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nutrients
Article
Acute Caffeine and Coconut Oil Intake, Isolated or
Combined, Does Not Improve Running Times of
Recreational Runners: A Randomized,
Placebo-Controlled and Crossover Study
Gabrielle de Lima Borba 1, Julianne Soares de Freitas Batista 1, Ludmilla Marques Queiroz Novais 1,
Myrnzzia Beatriz Silva 1, João Batista da Silva Júnior 1, Paulo Gentil 2, Ana Clara Baretto Marini 1,
Bruna Melo Giglio 1and Gustavo Duarte Pimentel 1, *
1Laboratory of Research in Clinical Nutrition and Sports (Labince), Faculty of Nutrition, Federal University
of Goiás, Rua 227, Quadra 68 s/n◦, Setor Leste Universitário, Goiânia 74605080, GO, Brazil
2College of Physical Education and Dance, Federal University of Goiás, Goiânia 74605080, GO, Brazil
*Correspondence: gupimentel@yahoo.com.br; Tel.: +55-062-3209-6270
Received: 3 June 2019; Accepted: 17 July 2019; Published: 20 July 2019
Abstract:
The aim was to evaluate the effect of caffeine (CAF) and extra virgin coconut oil (CO), isolated
or combined, on running performance in runners. Methods: A randomized, placebo-controlled,
and crossover study was conducted with thirteen recreational runners aged 18–40. All volunteers
performed a 1600 m time trial at a 400 m track, each ingesting four different substances: (1) placebo
(water), (2) decaffeinated coffee plus isolated CAF (DECAF +CAF), (3) decaffeinated coffee plus
isolated CAF plus soy oil (DECAF +CAF +SO), and (4) decaffeinated coffee plus isolated CAF plus
extra virgin coconut oil (DECAF +CAF +CO). The substances were ingested 60 min before the
trials, the order of the situations was randomized, and there were one-week intervals between them.
At the end of the trials, the Borg scale was applied to evaluate the rating of perceived exertion (RPE)
and the time was measured. Results: Our data did not show differences in running time among the
trials (placebo: 7.64
±
0.80, DECAF +CAF: 7.61
±
1.02, DECAF +CAF +SO: 7.66
±
0.89, and DECAF
+CAF +CO: 7.58
±
0.74 min; p=0.93), nor RPE (placebo: 6.15
±
2.03, DECAF +CAF: 6.00
±
2.27,
DECAF +CAF +SO: 6.54
±
2.73, and DECAF +CAF +CO: 6.00
±
2.45 score; p=0.99). Lactate
concentrations (placebo: 6.23
±
2.72, DECAF +CAF: 4.43
±
3.77, DECAF +CAF +SO: 5.29
±
3.77,
and DECAF +CAF +CO: 6.17
±
4.18 mmol/L; p=0.55) also was not modified.
Conclusion
: Our
study shows that ingestion of decaffeinated coffee with the addition of isolated CAF and extra virgin
CO, either isolated or combined, does not improve 1600 m running times, nor influence RPE and
lactate concentrations in recreational runners. Thus, combination of coffee with CO as a pre-workout
supplement seems to be unsubstantiated for a short-distance race.
Keywords: coffee; caffeine; coconut oil; nutrients; running; performance
1. Introduction
Dietary supplements are widely used with the purpose of improving physical performance and
preventing fatigue [
1
]. Among the supplements, caffeine (CAF, 1,3,7-trimethylxanthine) is one of the
most consumed ergogenics in the world, and can be found in many foods and beverages, such as
chocolate, teas, guarana, and coffee [
2
]. CAF has been studied because of its apparent positive effects
in endurance sports [
3
–
5
]. During exercise, CAF can reduce the use of the glycogen and increase the
release of free fatty acids [
6
,
7
], which might delay fatigue and increase endurance. The ergogenic
potential of CAF might also be observed in the cellular matrix, where it acts as a competitive antagonist
Nutrients 2019,11, 1661; doi:10.3390/nu11071661 www.mdpi.com/journal/nutrients
Nutrients 2019,11, 1661 2 of 9
against adenosine receptors, releasing calcium to skeletal muscle, which is able to maximize the
strength for muscular contractions [8,9].
Coconut oil (CO), in turn, is a saturated fat composed of about 50% medium chain fatty acids
or medium chain triglycerides (MCT), namely lauric acid (C 12:0) and caprylic acid (C 8:0) [
10
].
However, less than 30% of lauric acid is released to the liver to be used as an energy source [
11
].
Fatty acids provide rapid energy availability and contain approximately 8–9 kcal per gram; however,
because its structure contains many carbon atoms attached to oxygen, there is greater difficulty in
oxidization [
12
]. Although no evidence demonstrated that pre-workout supplementation of long
chain and medium chain fatty acids, as well as conjugated linoleic acid, has any effect on endurance
performance [
13
,
14
], a recent study showed that four weeks (30 mL/d) of virgin CO associated with
a single bout of moderate-intensity cycling in young adults was able to increase popliteal artery
endothelial-dependent dilation, but did not change the post exercise-mediated hyperemia, nor plasma
total antioxidant capacity [
15
]. Additionally, an isoenergetic ketogenic diet containing CO did not
affect the run-to-exhaustion at 70% VO2max in men [
16
]. Although CAF is reported to positively
effect physical performance [
3
,
8
], it is not fully understood whether or not CAF combined with extra
virgin CO improves running time in humans. Likewise, it is unknown if this combination leads to an
ergogenic effect.
Therefore, knowing the potential ergogenic effect of CAF, and that the pre-workout mix of CAF
with extra virgin CO has been used in clinical practice without scientific evidence, we hypothesized
that ingestion of decaffeinated coffee (DECAF) with CAF, but not with CO could improve running
time. Thus, this study aimed to evaluate the effect of CAF and extra virgin CO, isolated or combined,
on the running time in recreational runners.
2. Methods
2.1. Subjects and Recruitment
Thirty healthy recreational runners aged 18 to 40 initially volunteered to participate in the
study. The volunteers were invited through social medial and by word of mouth. The exclusion
criteria involved those who ran less than two times per week; having renal, cardiovascular, or hepatic
diseases; being pregnant; having dietary restrictions; or currently using dietary supplements or
anti-inflammatory medications. After removing a number of candidates based on the exclusion
criteria, thirteen (8M/5F) volunteers were selected (Figure 1). All the runners signed a written consent
that was approved by the Research Ethics Committee of the Federal University of Goias under the
number 010883/2018.
After signing a written consent, the volunteers replied the initial anamneses one week before the
familiarization test. This anamnesis consisted of body composition assessment, frequency of CAF
consumption and habitual food intake evaluation.
Nutrients 2018, 10, x FOR PEER REVIEW 2 of 9
antagonist against adenosine receptors, releasing calcium to skeletal muscle, which is able to
maximize the strength for muscular contractions [8,9].
Coconut oil (CO), in turn, is a saturated fat composed of about 50% medium chain fatty acids or
medium chain triglycerides (MCT), namely lauric acid (C 12:0) and caprylic acid (C 8:0) [10].
However, less than 30% of lauric acid is released to the liver to be used as an energy source [11]. Fatty
acids provide rapid energy availability and contain approximately 8–9 kcal per gram; however,
because its structure contains many carbon atoms attached to oxygen, there is greater difficulty in
oxidization [12]. Although no evidence demonstrated that pre-workout supplementation of long
chain and medium chain fatty acids, as well as conjugated linoleic acid, has any effect on endurance
performance [13,14], a recent study showed that four weeks (30 mL/d) of virgin CO associated with
a single bout of moderate-intensity cycling in young adults was able to increase popliteal artery
endothelial-dependent dilation, but did not change the post exercise-mediated hyperemia, nor
plasma total antioxidant capacity [15]. Additionally, an isoenergetic ketogenic diet containing CO did
not affect the run-to-exhaustion at 70% VO2max in men [16]. Although CAF is reported to positively
effect physical performance [3,8], it is not fully understood whether or not CAF combined with extra
virgin CO improves running time in humans. Likewise, it is unknown if this combination leads to an
ergogenic effect.
Therefore, knowing the potential ergogenic effect of CAF, and that the pre-workout mix of CAF
with extra virgin CO has been used in clinical practice without scientific evidence, we hypothesized
that ingestion of decaffeinated coffee (DECAF) with CAF, but not with CO could improve running
time. Thus, this study aimed to evaluate the effect of CAF and extra virgin CO, isolated or combined,
on the running time in recreational runners.
2. Methods
2.1. Subjects and Recruitment
Thirty healthy recreational runners aged 18 to 40 initially volunteered to participate in the study.
The volunteers were invited through social medial and by word of mouth. The exclusion criteria
involved those who ran less than two times per week; having renal, cardiovascular, or hepatic
diseases; being pregnant; having dietary restrictions; or currently using dietary supplements or anti-
inflammatory medications. After removing a number of candidates based on the exclusion criteria,
thirteen (8M/5F) volunteers were selected (Figure 1). All the runners signed a written consent that
was approved by the Research Ethics Committee of the Federal University of Goias under the number
010883/2018.
Figure 1. Flow diagram of study.
After signing a written consent, the volunteers replied the initial anamneses one week before the
familiarization test. This anamnesis consisted of body composition assessment, frequency of CAF
consumption and habitual food intake evaluation.
Figure 1. Flow diagram of study.
Nutrients 2019,11, 1661 3 of 9
2.2. Study Design
A randomized, placebo-controlled, and crossover design was conducted at the same time each
day (~7 to 9 a.m.), to avoid possible circadian interferences. The study was conducted over a five-week
period. In the first week, the volunteers did a five-minute warm-up and, after resting for 3–5 min,
performed practice laps of 1600 m on the 400 m circuit where the time trial test would later take
place to familiarize themselves with the track. On the day of the practice laps, the volunteers
were instructed to run in the shortest possible time and the runner’s order was randomized using
https://www.randomizer.org. During the second to fifth weeks, the trials were performed with the
ingestion of different pre-test substances.
The volunteers were instructed not to do vigorous physical activities for a period of 24 h, and not
to consume foods and beverages containing CAF in their composition (such as coffee, chocolate, mat
é
,
guaran
á
powder and soft drinks) and alcohol in the 48 h preceding the trials. In addition, they were
strongly encouraged to maintain the same dietary and physical activity habits in order to avoid possible
discrepancies in energy balance.
The tests were conducted in a randomized, crossover and placebo-controlled manner on the
weekend (Saturday or Sunday).
The experimental tests consisted of four groups: (1) placebo: who receive 100 mL of warm water;
(2) DECAF +CAF: decaffeinated coffee with 100 mL of warm water plus 6 mg/kg of CAF isolated;
(3) DECAF +CAF +SO: decaffeinated coffee with 100 mL of warm water plus 6 mg/kg of CAF plus
15 g soy oil; and (4) DECAF +CAF +CO: decaffeinated coffee with 100 mL of warm water plus 6 mg/kg
of CAF plus 15 g of extra virgin CO. All trials were separated by a one-week interval.
2.3. Supplementation
Administration of CAF anhydrous (6 mg/kg) was provided by the manipulation pharmacy and
the amount was adjusted according to the weight of each runner [
17
,
18
]. The corresponding amount of
CAF was weighed on an analytical balance (Shimadzu Automatic Digital Analytical Balance, ATX124;
Kyoto, Japan) and kept in aluminium foil packets that were organized and identified by a qualified
individual that was not participating in the research.
The extra virgin CO (Copra Alimentos, Macei
ó
, Alagoas, Brazil, lot 792711818) and the refined
SO (Leve, Imcopa
®
, Arauc
á
ria, Paran
á
, lot c1017) were odorless and flavorless to minimize any bias,
or identification, on the part of the participants in the study. SO was used because it presents improved
palatability, similar to that of CO [
10
]. The amount of both oils of 15 g is equivalent to 16.5 mL. At the
time of the supplement manipulation, 20 mL syringes were used to better determine the amount of
either CO or SO.
Supplements were administered in unmarked containers and handled by a qualified individual
who was not involved in the research, so researchers and runners would not know which supplements
would be given. The DECAF coffee (DECAF coffee with water) was prepared 30 min prior to being
ingested and standardized to be served using the same amount of coffee grinds (36 g coffee grinds in
1
2
L
of mineral water) kept at ~45–40
◦
C and stored in bottles until the moment of the tests. The hot water
trial was used for the placebo group, as in previous studies [
19
,
20
]. All substances, either containing
DECAF coffee and oil (experimental groups) or only warm water (placebo groups), were ingested
60 min before participants started their time trial. Additionally, volunteers were questioned about
which supplement they believed to have received.
2.4. Evaluation of Food Sources of Caffeine and Dietary Intake
The frequency of consumption of food sources of CAF was obtained using a previously-published
adapted questionnaire [21].
Dietary intake was obtained using the 24 h food recall applied throughout the trials. From the
total of six food recalls recorded, two were performed during participant recruitment (anamnesis
Nutrients 2019,11, 1661 4 of 9
application), one in the first time trial test, one in last week of the time trial tests, and two others on
weekdays (in contrast to the normal time trial tests, which were held on the weekend).
The 24 h food recall was applied by a trained nutritionist. We obtained data about serving sizes,
frequency and daily total calorie, carbohydrate, protein, lipids and water intake. For food intake
analysis, DietPro
®
software (version 5.8, Viçosa, Minas Gerais, Brazil) was used. The volunteers were
encouraged to maintain their habitual food consumption during the whole experimental period.
2.5. Running Trials
On the day of the trials, the participants woke up after eight hours of rest and were instructed to
ingest their habitual breakfast without caffeine-sourced foods. After one hour, the volunteers went to
the race track.
After supplementation, volunteers were instructed to remain in a resting state for 50–55 min.
Approximately 5 min prior to the tests, a warm-up consisting of stretches and light walking was
done. Then, 60 min after supplementation, the 1600 m time trial test on the 400 m outdoor race track
commenced. The volunteers were instructed to run in the shortest possible time and this was recorded
(in minutes) using a stopwatch.
There were no differences (p>0.05) in the climatic features during the four days of data collection
(temperature on first day: 20.5, second: 19.71, third: 20.8, and fourth: 19.8
◦
C, and relative humidity on
first day: 54.0, second: 56.3, third: 54.0, and fourth: 61.1), as well as no difference in humidity.
2.6. Anthropometry, Blood Lactate, and Rating of Perceived Effort (RPE) Assessment
The anthropometric evaluation consisted of body weight, height, body mass index, and waist
circumference. Moreover, skinfolds of the thighs, pectorals, supra iliac, and triceps were measured for
calculation of body fat percentage [22,23].
Blood was collected from the finger at baseline and immediately after the tests. Lactate concentrations
were determined using a portable lactate analyzer (Accutrend Plus, Roche
®
, Mannheim, Germany).
The rating of perceived effort (RPE) was taken immediately after the trials using the Borg scale [24].
2.7. Statistical Analyses
The sample size was determined using the G*Power
®
software version 3.1.9.2. The priori analysis
of variance (ANOVA) test was used for repeated measurements, with 5% alpha error, 95% beta, and
effect power of 0.75, resulting in a minimum sample of 13 volunteers. Shapiro–Wilk test was performed
to check the normality of the variables and values were expressed as means
±
standard deviation.
Paired t-test was used to compare the food intake. ANOVA two-way was used to compare the effects
of time x intervention of blood lactate concentrations. ANOVA one-way was performed to compare the
delta of time trial performance and RPE score. Effect sizes were calculated using Cohen’d following
the scale for interpretation <0.50 (small);
≥
0.50 to <0.80 (medium);
≥
0.80 (large). SPSS version 21.0 and
Prism version 5.0 were used to perform the statistical analyses and graphs, respectively. The level of
significance was set at 5% (p<0.05).
3. Results
The volunteers’ characteristics are described in Table 1. They were young, eutrophic, and with
normal waist circumference and body fat percentage. There was no difference between the two
first trials compared with the two last trials for calories, macronutrients, amino acids, and water
consumption (p>0.05) (Table 2).
CAF was sourced mainly from the following: caffeinated coffee (85%), black tea (54%), soft drinks
(54%), and chocolate (46%), and no volunteers reported ingesting guaran
á
powder, nor CAF alone.
The weekly consumption of food/beverage sources containing CAF included the following: CAF coffee
(4.18 times) >black tea (2.66 times) >chocolate (2.60 times) >soft drink (2.14 times). Therefore, all of
the participants are moderate CAF consumers.
Nutrients 2019,11, 1661 5 of 9
Table 1. Characteristics of volunteers.
Variables Mean ±SD
Age (years) 28.46 ±5.63
Body mass index (kg/m2)23.58 ±3.90
Waist circumference (cm) 75.88 ±11.24
Body fat (%) 16.19 ±6.00
Table 2. Food intake among the volunteers.
Nutrients Initial Final p
Calories (kcal) 2439.28 ±948.33 2298.50 ±672.15 0.666
Calories (kcal/kg) 35.48 ±9.78 35.04 ±10.90 0.915
Carbohydrate (%) 47.64 ±7.77 51.59 ±17.06 0.455
Carbohydrate (g) 282.29 ±107.88 288.68 ±100.64 0.877
Protein (%) 20.19 ±3.69 20.67 ±5.93 0.807
Protein (g) 120.64 ±51.67 117.47 ±50.43 0.876
Isoleucine (g) 3.02 ±1.93 3.16 ±2.04 0.862
Leucine (g) 5.41 ±3.37 5.77 ±3.74 0.797
Valine (g) 3.51 ±2.28 3.57 ±2.21 0.954
Lipids (%) 32.72 ±5.81 33.06 ±9.27 0.913
Lipids (g) 92.23 ±48.02 82.15 ±26.42 0.858
Water intake (L) 2.10 ±1.01 2.06 ±0.82 0.856
Values are expressed in means ±standard deviation.
Blood lactate concentrations at pre- and post-test were not different between trials (placebo:
0.91
±
0.36 to 7.14
±
2.84, DECAF +CAF: 1.00
±
0.50 to 5.43
±
3.88, DECAF +CAF +SO: 0.95
±
0.27 to
6.24
±
3.86, and DECAF +CAF +CO: 1.12
±
0.51 to 7.28
±
4.00; ptime <0.001, ptime
×
intervention
p>0.05
), nor when evaluated using the delta values (placebo: 6.23
±
2.72, DECAF +CAF: 4.43
±
3.77,
DECAF +CAF +SO: 5.29
±
3.77, and DECAF +CAF +CO: 6.17
±
4.18 nmol/L; p=0.55, with small
effect size between the groups) (Figure 2).
Nutrients 2018, 10, x FOR PEER REVIEW 5 of 9
CAF was sourced mainly from the following: caffeinated coffee (85%), black tea (54%), soft
drinks (54%), and chocolate (46%), and no volunteers reported ingesting guaraná powder, nor CAF
alone. The weekly consumption of food/beverage sources containing CAF included the following:
CAF coffee (4.18 times) > black tea (2.66 times) > chocolate (2.60 times) > soft drink (2.14 times).
Therefore, all of the participants are moderate CAF consumers.
Table 2. Food intake among the volunteers.
Nutrients Initial Final p
Calories (kcal) 2439.28 ± 948.33 2298.50 ± 672.15 0.666
Calories (kcal/kg) 35.48 ± 9.78 35.04 ± 10.90 0.915
Carbohydrate (%) 47.64 ± 7.77 51.59 ± 17.06 0.455
Carbohydrate (g) 282.29 ± 107.88 288.68 ± 100.64 0.877
Protein (%) 20.19 ± 3.69 20.67 ± 5.93 0.807
Protein (g) 120.64 ± 51.67 117.47 ± 50.43 0.876
Isoleucine (g) 3.02 ± 1.93 3.16 ± 2.04 0.862
Leucine (g) 5.41 ± 3.37 5.77 ± 3.74 0.797
Valine (g) 3.51 ± 2.28 3.57 ± 2.21 0.954
Lipids (%) 32.72 ± 5.81 33.06 ± 9.27 0.913
Lipids (g) 92.23 ± 48.02 82.15 ± 26.42 0.858
Water intake (L) 2.10 ± 1.01 2.06 ± 0.82 0.856
Values are expressed in means ± standard deviation.
Blood lactate concentrations at pre- and post-test were not different between trials (placebo: 0.91
± 0.36 to 7.14 ± 2.84, DECAF + CAF: 1.00 ± 0.50 to 5.43 ± 3.88, DECAF + CAF + SO: 0.95 ± 0.27 to 6.24 ±
3.86, and DECAF + CAF + CO: 1.12 ± 0.51 to 7.28 ± 4.00; p time < 0.001, p time × intervention p > 0.05),
nor when evaluated using the delta values (placebo: 6.23 ± 2.72, DECAF + CAF: 4.43 ± 3.77, DECAF +
CAF + SO: 5.29 ± 3.77, and DECAF + CAF + CO: 6.17 ± 4.18 nmol/L; p = 0.55, with small effect size
between the groups) (Figure 2).
Figure 2. Delta of lactate concentrations. ES: effect size (small).
RPE did not show any difference between the trials at the end of the trial (placebo: 6.15 ± 2.03,
DECAF + CAF: 6.00 ± 2.27, DECAF + CAF + SO: 6.54 ± 2.73, and DECAF + CAF + CO: 6.00 ± 2.45 score;
p = 0.99) (Figure 3A). No difference in running time was found (placebo: 7.64 ± 0.80, DECAF + CAF:
7.61 ± 1.02, DECAF + CAF + SO: 7.66 ± 0.89, and DECAF + CAF + CO: 7.58 ± 0.74 min; p = 0.93, with
small effect size between the groups) (Figure 3B).
Figure 2. Delta of lactate concentrations. ES: effect size (small).
Nutrients 2019,11, 1661 6 of 9
RPE did not show any difference between the trials at the end of the trial (placebo: 6.15
±
2.03,
DECAF +CAF: 6.00
±
2.27, DECAF +CAF +SO: 6.54
±
2.73, and DECAF +CAF +CO: 6.00
±
2.45 score;
p=0.99) (Figure 3A). No difference in running time was found (placebo: 7.64
±
0.80,
DECAF +CAF:
7.61
±
1.02, DECAF +CAF +SO: 7.66
±
0.89, and DECAF +CAF +CO: 7.58
±
0.74 min; p=0.93, with
small effect size between the groups) (Figure 3B).
Nutrients 2018, 10, x FOR PEER REVIEW 6 of 9
Figure 3. Rating of perceived exertion (RPE) (A) and time trial (B) performance at the end of running.
ES: effect size (small).
All volunteers correctly indicated the ingestion of placebo-water (n = 13), 92.3% DECAF + CAF
(n = 12), 53.8% DECAF + CAF + SO (n = 7), and 46.1% DECAF + CAF + CO (n = 6) (p = 0.0004). Overall,
correct identifications were made 73% of the time.
4. Discussion
To our knowledge, this is the first study to examine the ergogenic effects of pre-workout coffee
ingestion combined with CO on running time in recreational runners. On the basis of our findings, a
mixture of DECAF coffee with isolated CAF or extra virgin CO, either isolated or combined, does not
improve 1600 m running times, nor change blood lactate concentrations and RPE.
Among the ergogenic properties of CAF is the increase in time trial performance, through
mechanisms of central and peripheral action [25]. However, similar to the present study, two
previous studies showed that DECAF coffee plus isolated CAF did not improve endurance
performance [26,27], suggesting that other components of coffee can affect the ergogenic effect of
CAF alone [27].
Contrary to our findings, previous studies showed that both CAF coffee (containing 5 mg/kg) or
isolated CAF (5 mg/kg) is able to enhance endurance performance in cycling [28], and that CAF coffee
improves 5 km time trial performance on the treadmill compared with DECAF coffee [29]. However,
one of our previous studies found no difference in time trial performance in 800 m trials when
comparing the effects of CAF coffee versus DECAF coffee [5]. Thus, one hypothesis for
inconsistencies between studies may be related to how the CAF is administered, either isolated/alone
or in a CAF coffee form.
In the present study, we did not find any difference in 1600 m performance between the
consumption of placebo (water) compared with DECAF coffee plus isolated CAF. Similarly, a
previous study also did not find any difference on endurance performance when comparing DECAF
coffee versus the other three groups (either DECAF coffee plus isolated CAF or placebo) [27].
Although our data did not evaluate the blood CAF levels, Graham et al. [27] suggest that absence of
an ergogenic effect may be independent of blood caffeine, paraxanthine, and theophylline
concentrations, reinforcing the idea that the administration procedure (vehicle) appears to modify
the ergogenic response of CAF. Likewise, other studies that combine DECAF coffee and isolated CAF
or CAF coffee or isolated CAF alone require further investigation.
Church et al. 2015 [29] investigated the effects of CAF coffee or DECAF coffee ingested prior to
a 5 km run on a treadmill, and no changes in blood lactate between trials were found. The findings
of Church et al. 2015 [29] are in agreement with the present study, as we did not observe any
Figure 3.
Rating of perceived exertion (RPE) (
A
) and time trial (
B
) performance at the end of running.
ES: effect size (small).
All volunteers correctly indicated the ingestion of placebo-water (n=13), 92.3% DECAF +CAF
(
n=12)
, 53.8% DECAF +CAF +SO (n=7), and 46.1% DECAF +CAF +CO (n=6) (p=0.0004).
Overall, correct identifications were made 73% of the time.
4. Discussion
To our knowledge, this is the first study to examine the ergogenic effects of pre-workout coffee
ingestion combined with CO on running time in recreational runners. On the basis of our findings,
a mixture of DECAF coffee with isolated CAF or extra virgin CO, either isolated or combined, does not
improve 1600 m running times, nor change blood lactate concentrations and RPE.
Among the ergogenic properties of CAF is the increase in time trial performance, through
mechanisms of central and peripheral action [
25
]. However, similar to the present study, two previous
studies showed that DECAF coffee plus isolated CAF did not improve endurance performance [
26
,
27
],
suggesting that other components of coffee can affect the ergogenic effect of CAF alone [27].
Contrary to our findings, previous studies showed that both CAF coffee (containing 5 mg/kg)
or isolated CAF (5 mg/kg) is able to enhance endurance performance in cycling [
28
], and that CAF
coffee improves 5 km time trial performance on the treadmill compared with DECAF coffee [
29
].
However, one of our previous studies found no difference in time trial performance in 800 m trials when
comparing the effects of CAF coffee versus DECAF coffee [
5
]. Thus, one hypothesis for inconsistencies
between studies may be related to how the CAF is administered, either isolated/alone or in a CAF
coffee form.
In the present study, we did not find any difference in 1600 m performance between the
consumption of placebo (water) compared with DECAF coffee plus isolated CAF. Similarly, a previous
study also did not find any difference on endurance performance when comparing DECAF coffee
versus the other three groups (either DECAF coffee plus isolated CAF or placebo) [
27
]. Although our
data did not evaluate the blood CAF levels, Graham et al. [
27
] suggest that absence of an ergogenic
effect may be independent of blood caffeine, paraxanthine, and theophylline concentrations, reinforcing
Nutrients 2019,11, 1661 7 of 9
the idea that the administration procedure (vehicle) appears to modify the ergogenic response of CAF.
Likewise, other studies that combine DECAF coffee and isolated CAF or CAF coffee or isolated CAF
alone require further investigation.
Church et al. 2015 [
29
] investigated the effects of CAF coffee or DECAF coffee ingested prior to a
5 km run on a treadmill, and no changes in blood lactate between trials were found. The findings of
Church et al. 2015 [
29
] are in agreement with the present study, as we did not observe any differences
in the blood lactate concentrations between groups. In addition, the lack of modification in lactate
concentrations has already been found in previous work of our group [
5
], when testing the effects of
CAF coffee compared with DECAF coffee on 1600 m running performance. Similar findings were
reported by another group that also analyzed the effects of consumption of CAF coffee and isolated
CAF alone on participants that ran to exhaustion [10].
Considering that high intensity exercise increased blood lactate concentrations [
30
] and the reduced
consumption of fatty acids during exercise, we hypothesized that increases in lactate concentrations
are time-dependent, but not those of fatty acids, as we used a short-term running protocol. In addition,
pre-workout supplementation with long chain and medium chain fatty acids and conjugated linoleic
acid does not produce an ergogenic effect [
13
,
14
]. Therefore, pre-exercise supplementation with fatty
acids does not make sense in clinical practice.
Additionally, young adults that consume CO do not experience a change in total plasma antioxidant
capacity following a bout of moderate-intensity cycling exercise [
15
] Likewise, it was found in rats
that CO supplementation, with or without exercise, enhanced blood triacylglycerol and VLDL-c
concentrations [
31
]. Therefore, lipid supplements did not seem to be a healthy option. Regarding
performance, a recent study observed in men that a ketogenic diet containing CO did not change
run-to-exhaustion with a 70% VO2max in men [16].
A previous study showed that theophylline, present in coffee, can also inhibit adenosine receptors
and increase carbohydrate oxidation during a 30 min cycling exercise [
32
]. Thus, in the present study,
theophylline may have influenced a greater availability of carbohydrates and lactate and, consequently,
a greater energy supply in the trials, which may explain the non-effect of the additional energy supply
from either CO or SO. However, the placebo group received only water and, when compared with the
DECAF coffee group, no ergogenic effect was reported. Thus, we suggested that breakfast prior to
races may have indicated that extra calories negatively impacted the running performance among the
groups, despite CAF or CO.
In the present study, we observed that the type of oil, whether SO or CO, did not influence
palatability, as the volunteers were not able to distinguish them. Additionally, the taste identification
of the oils was minimized, as the CO is unscented and tasteless, triggering many volunteers to not be
able to identify the oil type when mixed with the coffee.
One important finding in the present study was that most of the participants were able to correctly
identify the substances they took. Previous studies suggested that the placebo effect might be an
important mediator of CAF ergogenic effects [
33
,
34
]. Therefore, precise identification of placebo may
have been associated with an absence of improvement in performance in some runners.
Although the CAF ergogenic effect (3 and 6 mg/kg) on 30.6
◦
C and 50% relative humidity led to
performance loss [
35
], our study done in cooler environmental conditions (range 19.7–20.8
◦
C) did
not affect the running time. Therefore, it is unlikely that climatic conditions led to dehydration and
dropping performance in all trials. In addition, one of our previous studies found no difference in
sweating rate between acute CAF and placebo supplementations [36].
Some limitations must be acknowledged. First, the small number of participants; therefore, the
data should be interpreted with caution. Second, we are unable to measure the blood CAF and its
metabolites concentrations; thus, we can not to confirm that all participants achieved similar amounts of
CAF and its metabolites following the race. Third, although temperature and humidity were measured,
wind speed was not; thus, we recognize that this could have hampered the running performance.
Nutrients 2019,11, 1661 8 of 9
5. Conclusions
Our study shows that the consumption of DECAF coffee with CAF and CO, isolated or combined,
does not improve 1600 m running time, influence RPE, nor lactate concentrations in recreational runners.
Thus, combination of coffee with CO as a pre-workout supplement seems to be unsubstantiated for a
short-distance race.
Author Contributions:
G.d.L.B., J.S.d.F.B., L.M.Q.N., M.B.S., J.B.d.S.J., P.G., A.C.B.M., B.M.G., and G.D.P. collected
data, data analyses, interpretation, and drafted the manuscript. All authors read and approved the final version.
Funding: This research received no external funding.
Acknowledgments:
We would like to thank the Patr
í
cia Barreto Lobo, Alexandre Soares, and Vanessa Alves de
Araújo for assistance during the collection data.
Conflicts of Interest: The authors declare no conflict of interest.
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