Desch S, Schmidt J, Kobler D, Sonnabend M, Eitel I, Sareban M, Rahimi K, Schuler G, Thiele H. Effect of cocoa products on blood pressure: systematic review and meta-analysis. Am J Hypertens. 2010 Jan; 23(1): 97-103.
PubMed ID: 19910929
Determine the effects of cocoa products on blood pressure (BP).
- Investigated flavanol-rich cocoa products such as dark chocolate and cocoa beverages
- Random allocation to treatment and control group
- BP measurements at baseline and at a minimum of one more time point
- Because the meta-analysis was designed to study the effects of habitual intake of cocoa products on BP, studies included in the analysis were larger than single dose trials
- Minimum of two weeks of treatment duration was required.
30 articles were excluded because:
- Study design did not meet pre-specified criteria, N=16
- Blood pressure reporting was insufficient to calculate effect size, N=one
- Publication or study did not examine blood pressure, N=three
- Single dose trial
- Studies with subjects on anti-hypertensive medication.
Selection of studies included in systematic review:
- 332 articles were identified from literature search
- 40 potentially relevant articles were identified for full text review
- 10 RCTs were identified for review and meta-analysis.
Systematic review and meta-analysis of 10 RCTs (six crossover design and four parallel design studies).
Adequate blinding was not possible with dark vs. white chocolate studies (50% of studies). Investigators and end point assessment were blinded in most studies.
The studies investigated flavanol-rich cocoa products such as dark chocolate and cocoa beverages. Flavanol intake varied across studies, between five and 17mg of the flavanol sub-compound epicatechin.
Timing of Measurements
BP measurements at baseline and at a minimum of one more time point. Single dose trials were not included. Treatment duration ranged from two to 18 weeks.
Systolic and diastolic blood pressure (SBP and DBP).
Dietary flavanol-rich cocoa intake: Flavanol intake varied widely across studies (e.g., between five to 17mg epicatechin).
- Position when subject BP was measured (sitting, standing or supine)
- No restriction made regarding age, gender, medication, baseline BGP, risk profile or comorbidities.
- Initial N: Studies excluded with N<16
- Attrition (final N): Not specified; variable across the 10 RCTs included
- Age: No restriction on age
- Ethnicity: No restriction on ethnicity
- Other relevant demographics: Majority of studies used office BP to assess treatment effects
- Anthropometrics: Populations were either healthy normotensive adults or patients with pre-hypertension or stage 1 hypertension without anti-hypertensive medication.
Mean Difference in Systolic BP
(mmHg, 95% CI)
|Mean Difference in Diastolic BP
(mmHg, 95% CI)
-5.2 (-6.9 to -3.5)
-2.9 (-4.6 to -1.2)
|Medium-term trials||-3.0 (-3.5 to -2.5)||-1.8 (-2.5 to -1.0)|
|Lower baseline BP||
-3.6 (-5.5 to -1.8)
|-3.6 (-5.5 to -1.8)|
|Higher baseline BP||-5.3 (-7.9 to -2.6)||-5.3 (-7.9 to -2.6)|
|Lower flavanol content||-5.2 (-7.0 to -3.3)||-5.2 (-7.0 to -3.3)|
|Higher flavanol content||-4.0 (-5.6 to -2.3)||-4.0 (-5.6 to -2.3)|
- Ten RCTs comprising 297 individuals were included in the analysis
- Populations studied were either normotensive or pre-hypertensive adults
- Treatment duration was two to eight weeks
- Mean BP change in the active treatment arms across all trials:
- SBP: -4.5mmHg (95% CI: -5.9 to -3.2, P<0.001
- DBP: -2.5mmHg (95% CI, -3.9 to -1.2, P<0.001)
- Meta analysis confirmed BP-lowering effect of flavanol-rich cocoa products in a larger set of trials than previously reported.
The meta-analysis confirms the BP-lowering capacity of flavanol-rich cocoa products in a larger set of trials than previously reported.
- Authors note that there was significant statistical heterogeneity across studies
- Questions about the most appropriate dose and long-term side effects warrant further investigations before cocoa products can be recommended as a treatment option for hypertension.
Research Design and Implementation Criteria Checklist: Review Articles
|1.||Will the answer if true, have a direct bearing on the health of patients?|
|2.||Is the outcome or topic something that patients/clients/population groups would care about?|
|3.||Is the problem addressed in the review one that is relevant to nutrition or dietetics practice?|
|4.||Will the information, if true, require a change in practice?|
|1.||Was the question for the review clearly focused and appropriate?|
|2.||Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search terms used described?|
|3.||Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified and appropriate? Were selection methods unbiased?|
|4.||Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methods specified, appropriate, and reproducible?|
|5.||Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined?|
|6.||Was the outcome of interest clearly indicated? Were other potential harms and benefits considered?|
|7.||Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently across studies and groups? Was there appropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described?|
|8.||Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels of significance and/or confidence intervals included?|
|9.||Are conclusions supported by results with biases and limitations taken into consideration? Are limitations of the review identified and discussed?|
|10.||Was bias due to the review’s funding or sponsorship unlikely?|