
A
) their
stage on the national talent pathway; and (
B
) their sex. * Proportional difference between groups
(p< 0.05).
3.4. Information Sources
Seventy-five percent of all reported supplements were informed by a parent/guardian
or a performance nutritionist, though this distribution was not equal across groups
(Table 3)
.
Development swimmers were most reliant on parent/guardian information, whose in-
fluence was less present in national swimmers (p< 0.001, V= 0.50). In contrast, national
and age-group swimmers both reported a performance nutritionist as the most influen-
tial supplement advisor, compared to no swimmers at the development level (p< 0.001,
V= 0.51
). Additionally, a greater proportion of national swimmers reported gaining sup-
plement information from their swimming coach compared to the other training stages
(p= 0.007,
V= 0.2
1), whereas the development group sourced more information from the
media (p= 0.012, V= 0.20). A sex-based difference was also found, whereby a greater
proportion of female swimmers sourced their supplement information from a performance
nutritionist (p< 0.001, V= 0.29), compared to males who sourced more information from a
parent/guardian (p= 0.010, V= 0.17) and other coaches (p= 0.050, V= 0.13).
Nutrients 2023,15, 3306 8 of 13
Table 3.
Distribution (%) of supplement information sources reported by swimmers within a high-
performance swimming club.
Information Source Overall
(n= 228)
National
(n= 89)
Age-Group
(n= 62)
Development
(n= 77)
Males
(n= 122)
Females
(n= 106)
Performance nutritionist (%) * 33 51 50 0 20 48 #
Swim coach (%) * 6 12 3 1 7 5
Parent/guardian (%) * 42 16 40 74 50 #33
NGB (%) 3 4 2 1 4 1
Medical doctor (%) 3 1 3 4 4 1
Other coach (%) 4 7 0 3 6#1
Teammate (%) 3 3 0 4 2 2
Friends and siblings (%) 2 2 0 4 1 0
Media (%) * 3 1 0 8 3 5
Self-Research (%) 2 2 2 1 1 1
* Proportional difference between talent stages (p< 0.05);
#
proportional difference between sexes (p< 0.05);
n= total number of supplements reported by each group.
3.5. Supplement Frequency
The frequency that swimmers consumed nutritional supplements differed by talent stage
(
p< 0.001).
This change occurred as national swimmers reported consuming
3.8 ±1.8 supplements
on a daily basis, which was more than the swimmers at the age-group (
1.8 ±1.6 supplements
,
p= 0.010,
g= 1.17) and development levels (
0.9 ±0.9 supplements,
p< 0.001, g= 2.20). No
further differences were identified between groups for the number of supplements con-
sumed regularly (national: 2.4
±
1.7; age-group:
1.7 ±1.2
; development: 1.5
±
0.9 supple-
ments; p= 0.255) or occasionally (national: 1.9
±
1.3; age-group: 1.3
±
0.6; development:
1.6 ±0.9 supplements
;p= 0.526). Between sexes, males reported using more supplements
than females on a daily (2.3
±
1.6 vs. 1.4
±
1.9 supplements; p= 0.033,
g= 0.49
) and regular
basis (2.1
±
1.1 vs. 1.4
±
1.3 supplements; p= 0.045, g= 0.52), but no differences occurred
in occasional supplements use (1.4 ±0.9 vs. 1.7 ±1.0 supplements; p= 0.226, g= 0.37).
3.6. Supplement Sources
Within national swimmers, an increased proportion of supplements were purchased
from online sport nutrition outlets (p< 0.001, V= 0.76), whereas development swimmers
purchased most supplements from grocery stores (p< 0.001, V= 0.35) (Figure 2B). National
swimmers were also the only group to source supplements directly from a performance
nutritionist (p= 0.002, V= 0.24), which were all ergogenic aids. No sex differences were
observed for most supplement sources (all p> 0.05, V< 0.10), though three male swimmers
were clinically prescribed iron from a pharmacy, leading to a proportional difference
compared to female swimmers (p= 0.035, V= 0.14).
Nutrients 2023,15, 3306 9 of 13
Nutrients 2023, 15, x FOR PEER REVIEW 9 of 13
Figure 2. The supplement information sources reported by swimmers within a high-performance
swimming club based on (A) their stage on the national talent pathway; and (B) their sex. * Propor-
tional dierence between groups (p < 0.05).
4. Discussion
The key nding from this study was that swimmers of all talent stages engaged in
widespread supplement use, with swimmers at the development phase (aged 11–14 years)
utilising sports supplements at competitions and national swimmers (aged ≥ 16 years)
using an array of health and ergogenic supplements on a more regular basis. Indeed, na-
tional swimmers reported consuming a similar number of ergogenic and health supple-
ments as international-level adult swimmers in previous research [4,12]. Moreover, swim-
mers from all three training stages reported ‘performance’ as a key motivator for supple-
ment use, which was in accordance with other swimming cohorts [12,23]. The prevalent
use of ergogenic aids in this study was likely due to swimmers having increased access to
sport nutrition support as they progressed in training status, as evidenced since par-
ents/guardians were displaced by performance nutritionists as supplement informers in
swimmers of age-group and national levels. It is therefore prudent to suggest that supple-
ment education could be best implemented to parents/guardians at the development stage
to facilitate safe and eective supplement use later in the swimming career.
Development swimmers all reported using nutritional supplements, with approxi-
mately four dierent supplements being used across a swimming season (~1 daily, ~1–2
Figure 2.
The supplement information sources reported by swimmers within a high-performance
swimming club based on (
A
) their stage on the national talent pathway; and (
B
) their sex. * Propor-
tional difference between groups (p< 0.05).
4. Discussion
The key finding from this study was that swimmers of all talent stages engaged in
widespread supplement use, with swimmers at the development phase (aged 11–14 years)
utilising sports supplements at competitions and national swimmers (aged
≥
16 years) us-
ing an array of health and ergogenic supplements on a more regular basis. Indeed, national
swimmers reported consuming a similar number of ergogenic and health supplements
as international-level adult swimmers in previous research [
4
,
12
]. Moreover, swimmers
from all three training stages reported ‘performance’ as a key motivator for supplement
use, which was in accordance with other swimming cohorts [
12
,
23
]. The prevalent use of
ergogenic aids in this study was likely due to swimmers having increased access to sport nu-
trition support as they progressed in training status, as evidenced since parents/guardians
were displaced by performance nutritionists as supplement informers in swimmers of
age-group and national levels. It is therefore prudent to suggest that supplement education
could be best implemented to parents/guardians at the development stage to facilitate safe
and effective supplement use later in the swimming career.
Development swimmers all reported using nutritional supplements, with approximately
four different supplements being used across a swimming season (~1 daily,
~1–2 regularly
,
~1–2 occasionally).
Sports drinks were used most frequently (95%), followed by multivita-
Nutrients 2023,15, 3306 10 of 13
mins (50%) and protein supplements (40–45%), which was comparable to the supplement
use in adult and adolescent swimmers of international competitive status (sports drinks:
92–100%, multivitamins: 32–46%, protein powder: 46–58%) [
4
,
28
]. This early use of sup-
plements was mostly informed by parents/guardians (74%), who were responsible for
purchasing supplements and often supplied them to swimmers without rationale (swim-
mers were unsure why they consumed 18% of all supplements). The primary motivation for
supplement use in this cohort was performance (38%), though it was unclear whether this
rationale was led by parents/guardians or influenced by swimmers while shopping with
parents/guardians at grocery stores. However, the ‘performance supplements’ reported by
this cohort were mostly from the sports supplement category (96%) as opposed to ergogenic
aids (4%), which was appropriate at this training age given that sports supplements carry
lower risks of side-effects and/or inadvertent doping [
2
]. This outcome may therefore
be viewed positively as swimmers and their parents/guardians identified nutrition as an
important factor for swimming performance. Though, this should be interpreted cautiously
as a performance nutritionist provided resources to parents/guardians at the development
level in this study, whereas other swimming parents/guardians might rely on supplement
information from coaches and the internet [
11
,
12
,
18
]. As such, it is difficult to generalise
the outcomes of this study to the wider swimming community at present, requiring further
investigation across multiple swimming clubs with varying levels of nutrition support.
Age-group swimmers consumed a similar number of supplements as development
swimmers (~5 per swimmer), albeit with a change in their supplement choices, reasoning,
and information sources. Indeed, the percentage of swimmers using pill and powder
sports supplements was increased compared to the development group (electrolytes: +33%,
protein powder: +42%), whereas more swimmers also consumed ergogenic aids (46 vs. 5%).
The use of caffeine (23%), creatine monohydrate (8%), beta-alanine (8%), and beetroot juice
(8%) was reported, with each of them having strong evidence of a performance-enhancing
effect [
1
], and they were consumed in equal proportion to highly trained adolescents from
mixed sporting backgrounds (i.e., caffeine: 19%, creatine monohydrate: 25%, beta-alanine:
5%, nitrates: 3%) [
11
]. However, despite declaring more ergogenic aids, less age-group
swimmers used supplements for ‘performance’ compared to development swimmers
(
−
12%), instead citing ‘recovery’, ‘immunity’, and ‘convenience’ as motivating factors. This
change was partly due to the introduction of formal sports nutrition education, with a
performance nutritionist appearing to replace parents/guardians as the primary source
of supplement information (performance nutritionist: +50%, parent/guardian:
−
34% vs.
development swimmers). In turn, this may have enabled age-group swimmers to provide
more appropriate reasons for their supplement use. Based on these findings, a transitional
stage in supplement use was identified, whereby age-group swimmers become more
exposed to sport nutrition and begin trialling ergogenic aids. It is therefore imperative that
a ‘performance-enhancing’ diet is not undermined at this age, which may be supported by
practical workshops that develop food literacy and cooking skills [
29
]. Furthermore, strong
anti-doping messages would also be of benefit, informing swimmers and guardians of the
risks of inadvertently ingesting banned substances when using pill and powder nutritional
supplements [2].
National swimmers used an average of eight different nutritional supplements (~3 health,
~3 ergogenic, ~2 sports), which was in line with previous observations in international- and
national-level swimmers (6–10 individual supplements) [
4
,
12
]. This was, however, higher
than the total number of supplements used by age-group swimmers, most notably since
more swimmers reported using ergogenic aids (creatine monohydrate: +47%, beta-alanine:
+37%) and health supplements (omega-3 fatty acids: +55%, vitamin D
3
: +35%) on a daily
basis. Moreover, national swimmers used more ergogenic aids than age-group swimmers
at competitions (caffeine: +59, sodium bicarbonate: +36%), some of which were directly
sourced from a performance nutritionist. These supplement behaviours follow the step-
like process outlined by Garthe and Maughan [
2
], whereby an increased training status
is accompanied by increased access to professional competence, the use supplements to
Nutrients 2023,15, 3306 11 of 13
enhance training adaptations, and more tailored use of ergogenic aids for competition.
However, performance nutritionists in this study were of greater influence compared to
previous observations in national and international swimmers (51% vs. 20–36%) [
4
,
12
].
Indeed, previous studies in swimmers and other highly trained young athletes typically
cite their coach as the main supplementation informant (38–40%) [
11
,
12
], which was in
contrast to the present study (12%). This could indicate that sport nutrition support was
more prioritised at the investigated swimming club than in others, making it unclear if
these supplement practices can be generalised to the wider UK swimming population.
In addition, the national swimmers in this study utilised a large number and variety
of ergogenic supplements despite the fact that they were yet to have strong evidence
specifically in applied swimming settings, thus supporting the need for further supplement
research within this population.
Males and females both utilised a similar number of nutritional supplements, although
there were sex-based differences in the individual supplements that were used. Female
swimmers were more likely to state ‘performance’ as their primary reason for using sup-
plements (+18% vs. males) and engaged in a greater use of caffeine anhydrous (+29% vs.
males). However, this was likely due to the national group of swimmers consisting of a
larger proportion of females (8 of 11 swimmers), meaning that more females would have
been receiving ergogenic supplement support directly from a performance nutritionist. In
contrast, male swimmers utilised more protein-based supplements (enhanced foods: +32%,
bars: +17%, powder: +13% vs. females) and multivitamin preparations (+40% vs. females),
resulting in male swimmers using more supplements on a daily and regular basis. This was
in combination with more male swimmers reporting the use of supplements for ‘muscle
gain’ (8% vs. no females), which was in accordance with previous investigations in young
athletes [
11
,
30
,
31
]. In all, since there were little differences in the supplement behaviours of
male and female swimmers, these results suggest that sex-based supplement education is
not required.
A limitation of this study was that supplement interviews were based on a previously
validated supplement intake questionnaire that was originally produced and validated
for mass dissemination within the Spanish sports population [
32
]. This therefore limited
the number of questions that were included, meaning that participants did not elucidate
any information regarding dosing strategies or whether supplements were sourced from
batch-tested suppliers, both of which are important considerations for determining whether
supplements are being consumed in a safe and effective manner [
2
]. It is also worth noting
that the data collected in this study are from one high-performance club in the UK, and
therefore, further clubs could have been recruited (i.e., this would also improve the sample
size in the study). Equally, we acknowledge that the sample size priori power calculation
was not met for the national group in this study (n= 11 vs. n= 14). It is important,
therefore, to interpret these findings with caution. However, it is important to note that
sample size determination is not only determined by a prior power calculation, and factors
such as resource constraints, accuracy, and heuristics are also important [
33
]. Moreover,
given the difficulty of recruiting high performance athletes, the lack of athletes in this
population, and the time-constraints on research, this was not possible for this study.
This could have been overcome with the currently used interview method; hence, future
investigations should consider utilising this approach with more in-depth questioning
surrounding the use of each individual supplement. Nonetheless, the current methods
were sufficient to appropriately identify general supplement practices in swimmers of
different training status.
In summary, swimmers were identified as prevalent users of nutritional supplements
from the development age (aged 11–14 years) through to those performing consistently at
the national level. Development swimmers’ supplement practices were largely influenced
by parents/guardians, resulting in many sports supplements being consumed for the
purpose of ‘performance enhancement’. However, increased access to sport nutrition
support was granted at the age-group (aged 13–17 years) and national (aged
≥
16 years)
Nutrients 2023,15, 3306 12 of 13
levels, which subsequently led to the influence of parents/guardians being displaced by
performance nutritionists. It was at these talent stages that a greater uptake of ergogenic
aids was identified, likely requiring targeted nutrition interventions at the age-group and
national levels to ensure safe practices are being followed. Moreover, since many ergogenic
aids were used without much supporting evidence, further research in applied swimming
settings is required to understand which, if any, of these supplements can benefit the
training and/or competitive performances of highly trained adolescent swimmers.
Author Contributions:
Conceptualization, J.W.N. and L.A.G.; methodology, J.W.N.; formal analysis,
J.W.N. and S.A.S.; investigation, J.W.N.; writing—original draft preparation, J.W.N.; writing—review
and editing, S.A.S., M.C., A.L.K. and L.A.G.; visualization, J.W.N. All authors have read and agreed
to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement:
The study was conducted according to the guidelines of
the Declaration of Helsinki and approved by the Ethics Committee of Birmingham City University
(Newbury/7594/R(B)/2020/Aug/HELS FAEC).
Informed Consent Statement:
Informed consent was obtained from all subjects involved in the
study, including from all parents/guardians for all participants aged < 18 years.
Data Availability Statement:
Data sets can be obtained through contacting the corresponding author.
Acknowledgments:
We would like to acknowledge the support of Carl Grosvenor, Chris Littler, and
Joey Stanger from City of Birmingham Swimming Club for facilitating the research process.
Conflicts of Interest: The authors declare no conflict of interest.
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