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In the news: Dark Chocolate May Support Some Measures of Vision and Attention

Dark Chocolate: More Than a Sweet Delight

If you’re already a fan of dark chocolate, you probably know that this sweet treat also brings the promise of health benefits. Dark chocolate or cocoa consumption has been linked to a lower risk of heart disease, for example, most likely due to reducing blood pressure and inflammation. Compared with milk chocolate, the dark version is far more abundant in flavanols – a type of bioflavonoid that has been shown to promote the production of artery-relaxing nitric oxide.

Two recent studies have explored the effects of cocoa or dark chocolate on vision and cognitive function. The findings, though preliminary, suggest that these flavanol-rich foods could help support visual function and some aspects of cognitive function as well.

Dark Chocolate May Support Eyesight

While studies have shown that dark chocolate can improve blood flow, mood, and cognition in the short term, not much is known about the possible effects of dark chocolate on visual performance. To learn more, university researchers compared the effects of milk vs. dark chocolate on visual testing in 30 healthy adults without eye disease (1).

Every participant ate a dark and a milk chocolate bar in separate sessions, with visual tests conducted about 1 ¾ hours after consumption. The dark chocolate bar (47 g, 72% cacao) contained 316 mg of flavanols, while the milk chocolate bar (40 g, 12.4 g milk chocolate cocoa) contained 40 mg of flavanols, about 8 times less than the dark bar.

The researchers found that small-letter contrast sensitivity was higher after the dark chocolate bar was consumed compared to the milk chocolate bar. Large-letter contrast sensitivity was slightly higher as well. Contrast sensitivity is the ability to distinguish an object – in this case small and large letters – from its background.

Visual acuity – clarity or sharpness of vision – was also slightly enhanced after the dark chocolate was eaten.

When the results from all tests were combined, there were significant improvements after dark vs. milk chocolate consumption.

The authors concluded that further testing is needed to understand how these effects will influence ‘real-world’ visual performance and how long the effects may last. They also theorize that the improvements seen may be due to flavanols increasing blood flow to bring more oxygen and nutrients to eye tissues.

Cocoa Flavanols May Support Attention

A number of previous studies have sought to understand if and how dark chocolate or cocoa might affect various aspects of brain function and mood. In the current investigation, researchers explored the effects of cocoa flavanols on spatial and temporal attention.

To study this question, 48 university students were enrolled in the trial with each of them completing experimental tasks in separate sessions: at baseline, after taking a placebo, after supplemental low dose flavanols (373 mg) and high dose flavanols (747 mg) (2).

Neither dose of flavanols influenced the outcome of all the tests, but both the low and high dose flavanols improved the students’ visual search efficiency – a measure of attention that requires determining whether an object is present or absent in a changing visual array of items, including items meant to distract the participant. Reaction times on this test were significantly faster after flavanol consumption.

The findings suggest that flavanols may affect some aspects of attention, but not others. More research is needed to learn about the influence of dark chocolate and natural cocoa on brain function. In the meantime, treat yourself to a dark chocolate bar – it’s good for the heart, and perhaps and the mind, mood and vision too.  

References

1. Rabin JC, et al. Effects of milk vs. dark chocolate consumption on visual acuity and contrast sensitivity within 2 hours: A randomized clinical trial. JAMA Ophthalmol 136:678-681, 2018.
2. Karabay A, et al. The acute effects of cocoa flavanols on temporal and spatial attention. Psychopharmacol. 235: 1497–1511, 2018.