How Diet Influences Depression

About 14.8 million U.S. adults had a major depressive episode in 2020, and about 20 million currently suffer from prolonged depressed mood that interferes with their daily lives. At the same time, 31 percent of Americans over age nine have anemia or at least one vitamin deficiency, and nutrient deficiencies are a major risk factor for depression. There are many dietary and nutrition-related health issues that contribute to increased depression risk, with different mechanisms that affect the central nervous system and thus mood and cognition. So how exactly does your diet affect your mood, and how can you eat to help improve your mental health?

Serotonin Synthesis

Serotonin is thought to be an important neurotransmitter for mood. The body makes it from tryptophan, an essential amino acid that it can’t make from other compounds, and so has to attain from the diet. In some studies, removing tryptophan from the diet produced high depression rates. Converting tryptophan into serotonin requires vitamin B6. Without adequate B6, tryptophan is instead made into other proinflammatory molecules, which exacerbate depression. Birth control pills and hormone replacement therapy deplete B6, and B6 levels are typically low in depression patients. Iron, thiamin (B1), niacin (B3), folate (B9) and B12 also play pivotal roles in converting tryptophan to serotonin. Similar nutrients are needed to make dopamine and other neurotransmitters that also play a role in depression.

Energy Production

Several vitamins and minerals are crucial to the conversion of glucose to energy. The brain uses 20 percent of all energy produced by the body, so inadequate amounts of any of these can cause fatigue and lethargy, brain fog and depressed mood. Vitamins thiamin (B1), riboflavin (B2), niacin (B3) and pantothenic acid (B5) and minerals calcium, iron, magnesium and phosphorus all provide vital components to the tricarboxylic acid (TCA) cycle, which generates two-thirds of all ATP, the energy currency of the body. Potassium helps bring oxygen, another vital component of the TCA cycle, to the brain. 

Nerve and Brain Health

Myelin is a substance that forms a protective covering, or sheath, around nerve cells and allows for efficient transmission of nerve signals. Adequate levels of B5, B12, folate, choline, iron, copper and iodine are all needed to make and support healthy myelin. Monounsaturated fatty acids (MUFAs) found in olive oil help build myelin and cell membranes. Potassium enables every nerve signal, regulates serotonin levels and reduces chronic pain. Selenium regulates DNA synthesis and brain signaling pathways, along with vitamin C.

Synapses are the gaps between neurons where neurotransmitters travel from neuron to neuron to transmit signals. Magnesium is the relaxation mineral, and was one of the first supplements used to treat depression. Nerve and brain cells rely on it for proper functioning and it helps synapses transmit signals. DHA, a type of omega-3 fatty acid, improves synaptic function. Vitamin A plays a role in the body's production of DHA.

Neuroplasticity is the concept of the brain adapting to change and forming new neural links. These changes are the key to why psychotherapy is effective in reducing depression – how you think literally changes your brain structure. Making these changes requires omega-3 fatty acids, which stimulate the brain to make more nerve growth factors, magnesium, which directly stimulates brain growth and helps produce DNA, and vitamin A, which regulates cell growth and division. Adequate vitamin A reduces dementia, cancer and depression risk. Phytonutrients such as polyphenols and flavonoids promote neuron synthesis.

Brain cell health is promoted by magnesium, which helps dispose of cellular waste, potassium, which helps pump nutrients in and wastes out of cells, and DHA, which helps form healthy brain cell membranes. Vitamin C is a cofactor in many chemical reactions that help with cell health, and low vitamin C levels can lead to fatigue, depression and anxiety.

Inflammation

Inflammation is commonly seen in those with depression. Folate, B6 and B12 help break down homocysteine, a major proinflammatory molecule in the body. About a third of depressed patients have inadequate folate and/or B12 levels. Vitamins A and C have antioxidant functions in the brain, and selenium protects brain cells from damage from free radicals by helping the body make the antioxidant glutathione. EPA, another type of omega-3, lowers the concentration of inflammatory molecules in brain cells. Antioxidants in plant foods and MUFAs in olive are anti-inflammatory, soaking up free radicals before they can damage cells and cause inflammation.

Dysbiosis

Phytonutrients, fiber and fermented foods promote healthy gut flora, which play a role in regulating mood, improving cognition and decreasing anxiety. Gut microbes actually produce more neurotransmitters like serotonin and GABA than are produced by the body. In dysbiosis, there can be a reduction in those that produce these feel-good neurotransmitters and a proliferation of those that produce stress neurotransmitters like norepinephrine. Certain bacteria use tryptophan to help produce a depression and anxiety-inducing compound called indoxyl sulfate, while reducing the availability of tryptophan to produce serotonin. Some microbes can change cytokine expression and create an inflammatory state which affects mood. 

Ways to Eat to Improve Depression

There are so many nutrients implicated in diet and depression, a healthy diet for mental is a health-promoting diet in general. The current gold standard for healthy eating is the Mediterranean diet, with staple foods that include MUFA-rich olive oil, antioxidant-rich fruits, fiber-rich vegetables, beans and whole grains and omega-3 seafood, plus meat in moderation. Eating this way improves your gut microbiome, supplies crucial vitamins and minerals and supports efficient energy production and brain health. Add fermented foods like kimchi, miso and sauerkraut for an extra boost to gut health. Enjoy alcohol, refined carbohydrates and sugar in moderation on special occasions like birthdays and holidays, as they feed pathogenic microbes and disrupt blood sugar, which leads to inflammation and depression. Wash produce well to limit pesticide exposure, and avoid synthetic chemicals, drugs and antibiotics whenever possible.