Effect of cocoa on blood pressure

Karin Ried; Peter Fakler; Nigel P Stocks

doi:10.1002/14651858.CD008893.pub3

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Figure 1

PRISMA Flow diagram

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Figure 2

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

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Figure 3

Forest plot of comparison: 1 Effect of cocoa on BP, outcome: 1.1 SBP.

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Figure 4

Forest plot of comparison: 1 Effect of cocoa on BP, outcome: 1.2 DBP.

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Figure 5

Forest plot of comparison: 2 Hypertensive or normotensive subjects, outcome: 2.1 SBP.

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Figure 6

Forest plot of comparison: 2 Hypertensive or normotensive subjects, outcome: 2.2 DBP.

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Analysis 1.1

Comparison 1 Effect of cocoa on BP, Outcome 1 SBP.

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Analysis 1.2

Comparison 1 Effect of cocoa on BP, Outcome 2 DBP.

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Analysis 2.1

Comparison 2 Hypertensive or normotensive participants, Outcome 1 SBP.

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Analysis 2.2

Comparison 2 Hypertensive or normotensive participants, Outcome 2 DBP.

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Analysis 3.1

Comparison 3 Flavanol‐free or low flavanol control, Outcome 1 SBP.

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Analysis 3.2

Comparison 3 Flavanol‐free or low flavanol control, Outcome 2 DBP.

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Analysis 4.1

Comparison 4 Double‐blinded or unblinded/single‐blinded, Outcome 1 SBP.

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Analysis 4.2

Comparison 4 Double‐blinded or unblinded/single‐blinded, Outcome 2 DBP.

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Analysis 5.1

Comparison 5 Participants ≥50 or <50 years old, Outcome 1 SBP.

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Analysis 5.2

Comparison 5 Participants ≥50 or <50 years old, Outcome 2 DBP.

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Analysis 6.1

Comparison 6 Study duration 2 ‐ 4 weeks or > 4 weeks, Outcome 1 SBP.

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Analysis 6.2

Comparison 6 Study duration 2 ‐ 4 weeks or > 4 weeks, Outcome 2 DBP.

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Analysis 7.1

Comparison 7 Sensitivity analysis: excl studies with industry employed authors, Outcome 1 SBP.

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Analysis 7.2

Comparison 7 Sensitivity analysis: excl studies with industry employed authors, Outcome 2 DBP.

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Summary of findings for the main comparison. Flavanol‐rich cocoa products for blood pressure

Flavanol‐rich cocoa products for blood pressure
Patient or population: adults with or without hypertension Settings: Primary healthcare practice, community Intervention: flavanol‐rich cocoa products versus control
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	No of Participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Control	Flavanol‐rich cocoa products
Systolic blood pressure clinical digital sphygmomanometer Follow‐up: mean 9 weeks	The mean systolic blood pressure ranged across control groups from 107 to 154 mm Hg	The mean systolic blood pressure in the intervention groups was 1.76 mmHg lower (3.09 to 0.43 lower)		1804 (35 trials with 40 treatment comparisons)	⊕⊕⊕⊕ moderate^1,2,3,4
Diastolic blood pressure clinical digital sphygmomanometer Follow‐up: mean 9 weeks	The mean diastolic blood pressure ranged across control groups from 66 to 92 mm Hg	The mean diastolic blood pressure in the intervention groups was 1.76 mmHg lower (2.57 to 0.94 lower)		1772 (34 trials with 39 treatment comparisons)	⊕⊕⊕⊕ moderate^1,2,3,4
Withdrawals due to adverse effects	8 trials reported no withdrawals and no adverse effects. 9 trials reported adverse effects, including gastrointestinal complaints (cocoa groups: n = 8/760 (1%), control groups: n = 3/754 (0.4%)); dislike of the trial product (cocoa: n = 4/760; control: n = 1/754), headache (cocoa: n = 2/760; control: n = 1/754), and jitteriness (cocoa: n = 1/760, control: n = 0/754).			1514 (31 trials) reported on withdrawals and adverse effects	⊕⊕⊕⊕ moderate^1,2,3,4
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval;
GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate.
^1.Downgraded to moderate quality due to high heterogeneity which cannot be explained by subgroup analyses. SBP/DBP: I² = 87%/78%. ^2.Good quality across 40 treatment comparisons. Only 5 trials (12.5%) had 2 items at high risk of bias, 19 trials (47.5%) had 1 item at high risk of bias, and 16 trials (40%) had no items at high risk of bias. 17 trials were unblinded or single‐blinded. 7 industry‐sponsored trials had authors employed by industry. Only 4 trials (10%) had more than 20% attrition. We explored influence of trials with items at high risk of bias by subgroup and sensitivity analysis. ^3.Statistically significant SBP: P = 0.009; DBP: P < 0.001. ^4.Sensitivity analysis excluding treatment comparisons (n = 7) with authors employed by trials sponsoring industry revealed reduced effect size and statistical significance.

Summary of findings for the main comparison. Flavanol‐rich cocoa products for blood pressure

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Table 1. Adverse events & withdrawals

Study	Study design	Participants Cocoa/ Control	Withdrawn Cocoa/Control	Reasons for withdrawal including adverse effects Cocoa/Control
Taubert 2003	C	13/13	0/0	‐
Murphy 2003	P	13/15	3 in total	Family illness (2) Non‐compliance in final week (1)
Engler 2004	P	11/10	0/0	‐
Fraga 2005	C	14/14	1/0	No reason given
Grassi 2005a	C	15/15	0/0	‐
Grassi 2005b	C	20/20	0/0	‐
Taubert 2007	P	22/22	0/0	‐
Crews 2008	P	45/45	6/5	Gastrointestinal upset/headache/cold sweat (2/1) Bronchitis (1/0) Jitteriness/increased energy (1/0) Atrial arrhythmia/medication change (1/0) Dislike of study product (1/1) Family illness (0/1) Unspecified reason (0/1) No adherence to trial regimen (0/1)
Grassi 2008	C	19/19	0/0	‐
Muniyappa 2008	C	20/20	5/4	Lost to follow‐up (0/1) Discontinued intervention (4/2) due to Intolerance to treatment, family emergencies, personal problems excluded from analysis (1/1)
Davison 2008a	P	12/11	7 in total	Time restrictions, personal circumstances (14) Non‐compliance (exercise or diet) (2)
Davison 2008b	P	13/13	5 in total
Al‐Faris 2008	P	30/29	0/0	‐
Shiina 2009	P	20/19	0/0	‐
Ried 2009	P	11/10	2/2	Study product unpalatable (2/0) Gastrointestinal upset (0/1) Illness unrelated to study (0/1)
Monagas 2009	C	42/42	0/0	Constipation (resolved with fibre intake)
Bogaard 2010	C	41/41	3 in total	Nausea (1) Headache (1) Arrythmia unrelated (1) Laxative effect (12/2) – did not withdraw
Heiss 2010	C	16/16	3 in total	Did not come to first visit
Davison 2010	P	13/14	7 in total	Mild gastric symptoms (1) Non‐compliance with study protocol (1) Withdrew due to personal circumstances (5)
Njike 2011	C	38/38	7 in total	Non‐compliance with study protocol (1) Withdrew for personal reasons (6)
Almoosawi 2012a	C	21/21	1/1	Personal reasons unrelated to study
Desideri 2012	P	30/30	0/1	Gastric discomfort (1)
Khan 2012	C	42/42	1/0	Constipation
Mogollon 2013	P	22/20	1/1	Unrelated to study (1)/headache (1)
Neufingerl 2013	P	10/10	1/1	Nausea (1)/unrelated (1)
Sorond 2013	P	29/29	1/1	No details provided
Esser 2014	C	41/41	3 in total	Medical reasons (1), disliked chocolate (1), poor compliance (1)
Ibero‐Baraibar 2014	P	24/23	2/1	Personal reason (2), poor compliance (1)
Nickols‐Richardson 2014	P	30/30	0/0	None
Sarria 2014 (a)	C	24/24 20/20	?	No information given
Heiss 2015 (a)	P	11/11 10/10	0/0	None
Massee 2015	P	19/19	1/1	Personal reasons (1)
Rostami 2015	P	32/28	2/6	No information given
Koli 2015	C	22/22	0/0	No side effects reported
Mastroiacovo 2015	P	30/30	1/0	Personal reasons (1) No side effects reported (1 gastric discomfort in IF (intermediate flavanol) group not included in this meta‐analysis)
Rull 2015	C	21/21	11	No details provided
Sansone 2015	P	50/50	?	No information given
C:Cross‐over P: Parallel

Table 1. Adverse events & withdrawals

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Comparison 1. Effect of cocoa on BP

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 SBP Show forest plot	40	1804	Mean Difference (Random, 95% CI)	‐1.76 [‐3.09, ‐0.43]

2 DBP Show forest plot	39	1772	Mean Difference (Random, 95% CI)	‐1.76 [‐2.57, ‐0.94]

Comparison 1. Effect of cocoa on BP

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Comparison 2. Hypertensive or normotensive participants

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 SBP Show forest plot	40	1804	Mean Difference (Random, 95% CI)	‐1.76 [‐3.09, ‐0.43]

1.1 Hypertensive (> 140 mmHg)	9	401	Mean Difference (Random, 95% CI)	‐4.00 [‐6.71, ‐1.30]
1.2 Prehypertensive (> 130 mmHg)	8	340	Mean Difference (Random, 95% CI)	‐2.43 [‐5.02, 0.17]
1.3 Normotensive	23	1063	Mean Difference (Random, 95% CI)	‐0.65 [‐2.13, 0.84]
2 DBP Show forest plot	39	1772	Mean Difference (Random, 95% CI)	‐1.76 [‐2.57, ‐0.94]

2.1 (Pre)hypertensive (> 80 mmHg)	16	735	Mean Difference (Random, 95% CI)	‐1.98 [‐3.38, ‐0.57]
2.2 Normotensive (< 80 mmHg)	23	1037	Mean Difference (Random, 95% CI)	‐1.57 [‐2.54, ‐0.61]

Comparison 2. Hypertensive or normotensive participants

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Comparison 3. Flavanol‐free or low flavanol control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 SBP Show forest plot	40	1804	Mean Difference (Random, 95% CI)	‐1.76 [‐3.09, ‐0.43]

1.1 Flavanol‐free control	26	1116	Mean Difference (Random, 95% CI)	‐1.80 [‐3.46, ‐0.13]
1.2 Low flavanol control	14	688	Mean Difference (Random, 95% CI)	‐1.67 [‐4.03, 0.69]
2 DBP Show forest plot	39	1772	Mean Difference (Random, 95% CI)	‐1.76 [‐2.57, ‐0.94]

2.1 Flavanol‐free control	26	1116	Mean Difference (Random, 95% CI)	‐1.82 [‐2.95, ‐0.68]
2.2 Low flavanol control	13	656	Mean Difference (Random, 95% CI)	‐1.62 [‐2.56, ‐0.68]

Comparison 3. Flavanol‐free or low flavanol control

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Comparison 4. Double‐blinded or unblinded/single‐blinded

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 SBP Show forest plot	40	1804	Mean Difference (Random, 95% CI)	‐1.76 [‐3.09, ‐0.43]

1.1 Double‐blind	23	1059	Mean Difference (Random, 95% CI)	‐0.95 [‐2.77, 0.86]
1.2 Unblinded, single‐blinded	17	745	Mean Difference (Random, 95% CI)	‐2.71 [‐4.66, ‐0.76]
2 DBP Show forest plot	39	1772	Mean Difference (Random, 95% CI)	‐1.76 [‐2.57, ‐0.94]

2.1 Double‐blind	21	927	Mean Difference (Random, 95% CI)	‐1.16 [‐2.05, ‐0.27]
2.2 Unblinded, single‐blinded	18	845	Mean Difference (Random, 95% CI)	‐2.33 [‐3.62, ‐1.04]

Comparison 4. Double‐blinded or unblinded/single‐blinded

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Comparison 5. Participants ≥50 or <50 years old

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 SBP Show forest plot	38	1762	Mean Difference (Random, 95% CI)	‐1.36 [‐2.79, 0.06]

1.1 < 50 years	18	726	Mean Difference (Random, 95% CI)	‐1.79 [‐4.05, 0.48]
1.2 ≥ 50 years	20	1036	Mean Difference (Random, 95% CI)	‐0.98 [‐2.87, 0.90]
2 DBP Show forest plot	37	1688	Mean Difference (Random, 95% CI)	‐1.62 [‐2.49, ‐0.76]

2.1 < 50 years	18	726	Mean Difference (Random, 95% CI)	‐2.01 [‐3.45, ‐0.58]
2.2 ≥ 50 years	19	962	Mean Difference (Random, 95% CI)	‐1.28 [‐2.32, ‐0.24]

Comparison 5. Participants ≥50 or <50 years old

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Comparison 6. Study duration 2 ‐ 4 weeks or > 4 weeks

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 SBP Show forest plot	40	1804	Mean Difference (Random, 95% CI)	‐1.76 [‐3.09, ‐0.43]

1.1 2 ‐ 4 week duration	24	1043	Mean Difference (Random, 95% CI)	‐1.37 [‐3.23, 0.49]
1.2 > 4 week duration	16	761	Mean Difference (Random, 95% CI)	‐2.37 [‐4.30, ‐0.44]
2 DBP Show forest plot	39	1772	Mean Difference (Random, 95% CI)	‐1.76 [‐2.57, ‐0.94]

2.1 2 ‐ 4 week duration	23	1011	Mean Difference (Random, 95% CI)	‐1.55 [‐2.71, ‐0.39]
2.2 > 4 week duration	16	761	Mean Difference (Random, 95% CI)	‐2.04 [‐3.18, ‐0.91]

Comparison 6. Study duration 2 ‐ 4 weeks or > 4 weeks

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Comparison 7. Sensitivity analysis: excl studies with industry employed authors

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 SBP Show forest plot	33	1482	Mean Difference (Random, 95% CI)	‐1.08 [‐2.60, 0.43]

2 DBP Show forest plot	33	1482	Mean Difference (Random, 95% CI)	‐1.37 [‐2.31, ‐0.43]

Comparison 7. Sensitivity analysis: excl studies with industry employed authors

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