Eating habits affect brain chemistry and mental health


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Eating a poor-quality diet can lead to brain changes linked to depression and anxiety. This is evident from a first-of-its-kind study into the chemistry and structure of the brain and the diet quality of 30 volunteers.

Brain scans show changes in neurotransmitters and gray matter volume in people who eat a poor diet, compared to those who eat a Mediterranean diet, which is considered very healthy. The researchers also found that these changes are linked to rumination, part of the diagnostic criteria for conditions that affect mental health such as depression and anxiety.

This research was conducted by the University of Reading, Roehampton University, FrieslandCampina (Netherlands) and Kings College London, and published in Nutritional neuroscience.

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When someone eats a poor-quality diet, there is less gamma-aminobutyric acid (GABA) and increased glutamate – both neurotransmitters, along with reduced gray matter volume – in the front part of the brain. This could explain the connection between what we eat and how we feel.

Dr. Piril Hepsomali, University of Reading, said: “We can eat ourselves well! Ultimately, we see that people who eat an unhealthy diet – high in sugar and saturated fat – have an imbalance in excitatory and inhibitory neurotransmission, as well as a reduced volume of gray matter in the front part of the brain. This part of the brain is involved in mental health problems such as depression and anxiety.”

The exact reason diet affects the brain in this way is still under investigation. It is possible that obesity and diets high in saturated fats cause changes in glutamate and GABA metabolism and neurotransmission, as has been shown in animal studies.

Marked changes in the gut microbiome, resulting from diets high in saturated fats, are thought to impact the cell machinery that controls both GABA and glutamate production.

A high saturated fat, high sugar diet has also been shown to reduce the number of parvalbumin interneurons, which perform the role of delivering GABA where it is needed.

An unhealthy diet also affects glucose levels, causing blood glucose and insulin to rise. This increases glutamate in the brain and plasma, reducing GABA production and release. Having a diet high in fat and cholesterol can cause changes in cell membranes that also alter the release of neurotransmitters.

These changes in brain chemistry can lead to changes in the volume of gray matter in the brain, as observed in this study.

Dr. Hepsomali continued: “I would like to note that GABA and glutamate are also intimately involved in appetite and food intake. Decreased GABA levels and/or increased glutamate levels can also be a driving factor in making unhealthy food choices. So there may be a circular relationship between eating well, healthier brains and better mental wellbeing, and making better food choices to eat well.’

Reference: Hepsomali P, Costabile A, Schoemaker M, Imakulata F, Allen P. Adherence to unhealthy diets is associated with altered frontal gamma-aminobutyric acid and glutamate concentrations and gray matter volume: preliminary findings. Nutrit Neurosci. 2024:1-13. doi: 10.1080/1028415X.2024.2355603

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