Depression exacts a high cost. In addition to quality of life issues, it may increase risk for suicide as well as diseases including cancer and heart disease.
Alternate therapies are urgently needed.
Evidence in animals and humans
Evidence suggests that probiotics as a part of a healthy diet act as possible anxiolytic and anti-depressive agents.
Animal studies reveal that oral probiotics increased the level of critical neurotransmitters in depression such as γ-aminobutyric acid, serotonin and its precursor, as well as brain-derived neurotrophic factor. Further work showed treatment resulted in reduced levels of proinflammatory cytokines with less anxiety and depressive-like behaviors.
In addition, probiotic supplementation in patients with major depression showed reduced severity of depression in a self-reported mood test.
Mode of action
- The gut microbiota interacts with the host central nervous system via the gut–brain axis.
- Improvements in gut dysbiosis suppress inflammation, thereby leading to changes in brain function, behavior, and mood.
- Certain bacteria produce neurotransmitters which are known to alter neural biochemistry and thus affect mood and behavior.
- Specific probiotics activate the vagal nerve, a network linking the brain and gut.
New population-based study
A nationwide, large population-based database among more than 26,000 Korean adults and using the Korean National Health and Nutrition Examination Survey (KNHANES, 2012–2016) data found that intake of probiotic food is significantly associated with lower severity and prevalence of depressive symptoms measured by a PHQ-9 questionnaire.
Probiotic food consumption is associated with lower severity and prevalence of depression: A nationwide cross-sectional study appeared in Nutrition journal in 2019.
In addition, the study showed a significant effect of probiotic food consumption on lower self-reported clinical depression in men but not in women.
We know that there is a sex difference in depression. Possible factors that resulted in the sex gap in this study may include genetic predisposition and hormonal differences.
Adjustment for health status and lifestyle was controlled however the authors could not rule out definitively the confounder in which people with healthier lifestyles tend to be more motivated.
Interestingly, probiotic food intake increased with higher age groups. Older groups in the Korean population tend to have a higher intake of fermented vegetables, mainly kimchi, which is known to contain various lactic acid–producing bacteria such as Leuconostoc, Lactobacillus, and Weissella.
To our knowledge, this is the first study to suggest that probiotic food consumption is significantly linked with decreases in the prevalence and severity of depression in Korean adults. The results from the present study support the suggestion that use of probiotics could be a promising preventative strategy for depression.Chong-SuKimM.S and Dong-MiShinPh.D., Seoul National University, Seoul, Korea