Research published in JAMA Psychiatry¹ adds more support to the importance of probiotics for mental health. The study, by researchers with the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, found supplementing with probiotics led to greater improvements in symptoms of depression compared to placebo, along with relieving anxiety symptoms as well.²

The beneficial results were achieved after just eight weeks of daily supplementation, showing the microbiota-gut-brain axis remains an important target in depression. As it stands, about 60% of people with major depressive disorder (MDD) don’t respond to first-line treatments like antidepressants, while one-third still experience symptoms even with treatment.³

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Probiotics Relieve Depression Symptoms

The study involved 50 patients with major depressive disorder who were taking an antidepressant. They were randomly assigned to take either four capsules daily of probiotic or a placebo. The probiotics contained 14 different strains that had previously shown antidepressant effects:⁴

While depression symptoms improved in both groups, by week four there was a greater improvement among the probiotics group.

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Meta-Analysis Shows Probiotics Work for Depression

Previously, the team conducted a review and meta-analysis involving seven studies to examine the use of probiotics for the treatment of clinical depression. They found probiotics effectively relieved depressive symptoms when given along with antidepressants, noting, “Potential mechanisms of action may be via increases in brain-derived neurotrophic factor (BDNF) and decreases in C-reactive protein (CRP).”⁸

Bacterial imbalances in the gut — known as gut dysbiosis — have been found in people with mental health conditions, which in turn have been linked to several biomarkers of depression, such as increases in cortisol and proinflammatory cytokines and lower levels of brain-derived neurotrophic factor (BDNF).⁹

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Is High-Dose Probiotic Supplementation the Answer?

As for the best dose of probiotics for mental health, the researchers noted, “In terms of optimal probiotic supplement content and dosage, there is little consensus at present.”¹¹ However, a separate randomized controlled trial demonstrated that high-dose probiotic supplementation is beneficial for people with depression.

In a four-week study published in Translational Psychiatry,¹² 21 people receiving medical help for depression received probiotics along with antidepressants, while 26 received a placebo containing maltose along with an antidepressant. The probiotic supplement contained eight different strains, amounting to a high daily dose of 900 billion colony forming units (CFUs). For comparison, the JAMA Psychiatry study used a probiotic with 8 billion colony-forming units per day.¹³

“As there is still no clear evidence which specific bacteria improve depressive symptoms,” they explained, “we decided to use a probiotic supplement that is easily accessible in drug stores and, thus, easy to implement in clinical practice.”¹⁴

Stool samples, brain imaging and depression assessments were used to evaluate the patients before, during and after the probiotics or placebo. An improvement in mood was noted among all of the patients, but those in the probiotic group had significantly greater improvements, along with an increased abundance of beneficial Lactobacillus in their gut.¹⁵

Past studies have found that Lactobacillus rhamnosus supplementation during pregnancy and postpartum led to significantly lower scores for depression and anxiety in women during the postpartum period.¹⁶ Lactobacillus has also been found to produce the gamma aminobutyric acid (GABA) neurotransmitter, which inhibits excessive neuronal firing, helping to induce a natural state of calm,¹⁷ in animal studies,¹⁸ while also reducing depression-related behavior.¹⁹

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Another study involving adults diagnosed with irritable bowel syndrome (IBS) and depression found the probiotic Bifidobacterium longum provided depression relief. At six weeks, 64% of the treatment group had reduced depression scores compared to 32% of the control group that received a placebo.^23,24

Those receiving the probiotic also reported fewer symptoms of IBS and improved overall quality of life. At the end of 10 weeks, approximately twice as many in the treatment group were still reporting lower levels of depression.

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Fermented Foods Help Relieve Stress

Long-term stress can play a role in depression, so strategies that relieve stress are important. Fermented foods, which also boost gut health, are among them. Your daily dietary patterns influence the microbes in your gut,²⁶ so researchers with APC Microbiome Ireland at University College Cork (UCC) investigated the influence of a psychobiotic diet on the microbial profile and mental health of 45 adults.²⁷

Participants were randomized to eat either a psychobiotic diet or a control diet for four weeks. The psychobiotic diet included fruits and vegetables high in prebiotic fiber, including onions, leeks, cabbage, apples and bananas, along with fermented foods, such as sauerkraut and kefir.²⁸

After four weeks, those following the psychobiotic diet had a reduction in perceived stress. Those who followed the psychobiotic diet the most had the greatest decreases in stress. Further, significant changes were found in 40 different chemicals, along with subtle changes in microbial makeup.

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Try Vitamin B12, Other Nutrient Deficiencies for Depression

In addition to probiotics, other dietary factors and nutrient deficiencies may also play a role in mental health. A study published in the British Journal of Nutrition, for instance, found an association between vitamin B12 deficiency and the incidence of depression in older people living in the community.³⁰

Older adults with low vitamin B12 levels had a 51% increased risk of developing depression during the study.³¹ Low levels of vitamin B12 may result from poor diet, or poor absorption related to lower levels of pepsin secretion that releases vitamin B12 from food. Other nutrient deficiencies associated with depression include vitamin D³² and omega-3 fats.³³

Individuals with depression are also known to have lower magnesium levels in the blood,³⁴ brain³⁵ and cerebral spinal fluid.³⁶ Only magnesium L-threonate, as opposed to magnesium chloride or magnesium gluconate, increases cerebrospinal fluid magnesium levels in animal models.³⁷

So, in addition to tending to your gut health via a healthy, whole foods diet rich in fermented foods — and possibly a probiotic supplement — people with depression may also want to consider optimizing their vitamin D levels, consuming more omega-3 fats and supplementing with magnesium L-threonate.

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Via https://articles.mercola.com/sites/articles/archive/2023/07/20/probiotics-major-depressive-disorder.aspx