The research examined 27,842 men, all health professionals, with an average age of 51.
Participants were asked to fill 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.
The 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.
Over time, the researchers discovered that the men who ate the most fruit each day were less likely to develop poor thinking skills.
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.
“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 study author Changzheng Yuan of Harvard T.H. Chan School of Public Health in Boston.
“Our studies provide further evidence dietary choices can be important to maintain your brain health.”
The researchers noted that the study was only able to establish an association between dietary choices and lower memory loss.