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Major depressive disorder (MDD) affects about 10.4 percent of adults in one year and 20.6 percent over a lifetime (Hasin, 2018). Unfortunately, by themselves, psychotherapy and antidepressants only achieve full relief from symptoms in about 38 percent of treated patients. Combining psychotherapy and antidepressants modestly improves the outcomes.
Clearly, more must be done for patients with MDD who have only a partial improvement from psychotherapy and/or antidepressants. Fortunately, there are several options, including adding additional medications, transcranial magnetic stimulation, electroconvulsive therapy, intranasal esketamine, and lifestyle interventions.
Lifestyle interventions typically include behavioral activation (engaging in enjoyable, meaningful, or mastery-building activities, engaging in physical exercise, etc.), enhancing relationships, improving sleep, and dietary changes. Utilizing food and fluids to improve mental health is receiving greater attention due to increasing interest in nutritional psychiatry.
What we eat and drink is vitally important for brain health, but what is equally important is what not to eat. Limiting ultra-processed foods is one of the most important nutrition-related things we can do to enhance our health, including brain health. In fact, “…greater ultra-purified food intake, particularly artificial sweeteners and artificially sweetened beverages, is associated with increased risk of depression” (Samuthpongtorn, 2023).
Although dietary interventions are used to treat a range of mental disorders, this review is focused on depression. We know that “diet and nutrition play significant roles in the prevention of depression and its clinical treatment” (Huang, 2019).
The SMILES trial treated adults with Major depressive disorder and poor dietary habits with a modified Mediterranean diet. The primary modification was allowing research subjects to include additional red meat in their diets.
It was a randomized, controlled research study, which improved the quality of foods eaten and was “associated with changes in depressive symptoms” (Opie, 2018). The control group was provided with social support without any recommendations about altering their diet. They did not have the same reduction in depressive symptoms as the treatment group.
The Mediterranean diet is the traditional diet of Greek and Southern Italian people. It is based on plant foods, healthy fats (especially extra-virgin olive oil), fish, only small amounts of red meat, and few, if any, ultra-processed foods. The diet consists of a daily intake of fruits, vegetables, whole grains, beans, lentils, nuts, seeds, and lots of olive oil. The food is eaten slowly.
This diet is beneficial for patients with depression who are also receiving standard treatment, such as psychotherapy and/or antidepressants. Food is not used as a treatment by itself, but as an adjunctive treatment (Nicolaou, 2020).
One of the ways that the Mediterranean diet benefits depression is due to its anti-inflammatory and antioxidant properties. A significant percentage of depressed patients have systemic inflammation and oxidative stress (unstable molecules that injure cells). Reducing inflammation and oxidative stress plays a role in preventing and treating depression.
A second dietary treatment for depression is the ketogenic diet. Currently, we do not have sufficient controlled research data to recommend it for use in preventing and treating depression routinely. It is considered semi-experimental and should be overseen by a physician and a nutritionist. It is recommended to be an adjunctive treatment only.
Depression Essential Reads
Nevertheless, there is data that the ketogenic diet can be helpful for depression. It is a low-carbohydrate diet that allows only 20 to 50 grams of carbohydrate per day. It is high in fats and moderate in protein.
Examples of food included in the diet are eggs, meats (especially chicken and turkey), fish, avocados, nuts, and low-carb vegetables. Typical menus are available online, but it is optimal to be guided by a nutritionist.
The brain is only 2 percent of the body’s mass, but it uses 20 percent of the energy. Its primary source of energy is glucose, a simple sugar. When there is not enough glucose to meet the brain’s needs, it shifts to using ketones. These are chemicals produced when fat is broken down in the liver, providing energy for the body. Having elevated blood ketone levels is called ketosis.
Ketosis occurs when fasting, on a ketogenic diet, after prolonged exercise, or in diabetics, when insufficient insulin causes the body to burn fat for energy. In depressed people with insulin resistance (for example, from diabetes or in obese individuals), the intensity of their depressive symptoms correlates with the degree of insulin resistance.
The ketogenic diet creates an environment in the brain that reduces inflammation, has antioxidant properties, and supports mitochondrial activity. Mitochondria are small structures in cells that are known as the “powerhouse of the cell,” providing chemical energy for cell functioning (Murugan, 2020).
A ketogenic diet may be considered in patients with treatment-resistant depression who are obese, have insulin resistance, or have metabolic syndrome.
This diet is not safe for people who are taking glucagon-like peptide-2 (GLP-2) medications, people with chronic kidney disease, or those with various other contraindications. This is an additional reason to consult with your physician before starting a ketogenic diet; your doctor needs to determine if it is safe for you.
The bottom line is that diet plays a role in preventing and treating depression. It should not be used alone but can be an effective adjunct for treatment. The Mediterranean diet is well researched as an excellent diet for general health and specifically for people struggling with depression. The ketogenic diet can benefit people with depression, but should only be used as recommended by a physician and, ideally, overseen by a nutritionist.
