Sometimes scientists tell us things that we're fairly certain we already believe. Still, it's always nice to know that what we believe to be true is in fact true. A group of scientists in France investigated whether eating fruits and vegetables for thirteen years (!) would actually protect against a decline in cognitive abilities that humans commonly experience with normal aging. It does, and this is how they proved it.
The study began with a very large group of adults, over 6800; however, only 2500 finished the study by adequately completing all the dietary and cognitive evaluations. The subjects were between the ages of 45 and 60 years old at the beginning of the thirteen year study and each was required to maintain careful and detailed records of their daily diets. The subjects were evaluated at the beginning and end of the study for a variety of cognitive abilities, including verbal memory and higher executive functions such as decision-making and mental flexibility, among many other tests. Their results were published in the November 2011 issue of The American Journal of Clinical Nutrition. There is good news and bad news.
First of all, their diets were composed of a variety of fruits and vegetables, but specifically excluded potatoes, legumes and dried fruits (they each introduce specific complications that might interfere with the outcome). The adults were divided into the folate-rich diets containing both fruits and vegetables, the beta-carotene-rich diets containing both fruits and vegetables, the vitamin C-rich diets of both fruits and vegetables, and the vitamin E diets containing both fruits and vegetables. The individual consumption of specific nutrients, i.e. folate, beta-carotene, and vitamins C and E were also monitored. The subjects were allowed to choose how much of each diet they wished to consume each day; therefore, daily intakes of each nutrient varied. This was allowed in order to more closely reproduce how most of us actually select our daily intakes. At the end of the study, this is what they found.
Eating fruits and vegetables have differential and significant beneficial effects on different aspects of brain function. When the specific diets were examined more closely diets that consisted of only fruits or diets with vitamins-C & E rich fruits and vegetables selectively benefited only verbal memory scores. This test involved being told to remember 48 different words and then recalling them after a delay with distractions. If this sounds like your job then you're in luck. Now the bad news.
Diets that consisted of vegetables alone or diets that were beta-carotene-rich were negatively associated with executive functioning scores. If your job involves making difficult executive decisions then you might want to avoid beta-carotene-rich diets. These fruits and vegetables typically have bright orange and yellow pigmentation.
This study is valuable because the authors tried to determine the effects of specific aspects of our diet upon brain function. Clearly, our diets can influence how well our brain works and how we feel. As an added bonus, these diets tend to reduce the risk of cardiovascular disease and cancer—and you'll be thinner while doing so.
© Gary L. Wenk, Ph.D. Author of Your Brain on Food (oxford, 2010)