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Diet, Microbiota, and Mood: A Comprehensive Review

11/13/2018 1:46:20 PM
Studies suggest that the intestinal microbiota influence depression, anxiety, and stress. The bidirectional communication of the gut-brain axis is thought to link the microbiome to mood, and the microbiome is known to be affected by diet. A review of studies related to diet, the microbiome, and mood was published in 2018 in Nutritional Neuroscience
Observational studies have found the Mediterranean diet pattern and other diets with a low inflammatory potential to reduce the risk of depression. Suggested beneficial components of these dietary patterns include high fiber (as a fuel source for beneficial bacteria) and high antioxidants (to reduce inflammation associated with depression). Depressed individuals have been found to eat more sweets and fast-foods and fewer fruits and vegetables, but the directionality of these relationships is not certain. 
Six clinical trials related to diet quality and mood were reviewed, and the common characteristics of diets that improved mood were high omega-3 polyunsaturated fatty acids and high fiber. The Mediterranean diet with fish oil supplementation improved mental health in depressed subjects in one clinical trial, and a modified Mediterranean diet (ModiMed) helped depression in a second trial. A comparison study of a low-carbohydrate and high-carbohydrate diet demonstrated benefit in both groups, yet a comparison of high- and low-glycemic diets found a benefit of low-glycemic load for depression. 
Fourteen clinical trials related to probiotics and mood were reviewed, but few of them evaluated the gut microbiota. Bifidobacterium longum and Lactobacillus casei Shirota showed the most promise for having a therapeutic effect in patients with mood disorders, including anxiety and depression. The effects of probiotics appear to be strain dependent, with L. rhamnosus JB-1 showing no benefit but L. rhamnosus HN001 lowering anxiety and depression scores postpartum. Combination probiotic formulas have demonstrated mixed results across studies.   
Only 3 clinical trials were identified that evaluated prebiotics and mood. The results showed that fructooligosaccharides (5 g/day) and trans-galactooligosaccharides (7 g/day) altered the intestinal microbiota and improved mood. However, galactooligosaccharides administered to healthy women had the paradoxical effect of inducing anxiety. 
Overall, observational and interventional studies suggest that diets with a low glycemic load, a low inflammatory potential, and a high amount of omega-3 fatty acids, fiber, fruits, and vegetables are beneficial for mood. The Mediterranean diet pattern has been the most extensively studied in this regard. In addition, supplementation with specific probiotic strains may support mood, whereas more research is needed to understand the effects of prebiotics.
Taylor AM, Holscher HD. A review of dietary and microbial connections to depression, anxiety, and stress. Nutr Neurosci. 2018; 1-14.

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