“Since fruit juice is usually high in calories from concentrated fruit sugars, it’s generally best to consume no more than a small glass (four to six ounces) per day,” Yuan added.
To assess the impact of eating habits in middle age on cognitive function later in life, researchers administered questionnaires designed to measure memory and reasoning skills.
Among other things, they asked whether men had trouble remembering things like recent events or items on shopping lists; whether they had trouble following instructions or keeping track of plots on television shows; and whether they got lost on familiar streets.
In these tests, 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.
Researchers sorted participants into five groups based on their fruit and vegetable consumption. The group with the highest vegetable consumption ate about six servings per day, compared to about two servings for the group with the lowest intake. For fruits, the top group ate about three servings per day, compared to half a serving in the bottom group.
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.
Overall, 6.6 percent of men who ate the most vegetables developed poor cognitive function, compared with 7.9 percent of men who ate the least.
And 6.9 percent of men who drank orange juice every day developed poor cognitive function, compared with 8.4 percent of men who drank orange juice less than once a month.