Effects of Flavanol-Rich Dark Chocolate on Visual Function and Retinal Perfusion Measured With Optical Coherence Tomography Angiography: A Randomized Clinical Trial

Abstract

Importance: A recently reported randomized clinical trial suggested beneficial effects of vasodilating flavanols in dark chocolate on visual function without objective quantification of retinal perfusion.

Objective: To assess the effects of dark chocolate flavanols on subjective visual function and retinal perfusion objectively quantified on optical coherence tomography (OCT) angiography.

Design, setting, and participants: This randomized, masked double-blind crossover clinical trial analyzed 22 healthy participants at the Department of Ophthalmology, Ludwig-Maximilians-University Munich, Germany, in July 2018. Analysis was intention to treat. Analysis began in July 2018.

Interventions: Participants were randomized to consume 20 g of dark chocolate containing 400 mg of flavanols or 7.5 g of milk chocolate. Two hours later, visual function and retinal perfusion on OCT angiography were evaluated. Systemic blood pressure was measured to rule out artifacts on OCT angiography.

Main outcomes and measures: The primary end point was macular retinal perfusion quantified as vessel density on OCT angiography. The secondary end point was subjective visual function (Early Treatment Diabetic Retinopathy Study visual acuity, Pelli-Robson chart, and Mars chart contrast sensitivity).

Results: All 22 participants (13 women [59.1%]; mean [SD] age, 27.3 [11.1] years) completed the trial. No relevant differences in baseline parameters between groups were identified. No change in the primary outcome measure, retinal perfusion, could be detected after consumption of dark vs milk chocolate (superficial plexus 48.0% vs 47.5%, treatment effect: -0.59 [95% CI, -2.68 to 1.50], P = .56; deep plexus 54.1% vs 54.0%, treatment effect: -1.14 [95% CI, -4.01 to 1.73], P = .42). No differences in changes in the secondary outcome parameters Early Treatment Diabetic Retinopathy Study visual acuity, Pelli-Robson chart, or Mars chart contrast sensitivity could be detected. Potentially confounding effects of changes in blood pressure were excluded.

Conclusions and relevance: In contrast to a previous similarly sized randomized clinical trial reporting beneficial effects on visual function, no short-term effects of flavanol-rich dark chocolate on automatically assessed retinal blood flow on OCT angiography or subjective visual function were observed in this study. As this small trial does not rule out the possibility of benefits, further trials with larger sample sizes would be needed to rule in or out possible long-term benefits confidently.

Trial registration: German Clinical Trials Register identifier: DRKS00015065.

Conflict of interest statement

Conflict of Interest Disclosures: Dr Siedlecki received previous speaker fees and travel expenses from Novartis Pharma GmbH, Carl Zeiss Meditec AG, Oculentis OSD Medical GmbH, and Pharm-Allergan GmbH and received personal consultation fees from Bayer AG. Nikolaus Luft received income from honoraria as a lecturer from Alcon Laboratories, Nidek Co Ltd, and CenterVue SpA. Dr Schworm received previous speaker fees and travel expenses from Novartis Pharma GmbH and Topcon. Dr Priglinger received previous speaker fees and/or travel expenses from Novartis Pharma GmbH, Oertli Instrumente AG, Bayer AG, Alcon Pharma GmbH, and Pharm-Allergan GmbH. No other disclosures were reported.

Figures

Figure 1.. Flow of Participants Through the Study

Figure 2.. Comparison of Effects of Dark Over Milk Chocolate on Primary and Secondary Outcome Measures

No treatment effect of dark chocolate (linear mixed model) could be observed on the secondary end points visual acuity as measured with Early Treatment Diabetic Retinopathy Study (ETDRS) letters (P = .09), Pelli-Robson chart contrast sensitivity (P = .21), and Mars chart contrast sensitivity (P = .83, data not shown). No treatment effect of dark chocolate could be observed on the primary end point retinal perfusion measured as vessel density on optical coherence tomography angiography in the central 3 mm of the posterior pole centered on the fovea (superficial plexus: P = .56, deep plexus: P = .42). Confounding effects of blood pressure on vessel density were ruled out as tertiary outcome measure (P = .21, data not shown). LogCS indicates logarithm of contrast sensitivity.