Depression, a widespread mental health disorder, plagues millions of individuals worldwide. With over 280 million people grappling with depression across the globe, the search for effective treatments remains paramount. Conventional approaches, such as therapy and medication, may not always yield satisfactory results or may bring about undesired side effects. Consequently, researchers and healthcare practitioners have turned their attention to alternative and complementary treatments, including the promising role of probiotics in managing depression.
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What is Depression?
Depression, sometimes referred to as major depressive disorder or clinical depression, is more than just an occasional bout of feeling down or having an off day. It's a mood disorder that leads to a constant state of sadness and disinterest in activities you once enjoyed. This enduring emotional state can significantly impact your daily life, making it difficult to function and causing both emotional and physical challenges.
It's essential to understand that depression isn't a sign of weakness, and it's not something you can simply will yourself out of. Many individuals who face depression require long-term treatment, which may involve medication, psychotherapy, or a combination of the two. It's important not to lose heart – most people dealing with depression can find relief through appropriate treatment.
Researchers have recently discovered the gut-brain axis, a fascinating connection between the trillions of microorganisms living in our digestive system (gut microbiome) and our mental health. This intricate network involves neural, hormonal, and immunological pathways. An imbalance in the gut microbiome can lead to various health issues, including mood disorders such as depression.
Symptoms of Depression
During a depressive episode, individuals may experience a range of unique symptoms that vary in severity, frequency, and duration. These symptoms can provide insights into the stage of the illness and guide functional testing and treatment.
Common emotional symptoms of depression may include:
- Persistent feelings of sadness, emptiness, or irritability
- Loss of interest or pleasure in activities once enjoyed
- Anxiety or restlessness
- Difficulty concentrating, making decisions, or recalling information
- Feelings of worthlessness, guilt, or helplessness
- Thoughts of suicide or self-harm
Physical symptoms accompanying depression can involve:
- Sleep disturbances, such as insomnia or oversleeping
- Fatigue or low energy levels
- Appetite changes, leading to weight loss or gain
- Chronic body pain
Depressive episodes can be categorized as mild, moderate, or severe based on the number, intensity, and impact of the symptoms on daily functioning. Different patterns of depressive episodes include:
- Single-episode depressive disorder, in which an individual experiences only one episode
- Recurrent depressive disorder, where a person has a history of at least two depressive episodes
- Bipolar disorder, characterized by alternating depressive episodes and periods of manic symptoms, such as elevated or irritable mood, increased activity or energy, heightened self-esteem, reduced need for sleep, distractibility, and impulsive or reckless behavior (1,2).
What are Probiotics?
Probiotics are living microorganisms that provide health benefits to the person consuming them when taken in sufficient amounts. These beneficial microorganisms support the human microbiome, the community of microbes that reside on and within our bodies. Probiotics interact with the nervous system, inhibit the growth of harmful organisms, populate the gut microbiome, modulate immune function, and synthesize vitamins, enzymes, and short-chain fatty acids (SCFAs). Additionally, they play a role in regulating digestion and metabolism. Probiotics naturally reside within our bodies and contribute to maintaining a balance of good and bad bacteria in our microbiome. You can obtain probiotics from supplements or naturally from fermented foods like yogurt, kefir, sauerkraut, and kombucha. There are three primary types of probiotic supplements: Lactobacillus and Bifidobacterium blends, Saccharomyces boulardii, and soil-based probiotic blends. Choosing the appropriate probiotic strains is essential, as each strain offers specific health benefits (6,7).
How Do Probiotics Help With Depression
Probiotics have demonstrated the potential to improve mental health disorders like depression, particularly strains of Lactobacillus and Bifidobacterium bacteria. These probiotics can influence the gut-brain axis, which is crucial to overall mental health. It's important to note that the effectiveness of probiotics is species- and strain-specific.
The gut synthesizes several neurotransmitters, hormones, and vitamins vital for mood health, such as serotonin, GABA, and dopamine. Numerous studies have shown that the intestinal microbiota of patients with depression is significantly different from that of healthy subjects. Differences in microbiota composition in depressive patients have been observed at the phylum, family, and genus levels of bacteria. For instance, the abundance of Firmicutes, Lactobacillaceae family, Bifidobacterium, and Faecalibacterium is significantly lowered in the gastrointestinal tracts of major depressive disorder patients compared to healthy individuals. In addition, the reduced abundance of certain bacteria leads to a decrease in the production of short-chain fatty acids (SCFAs), resulting in intestinal barrier dysfunction and inflammation. Some specific bacteria have also been correlated with the severity of depressive symptoms, such as the Bacteroides and Coprococcus spp. being responsible for more severe depressive symptoms.
Given the role of gut microbiota in neurotransmitter synthesis and the observed differences in microbiota composition between depressive patients and healthy subjects, probiotics may help treat depression by rebalancing the gut microbiota. Identifying the specific probiotic strains or combinations with the most significant positive effects on mental health could lead to targeted treatment options for depression (8,9).
Functional Medicine Lab Test That Can Help You Determine Which Probiotics You Need
The intricate relationship between gut health, probiotics, and depression can be better understood using two diagnostic tools: stool testing and neurotransmitter testing. These tests facilitate a comprehensive evaluation of an individual's gut microbiota and neurotransmitter levels, laying the foundation for tailored treatment plans to rectify imbalances and enhance mental well-being.
Stool Testing
Tests such as the GI-MAP stool test delve into various facets of an individual's gastrointestinal health, encompassing the presence and equilibrium of bacteria, parasites, fungi, and viruses. This information enables healthcare professionals to pinpoint imbalances, infections, and inflammation in the gastrointestinal tract, which may be linked to mental health concerns such as depression.
The test can also detect potentially harmful opportunistic bacteria that may disturb gut balance and trigger inflammation by examining the abundance of beneficial bacteria that can influence mood and overall health. Moreover, it identifies pathogenic bacteria, parasites, and viruses that can cause infections and result in gastrointestinal issues affecting mental health.
The GI-MAP test or the GI Effects® Comprehensive Profile also evaluates digestive function markers to ascertain the body's capacity to break down and absorb nutrients, which is essential for proper brain function and mental health. Inflammation markers are analyzed to detect gut inflammation, which can contribute to depression and other mental health disorders.
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Integrative Nutrition For Depression
The significance of diet in mental health has led to the emergence of nutritional psychiatry, a field exploring the connection between diet and emotional well-being. Research has consistently demonstrated a link between specific dietary patterns and depression risk. A diet rich in fruits, vegetables, whole grains, fish, olive oil, low-fat dairy, antioxidants, and reduced animal food consumption is associated with a decreased risk of depression. In contrast, a diet high in red and processed meats, refined grains, sweets, high-fat dairy products, butter, potatoes, and high-fat gravy, and low in fruits and vegetables, is associated with an increased risk of depression.
The Mediterranean diet is a healthy diet that has been linked to a significantly lower risk of developing depressive symptoms. This diet emphasizes the consumption of plant-based foods, whole grains, seeds and nuts, lean proteins like fish, and yogurt while avoiding added sugars, flours, animal fats, processed meats, and butter. A systematic review of various studies supports this notion, as it found that dietary changes, particularly those rich in plant chemicals called polyphenols and flavonoids, improved depression symptoms. These chemicals, known for their antioxidant and anti-inflammatory properties, are abundant in the Mediterranean diet. While maintaining consistent intake can be challenging due to varying levels of these chemicals in food, the findings of the review suggest that incorporating a Mediterranean diet for a longer duration may yield even better results in reducing depression symptoms.
The microbiome diet, another option focusing on restoring gut health, consists of a three-phase program. The first phase, the elimination diet, lasts 21 days and aims to remove foods that negatively impact a healthy microbiome, repair the gut wall, replace stomach acid and pancreatic enzymes, and reintroduce beneficial probiotic bacteria. During this phase, individuals are encouraged to consume prebiotic and probiotic foods, such as artichokes, onions, garlic, kimchi, and sauerkraut, which nourish the gut's healthy bacteria. The second phase, known as the metabolic boost, lasts for 28 days and introduces a wider range of foods, including sheep or goat's milk dairy, kefir, coconut yogurt, organic free-range eggs, gluten-free grains, beans, and sweet potatoes. The third and final phase, the lifetime tune-up, focuses on maintaining the results achieved in the previous phases by avoiding processed foods and added sugar as much as possible.
In addition to diet, consuming probiotic-rich foods can help balance the gut microbiome. Examples of such foods include yogurt containing strains like Bifidobacterium Bifidum, Lactobacillus Acidophilus, and Lactobacillus Reuteri; sauerkraut with Lactobacillus Brevis and Lactobacillus Plantarum; fermented pickles with Lactobacillus; kimchi with Lactobacillus; and tempeh with Bifidobacterium or Lactobacillus. The brain-gut connection plays a crucial role in the relationship between food and mood. Studies suggest that the gut microbiota in healthy individuals differs significantly from that in depressed individuals. A balanced gut microbiome, rich in "good" bacteria like Lactobacillus and Bifidobacterium, positively impacts the production of serotonin, a neurotransmitter that regulates sleep, appetite, moods and inhibits pain. Consuming whole, unrefined foods with protein, healthy fats, and fiber can help stabilize blood sugar levels after meals, which contributes to improved mood. Prebiotics can also play a role in reducing symptoms and supporting a healthy microbiome. Studies show that lower levels of Faecalibacterium, a gut bacteria with anti-inflammatory properties, are found in people with MDD. Consuming more prebioitics can potentially increase this bacterium, possibly reducing depressive symptoms by limiting low-grade inflammation.
Best Probiotics for Depression
Many different types of probiotics exist for gut health. Here are the most commonly supplemented probiotics used in functional nutrition that can help with symptoms of depression.
Lactobacillus helveticus and Bifidobacterium longum for Depression
L. helveticus R0052 and B. longum R0175 are probiotics that have shown promise in helping people with depression when studied together. Human research indicates that this probiotic duo can lead to notable improvements in depression symptoms. One of the ways they work is by calming the body's stress response systems, such as the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS). These systems, when overstimulated, generate high levels of stress hormones, including corticosterone, adrenaline, and noradrenaline. Research reveals that the combination of L. helveticus R0052 and B. longum R0175 can reduce these hormone levels, thus alleviating stress. In clinical trials, individuals who took both L. helveticus R0052 and B. longum R0175 experienced significant reductions in depression symptoms and decreased cortisol levels, a hormone associated with stress.
In a separate study, researchers investigated the impact of the probiotic Bifidobacterium longum NCC3001 (BL) on anxiety and depression in individuals with irritable bowel syndrome (IBS). This double-blind, randomized, placebo-controlled study involved 44 adults with IBS and mild to moderate anxiety or depression who received either BL or a placebo daily for six weeks. The findings showed that after six weeks, the participants in the BL group experienced a significant improvement in their depression scores compared to the placebo group. The BL group also reported increased quality of life scores. Functional magnetic resonance imaging (fMRI) demonstrated that BL lowered responses to negative emotional stimuli in various brain areas, including the amygdala and frontal-limbic regions. Both groups exhibited similar gut microbiota profiles, inflammation markers, and levels of neurotrophins and neurotransmitters. Nevertheless, the BL group had lower urine levels of methylamines and aromatic amino acid metabolites. At week 10, the BL group maintained lower depression scores compared to the placebo group.
Dosing: While not specific to these probiotics, the AAFP recommends 10 to 20 billion colony-forming units per day for adults taking probiotics. This follows the guidance of the first and second studies, which dosed 10 billion CFU for 8 weeks, and 10 billion CFU for 10 weeks, respectively.
Duration: 8-10 weeks, or ongoing
Bifidobacterium breve for Depression
Bifidobacterium breve has demonstrated potential in assisting individuals with major depressive disorder (MDD) and related gastrointestinal issues. In a study involving 45 participants diagnosed with MDD, researchers administered either a daily dose of CCFM1025 or a placebo for four weeks. Subsequently, they assessed improvements in mood and gastrointestinal symptoms using various rating scales.
The results revealed that those who took CCFM1025 experienced more significant improvements in their mood compared to the placebo group. Additionally, the study suggested that CCFM1025 could potentially alleviate emotional and gastrointestinal problems by influencing the serotonin system, which plays a crucial role in mood regulation. Specifically, CCFM1025 was found to notably decrease the turnover of serotonin in the bloodstream, which may contribute to its mood-enhancing effects.
Researchers believe that the benefits of CCFM1025 stem from the changes it induces in the gut's natural bacterial community and the metabolism of tryptophan, an essential amino acid involved in serotonin production. These changes might include variations in the diversity of gut bacteria, tryptophan levels, and certain tryptophan-related compounds.
Dosing: While not specific to this probiotic, the AAFP recommends 10 to 20 billion colony-forming units per day for adults taking probiotics. This follows the guidance of the study specific to B. breve, which dosed 10 billion CFU for 4 weeks.
Duration: 4 weeks, or ongoing
Combined Probiotics for Depression
Taking a mix of probiotics (including L. helveticus, B. longum, L. acidophilus, and L. casei) for eight weeks showed promising results in people with major depressive disorder. The study found that these individuals experienced significant improvements in their depression symptoms, as measured by the Beck Depression Inventory (a widely-used tool for assessing depression severity), when compared to those who received a placebo.
Dosing: While not specific to this probiotic, the AAFP recommends 10 to 20 billion colony-forming units per day for adults taking probiotics.
Duration: Ongoing
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Summary
The emerging understanding of the gut-brain axis has opened new avenues for treating depression through dietary interventions, particularly with the use of probiotics. By promoting a healthy balance of gut microbiota, probiotics may help reduce inflammation, regulate stress responses, and support the production of mood-regulating neurotransmitters. Functional medicine lab tests can guide personalized probiotic recommendations, and adopting an integrative nutrition approach can further support mental well-being. As research on this topic continues to evolve, it is essential to collaborate with healthcare professionals to determine the most effective strategies for addressing depression symptoms and promoting overall emotional health.
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