Studies provide further evidence that dietary choices can be important to maintain brain health.
Boston: Eating leafy greens, dark orange or red vegetables and berry fruits, and drinking orange juice may lower risk of memory loss over time, especially in men, a study has found.
The study, published in the journal Neurology, looked at 27,842 men with an average age of 51 who were all health professionals.
Participants filled out questionnaires about how many servings of fruits, vegetables and other foods they had each day at the beginning of the study and then every four years for 20 years.
A serving of fruit is considered one cup of fruit or half a cup of fruit juice.
A serving of vegetables is considered one cup of raw vegetables or two cups of leafy greens.
"One of the most important factors in this study is that we were able to research and track such a large group of men over a 20-year period of time, allowing for very telling results," said Changzheng Yuan, from Harvard T H Chan School of Public Health in the US.
"Our studies provide further evidence dietary choices can be important to maintain your brain health," said Yuan.
Participants also took subjective tests of their thinking and memory skills at least four years before the end of the study, when they were an average age of 73.
The test is designed to detect changes that people can notice in how well they are remembering things before those changes would be detected by objective cognitive tests.
Changes in memory reported by the participants would be considered precursors to mild cognitive impairment.
A total of 55 per cent of the participants had good thinking and memory skills, 38 per cent had moderate skills, and seven per cent had poor thinking and memory skills.
The participants were divided into five groups based on their fruit and vegetable consumption.
For vegetables, the highest group ate about six servings per day, compared to about two servings for the lowest group. For fruits, the top group ate about three servings per day, compared to half a serving for the bottom group.
The men who consumed the most vegetables were 34 per cent less likely to develop poor thinking skills than the men who consumed the least amount of vegetables.
A total of 6.6 per cent of men in the top group developed poor cognitive function, compared to 7.9 per cent of men in the bottom group.
The men who drank orange juice every day were 47 per cent less likely to develop poor thinking skills than the men who drank less than one serving per month.
This association was mainly observed for regular consumption of orange juice among the oldest men, researchers said.
A total of 6.9 per cent of men who drank orange juice every day developed poor cognitive function, compared to 8.4 per cent of men who drank orange juice less than once a month.
The researchers also found that people who ate larger amounts of fruits and vegetables 20 years earlier were less likely to develop thinking and memory problems, whether or not they kept eating larger amounts of fruits and vegetables about six years before the memory test.