“When I am king they shall not have bread and shelter only, but also teachings out of books, for a full belly is little worth where the mind is starved.”
― Mark Twain, The Prince and the Pauper
Do we choose to eat certain foods because we are in a certain mood?
Or are we in a certain mood because of certain foods we eat?
If the right food can bring us joy, can the wrong food bring us misery?
The increasing complexity and subtlety of the ongoing dialogue between our brain and our gut, often referred to as the brain-gut axis, threatens to turn the entire discussion into a chicken or egg conundrum. Recent studies continue to strengthen the hypothesis that there is a connection between what we choose to eat and our mental health and cognitive function, but at the same time, these studies also deepen the depths of interconnectedness, increasingly obscuring the distinction between the two.
A recent meta-analysis examining data from the NutriNet Brasil cohort study prospectively evaluated almost 16,000 adults.[1] The researchers analyzed the consumption of ultra-processed food and demonstrated that “each 10% increase in the dietary share of ultra-processed foods (UPFs) was associated with a 10% increase in the hazard of incident cases of depressive symptoms.” The meta-analysis concluded that the highest consumers of UPFs, compared to those who consumed the least amount of UPFs, had a 32 percent increased risk of developing depression. Although the study was prospective in nature, following an initially depression-free population and correlating the consumption of UPFs to the development of depression, the chicken and egg question remains: is the correlation present because the consumption of ultra-processed foods makes those who consume them more likely to manifest depression (a causal association)? Or are people who develop depression more likely to seek out and consume ultra-processed foods (a noncausal, linked association)?
Another recently published study may provide some insights. This study utilized data from more than 180,000 participants in the UK Biobank program. In one of the first studies of its kind, the researchers first categorized participants by food preference. That is, the study groups were determined by what people said they liked to eat. The researchers then confirmed that what people said they liked to eat was pretty much what they did actually eat.
A crucial point is that this study separated groups of people by the foods they liked to eat. This is a very different approach than many other studies that prescribe a specific dietary regimen to be followed (low-fat, keto, etc.), hope for adherence, and measure the results. After identifying the four naturally occurring consumptive patterns, the researchers examined many different markers of brain health and correlated them to cognitive function and mental health outcomes.
- The study identified four main categories of food preferences:
- subtype one: a reduced-starch preference (think “low-carb”),
- subtype two: a vegetarian preference,
- subtype three: a high-protein and low-fiber preference (think an “Atkins” or “Paleo”-type approach),
- subtype four: a balanced approach.
- The study group consisted of 181,990 participants in the UK Biobank program.
- The mean age of the group was 70.7 ± 7.7 years, and 57 percent were female.
- Each subgroup comprised the following percentage:
- subtype one (“low-carb”): 18.09 percent
- subtype two (vegetarian): 5.54 percent
- subtype three (“Atkins-type”): 19.39 percent
- subtype four (balanced): 56.98 percent
The Take-Away:
- The balanced approach was associated with the best mental health measures and the highest measures of well-being.
- The vegetarian and “Atkins-type” approaches were associated with higher anxiety and depressive symptoms and lower levels of well-being.
- Compared to a balanced approach, the vegetarian and “Atkins-type” approaches were associated with an approximately 20 percent greater risk of depression.
- The “low-carb” and “Atkins-type” approaches, compared to a balanced approach, had an increased risk of stroke.
- When compared to a balanced approach, all the other approaches were associated with a higher risk of anxiety.
- Compared to a balanced approach, a vegetarian approach was associated with more than 2.5 times the risk of displaying an eating disorder.
- There were significant differences between the groups with respect to metabolic biomarkers such as fatty acids, omega-3 fatty acids, omega-6 fatty acids, cholesterol esters, HDL cholesterol, and C-reactive protein.
- There were significant differences in 23 out of 94 brain regions subjected to neuroimaging across the four subtypes.
- The vegetarian approach was associated with a higher genetic predisposition for several mental disorders, including Alzheimer’s disease, Parkinson’s disease, bipolar disorder, schizophrenia, and suicide attempts, than other subtypes.
- The “Atkins-type” approach was associated with a higher genetic susceptibility to ischemic stroke.
- Genome-wide association studies (GWAS) using the balanced approach group as the reference found significant differences between it and the “Atkins-type” group, identifying more than 1,200 different single-nucleotide polymorphisms (SNPs).
- GWAS demonstrated two SNPs that were significantly different between the “low-carb” group and the balanced approach group.
The Caveat:
Our food preferences result from many complex variables, but understanding the equation is incredibly important as it is amongst the most critical—if not the most critical—factors driving food choices and consumption.[2] This study is one of the first to examine cognitive function and mental health from the context of naturally developed dietary patterns based on what people like to eat.
The brain is directly impacted by the metabolic effects reflected in the biomarker analysis. The neuroimaging data suggest that the choices we make about what we consume directly impact the brain in structural ways, as the MRI analysis displayed distinct brain patterns. The researchers observed that individuals with specific food preferences displayed distinct patterns of brain MRI traits. The investigators concluded that the “plasticity and adaptability of the brain, influenced by dietary choices, can lead to structural changes that influence cognitive functions and mental health.” Food preferences were significantly associated with mental health, which, in turn, significantly predicted cognitive function.
While GWAS identified differing SNPs between certain dietary approaches, it is their interaction with the diet we choose that ultimately modulates their expression and, thus, the genetic impact on brain health and cognition. Our genetics are not a predetermined curse written in stone but manifest as the expression of our conversation with our environment.
Of the four naturally occurring dietary preferences, a balanced dietary approach, subtype four, had “less mental health problems and a higher well-being score than other subtypes, suggesting that a balanced intake of various food categories may be associated with better mental health.” Perhaps in some ways, this is not a surprise as it reaches back to our omnivore ancestors. As epi-genetics continues to blur the line between what is written and what is done, the separation between nature and nurture, person and place, mind and body, brain and gut continues to narrow. Perhaps one can argue that the distinction never really existed in the first place.
[1] (Werneck, 2024)
[2] (Recio-Román, 2020)
