A study out of the University of Reading in England has found that a poor-quality diet may be associated with changes in brain structure that are linked to depression and anxiety. This research provides new insights into the connection between what we eat and our mental well-being.

While the authors did not find a direct association between brain changes and anxiety or depression, they did see an increase in rumination, a common risk factor for both.

What the Study Found

The study is among the first to examine the relationship between diet quality and brain neurochemistry in humans. Thirty adults were divided into two groups based on whether they followed a high- or low-quality diet. Participants in both groups were similar in age, gender, education, income, and caloric and macronutrient intake.

The quality of the diet was defined by adherence to the Mediterranean diet. Participants reported how frequently they ate 130 different food items and other food intake habits. Screening questionnaires were administered to assess current depression, anxiety, and rumination levels. Whole-brain MRI scans measured prefrontal cortex metabolite concentrations and gray matter volume.

The study found that participants in the low-quality-diet group had unbalanced levels of two neurotransmitters, with lower levels of GABA and higher levels of glutamate, as well as reduced gray matter volume in the brain. These are all markers commonly seen in depression and anxiety. Participants in the high-quality diet group had balanced levels of GABA and glutamate and a larger volume of gray matter.

Neurotransmitters, such as GABA and glutamate, are chemical messengers that transmit signals between nerve cells and regulate various processes in the brain and body, including mood, sleep, and cognition. Gray matter is involved in memory and emotions.

The researchers noted a trending relationship between increased rumination and decreased frontal gray-matter volume. They also observed a correlation between increased glutamate concentrations and increased rumination. Rumination is a major risk factor for anxiety and depression.

A 2019 animal study published in Food & Function showed that a diet high in sugar and saturated fat can reduce a person’s parvalbumin interneurons (which contain and release GABA).

Poor-quality diets can also influence glucose and raise blood sugar and insulin levels. Studies show that high blood sugar may raise glutamate levels and subsequently lower the production and release of GABA.

Additionally, high-fat and high-cholesterol diets can also alter cell membranes, which can affect the release of neurotransmitters. A mouse study published in Nutritional Neuroscience in 2019 found that changes to the gut microbiome due to a poor diet are associated with depression-like behaviors. Mice that were fed a substandard diet were less social and exhibited an increased preference for sucrose, or table sugar.

Specifically, a reduction in good bacteria resulting from a diet rich in saturated fats is believed to influence the processes responsible for producing GABA and glutamate, according to the study.

GABA and glutamate also play a significant role in regulating appetite and food intake. Decreased GABA or elevated glutamate levels may affect inhibitory control and could contribute to unhealthy food choices and overeating.

The Diet and Mental Health Connection

Andreas Michaelides, chief of psychology at food intake and exercise-tracking app Noom, told The Epoch Times in an email, “GABA (Gamma-Aminobutyric Acid) is an inhibitory neurotransmitter, meaning it reduces neuronal excitability and helps calm the brain. When GABA levels are stable and adequate, they help reduce anxious thoughts by calming the brain.”

Michaelides explained that glutamate is an excitatory neurotransmitter that heightens neuronal activity and is involved in learning and memory. Excessive glutamate activity can injure or kill neurons and damage the brain.

“The balance between GABA and glutamate is crucial for healthy brain function,” Michaelides said. “When we have low levels of GABA, we have increased anxiety and depression.”

Concerning glutamate levels, “certain symptoms and conditions, including anxiety, insomnia, and headaches, may indicate excessive glutamate activity,” he said.

How to Optimize Mental Health With Diet

Removing from your diet common culprits that disrupt neurotransmitter balance may support mental health and well-being.

“Certain foods can lower GABA levels or interfere with its natural function. Those foods are processed foods, alcohol, and caffeine,” Michaelides said.

“Diets high in processed foods, refined sugars, and excessive protein can increase glutamate levels. These foods either directly contain glutamate or promote its production,” he said.

Processed foods and sugary snacks and beverages are also high in trans fats and refined sugars.

“These foods can cause inflammation and have been linked to higher rates of depression and anxiety. They can disrupt brain function and mood stability,” Michaelides said.

Rapid blood sugar fluctuations may also lead to mood swings and anxiety, with consistent consumption contributing to long-term mood instability.

It’s also best to limit alcohol consumption. Michaelides said, “Alcohol is a depressant that can disrupt neurotransmitter balance, leading to increased anxiety and depression over time.”

Excessive amounts of caffeine are also best avoided, as they can interfere with sleep and exacerbate anxiety.

When it comes to what to include in your diet to support mental health, appropriate protein intake is key.

“To have healthy neurotransmitter production, you must have proper protein intake,” Michaelides said.

When our bodies digest proteins, they are broken down into smaller molecules called amino acids. Amino acids provide the building blocks for neurotransmitters.

“In short, ensuring a varied protein intake supports optimal neurotransmitter function and mental health,” he said.

Sources of high-quality protein from fatty fish such as salmon and mackerel come with an added mental health boost. These high-quality proteins are rich in omega-3 fatty acids, which reduce inflammation and support neurotransmitter production, which is linked to lower risks of depression and improved cognitive function.

Other foods to add to your diet for a mental health boost include leafy green vegetables for their folate content. Michaelides noted that a folate deficiency is associated with a higher risk of depression.

Berries offer a boost in antioxidants and “protect the brain from oxidative stress, a factor linked to mental health disorders,” he added.

Nuts and seeds are excellent sources of magnesium, and sufficient magnesium intake is linked to reduced symptoms of anxiety and depression, according to Michaelides.

He also recommends fermented foods such as kimchi and yogurt. “They promote a healthy gut microbiome, which can influence brain chemistry and improve mood.”