‘Balanced’ diet most protective for mental health, cognitive function

People can develop preferences for certain foods, which can impact overall dietary patterns over time. Researchers are interested in discovering how these preferences can influence brain function and mental health, and whether specific diets are better for mental health.

Some research supports the notion that certain diets and food choices are better for mental well-being. In contrast, others may contribute to poor mental health.

For example, following 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 impact how well the brain functions. For example, following the Mediterranean diet may help slow cognitive decline.

Isabel M. Vazquez, MS, RD, a registered dietitian at Memorial Hermann Health System, who was not involved in the recent study, noted the following to Medical News Today:

“We know that diet plays a significant role in brain health. Research suggests that diets rich in fruits, vegetables, whole grains, lean protein, and healthy fats can support cognitive function and reduce the risk of cognitive decline. Conversely, diets high in processed foods, saturated fats, and sugars may have negative effects on the brain.”

“Previous research has consistently shown that diet plays a fundamental role in brain health, influencing cognitive functions and emotional well-being. Nutrient-rich, balanced diets are often linked with reduced risk of cognitive decline and better mental health outcome,” Vazquez added.

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-fiber — 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.

The researchers who conducted the current study looked at data from the UK Biobank, focusing on food-preference data. Researchers asked about food preferences in several categories, including dairy, fruits, flavorings, 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-fiber diet group scored the best on a cogntion test involving symbol substitution

People in the balanced dietary group also had higher levels of gray matter in certain areas of the brain compared to the high-protein, low-fiber group.

However, the vegetarian group also showed higher levels of gray 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-fiber group had a higher genetic risk for ischemic stroke.

Researchers also found that several genes were different between the balanced group and the high-protein, low-fiber 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.

Molly Rapozo, RDN, registered dietician nutritionist, and senior nutrition and health educator at Pacific Neuroscience Institute in Santa Monica, CA, not involved in the research, shared her thoughts on the findings with MNT.

“This study found that a ‘healthier’ diet with balanced preferences in various food categories — fruit, vegetables, starches, protein, and snack foods were noted — is associated with better mental health status, higher levels of cognitive functions and fewer risks of mental disorders,” she explained.

“It’s exciting to see this result in such a large study (181,990 participants) with lots of data — behavioral, neuroimaging, biochemical and genetic analyses. It was also found that high-protein, low-fiber diets with an emphasis on snack foods were associated with lower well-being scores, higher levels of inflammatory markers, and an increased stroke risk. These findings appear to agree with what we already know about diet and brain health.”

– Molly Rapozo, RDN

This study adds to the evidence suggesting that what people eat affects multiple areas of health. However, the study also has certain limitations.

First, it utilized data from the UK Biobank, which does not entirely reflect the diversity of the population in the United Kingdom, where the Biobank collects these data.

This is as the cohort was recruited over 20 years ago, and while the cohort reflects the ethnic make-up of the UK in 2001, this has changed since then. The cohort is also comprised of older individuals, and all members of this cohort were between the ages of 53–87.

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.