FNOA: Antioxidants (2011-2012)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To examine the short-term (six-week) effects of dark chocolate and cocoa on variables associated with neuropsychological functioning and cardiovascular health in healthy older adults.

Inclusion Criteria:

To be considered cognitively intact (CI) and included in the trial, participants were required to obtain a total score on the Mini-Mental State Examination (MMSE) of 24 or more out of a possible 30. 

Exclusion Criteria:
  • Those with histories of active or clinically significant cardiovascular, neurological, pulmonary, endocrine, renal or urological, hepatic, gastrointestinal or hematological disorders; uncontrolled hypertension; significant head injuries; episodes of anoxia or hypoxia; learning disabilities; color blindness; or psychiatric or substance abuse disorders
  • Persons being treated with antihypertensive, hypolipidemic, non-steroidal anti-inflammatory, anticoagulant or psychotropic medications.
Description of Study Protocol:

Recruitment

Healthy, volunteer men and women 60 years old or older who reported no history of dementia or significant neurocognitive impairment were initially enrolled and randomly assigned to the study. 

Design

Randomized, placebo-controlled, fixed-dose, parallel-group clinical trial. 

Blinding Used

Double-blind. 

Intervention

37g dark chocolate bar and eight ounces of an artificially sweetened cocoa beverage or similar products each day for six weeks. 

Statistical Analysis

  • Separate analysis of variance (ANOVAs) were used to examine differences between the treatment groups
  • A Pearson chi-square analysis was used to analysis sex variables (men or women) and treatment group
  • Two-factor mixed ANOVAs were used to examine the neuropsychological measures and test scores, hematologic test results and the physiological variables of systolic and diastolic BP
  • Separate Pearson chi-square analysis were conducted with the use of the treatment groups' self-reported data
  • Post-hoc analysis using Tukey's test was used for mean pulse rate.

 

Data Collection Summary:

Timing of Measurements

Baseline, midpoint and end of treatment.

Dependent Variables

  • Neuropsychological test scores: 
    • Selective Reminding Test
    • Wechsler Memory Scale-III
    • Wechsler Adult Intelligence Scale-III
    • Trail Making Test
    • Stroop Color-Word Test
    • Activation-Deactivation Adjective Checklist
  • Self-reported questionnaire frequency data: 
    • Memory
    • Thinking processes
    • Mood
    • Energy
    • Overall health
    • Product group
  • Hematologic test results: 
    • Total cholesterol
    • LDL-cholesterol
    • VLDL cholesterol
    • HDL-cholesterol
    • Triacylglycerol
    • C-reactive protein
  • Systolic BP
  • Diastolic BP
  • Pulse rate.

Independent Variables

Dark chocolate and cocoa group or placebo group. 

Control Variables

  • Age
  • Education level
  • MMSE total score
  • Treatment regimen adherence
  • Body mass index (BMI) at baseline and end of treatment.
Description of Actual Data Sample:
  • Initial N: 101
  • Attrition (final N): 90
  • Age: 
    • Chocolate and cocoa group: 68.76±8.62
    • Placebo group: 68.73±8.01
  • Other relevant demographics: 
    • Education level: 15.52±2.66 for the chocolate and cocoa group and 15.18±2.75 for the placebo group.

Anthropometrics

  Chocolate and Cocoa Group Placebo Group
BMI baseline 25.16±3.4 25.51±3.56
BMI end of treatment 25.09±3.47 25.56±3.55

Location

Virginia.

 

Summary of Results:

Key Findings

Differences Between Treatment Groups

  • ANOVAs were conducted on the descriptive and criterion measures in the study including:
    • Age
    • Education level
    • MMSE total score
    • Treatment regimen adherence and
    • BMI
  • No significant differences were observed among any of these variables
  • A Pearson chi-square analysis was conducted on the variable of sex (men or women) and treatment group and no significant relation was found between the numbers of men and women who constituted the two groups.

Neuropsychological Measures and Test Scores

  • For the neuropsychological measures and test scores, two-factor ANOVAs were conducted to examined possible interaction effects by using the fixed factor of group (dark chocolate and cocoa or placebo) and repeated measures of trial (baseline and end of treatment assessments)
  • There was an absence of previous clinical trials that have examined the effects of dark chocolate and cocoa on the neuropsychological test performance of CI older adults, so primary and secondary endpoints were not defined in advance
  • A series of endpoints was chosen that could be more rigorously defined and tested in future trials and no significant group-by-trial interactions were found for any of the variables
  • For A-DACL scores, a two-factor mixed ANOVA was conducted by using the fixed factor of group (dark chocolate and cocoa or placebo) and repeated measures of trial (baseline, midpoint or end-of-treatment assessments). The group-by-trial interaction was non-significant.

Follow-up of Self Reported Questionnaire Items

  • For questions concerning participants' subjective perceptions of changes from pre-treatment baseline to the end-of-treatment phase in their overall abilities to remember, thinking abilities and processes, mood, energy levels and health, separate chi-square analysis were conducted and no significant relations were found across any of these areas.
  • For the questionnaire item regarding the products that participants believed they had consumed during the initial trial (dark chocolate and cocoa or unknown), a Pearson chi-square analysis showed the following: 
    • A significant (P=0.004) relationship existed between the treatment group to which participants had been assigned and the products that participants believed they had consumed
    • In particular, more than half (55.6%) of the participants who received the dark chocolate and cocoa products, correctly believed that they had consumed these products
    • Only 22.2% of that group believed that they had consumed the placebo.

Hematological Test Results

For the hematological test results, none of the interactions were significant.

Pulse Rates and BP

On comparison of group's mean pulse rates, a significant (P=0.007) group-by-trial interaction was found: 

  • When post-hoc analysis using Tukey's test showed that the man pulse rate of the three-week assessment was significantly higher in the dark chocolate and cocoa group than at baseline (P<0.01) and than in the placebo group at midpoint (P<0.01)
  • It was also indicated that the chocolate and cocoa group had a significantly higher mean pulse rate at the six-week assessment compared with that group's baseline mean pulse rate (P<0.01) and the control subjects end of treatment assessment mean pulse rate (P<0.01)
  • No significant differences were found between the groups with respect to any of the remaining pulse rate or BP variables.
Author Conclusion:
  • The results of this study failed to support the predicted beneficial effects of short-term six-week consumption of dark chocolate and cocoa on any of the neuropsychological, hematologic or physiological variables included in the investigation.  The null neuropsychological and mental energy findings were in contrast to past research involving laboratory animals and humans that has shown beneficial neuronal, neurocognitive and neuroprotective effects of herbal compounds that are rich in antioxidants and phytochemicals.
  • The relatively high mean levels of education (more than 15 years) of subjects in this study may have negatively affected the results because higher levels of education compared with lower levels have been associated with greater cognitive reserve. Also, persons with higher education levels have more test-taking experiences than do persons with less education. These factors plus the fact that participants appeared to be CI at the onset of the study, may have enabled the participants to optimize their neuropsychological test performances to a degree that precluded the identification of significant differences in favor of the dark chocolate and cocoa group.
  • This trial used a sample of healthy participants whose mean baseline serum HDL and VLDL cholesterol, triacylglycerol and ultra-sensitive CRP concentrations fell with in the normal reference ranges. It is possible that participant's baseline hematologic values were not elevated to the degree necessary for the effects of short-term dark chocolate and cocoa to be observed. This possibility is only speculative at this time.
  • The null hematologic results were in contrast to the results of past studies, which showed the favorable effects of dark chocolate and cocoa on LDL-cholesterol concentrations. The present null BP findings were consistent with past short-term studies investigating the effectiveness of dark chocolate and cocoa in healthy adults. The higher pulse rates in the dark chocolate and cocoa group were likely related to the well-known stimulant effects of methylxanthines that are found in dark chocolate and cocoa. 
  • Future research is needed to address some the limitations of this study. Large, heterogeneous samples consisting of diverse backgrounds, health statuses, educational levels and ages should be examined so that differential effects can be more readily shown. Also, longitudinal trials are needed that involve consumption of dark chocolate and cocoa over extended periods and that result in the consumption of larger quantities of such products which will likely promote more potent antioxidant and phytochemical effects.
Funding Source:
Industry:
The Hershey Company
Food Company:
In-Kind support reported by Industry: Yes
Reviewer Comments:

The authors note the following limitations:

  • The sample size of the trial may not have been of sufficient magnitude, which could have decreased the power of the statistical measures to find true, significant differences that may actually have existed between the treatment groups
  • The relatively short duration of the treatment phase and the quantity of dark chocolate and cocoa products consumed by participants in the present trial also may have contributed to the overall null findings
  • Despite the investigators' efforts to educate participates to limit their consumption of certain antioxidant or phytochemical rich products during this trial, control of every aspect of their diets  was not attempted. It is likely that members of both treatment groups continued to consume a diversity of other fruit and vegetables containing antioxidants or phytochemicals, which may have confounded the current results to some extent.
  • In the follow-up self-report questionnaire, more than half of the participants in the dark chocolate and cocoa and placebo groups correctly identified the types of products that they had ingested during the experiment. This suggests that more than half of the treatment group was not fully blinded to the trial's products. In light of the predominately null findings, no evidence was found for any type of participant expectancy effects or bias that may have confounded the results.

There was potential for conflict of interest because The Hershey Company provided the dark chocolate and cocoa products for the study; however, the results of the study were negative.

 

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? ???
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.) 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? Yes
  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? ???
  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? ???
  6.6. Were extra or unplanned treatments described? ???
  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? ???
  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)? ???
  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? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
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? ???