Eat enough of this stuff and you’ll start seeing sound. And probably weigh an extra 4 kgs.

If the sky’s going to be foggy on your drive home tonight, eat a dark chocolate bar an hour before you leave work. The flavonols in dark chocolate might improve your eyesight in difficult, low-contrast conditions, according to a new study in Physiology and Behavior.

Researchers at the University of Reading in England found that participants’ vision improved by 17 percent in contrasting light conditions after they ate a dark chocolate bar compared to when they ate a white chocolate bar, which contained far less cocoa flavonols. The study participants also performed better at several brain function tests after eating dark chocolate.

One likely reason that dark chocolate gives your eyes a boost is because flaoanols help to aid bloodflow in the body, according to lead researcher David Field, Ph.D., a psychology lecturer at the University of Reading. “The retina uses a lot of energy, but doesn’t have a very good blood supply. So flavonols improve the peripheral bloodflow to the retina, and better bloodflow equals more energy. That’s one possible explanation,” Field says.

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The researchers tested the participants two hours after they ate each bar, but Field suggests that the effects from flavonol could kick in as soon as an hour after eating.

As for how much dark chocolate you should eat to see the effects, Field isn’t sure. He and his team used a chocolate bar that contained 773 milligrams of cocoa flavonols, but since most SA chocolate manufacturers don’t list flavonol content, it’s tough to gauge how much you need to actually eat in order to upgrade your eyesight.

Is chocolate the only source of these eyesight-boosting benefits? Not necessarily. Flavonols are a member of a larger group of phytochemicals called flavonoids. All of the flavonoids (also found in certain teas, fruits, and veggies) have similar, though not identical, effects to cocoa, Field says. More research would need to be done to see if other foods could have similar effects on eyesight.