Recent research has found a link between higher intakes of certain nutrients and a lower risk of cognitive impairment in older adults. This large-scale study involving thousands of participants suggests that what we eat may play a crucial role in protecting our cognitive health as we age. The findings were published in the journal Alzheimer’s and Dementia.
The motivation behind the research stemmed from growing concerns about dementia and cognitive decline, especially as the global population ages. Dementia, including its most common form, Alzheimer’s disease, poses significant challenges not only for those affected, but also for healthcare systems and societies at large. Recognizing that approximately one-third of Alzheimer’s disease cases may be linked to modifiable risk factors, researchers focused on nutrition as a very important and modifiable element.
As Tiarnán Keenan, lead author of the study and National Eye Institute Stadtman Tenure Investigator, explains: “In Western medicine, we are beginning to rediscover the tremendous impact of diet on health: establishing that ‘there can be excellent medicine in food; bad medicine can be found in food’ (Hippocrates, De Alimento). In fact, nutrition is a critical 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 diseases of aging, such as dementia and age-related macular degeneration.”
“We have previously shown that there are very strong links between a healthy diet and a reduced risk of age-related macular degeneration. The next natural step was to examine the same question for cognitive impairment and dementia, as comprehensive cognitive function tests were conducted in a large population of study participants followed for at least five years.” and we had two excellent data sets with an unusual combination of detailed nutritional information.”
The study analyzed data from two major research projects conducted in the United States (known as the Age-Related Eye Disease Studies). While 4,757 participants between the ages of 55 and 80 participated in the first project, 4,203 participants between the ages of 50 and 85 participated in the second project. These participants were initially part of the study focused on eye health, but they also underwent detailed cognitive function tests. The researchers closely examined the participants’ diets, using comprehensive questionnaires to assess intake of various nutrients. They then investigated how these dietary patterns were related to the participants’ cognitive abilities.
Researchers have found that certain nutrients are linked to a lower risk of cognitive impairment. These included various vitamins, minerals, and certain types of fats (DHA and EPA) found in fish. On the other hand, some dietary components have been shown to increase the risk. Diets particularly high in saturated fats and foods that cause high blood sugar levels (high glycemic index/load) have been associated with a higher risk of cognitive decline.
“The main message is that a diet consisting of foods rich in certain nutrients is very strongly linked to a reduced risk of cognitive impairment and therefore possible dementia,” Keenan told PsyPost. “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., for example, omega-3 fatty acids) and fiber.
“In contrast, a diet consisting of foods containing high levels of certain fats (e.g., monounsaturated and saturated fatty acids) and a diet with a high glycemic index are strongly associated with an increased risk of cognitive impairment.”
“Overall, this supports the idea that a Mediterranean-like dietary pattern is strongly associated with reduced risk of cognitive impairment and dementia,” Keenan said. “Important aspects of the Mediterranean diet include frequent consumption of plant-based foods and infrequent consumption of saturated/monounsaturated fats (e.g. red meat) or high glycemic index foods (e.g. refined sugars). “These nutrients may maximize cognitive reserve against impairment and dementia and may be suitable candidates for randomized trials.”
Although specific dietary choices appeared to influence the risk of cognitive decline at a particular point in time, they did not significantly alter the rate of cognitive decline over time. However, the lack of a longitudinal relationship may be a result of methodological limitations.
“We did not observe a slower decline in cognitive function for any of these nutrients, despite significant implications for the risk of cognitive impairment in many cases,” Keenan explained. “The difference in significant results for cross-sectional but not longitudinal differences may seem surprising. But this is probably related to either insufficient power to detect longitudinal differences or a true distinction.”
Although the study provides valuable information, it is important to note that the findings are based on observational data, meaning they can show associations but not cause-effect relationships.
“Caveats to this study include the possibility of residual confounding, that is, the observed associations may be partly related to factors other than dietary intake of each nutrient,” Keenan said. “However, we took all possible steps to minimize confounding (for example, by adjusting for total calorie intake, body mass index, smoking status, and other factors). Similarly, because these are observational data, we found that varying nutritional intake is causally linked to altered risk of cognitive impairment.” “It is not possible to know for sure. Ultimately, the highest level of evidence will come from a randomized controlled trial.”
Still, this 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 underscores the need for further research in this vital area of public health.
The study, “Dietary nutrient intake and cognitive function in 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.