HTN: Cocoa and Chocolate (2007)

Citation:

Vlachopoulos C, Aznaouridis K, Alexopoulos N, Economou E, Andreadou I, Stefanidis C. Effect of dark chocolate on arterial function in healthy individuals. Am J Hypertens. 2005; 18 (6): 785-791.

PubMed ID: 15925737
 
Study Design:
Randomized Crossover Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To investigate whether dark chocolate affects endothelial function, aortic stiffness, wave reflections and oxidant status in healthy subjects.

Inclusion Criteria:
  • Young healthy volunteers
  • All were non-smokers and non-obese (BMI less than 27) and they did not have diabetes, hyperlipidemia or family history of premature vascular disease
  • They were clinically well and were taking no regular cardiovascular medications or antioxidant vitamin supplementation
  • Females were examined during follicular phase of menstrual cycle and none were using oral contraceptives.
Exclusion Criteria:

Excluded if not included above.

Description of Study Protocol:

Design

Randomized controlled crossover trial.

Blinding Used

Single-blind. Measurements taken by same observer blinded to randomization assignment.

Intervention

Subjects randomized to consumption of dark chocolate and water or to sham-eat (chew) and water.

Statistical Analysis

  • All variables tested for homogeneity of variance and normal distribution
  • Measurements compared using Student's T-test for paired measures
  • To evaluate the composite effect of the chocolate vs. placebo over time and overall 7x2 ANOVA for repeated measures was performed
  • A repeated-measures ANOVA was also performed to detect significant changes in variables over time within the two sessions separately.
Data Collection Summary:

Timing of Measurements

  • Subjects studied on two different days after an eight-hour fast: One day involving chocolate consumption; one day sham-eating (chewing)
  • Baseline measurements taken before consumption and repeated at 30, 60, 90, 120, 150 and 180 minutes afterwards. 

Dependent Variables

  • Endothelial function measured with flow-mediated dilation of the brachial artery using a high-resolution, linear-array ultrasonic transducer
  • Wave reflections measured with aortic augmentation index
  • Aortic stiffness measured with carotid-femoral pulse wave velocity
  • Plasma oxidant status evaluated with measurement of plasma malondialdehyde and total antioxidant capacity determined colorimetrically and spectrophotometrically.

Independent Variables

  • Consumption of 100g dark chocolate
  • Subjects abstained from caffeine and alcohol intake for at least 12 hours and from flavonoid-containing foods for 24 hours before each session.
Description of Actual Data Sample:
  • Initial N: 17 young healthy volunteers; 12 men, five women
  • Attrition (final N): 17 subjects
  • Age: Mean, 28.9 years; range, 24 to 32 years 
  • Anthropometrics: There were no significant differences in baseline characteristics between the chocolate consumption and control sessions
  • Location: Greece.
Summary of Results:

Findings

  • Chocolate led to a significant increase in resting and hyperemic brachial artery diameter throughout the study:
    • Resting: By 0.15mm at 90 minutes and steadily increased thereafter; P<0.001
    • Hyperemic: Maximum increase by 0.15mm at 60 minutes and 0.18mm at 180 minutes, respectively; P<0.001 for both.
  • The flow-mediated dilation increased significantly at 60 minutes (absolute increase 1.43%, P<0.05)
  • The aortic augmentation index was significantly decreased with chocolate throughout the study (maximum absolute decrease 7.8%, P<0.001), indicating a decrease in wave reflections, whereas pulse wave velocity did not change to a significant extent
  • Plasma malondialdehyde and total antioxidant capacity did not change after chocolate, indicating no alterations in plasma oxidant status
  • Heart rate increased significantly with chocolate consumption (maximum at 180 minutes, by 8.4 beats per minute, P<0.005)
  • Both peripheral and central systolic, diastolic and pulse pressures did not change significantly throughout the study (P=NS).
Author Conclusion:
  • The study shows for the first time that dark chocolate acutely dilates muscular arteries, decreases wave reflections and may improve endothelial function in healthy humans
  • These effects do not seem to be mediated through an improvement in antioxidant status. Thus, chocolate consumption may exert a protective effect on the cardiovascular system and further studies are warranted to assess any long-term effects.
  • Our results suggest that studies conducted on arterial function should control for flavonoid intake.
Funding Source:
University/Hospital: Hippokration Hospital, University of Athens (both Greece
Reviewer Comments:
  • Authors note that chocolate contains theobromine and caffeine that may have influenced the results
  • Only acute effects of chocolate measured.
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? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  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? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
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) N/A
  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.) Yes
  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? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  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%.) Yes
  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? N/A
  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? Yes
  6.6. Were extra or unplanned treatments described? N/A
  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? ???
  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? Yes
  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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? Yes
  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