During the Great Depression, a 33% increase in spinach consumption was widely attributed to Popeye’s popularity and his famous conviction that spinach will make him strong enough to beat up anyone.

As it turns out, the cartoon’s link between spinach and rapidly expanding muscles had its roots in a scientific mistake: due to a misplaced decimal point in an 1870 medical journal, many people in the Thirties believed spinach held 10 times more iron than it really did.

So, if the green stuff doesn’t miraculously make you stronger, does it do any other magic?

Actually, yes: consuming spinach and kale can keep you smarter for longer, says science.

Researchers from the University of Illinois have released a study on the benefits of lutein, a substance in kale and spinach that the human body can’t manufacture.

The study, which looked at 60 adults aged 25 to 45, found that middle-aged participants with higher levels of lutein – a nutrient found in green leafy vegetables such as spinach and kale, as well as avocados and eggs – had neural responses that were more on par with younger individuals than with their peers. In other words, their brains functioned like young brains.

Lutein accumulates in brain tissue and eyes. The researchers measured lutein levels in participants’ eyes by having them look into a scope and respond to a flickering light. Then, using electrodes on the scalp, the researchers measured neural activity in the brain while the participants performed a task that tested attention.

Anne Walk, the lead author of the paper, said: “The neuro-electrical signature of older participants with higher levels of lutein looked much more like their younger counterparts than their peers with less lutein. Lutein appears to have some protective role, since the data suggest that those with more lutein were able to engage more cognitive resources to complete the task.

“We want to understand how diet impacts cognition throughout the lifespan. If lutein can protect against decline, we should encourage people to consume lutein-rich foods at a point in their lives when it has maximum benefit.”

What’s next?

The researchers plan to run intervention trials, to see if increased dietary consumption of lutein will increase lutein in the eye, and how closely those levels relate to changes in cognitive performance. They also intent to learn more about lutein’s influence on learning and memory.

So, this is the deal:

Eat up your spinach and kale so you can stay bright till deep in your old age – and remember to  give your kids some too!