It’s been hailed as a mood enhancer and now eating dark chocolate is also being credited with helping your eyesight.

But before you crack open the family-size block, US researchers caution the improvement in visual clarity is only slight.

The consumption of dark chocolate high in cacao flavanols – a powerful antioxidant – is linked to short-term improvement in blood flow, mood, and cognition.

To investigate whether the positive effects flowed on to human vision, researchers at the University of the Incarnate Word Rosenberg School of Optometry in San Antonio conducted a randomised trial comparing the impact on visual performance of dark or a milk chocolate.

Participants were randomly given either a 40 gram dark chocolate bar containing 72 per cent cacao or a milk chocolate bar to eat.

They were then required to sit a vision test approximately 1.75 hours after ingestion.


Among the 30 participants, nine men and 21 women of an average age of 26, small-letter contrast sensitivity was significantly higher after consumption of dark chocolate compared to milk chocolate.

“Contrast sensitivity and visual acuity were significantly higher two hours after consumption of a dark chocolate bar compared with a milk chocolate bar, but the duration of these effects and their influence in real-world performance await further testing,” the authors wrote.

The researchers could not say how long the benefit would last or identify the biological mechanism for the result.

One possible explanation could be an increase in cerebral blood flow and oxygen to the eye, the researchers said.

The study is published in journal JAMA Opthalmology.



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