Researchers, who have long been interested in finding out what diets optimise brain function, which is affected by dietary patterns and food choices, have concluded that people following a balanced diet may have better mental health and cognitive functioning.
The latest study, published in Nature Mental Health and led by the University of Fudan, Shanghai, explored how dietary patterns had an impact on various areas of brain health, including mental health, cognitive function, metabolic biomarkers, and brain structure, as measured using MRI.
In their analysis of almost 182 000 participants, the researchers also noted genetic differences that may have influenced the outcomes among different dietary groups.
While research will continue in this area, the study points to the importance of making wise nutritional choices to improve brain function and mental health outcomes, reports Medical News Today.
Diet’s effect on mental health
People can develop preferences for certain foods, which can affect overall dietary patterns over time, and scientists are keen to discover how these preferences can influence brain function and mental health, and whether specific diets are better.
Some research suggests certain diets and food choices are better for mental well-being, while others may contribute to poor mental health.
For example, a diet with high levels of fruits, vegetables, and fish may help to decrease the risk of depression.
Similarly, eating more fruits and vegetables, and getting essential micronutrients, may help reduce anxiety risk, while eating a diet high in fat and refined carbohydrates may increase this risk.
Diet can also affect how well the brain functions. For example, following the Mediterranean diet may help slow cognitive decline.
For the current study, researchers focused on four main dietary patterns by looking at participants’ food preferences:
1. starch-free or reduced starch – this group preferred fruits, vegetables, and protein but showed a lower preference for starchy foods like bread or pasta
2. vegetarian – this group preferred fruits and vegetables but showed a lower protein preference
3. high-protein and low-fibre – this group preferred snacks and protein foods and had a lower preference for fruits and vegetables
4. balanced diet – this group showed similar preferences in all food groups.
The researchers found consistency with food preferences and actual food consumption traits.
Connection between diet and brain
The researchers looked at data from the UK Biobank, focusing on food-preference data, and asked about food preferences in several categories, including dairy, fruits, flavourings, alcohol, meat, snacks, starches, and vegetables.
They then looked at the association between these dietary preferences and several brain-related outcomes. First, they assessed mental health, collecting data on components including anxiety and depressive symptoms, mania symptoms, psychotic experience, trauma, self-harm, and well-being.
Higher scores indicated poorer mental health, except for the well-being measurement, where a higher score suggested better mental well-being.
Researchers further evaluated cognitive function with several tests, looked at blood biochemistry and metabolic biomarkers, and examined brain structure via MRI.
Finally, they looked at polygenic risk scores for mental disorders, which measure how genetics factor into risk for mental illness, and did a gene enrichment analysis.
The study found that the balanced dietary subtype saw the most benefit of all four groups – those in the balanced dietary subtype had lower scores for most mental health measurements and higher scores for well-being.
This group also had the best-measured reaction time, while the high-protein, low-fibre diet group scored the best on a cogntion test involving symbol substitution.
People in the balanced dietary group also had higher levels of grey matter in certain areas of the brain compared with the high-protein, low-fibre group.
However, the vegetarian group also showed higher levels of grey matter in certain brain regions.
The balanced dietary group also had a relatively lower genetic risk for most mental disorders. In contrast, the vegetarian group had a higher genetic risk for Alzheimer’s disease, bipolar disorder, schizophrenia, and several other mental disorders.
The high-protein and low-fibre group had a higher genetic risk for ischaemic stroke.
Balanced best for brain health
Researchers also found that several genes were different between the balanced group and the high-protein, low-fibre group.
These genes were “enriched in biological processes related to mental health and cognition”, which points to how genetics may be involved in the observed outcomes.
Overall, the results show how following a balanced diet may help improve brain health and mental well-being.
Limitations and clinical implications
This study adds to the evidence suggesting that what people eat affects multiple areas of health. However, it also has certain limitations.
First, it utilised data from the UK Biobank, which does not entirely reflect the diversity of the population in the United Kingdom.
The cohort was recruited more than 20 years ago, and while it reflects the ethnic make-up of the UK in 2001, this has changed since then. The cohort also comprises older individuals: all members of this cohort were between 53 and 87.
Then, the research focused mainly on healthy individuals. Those who responded to food-like questionnaires and those who did not may have also influenced the results.
The nature of the study also means that it cannot prove causality. The average age of participants was around 71-years-old, so future research could focus on younger participants.
Researchers further note that while they were able to examine levels of omega-3 and omega-6 fatty acids, they did not examine levels of tryptophan, which is linked to mental health and cognitive function.
They also did not gather detailed information on how omega-3 and omega-6 fatty acids were involved in the dietary patterns. These choices may have led to overlooked data, as these elements are important to serotonin synthesis and, thus, to overall mental health.
Finally, some data collection relied on participant reporting, which is not always factual. Researchers also focused on food preferences rather than data on the actual foods that participants ate, and they used simplified measurements of mental health factors.
Nevertheless, even taking these shortcomings into account, the results point to the importance of following healthy dietary patterns to support positive outcomes for brain health.
Study details
Associations of dietary patterns with brain health from behavioural, neuroimaging, biochemical and genetic analyses
Ruohan Zhang, Bei Zhang, Wei Cheng et al.
Published in Nature Mental Health on 1 April 2024
Abstract
Food preferences significantly influence dietary choices, yet understanding natural dietary patterns in populations remains limited. Here we identifiy four dietary subtypes by applying data-driven approaches to food-liking data from 181,990 UK Biobank participants: ‘starch-free or reduced-starch’ (subtype 1), ‘vegetarian’ (subtype 2), ‘high protein and low fibre’ (subtype 3) and ‘balanced’ (subtype 4). These subtypes varied in diverse brain health domains. The individuals with a balanced diet demonstrated better mental health and superior cognitive functions relative to other three subtypes. Compared with subtype 4, subtype 3 displayed lower grey matter volumes in regions such as the postcentral gyrus, while subtype 2 showed higher volumes in thalamus and precuneus. Genome-wide association analyses identified 16 genes different between subtype 3 and subtype 4, enriched in biological processes related to mental health and cognition. These findings provide new insights into naturally developed dietary patterns, highlighting the importance of a balanced diet for brain health.
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