Drinking orange juice and eating leafy greens may be linked to a reduction in memory loss over time in men, according to a new study published online in the journal Neurology.
“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, ScD, 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 study involved 27,842 men (average age of 51) who were all health professionals, such as dentists, optometrists, and veterinarians. 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 a half cup of fruit juice. A serving of vegetables is considered one cup of raw vegetables or two cups of leafy greens.
Volunteers completed a subjective test of cognition at least four years before the end of the study, when they were an average age of 73. The test was designed to identify any noticeable changes in memory 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.
The six questions include “Do you have more trouble than usual remembering a short list of items, such as a shopping list?” and “Do you have more trouble than usual following a group conversation or a plot in a TV program due to your memory?”
A total of 55 percent of the participants had good thinking and memory skills, 38 percent had moderate skills, and 7 percent had poor thinking and memory skills.
The participants were split 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.
Participants who ate the most vegetables were 34 percent less likely to develop poor thinking skills than the men who ate the least amount of vegetables. A total of 6.6 percent of men in the top group developed poor cognitive function, compared to 7.9 percent of men in the bottom group.
Men who drank orange juice every day were 47 percent less likely to develop poor thinking skills than those who drank less than one serving per month. This link was mainly observed for regular consumption of orange juice among the oldest men.
A total of 6.9 percent of men who drank orange juice every day developed poor cognitive function, compared to 8.4 percent of men who drank orange juice less than once a month. This difference in risk was adjusted for age but not adjusted for other factors related to reported changes in memory.
Men who ate the most fruit each day were less likely to develop poor thinking skills, but that association was weakened after researchers adjusted for other dietary factors that could affect the results, such as consumption of vegetables, fruit juice, refined grains, legumes and dairy products.
The findings also show that men 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.
The study does not show a direct cause and effect relationship between eating fruits and vegetables and a reduction in memory loss; it only shows a link between them.
A limitation of the research was that participants’ memory and thinking skills were not measured at the onset of the study to see how they changed over the course of the study. However, because all participants completed professional training, they can be assumed to have started with relatively high cognitive function in early adult life.
Further, the participants were all male health professionals; thus, the results may not apply to women and other groups of men.
Source: American Academy of Neurology