New study has found a link between older adults who get more of certain nutrients in their food and a lower risk of cognitive decline. The results of this huge study with thousands of participants show that what we eat may be very important for keeping our brains healthy as we age. The results have been written up in the journal Alzheimer’s & Dementia.
The study was started because people are becoming more worried about dementia and cognitive loss, especially as the world’s population ages. Alzheimer’s disease, which is the most common form of dementia, is very hard to deal with for both the people who have it and for society as a whole. Researchers focused on food as an important factor that can be changed because they knew that about one-third of Alzheimer’s cases may be linked to risk factors that can be changed.
Tiarnán Keenan, the study’s lead author and a Stadtman Tenure-Track Investigator at the National Eye Institute, said, “In Western medicine, we are starting to rediscover the huge effect that diet can have on health: ‘In food, excellent medicine can be found; in food, bad medicine can be found’ (Hippocrates, De Alimento).” As Brillat-Savarin said, “La destinée des nations dépend de la manière dont elles se nourrissent.” This shows how important diet is to public health. This may be especially true for long-term illnesses that come with getting older, like dementia and age-related macular degeneration.
“We had already shown that a healthy diet is strongly linked to a lower risk of age-related macular degeneration.” The next step that made sense was to look at the same question for cognitive impairment and dementia, since we had two great datasets that included detailed dietary information and comprehensive cognitive function tests from a large group of people who had been followed for at least five years.
The study looked at information from the Age-Related Eye Disease Studies, which are two large research projects that were done in the United States. People aged 55 to 80 took part in the first project, which had 4,757 participants. People aged 50 to 85 took part in the second project, which had 4,203 participants. These people took part in a study that was mostly about eye health, but they also had to go through a lot of tests to see how well their brains worked. Researchers closely looked at the diets of the participants and used detailed surveys to find out how much of different nutrients they were taking in. Then, they looked into how these eating habits affected the participants’ mental skills.
The experts found a link between some nutrients and a lower chance of getting dementia. Some of these were vitamins, minerals, and fats that are found in fish, like DHA and EPA. On the other hand, some parts of the food seemed to raise the risk. It was found that people who ate a lot of fatty fats and foods that raise blood sugar levels (high glycemic index/load) were more likely to lose their mental abilities.
To quote Keenan, “the main message is that a diet high in certain nutrients is strongly linked to a lower risk of cognitive impairment and, by extension, likely dementia.” Minerals (copper, magnesium, selenium, and zinc), carotenoids (lutein, zeaxanthin, beta-carotene, and lycopene), lipids (omega-3 fatty acids), and fiber are some of the foods that have been linked to these health benefits.
“On the other hand, eating a lot of certain fats (like monounsaturated and saturated fatty acids) and foods with a high glycemic index are strongly linked to a higher risk of cognitive impairment.”
“In general, this supports the idea that a diet pattern similar to the Mediterranean is strongly linked with a lower risk of cognitive impairment and dementia,” Keenan said. It’s important to follow the Mediterranean diet pattern, which includes eating lots of plant-based foods and not too many foods high in fatty or monounsaturated fats (like red meat) or sugars. These nutrients may help protect against cognitive decline and dementia and could be good options for randomized trials.
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At one point, some food choices seemed to affect the chance of cognitive impairment. However, over time, they did not have a big effect on the rate of cognitive decline. But the fact that there isn’t a longitudinal relationship could be because of problems with the way the data was collected.
“Even though these nutrients had significant effects on the risk of cognitive impairment in many cases, we did not see slower levels of decline in cognitive function for any of them,” Keenan said. “It might seem strange that there are significant results for cross-sectional differences but not for longitudinal differences. But this is probably because there isn’t enough power to find longitudinal changes or because there is a real difference.
The study gives us useful information, but it’s important to remember that the results are based on observational data, which means they can only show links between things, not direct causes and effects.
“One of the problems with this study is that there is a chance of residual confounding,” Keenan said. “This means that the links seen might be partly due to things other than the amount of each nutrient eaten.” But, we did everything we could to reduce confusion (for example, by taking into account smoking status, total calories eaten, and body mass index). Furthermore, since these are just observations, it is not possible to say for sure that nutrient intake changes the risk of cognitive disability. In the end, a randomized controlled study would provide the most solid proof.
However, the study is an important step toward better knowing how diet affects brain health. It shows that some nutrients might help keep your brain healthy and stresses the need for more study in this important area of public health.
“Dietary nutrient intake and cognitive function in the Age-Related Eye Disease Studies 1 and 2” was written by Tiarnan D. L. Keenan, Elvira Agrón, Emily Y. Chew, and the AREDS and AREDS2 Research Groups.