EAL

NAP: Training (2014)

Citation:

Chen Y, Wong S, Wong C, Lam C, Huang Y, Siu P. The effect of a pre-exercise carbohydrate meal on immune response to an endurance performance run. Br J Nutr. 2008;100: 1,260-1,268.

Study Design:

Randomized Crossover Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To examine the effect of a two-hour pre-exercise meal with different glycemic index (GI) and glycemic load (GL) on immune responses to an endurance performance run.

Inclusion Criteria:

Male
Trained runner (minimum 50km per week).

Exclusion Criteria:

Any medication in six weeks prior to study
Symptoms of upper respiratory infection in four weeks prior to study.

Description of Study Protocol:

Design

Randomized crossover design.
Study participants completed preliminary test to on the treadmill to establish VO₂-speed test and VO_2max as well as a lactate-speed test
Each study participant completed the experimental procedure three times, separated by a minimum of seven days. Each time the participant completed the experimental procedure, they were randomized to a different dietary intervention.
Following overnight fast, subjects arrived at the lab and conducted preliminary blood work. They consumed one of the three test meals within 15 minutes to 20 minutes and then remained quiet and stationary for two hours. On the treadmill, participants completed five minutes of warm-up and then the treadmill speed was increased to achieve 70% VO_2nax. Participants continued to run for one hour at 70% VO_2max (T1). Next, the participants completed a 10km run, also on the treadmill, with encouragement to run as fast as possible.

Blinding Used

Subjects were blinded to purpose of their meal composition, study director was blinded to which arm of the study participants were in while providing the verbal encouragement during the 10km run.

Intervention

Three isoenergetic meals were studied [high GI and high GL (H-H), low GI and low GL (L-L) and high GI and low-GL (H-L)]. The water content was standardized so that each of them provided 1,100ml fluid.

d	Estimated GI	Estimated GL	% CHO
H-H	79	82	66
L-L	40	42	66
H-L	78	44	36

Statistical Analysis

A two-way ANOVA (trial and time) with repeated-measured design was used to assess metabolic and immune differences between groups. Any significant F-ratios were assessed using a Holm–Bonferroni stepwise post-hoc test to determine the locations of variance.
P<0.05
SPSS version 11 was used for data analysis.

Data Collection Summary:

Timing of Measurements

Blood glucose concentrations were measured at 15 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes and 120 minutes post-meal
After running, blood samples were taken immediately, 60 minutes post-activity and 120 minutes post-activity.

Dependent Variables

Leucocute: Serum
Neutrophil: Serum
Lymphocyte: Serum
Monocyte: Serum
Cytokines: Serum
Cortisol: Serum.

Independent Variables

Estimated glycemic index and glycemic load of meals prior to intense running activity.

Control Variables

Meals were isocaloric
Water content in meals were the same
Subjects were instructed to keep daily exercise to a minimum and standardize diet during 72 hours prior to testing. Subjects were also fasted for 12 hours prior to testing.

Description of Actual Data Sample:

Initial N: Eight males
Attrition: Eight
Age: 24.3 years (SEM 2.2)
Other relevant demographics: VO_2max 55.9 (SEM 1.87).

Anthropometrics

Body mass: 66.7 (SEM 2.0).

Location

Hong Kong.

Summary of Results:

Key Findings

During exercise, the total CHO oxidation [H-H vs. L-L vs. H-L: 252.2g (SEM 14.3g) vs. 230.7g (SEM 10.4g) vs. 225.5g (SEM 12.1g) P<0.05] was higher in the H-H trial, with a compensatory decrease in fat oxidation
There were no differences in CHO and fat oxidation between the L-L and H-L trials
The post-prandial two-hour incremental area under the blood glucose curve was about 1.5 times larger in the H-H meal than that in the L-L and H-L trials
Consumption of H-H and L-L meals resulted in less perturbation of the circulating numbers of leucocytes, neutrophils and T-lymphocyte subsets, and in decreased elevation of the plasma IL-6 concentrations immediately after exercise and during two-hour recovery period as compared to the H-L trial.

Other Findings

All lymphocyte subsets returned to normal during the two-hour recovery
Serum cortisol concentrations increased after the onset of exercise in all trials, but no differences were found amount the trials throughout the exercise period.

Author Conclusion:

The low CHO (H-L) meal was associated with the higher perturbation of circulating leucocytes neutrophils, lymphocytes and lymphocyte subsets, which may be explained by greater responses of the stress hormone. The consumption of high-CHO meals two hours before exercise also minimized the increase in IL-6 immediately after exercise and during the two-hour recovery period compared with the low-CHO meal. Such responses also led to the attenuated increase in IL-10 at the end of the recovery period. These results suggested that the amount of CHO consumed may be the most important influencing factor of pre-exercise meal composition in modifying the immunoendocrine response to prolonged exercise irrespective of its GI and GL values.

Funding Source:

University/Hospital:

Chinese University of Hong Kong

Reviewer Comments:

Small sample size (N=8)
Method of recruitment to study was not described.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	No
2.	Was the selection of study subjects/patients free from bias?		No
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	No
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	No
	2.4.	Were the subjects/patients a representative sample of the relevant population?	N/A
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	Yes
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	???
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	No
	6.6.	Were extra or unplanned treatments described?	No
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	No
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	Yes
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	No
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes