The Role of Diet in Depression

anti-inflammatory diet antioxidants carbohydrates depression dopamine dysbiosis food additives glucose glycemic index gut microbiome inflammation insulin insulin resistance magnesium mental disorders mental health mental illnesses pro-inflammatory diet serotonin zinc Sep 09, 2023

In the U.S., 29 percent of adults say they have been diagnosed with depression at some point in their lives.¹ Factors that contribute to this mental disorder include genes and brain chemistry. Life events, drug abuse, and certain medical conditions can make people depressed too.² Though it can lead to disability and even death, depression can often be treated. Holistic treatment may involve changes in lifestyle, especially diet.³ ln this article, we'll explore how foods affect depression as we cover:

Serotonin, dopamine, and depression
Inflammation
Carbohydrates
The gut microbiome
Foods that fight depression

Let's start off with the neurotransmitters playing key roles in mental health.

Serotonin, dopamine, and depression

Neurotransmitters are molecules that carry signals from nerve cells to target cells.⁴ Serotonin, one of these chemical messengers, helps control mood, memory, sleep, appetite, and social behavior.⁵ Low levels of blood serotonin are linked to depression. In particular, people who lack serotonin constantly feel sad or irritable. They may have difficulty focusing or remembering things. They may also have trouble sleeping. Plus, they may crave sweet foods or binge eat. They fail to enjoy friendships and other relationships as well.^6,7

On the other hand, dopamine regulates the mesolimbic system, a major reward-related center in the brain. That is, dopamine drives behavior that promotes pleasure and survival. Thus, depression can also result from low levels of dopamine. People with dopamine-related depression usually show anhedonia. Rather than feeling sad, they have trouble feeling anything at all. They lose interest in things they enjoyed before, such as activities and relationships. This means they cannot motivate themselves to start or finish tasks. What's more, they may lack concern for family and friends.^8,9

Serotonin or dopamine levels fall for different reasons. So, depression happens through various pathways.

Inflammation

Harmful stimuli like toxins and microbes cause a series of events in the immune system. The events include the production of cytokines, which are proteins that trigger inflammation.¹⁰ Many studies have shown high levels of cytokines called interleukin-8 (IL-8), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and C-reactive protein (CRP) in depressed patients.¹¹ Dopamine seems to play a role in inflammation-related depression, as elevated cytokine levels are linked to low dopamine.⁹

Pro-inflammatory diets trigger or increase inflammation. This way, they can worsen depression. Such diets are high in vegetable oils, trans fats, preservatives, and refined sugars and starches (simple carbohydrates).¹²

Carbohydrates

The foods we eat get broken down into glucose, a simple sugar that is the body's main source of energy. The entry of glucose into the bloodstream makes the pancreas release insulin. This hormone helps glucose enter cells for energy use or storage. Insulin resistance happens when cells cannot respond as well as they should to the hormone. Cells that are too resistant to insulin promote high blood glucose, leading to prediabetes and Type-2 diabetes over time.¹³ Insulin resistance is linked to low serotonin levels, which partly explains why it is a risk factor for depression.¹⁴

Highly processed, high-carb foods get digested by the body fast, so eating them makes blood sugar spike. Such foods require the pancreas to produce more insulin, which can then lead to insulin resistance. In addition, a diet rich in sugars promotes the overgrowth of fungal species like Candida in the gut. For these reasons, eating a lot of refined carbs contributes to depression.^14,15,16

The gut microbiome

Trillions of bacteria, viruses, and fungi live in the gastrointestinal (GI) tract. Together, they make up the gut microbiome. The brain interacts with the gut microbiome through different signals. The microbes communicate with the brain as well, which means they can affect mental health and function. For instance, in several studies, the transfer of a depressed person's microbiome into a healthy rodent led to depression symptoms in the receiving animal. Another study involving fecal microbes links low amounts of certain bacteria to a higher risk of depression.¹⁵ Like many other illnesses, depression is associated with an imbalance in gut microbe species. This condition is called dysbiosis. Research shows that dysbiosis not only causes inflammation, but also lowers levels of tryptophan — an amino acid needed to produce serotonin.¹⁷

Aside from simple starches and sugars, certain other foods promote dysbiosis and increase the risk of depression. They include food additives like artificial sweeteners (aspartame and sucralose), flavor enhancers (monosodium glutamate), and emulsifiers (carboxymethylcellulose and polysorbate 80).^18,19 Alcohol and antibiotics also have a negative impact on mental health through the same mechanism.^20,21

Foods that fight depression

A diet that boosts the production of serotonin and dopamine can help with depression. Tryptophan-rich foods, such as cage-free eggs, chicken, and turkey, can raise serotonin levels. Nuts like almonds, cashews, and walnuts are high in tryptophan too.²² As for micronutrients, Vitamins B6 (pyridoxine hydrochloride), B9 (folic acid or l-methylfolate), and B12 (methylcobalamin) assist the body in making serotonin.^23,24,25 Among herbal supplements, St. John's wort increases brain serotonin by preventing nerve cells from reabsorbing the neurotransmitter.²⁶

Besides raising serotonin, eggs, chicken, poultry, and other protein-rich foods aid in depression by increasing dopamine. Foods high in protein are a good source of tyrosine, an amino acid that plays a vital role in dopamine production.²⁷ Taking B vitamins can be good too, since the body needs them to make dopamine.²⁴ When it comes to herbs, ginseng and ginkgo biloba have shown antidepressant effects.^28,29 Cowhage (an Ayurvedic herb) and oregano can help as well. These herbs are able to enhance dopamine levels.^30,31

Certain foods protect against depression by fighting inflammation. They include antioxidant-rich foods (tomatoes, broccoli, mushrooms, avocados, turmeric, and extra-virgin olive oil).³² Micronutrients like magnesium (threonate, glycinate, or taurate) and zinc (picolinate or picolinate bisglycinate) also seem to improve depression in various ways, including anti-inflammatory ones.²³

Anti-inflammatory diets typically include foods with a low glycemic index (i.e., foods that raise blood glucose and insulin levels slowly). Complex carbs help fight depression by giving the brain a stable and consistent supply of glucose. Foods rich in complex carbs include whole-grain breads and cereals, brown rice, and quinoa. Starchy vegetables like potatoes, corn, and winter squash are high in complex carbs as well.^15,33

Probiotic foods and supplements contain live strains of good bacteria and/or yeast. Prebiotics, on the other hand, are high-fiber foods that serve as food for gut microbes. Probiotics and prebiotics allow beneficial microbe species, including Bacteroides, Bifidobacterium, and Lactobacillus, to populate and thrive in the gut. Studies show that the relative abundance of these strains in the GI tract helps fight depression.^34,35

Conclusion

Low serotonin or dopamine leads to depression. Thus, the right treatment for this illness depends on which neurotransmitter is lacking in the body. Certain foods can worsen or improve depression through their impact on serotonin and/or dopamine levels, inflammation, blood sugar, and the gut microbiome.

Your mood and mental well-being is complex and unique. A diet that considers your needs as an individual is key to maximizing your overall health and performance. Learn more by clicking here.

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