Online articles with dietary advice for foods that are good for the brain abound. Some of those articles make reference to observational studies that suggest a connection between the consumption of certain foods and the risk of dementia.
However, clinical studies have not provided compelling evidence connecting specific diets or nutrients to cognitive function.
The Kenneth and Bette Volk Chair of Neurology at USC and associate professor of medicine and neurology at the Keck School of Medicine of USC, Hussein Yassine, MD, stated that “many trials have not found that making people eat healthy or exercise is translating into benefits in the ways that are expected from the epidemiological research.”
That suggests that either there is no causal relationship or that these studies were poorly designed.
In order to understand this discrepancy between epidemiological studies and clinical trials, Yassine oversaw the Diet for Dementia Prevention Working Group, a team of researchers who spent two years reviewing the literature on nutrition and dementia risk. Their review, which was recently published in The Lancet Healthy Longevity, identifies critical shortcomings in recent studies that relate to how nutrition affects the brain and makes suggestions for future investigation. A grant from the National Institutes of Health was used to pay for this study (NIH).
Challenges in nutritional research
Yassine makes the point that conducting good nutrition research can be difficult in general. Epidemiological studies have shown a reduced risk of dementia in people who consume fatty seafood like salmon. It can be challenging to separate nutritional data from other factors that might also be in play, such as a person’s location, concurrent healthy lifestyles, or their access to high-quality medical care.
Since it is unknown how long it takes for a healthy diet to have an impact on cognition, the majority of clinical trials on food and brain health may not have been conducted for long enough for the results to be useful. Yassine continued, “Studies that lasted for two years or less are not accurately reflecting the effect of the diet on cognition if it takes five to ten years.”
If it can be established how much of a specific vitamin an individual needs to have ideal brain health, future research will also advance. For example, there is a recommended amount of vitamin D to maintain strong bones, but this is not true of minerals that are known to have an impact on cognitive health.
embracing novel findings and innovations
The group argues that using biomarkers rather than cognitive tests, which are typically used to evaluate an intervention’s effectiveness, may lead to more significant early results that can guide more extensive treatments that put a focus on clinical outcomes. In order to track how the brain changes over time, technology such as brain imaging can be very helpful. Additionally, they point out that screening blood or stool samples for specific biomarkers, such as insufficient nutrient consumption, can be used to both select the best volunteers and determine how well study participants react to the intervention being tested.
Genetic testing, according to Yassine, who studies apolipoprotein E4, or APOE4, the most potent genetic risk factor for late-onset Alzheimer’s disease. He emphasized that people who have this version of the gene react to food differently from people who do not. In this situation, genetic testing can result in more accurate research and treatment plans.
Research outcomes may be improved by studying the microbiome. According to Yassine, variations in the microbiota cause dietary benefits to differ from person to person. According to Yassine, “you cannot fully study how the diet is working without studying the microbiome.” Additionally, there is a need for deeper understanding of the relationship that exists between the gut microbiome and cognition in sizable populations of diverse individuals.
new modes of thought
Finally, the panel reached the conclusion that trial participant selection must be given more thought and that researchers should consider using a wider variety of study designs, not just randomized controlled trials.
They note that one strategy would be to design small, individualized studies that take into account participant’s genetic susceptibility, the quality of their diet, and an analysis of their microbiome while using biomarkers that represent brain functioning. Another tactic entails designing sizable, realistic electronic health trials that are directed at people who have dementia risk factors and using mobile devices like smartphones or tablets to gather data.
Although the majority of research to date has focused on older adults, several high-quality cohort studies suggest that middle age may be the best time to begin this kind of research because it is before the onset of changes associated with dementia, allowing researchers to track changes over time. Additionally, the group stresses how important it is for studies to consider the eating patterns of underrepresented groups, some of which are disproportionately affected by dementia.
This is a crucial document for anyone conducting research on diet and how it relates to dementia, according to Lon Schneider, MD, Professor of Psychiatry and the Behavioral Sciences at the Keck School of Medicine and Della Martin Chair in Psychiatry and Neuroscience.
