After assessing the dietary habits and mental ability of more than 950 older adults over five years, the researchers found that in regular consumers of green vegetables the rate of cognitive decline was significantly reduced.

The analysis showed that those who had consumed one or two portions a day of green leafy vegetables such as spinach, kale and chard had the same cognitive abilities as a person more than a decade younger; a result that was not achieved by people who did not consume green leafy vegetables. The findings took into account the gender, age, education, smoking history, physical activity and increased Alzheimer's risk (family history) of the individuals monitored.

According to Martha Clare Morris of Rush University Medical Center in Chicago, lead author of the study funded by the National Institutes of Health, the brain benefits derived from consuming these vegetables depend on certain key nutrients, such as lutein, folic acid and beta-carotene, but in particular on the presence of vitamin K.

"Our analysis identified very significant associations between brain health and vitamin K: this is the first study on the subject. Moreover, only a limited number of other studies have investigated the links between lutein, folate and beta-carotene and slower cognitive decline," said Morris.

Vitamin K is already known for its effectiveness in cases of haemorrhage, liver disorders, colitis, urticaria and in antibiotic treatments that destroy the intestinal microbial flora. It is a natural anti-inflammatory. A deficiency of it promotes haemorrhaging and causes delays in blood clotting. In addition to dark green leafy vegetables, mustard greens, artichokes and yogurt are also sources of vitamin K.