Eating lots of fruits and vegetables and drinking orange juice through middle age and into late adulthood lowered the odds of self-reported poor cognitive function late in life in men, according to a prospective study published online in Neurology on November 21.
A team of researchers analyzed data on diet and self-reported cognitive decline of 27,842 men enrolled in the Health Professionals Follow-up Study in 1986, a 20-year prospective study of a group of professional men with an average age of 51.
The researchers assessed diet every four years between 1986 and 2002 and cognitive decline in 2008 and 2012. Every four years, participants completed a detailed questionnaire with 130 questions about diet, lifestyle, and medical history.
Participants recorded their intake of foods and beverages in the preceding year, with researchers categorizing the frequency of consumption of each food from "never or less than once per month" to "six or more times per day." Foods assessed included leafy green vegetables like spinach, kale, and lettuce; cruciferous vegetables such as broccoli, cauliflower, cabbage, sauerkraut, and Brussels sprouts; and carotenoid-rich food including tomatoes, tomato juice, tomato sauce, carrots, yams/sweet potatoes, and squash.
The researchers also tracked how much participants consumed of starchy and non-starchy vegetables, citrus fruits, berries, and other non-citrus fruits, as well as orange, grapefruit, and other juices.
On average, participants ate 3.5 servings a day of vegetables; 1.7 servings a day of fruit; and 0.8 servings a day of fruit juice. In the study, one fruit serving was defined as one cup of fruit or half a cup of fruit juice; a serving of vegetables was one cup of raw vegetables or two cups of leafy greens.
Participants also reported their cognitive function by answering six questions on the topic that ranged from "Do you have more trouble than usual remembering recent events?" to "Do you have trouble finding your way around familiar streets?"
Every "yes" received one point. Researchers categorized the scores as good cognition (0 points), moderate cognition (0.5–2.5 points), and poor cognition (3–6 points).
During the time of the cognitive assessment, the participants were an average age of 73; 54.7 percent reported good cognitive function, 38 percent reported moderate function, and 7.3 percent reported poor function.
Total vegetables, total fruits, and total fruit juice intake was significantly associated with a lower risk of moderate and poor scores on the cognitive questionnaire after controlling for age.
Men who ate the most fruit each day were least likely to have a poor cognitive score. However, this effect was weakened when the researchers accounted for the effect of other foods.
Men who ate an average of 5.7 servings of vegetables per day had 34 percent lower odds for a poor cognitive score, compared to those who ate an average of 1.7 servings.
Overall, 6.6 percent of men who consumed the most veggies developed poor cognitive function, compared with 7.9 percent of men who consumed the least.
Among men who drank orange juice, 6.9 percent who drank it every day scored poorly on cognitive function compared with 8.9 percent who drank it once a month or less. This association was strongest among older men.
Overall, eating more fruits and vegetables at the start of the study was associated with a lower likelihood of having a poor cognitive score approximately 20 years later.
Although the study found a link between consuming lots of fruits, vegetables, and fruit drinks and less cognitive decline, it did not prove that greater consumption leads to better brain health. Other factors could have influenced the findings.
Moreover, cognitive function was based on a self-reported assessment and not tested at baseline. The researchers assumed since all participants completed professional training, they started with relatively high cognitive function in early adult life.
Lastly, the study only focused on male health professionals, which limits the generalizability of these findings to other population groups, such as women.
The findings warrant further research to investigate the link between a long-term diet of fruits, vegetables, and orange juice, and cognitive function.