Middle-aged men who eat lots of fruits and vegetables may be lowering their odds of cognitive problems as they get on in years, compared to peers who don't consume these foods very often, a US study suggests.
Researchers followed almost 28,000 men for two decades starting when they were 51 years old, on average. Every four years, participants answered questionnaires about their consumption of fruits, vegetables and other foods. They also took tests of thinking and memory skills when they were 73 years old, on average.
Based on those test results, researchers found that by the time they were in their later 70s, men who had regularly eaten the most vegetables over the previous decades were 17 per cent less likely to have moderate cognitive problems and 34 per cent less likely to have more extensive cognitive deficits than men whose diets contained the least produce.
Fruit consumption, overall, didn't appear to influence the risk of moderate cognitive problems, but men who drank more orange juice were 47 per cent less likely to have extensive cognitive deficits than men who drank the least, the researchers note in the journal Neurology.
"Long-term intake of vegetables (eg., green leafy, dark orange and red vegetables), fruit (eg. berry fruits) and fruit juice (eg. orange juice) may be beneficial for late-life subjective cognitive function among U.S. men," lead study author Changzheng Yuan of the Harvard T.H. Chan School of Public Health in Boston said in an email.
Men should still go easy on the orange juice, however.
"The protective role of regular consumption of fruit juice was mainly observed among the oldest men," Yuan said.
"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 per cent had moderate skills and 7 per cent 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 per cent of men who ate the most vegetables developed poor cognitive function, compared with 7.9 per cent of men who ate the least.
And 6.9 per cent of men who drank orange juice every day developed poor cognitive function, compared with 8.4 per cent of men who drank orange juice less than once a month.
The study wasn't designed to prove whether or how fruit or vegetable consumption directly impacts memory loss. Researchers also lacked data on participants' memory and thinking skills before the tests and couldn't assess how diet might have influenced changes over time.
"Fruits and vegetables are rich in vitamins and nutrients, including antioxidants, that can help protect the brain from oxidative stress and preserve healthy vascular function that is important for cognitive health," said Hannah Gardener, a researcher with the University of Miami Miller School of Medicine.
"Fruit and vegetable consumption may be a piece of the puzzle to maintaining cognitive health and should be viewed in conjunction with other behaviors believed to support cognitive health, such as overall adherence to a Mediterranean diet, physical activity, healthy sleep, medication adherence, nonsmoking, mental stimulation and education," Gardener, who wasn't involved in the study, said by email.
