New research suggests dark chocolate could sharpen vision. The randomised, single-masked crossover design study by the University of the Incarnate Word in Texas, assessed 30 healthy-eyed participants’ visual acuity after eating dark or milk chocolate. Those who ate dark chocolate had a small, but measurable temporary improvement seeing low- and high-contrast targets, compared with those who ate milk chocolate, possibly due to increased blood flow, said study lead Dr Jeff Rabin.

It’s known that eating dark chocolate can improve blood flow, mood and cognition in the short term, but now a link to visual performance has been established. The participants each ate dark and milk chocolate in separate sessions, and within-participant paired comparisons were used to assess outcomes at the Rosenberg School of Optometry. Visual acuity (in logMAR units) and large- and small-letter contrast sensitivity were measured 1.75 hours after consumption.

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.