Recent research has found a link between higher intake of certain dietary nutrients and a lower risk of cognitive impairment in older adults. This large-scale study, involving thousands of participants, suggests that what we eat could play a crucial role in maintaining our cognitive health as we age. The findings have been published in the journal Alzheimer’s and dementia.
The motivation behind the research came from a growing concern about dementia and cognitive decline, especially as the world’s population ages. Dementia, including its most common form, Alzheimer’s disease, poses a major challenge not only for those affected, but also for healthcare systems and society as a whole. Recognizing that approximately one-third of Alzheimer’s disease cases may be linked to modifiable risk factors, the researchers focused on diet as a crucial, modifiable aspect.
As Tiarnán Keenan, lead author of the study and Stadtman Tenure-Track Investigator at the National Eye Institute, explained: “In Western medicine, we are beginning to rediscover the enormous impact that diet can have on health: ‘Excellent medicines can be found in food; bad medicines may be found in food’ (Hippocrates, De Alimento). Nutrition is indeed a crucial part of public health: ‘La destinée des Nations dépend de la manière don elles se nourrissent’ (Brillat-Savarin, Physiologie du Goût). This may be especially true for chronic age-related diseases, such as dementia and age-related macular degeneration.”
“We had previously shown a very strong link between a healthy diet and a reduced risk of age-related macular degeneration. The logical next step was to investigate the same question for cognitive impairment and dementia, as we had two excellent data sets with the unusual combination of comprehensive cognitive function tests and detailed nutritional information in a large population of study participants, which we followed for at least five years.”
The study analyzed data from two major research projects conducted in the United States (known as the Age-Related Eye Disease Studies). The first project involved 4,757 participants between the ages of 55 and 80, while the second project involved 4,203 people between the ages of 50 and 85. These participants were initially part of research focused on eye health, but also underwent detailed testing of cognitive function. Researchers looked closely at the participants’ diets and used extensive questionnaires to assess the intake of various nutrients. They then examined how these dietary patterns were related to the participants’ cognitive skills.
The researchers found that certain nutrients were linked to a lower risk of cognitive impairment. These include several vitamins, minerals and specific types of fats found in fish (DHA and EPA). On the other hand, some dietary components appeared to increase the risk. Specifically, diets high in saturated fats and foods that cause high blood sugar levels (high glycemic index/load) were associated with a greater risk of cognitive decline.
“The key message is that a diet containing foods rich in certain nutrients is very strongly associated with a reduced risk of cognitive impairment and therefore probably dementia,” Keenan told PsyPost. “The nutrients with these protective associations include vitamins (e.g. A, B, C and E), minerals (e.g. copper, magnesium, selenium and zinc), carotenoids (e.g. lutein, zeaxanthin, beta-carotene and lycopene). ), lipids (e.g. omega-3 fatty acids) and fiber.”
“In contrast, a diet containing foods high in certain fats (e.g. monounsaturated and saturated fatty acids) and diets with a high glycemic index are strongly associated with an increased risk of cognitive impairment.”
“Overall, this supports the idea that a Mediterranean-style diet is strongly associated with a reduced risk of cognitive impairment and dementia,” Keenan said. “Important aspects of the Mediterranean diet include the frequent consumption of plant foods and the infrequent consumption of saturated/monounsaturated fats (e.g. red meat) or foods with a high glycemic index (e.g. refined sugars). These nutrients may maximize cognitive reserve against disability and dementia and may be suitable candidates for randomized trials.”
Although certain dietary choices appeared to influence the risk of cognitive impairment at one point in time, they did not significantly change the rate of cognitive decline over time. But this lack of a longitudinal relationship may be a result of methodological limitations.
“Despite significant results for risk of cognitive impairment in many cases, we did not observe slower levels of decline in cognitive function for any of these nutrients,” Keenan explains. “The distinction between significant results for cross-sectional but not for longitudinal differences may seem surprising. However, this is probably due to insufficient power to detect longitudinal differences or a real distinction.”
While the study provides valuable insights, it’s important to note that the findings are based on observational data, meaning they can demonstrate associations, but not cause-and-effect relationships.
“The caveats to this study include the possibility of residual confounding, that is, the observed associations may be partly related to factors other than the dietary intake of each nutrient itself,” Keenan said. “However, we have taken every possible step to minimize disruptions (for example, by making adjustments based on total calorie intake, body mass index, smoking status, and other factors). Because these are observational data, it is also not possible to know with certainty that nutrient intake is causally related to an altered risk of cognitive impairment. Ultimately, the highest level of evidence would come from a randomized, controlled trial.”
Nevertheless, the study provides an important step in our understanding of the role of diet in cognitive health. It highlights the potential of certain nutrients in maintaining cognitive function and underlines the need for further research in this crucial area of public health.
The study, “Dietary Food Intake and Cognitive Function in the Age-Related Eye Disease Studies 1 and 2,” was authored by Tiarnan DL Keenan, Elvira Agrón, Emily Y. Chew, and the AREDS and AREDS2 research groups.