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Mary Lott, Alicia Johns, Joshua Oman, Julia Slocomb, Michael Herr, Robert Gabbay, David Quillen, Kerstin Bettermann; Short-term Effects of Cocoa on Retinal Reactivity in Individuals with Prediabetes and Type 2 Diabetes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4644.
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To examine the effects of short term cocoa flavanol ingestion (i.e. seven days) on retinal blood vessel endothelial function in individuals at different disease stages of diabetes. We hypothesize that short term ingestion of high flavanol cocoa compared to a placebo will be associated with enhanced vascular reactivity. We also hypothesize that the degree of vascular response to cocoa will likely be greater in groups without structural vessel damage (i.e. controls and prediabetics).
Individuals with prediabetes (n=5), type 2 diabetes (n=5) and healthy controls (n=5) were recruited. Subjects’ ages ranged from 40 to 71 years. Using a double blinded, randomized crossover design, this pilot study had subjects consume a high flavanol cocoa (13 grams of pure cocoa) vs. placebo (0 grams of pure cocoa) drink for seven days with a one week washout period. Retinal blood vessel vasoreactivity was measured using a flickering light stimulus (Dynamic Vessel Analyzer, Imedos, Jena, Germany). Fasting glucose and insulin were also measured.
High flavanol cocoa ingestion led to an increase in peak retinal vein vasodilation to flickering light in prediabetic individuals (pre 2.32% ± 0.59% vs. post 4.52% ± 0.75%, P=0.04). Similar effects were shown in the retinal artery but did not reach significance (pre 1.71% ± 0.82% vs. post 3.18% ± 0.80%, P=0.24). There was a trend for a small improvement the retinal vein with the placebo drink (pre 2.34% ± 0.60% vs. post 3.08% ± 0.33%, P=0.08) without any change in the artery diameter (pre 1.45% ± 0.72% vs. post 1.59% ± 0.29%, P=0.82). There were no significant diameter changes in the control or type 2 diabetic groups to high flavanol cocoa or placebo. Although the drinks did not alter fasting glucose and insulin in the prediabetic or control groups, fasting glucose slightly increased in individuals with type 2 diabetes (135 to 154 mg/dl; P=0.01).
Short term high flavanol cocoa appears to improve retinal endothelial function in individuals with prediabetes within one week. However, a larger sample size is needed to confirm these findings and a longer duration to potentially see improvements in type 2 diabetic individuals.
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