Recent research has found a connection 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 might play a crucial role in maintaining our cognitive health as we age. The findings have been published in the journal Alzheimer’s & Dementia.
The motivation behind the study stemmed from a growing concern about dementia and cognitive decline, particularly as the global population ages. Dementia, including its most common form, Alzheimer’s disease, poses significant challenges not only to those affected but also to healthcare systems and societies at large. 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, alterable aspect.
As Tiarnán Keenan, the study’s lead author and Stadtman Tenure-Track Investigator at the National Eye Institute, explained: “In Western medicine, we are starting to rediscover the enormous impact that diet can have on health: ‘In food, excellent medicine can be found; in food, bad medicine can be found’ (Hippocrates, De Alimento). Indeed, nutrition is a critical part of public health: ‘La destinée des nations dépend de la manière dont elles se nourrissent’ (Brillat-Savarin, Physiologie du Goût). This may be particularly true for chronic diseases of aging, such as dementia and age-related macular degeneration.”
“We had previously demonstrated very strong links between a healthy diet and decreased risk of age-related macular degeneration. The natural next step was to examine the same question for cognitive impairment and dementia, since we had two excellent datasets with the unusual combination of comprehensive cognitive function testing and detailed dietary information in a large population of study participants followed for at least five years.”
The study analyzed data from two significant research projects conducted in the United States (known as the Age-Related Eye Disease Studies). The first project enrolled 4,757 participants aged between 55 and 80 years, while the second involved 4,203 individuals aged 50 to 85 years. These participants were initially part of research focusing on eye health but also underwent detailed cognitive function testing. Researchers looked closely at the participants’ diets, using comprehensive questionnaires to assess the intake of various nutrients. They then explored how these dietary patterns related to the participants’ cognitive abilities.
The researchers found that certain nutrients were linked to a lower risk of cognitive impairment. These included several vitamins, minerals, and specific types of fats found in fish (DHA and EPA). On the flip side, some dietary components seemed to increase the risk. Notably, 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 main message is that a diet of foods rich in particular nutrients is very strongly linked to decreased risk of cognitive impairment and therefore likely 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.”
“By contrast, a diet of foods with high levels of particular fats (e.g., monounsaturated and saturated fatty acids) and diets with high glycemic index are strongly associated with increased risk of cognitive impairment.”
“Overall, this supports the idea that a Mediterranean-like diet pattern is strongly associated with decreased risk of cognitive impairment and dementia,” Keenan said. “Important aspects of the Mediterranean diet pattern include frequent consumption of plant-based foods and infrequent consumption of saturated/monounsaturated fats (e.g., red meat) or foods with high glycemic index (e.g., refined sugars). These nutrients may maximize cognitive reserve against impairment and dementia and could be suitable candidates for randomized trials.”
While certain dietary choices seemed to influence the risk of cognitive impairment at one point in time, they did not significantly alter the rate of cognitive decline over time. But this lack of a longitudinal relationship might be a result of methodological limitations.
“Despite the 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 explained. “The distinction between significant results for cross-sectional but not longitudinal differences may seem surprising. However, this is likely related either to insufficient power to detect longitudinal differences or to a genuine distinction.”
While the study offers valuable insights, it’s important to note that the findings are based on observational data, meaning they can show associations but not cause-and-effect relationships.
“The caveats to this study include the possibility of residual confounding, i.e., that the associations observed might be related partially to factors other than dietary intake of each nutrient itself,” Keenan said. “However, we took all steps possible to minimize confounding (e.g., by adjusting for total calorie intake, body mass index, smoking status, and other factors). Similarly, since these are observational data, it is not possible to know definitely that nutrient intake is causally linked to altered risk of cognitive impairment. Ultimately, the highest level of evidence would come from a randomized controlled trial.”
Nevertheless, the study offers an important stepping stone in our understanding of diet’s role in cognitive health. It highlights the potential of certain nutrients in maintaining cognitive function and underscores the need for further research in this vital area of public health.
The study, “Dietary nutrient intake and cognitive function in the Age-Related Eye Disease Studies 1 and 2“, was authored by Tiarnan D. L. Keenan, Elvira Agrón, Emily Y. Chew, and the AREDS and AREDS2 Research Groups.
