12 January - 20 June 2016

Eating fruits and vegetables and drinking orange may improve late-life subjective cognitive function

A study published in the journal Neurology has evaluated the “prospective association of long term intake of vegetables and fruits with late-life subjective cognitive function.”

A study published in the journal Neurology has evaluated the “prospective association of long term intake of vegetables and fruits with late-life subjective cognitive function.”  Fruit and vegetables are high in antioxidants and bioactive substances, however there have been inconsistent findings about their role in cognitive function with many studies being limited in size and some having limited periods of follow-up.

The current study by Yuan et al. involved 27,842 men with an average age of 51 who were all health professionals.  The participants completed dietary 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 questionnaire included 24 vegetable, 13 fruits items and 5 fruit juices. Subjective cognitive function was assessed twice.  The participants were asked 6 questions on changes in memory and cognition: do you have more trouble than usual remembering recent events? Do you have more trouble than usual remembering a short list of items such as a shopping list?  Do you have trouble remembering things from one second to the next?  Do you have any difficulty in understanding things or following spoken instructions?  Do you have more trouble than usual following a group conversation or a plot in a TV program due to your memory?  Do you have trouble finding your way around a familiar street?  When carrying out statistical analysis, the team also took into account lifestyle factors, medical history as well as age.

Yuan et al report that 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 divided into groups depending on how much fruit and vegetables they consumed. For vegetables, the highest group consumed about 6 servings per day, whilst the lowest group consumed 2 serving.  For fruit the high group consumed three servings per day, compared to half a serving for the bottom group.

The study found that “the average intakes of total vegetables, total fruits and total fruit juice were 3.5 servings/d, 1.7 serving/d and 0.8 serving/d respectively.”  Those who consumed the higher amounts of fruits and vegetables were found to be older, dentists and were physically active.  They also tended to take multivitamins, consume more fruit juice and total energy intake.  Again those with higher intake of fruit and fruits juices were dentists, non-smokers, have lower alcohol intake and engage more in physical activity.

The researchers found that the participants who drank orange juice every day were 47% less likely to develop poor thinking skills than the men who drank less than one serving per month. This association 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.

The 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 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.

The team conclude by stating that “our prospective findings relating to diet over 2 decades to subjective cognitive behaviour in later life support the hypothesis that higher long term intake of vegetables and fruits can have an important role in maintaining cognitive function.”  In a press release it states that “the study does not show that eating fruits and vegetables and drinking orange juice reduces memory loss; it only shows a relationship between them. “

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