Download Nutrient timing: a systematic review Cassandra Golden Florida

Nutrient timing: a systematic review
Cassandra Golden
Florida International University
HUN6248
ABSTRACT
Background: The method of supplement timing involves consumption either immediately
before, immediately after, or hours outside of training. Supplements containing caffeine,
creatine, amino acids, whey protein, and/or carbohydrate were reviewed.
Objective: To review and compare the results of original research previously conducted
involving the effects of nutrient timing in the effort of maximizing athletic recovery and
subsequent performance.
Design: Databases via the Florida International University research library were searched using
key words such as “whey protein”, “creatine”, “supplementation”, “histochemistry”, “lean body
mass”, and “resistance exercise”. Original research relevant to the effects of nutrient timing was
used as key reference material.
Results: Based on the studies reviewed, consuming a supplement immediately after a workout
has steadfastly revealed beneficial results in the areas of body composition, strength, fat-free
mass, and in levels of creatine and glycogen. Furthermore, supplements containing caffeine,
amino acids, and creatine have been shown to improve cardiovascular fitness, lean body mass
and critical velocity when paired with high-intensity interval training.
Conclusions: Based on the studies reviewed, proper nutrient timing has revealed positive
outcomes regarding athletic recovery and subsequent performance. With each study testing
different variables, it is difficult to determine an exact nutrient timing formula that will yield
benefits for all athletes.
INTRODUCTION
Previous literature evaluating the effects of supplements containing creatine,
carbohydrate, protein and caffeine has provided conflicting results concerning improvements in
muscle strength, endurance, anaerobic exercise, and exercise-induced muscle damage (1, 2).
When combined with resistance training, protein supplementation has shown to improve muscle
mass and increase protein synthesis (2). Correspondingly, carbohydrate intake surrounding
training times has been shown to increase insulin levels, improve skeletal muscle blood flow,
cause a reduction in protein breakdown, and enhance protein turnover (2, 3). Increased creatine
intake has resulted in improved muscle mass and increased strength during resistance training
exercise (3). Supplements containing caffeine have been found to stimulate the central nervous
system, which causes catecholamine levels to increase and therefore escalating the utilization of
fat (4). Previous research studies have examined the effects of timing nutrient intake in the effort
to capitalize athletic performance and recovery (2, 3).
RESEARCH RESULTS:
In 2006, a study conducted in Australia examined the effects of a supplement containing
protein, carbohydrate, and creatine on muscle hypertrophy, strength, and body composition of
male body builders (3). Authors hypothesized that proper nutrient timing would produce benefits
in fat-free mass, strength, and muscle hypertrophy. The single blind study randomly divided 23
participants in either the PRE-POST group or the MOR-EVE group. Baseline assessments were
completed before and after a 10-week resistance training program. Subjects belonging to the
PRE-POST group consumed a supplement containing whey protein, carbohydrate, and creatine
monohydrate directly before and after strength training exercise. This procedure was
administered four times a week for 10 weeks. Conversely, the MOR-EVE group received the
supplement in the morning and at nighttime hours (3).
When compared to the MOR-EVE group, the PRE-POST group showed greater
improvements in lean body mass, body fat percentage, 1RM squat, 1RM bench press, and a
greater improvement in the cross-sectional area of type II muscle fibers. Additionally, the PREPOST group revealed greater muscle creatine and glycogen levels when compared to the MOREVE group. Results indicate that when athletes consumed the supplement immediately before
and after training sessions, there are significant increases in strength and improvement in body
composition when compared to athletes who consumed the supplement in the morning and at
night (3).
Four years later in the UK, researchers assessed whether implementing proper timing of a
milk-based carbohydrate and protein supplement would ease exercise-induced muscle damage
(1). Milk-based supplements have been implemented in past research due to the potential
increase in protein synthesis. The study split 32 subjects into four groups, which were labeled
PRE, POST, TWENTY-FOUR, and CON. Participants belonging to the PRE group consumed
the milk-based carbohydrate and protein supplement before muscle damaging exercise and water
during all other times. The POST group consumed same supplement immediately after muscle
damaging exercise and water during all other times. The TWENTY-FOUR group received the
same supplement 24 hours after muscle damaging exercise and water during all other times. The
control group, CON, only consumed water (1).
Subsequent to hamstring muscle damaging activity, the measurement of muscle soreness,
peak torque, reactive strength index, and serum creatine kinase levels were recorded for each
group. When compared to participants in the PRE and CON groups, participants who belonged
to the POST group experienced a reduction in delayed muscle soreness. These participants also
confirmed beneficial changes in peak torque and reactive strength index. Similar to the control
group, subjects belonging to the PRE group did not demonstrate a reduction in muscle soreness
over 48 hours. Participants who consumed the supplement yielded stable in levels of creatine
kinase when compared to those participants who only consumed. This study indicated similar
results as the previous study, stating that when athletes consumed the supplement immediately
after training, the most beneficial changes in muscle recovery occurred (1, 3).
When discussing the effects of timing nutrient intake, it is important to discuss which
supplements have been previously researched to show enhancements in athletic performance.
One study evaluated whether combining a resistance training program with post exercise
supplementation would result in an increase of fat-free mass, muscle strength, endurance, and
improved anaerobic performance (2). Subjects belonging to the supplement group received an
anabolic recovery drink containing whey protein, amino acids, creatine, and carbohydrate,
whereas the control group received a beverage containing only carbohydrate (2). Similar to the
previous study, baseline measurements were administered before and after a 10-week strength
training program (1, 2).
Results did not show increased benefits on body composition, muscle strength,
endurance, or anaerobic exercise for participants who consumed the anabolic recovery drink
following strength training exercise. However, members of the supplement group had greater
tendencies in fat-free mass improvements when compared to the control group. In this study,
creatine is discussed to be the likely cause of the improvement in fat-free mass, due to previous
research indicating the positive effect of creatine on muscle fiber size and strength (2).
Another similar study assessed the effects of a pre-workout supplement containing
caffeine, creatine, and amino acids (4). In comparison to the previously discussed studies, this
study evaluated the effects of consuming a low calorie supplement on the aerobic and anaerobic
running performance of recreational athletes. Twenty four men were randomly divided into a
supplement group or a placebo group. The supplement group consumed a powdered beverage
consisting of whey protein, creatine and caffeine 30 minutes before training times. The placebo
group consumed a powdered beverage only containing maltodextrin, during the same times. Pre
and post tests evaluated the aerobic work capacity and critical velocity of participants (4).
All subjects experienced an increase in cardiovascular fitness due to the prolonged highintensity interval training. Participants who consumed the supplement containing caffeine,
creatine and amino acids 30 minutes prior to high-intensity interval training had a 2.9% increase
in critical velocity and a 3% decrease in body fat when compared to participants who consumed
a supplement only containing maltodextrin. Additionally, in comparison to the placebo group,
the supplement group had an 11.6% higher training volume (4).
DISCUSSION AND CONCLUSION
The idea of timed ingestion has become an emerging topic in sports research due to the
potential benefits in athletic performance and recovery. With each study testing different
variables, it is difficult to determine an exact nutrient timing formula that will yield benefits for
all athletes across the board. Based on the studies reviewed, consuming a supplement
immediately after a workout has steadfastly revealed positive results in the areas of body
composition, strength, fat-free mass, and levels of creatine and glycogen.
Determining which kind of supplement to implement for nutrient timing has also been
widely researched, with no determination of an unwavering gold standard. The nutrients that
make up a sports supplement will yield diverse results when combined with the training
techniques required by specific athletic events. Therefore, the premise of nutrient timing should
be considered on a case-by-case basis.
REFERENCES
1. Cockburn E, Stevenson E, Hayes PR, Robson-Ansley PR, Howatson G. Effect of
milk-based carbohydrate-protein supplement timing on the attenuation of exerciseinduced muscle damage. Appl Physiol Nutr Metab 2010; 35: 270-277.
2. Chromiak JA, Smedley B, Carpenter W, Brown R, Koh YS, Lamberth JG, Joe LA,
Abadie BR, Altorfer G. Effect of a 10-week strength training program and recovery
drink on body composition, muscular strength and endurance, and anaerobic power
and capacity. Nutrition 2004; 20: 420-427.
3. Cribb PJ, Hayes A. Effects of supplement timing and resistance exercise on skeletal
muscle hypertrophy. Medicine & Science in Sports Exercise 2006; 38: 1918-1925.
4. Smith AE, Fukuda DH, Kendall KL, Stout JR. The effects of a pre-workout
supplement containing caffeine, creatine, and amino acids during three weeks of high
intensity exercise on aerobic and anaerobic performance. Journal of the International
Society of Sports Nutrition 2010; 7:10.