DIET AND DEPRESSION: CAN DIETARY CHANGES IMPROVE DEPRESSION SYMPTOMS?

Many people worldwide struggle with depression, which can become debilitating and negatively affect their quality of life.

Although some approaches, like medications and therapy, can help some people manage their depression, these approaches do not work for everyone.

For many years, scientists have investigated how our gut microbiota affects our health and found a link between a disruption in gut bacteria and several diseases, including inflammatory bowel diseases, obesity, diabetes, chronic heart diseases, cancers, and autism.

More recently, researchers found a link between gut bacteria and depression symptoms.

Since what we eat affects the composition of our gut microbiome, could dietary changes help people with depression achieve better mental health?

Keep reading to find out. 

What Are Gut Bacteria?

The human gastrointestinal (GI) tract contains a dynamic population of microorganisms, including bacteria, called the gut microbiota.  

Scientists estimate that the GI tract alone has over 10¹⁴ microorganisms, and your body has around ten times more bacterial cells than human cells.

Gut bacteria protect your body against pathogens and affect your immunity and metabolism. They can also communicate with the brain and the central nervous system.

Dysbiosis, an imbalance in the gut’s microbiota, has been associated with many inflammatory diseases and infections.

Growing evidence suggests that gut microbiota can affect a person’s behavior and brain activity.

How Do Gut Bacteria Affect The Brain?

Your GI tract has its own nervous system called the enteric nervous system (ENS) which is known as your second brain. The phrase “trust your gut” is not merely figurative.

The enteric nervous system contains more than 100 million nerve cells allowing it to interact with your brain.  

There is bidirectional communication between your brain’s central nervous system and the enteric nervous system in your gut, which means that your gut can affect your brain like your brain affects your intestines.

For example, when you think of eating, your brain sends signals to your stomach to release digestive juices before the food arrives. Similarly, your gut’s microbiota can send signals through the ENS to your brain.

Scientists found that the interaction between the brain and gut bacteria can affect emotional and cognitive centers in your brain.

They also believe that the ENS can trigger emotional changes, like anxiety and depression, in people with irritable bowel syndrome (IBS), a gastrointestinal disorder characterized by an imbalance in gut bacteria.

What is the Link Between Gut Bacteria And Depression?

Depression is a mood disorder that negatively affects how you feel, think, and behave. Although the causes of depression are not yet fully understood, scientists believe several factors are involved, such as genetics, environmental factors, and a chemical imbalance in the brain.

Previous animal studies suggested that gut bacteria affect the neurological features of depression. Moreover, when researchers transferred the fecal gut microbiota of depressed humans to germ-free rats, the animals began displaying characteristic features of depression.

A new study shows that gut bacteria may play a key role in depression. The researchers investigated the relationship between the gut microbiota’s diversity and composition with depression symptoms.

The study included 2593 individuals with symptoms of depression who were not taking antidepressants.

After testing their fecal microbiota, the scientists identified thirteen groups of intestinal bacteria associated with depressive symptoms. Those bacteria are involved in the synthesis of neurotransmitters that play a role in depression.  

Can Diet Help With Depression Symptoms?

Your diet affects the number and type of bacteria in your GI tract. Since we now know that gut bacteria may be involved in the development of depression, it may be possible to improve depression symptoms by making dietary changes.

By changing your diet, you can change the abundance of specific bacterial groups in your gut. That would influence the communication between your gut microbiota and brain and possibly reduce depression. 

Many substances that act as antidepressants, including glutamate and butyrate, are synthesized by gut bacteria from a person’s diet. Therefore, consuming foods rich in bacteria that synthesize these substances could help reduce depression.

What Are the Best Diet Tips for Depression?

One study from April 2022 investigated whether a Mediterranean Diet (MD) can improve depression symptoms. A Mediterranean Diet focuses on plant-based foods and healthy fats. In general, a Mediterranean Diet involves the following:

• Eating lots of fruits, vegetables, nuts, lentils, and beans.
• Eating a lot of whole grains, such as brown rice and whole-wheat bread.
• Consuming plenty of extra virgin olive oil as a source of healthy fat.
• Eating a moderate amount of fish, especially ones rich in Omega-3 fatty acids.
• Eating moderate amounts of yogurt and cheese.
• Eating red meat only occasionally and choosing poultry instead.
• Only occasionally consuming sweets, butter, and sugary drinks. 
• Cutting back on wine.

The study included 72 young males diagnosed with moderate to severe depression.

Participants either switched to a Mediterranean Diet or received befriending therapy (individuals providing additional social support) for 12 weeks.

After 12 weeks, patients following the Mediterranean Diet had a more significant change in their Beck Depression Inventory Scale (BDI-II) than those receiving befriending therapy. Moreover, changes in the quality of life (QoL) score were also more significant in the MD group compared with the befriending group.  

The authors concluded that nutrition could have a crucial role in treating depression.

How does the Mediterranean Diet affect the gut microbiota?

The Mediterranean Diet focuses on food rich in fiber. Studies show that a high-fiber diet induces changes in the entire gut microbe community and increases the production of short-chain fatty acids (SCFA), like butyrate. 

Consequently, dietary changes can help improve depression symptoms by increasing butyrate production, which functions as an antidepressant and improves cognition.

Summary

Although depression is a complex condition with possibly multiple causes, a dietary change could be a simple and effective way to achieve better mental health. 

In summary, studies have shown that if you follow a healthy and balanced diet, like the Mediterranean Diet, you may be able to change your gut microbiome and possibly overcome your symptoms of depression.

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Sources:

• The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems - PMC
• Gut microbiome-wide association study of depressive symptoms | Nature Communications
• effect of a Mediterranean diet on the symptoms of depression in young males (the “AMMEND: A Mediterranean Diet in MEN with Depression” study): a randomized controlled trial | The American Journal of Clinical Nutrition | Oxford Academic
• Introduction to the human gut microbiota - PMC
• The bowel and beyond: the enteric nervous system in neurological disorders | Nature Reviews Gastroenterology & Hepatology    
• Irritable Bowel Syndrome and Depression: A Shared Pathogenesis - PMC

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