Regularly eating spinach and other leafy greens such as kale could help your brain stay sharper for longer.
Men and women monitored in a recent study who had just one or two helpings a day allegedly had the brainpower of people 11 years younger.
The US research team added that something as simple as eating more greens could even help protect against the onset of Alzheimer’s.
The researchers, from Rush University in Chicago, quizzed 950 men and women about their diet.
The volunteers, who had an average age of 81, then did a range of mental tests every year for up to ten years.
The brains of those who ate leafy green vegetables aged more slowly, the team found, and the effect was significant, with the slowing of cognitive decline equivalent to 11 years, on average.
It is thought that vitamin K, folate or vitamin B9, and the natural colourings lutein and beta-carotene were behind the effects.
Lead researcher Dr Martha Morris said: "Losing one’s memory or cognitive abilities is one of the biggest fears for people as they get older.
"Since declining cognitive ability is central to Alzheimer’s disease and dementias, increasing consumption of green leafy vegetables could offer a very simple, affordable and non-invasive way of potentially protecting your brain.
"With baby boomers approaching old age, there is huge public demand for lifestyle behaviours that can ward off loss of memory and other cognitive abilities with age.
"Our study provides evidence that eating green leafy vegetables and other foods rich in vitamin K, lutein and beta-carotene can help to keep the brain healthy to preserve functioning."
Morris presented the findings at the annual meeting of the American Society for Nutrition in Boston, USA, on Monday (30 March).
Research presented at meetings is usually considered preliminary until published in a peer-reviewed medical journal.