The study, published in the journal Neurology, also suggested that older adults who ate at least one serving of leafy green vegetables had minds that were significantly ‘younger’ than their physical age.

Researchers at Rush University Medical Center in Chicago used a food questionnaire to survey 960 people with an average age of 81 who had not been diagnosed with any form of dementia. The participants were asked about how often they ate certain foods. Participants then had their thinking and memory skills tested every year and were followed for nearly 5 years.

On the basis of their answers to the food questionnaire – which assessed how often and how many half-cup servings they ate of either spinach, kale/collards/greens, or a one-cup serving of lettuce/salad – participants were divided into groups based on their consumption of green, leafy vegetables.

The group that ate the most servings averaged 1.3 servings per day, while the group with the fewest servings ate on average 0.1 servings per day.

Younger brains

Overall, the participants’ scores on the thinking and memory tests declined over time at a rate of 0.08 standardised units per year. Over 10 years of follow-up, the rate of decline for those who ate the most leafy greens was slower by 0.05 standardized units per year than the rate for those who ate the least leafy greens. This difference was equivalent to their minds being 11 years younger in age.

The results remained valid after accounting for other factors that could affect brain health, such as seafood and alcohol consumption, smoking, high blood pressure, obesity, education level and amount of physical and cognitive activities.

Study author Martha Clare Morris, ScD, a nutritional epidemiologist at Rush commented:  “The study results do not prove that eating green, leafy vegetables slows brain aging, but it does show an association. She adds: “There continue to be sharp increases in the percentage of people with dementia as the oldest age groups continue to grow in number. Effective strategies to prevent dementia are critically needed.”