Probiotics: The Microbiome’s Effects on Mental Health
By Sherry Coleman Collins, MS, RDN, LD
Vol. 25 No. 1 P. 10
Can probiotics and prebiotics in food, as well as in supplementation, help improve depression and anxiety?
Following multiple years of managing a global pandemic, people seem more in need of ways to manage stress and improve their mental health than ever before.
According to a report from the American Psychological Association called Stress in America 2022: Concerned for the Future, Beset by Inflation, Americans are experiencing higher rates of stress and discouragement.1 The survey, conducted between August 18 and September 2, 2022, asked 3,192 Americans to weigh in on their biggest concerns and the role that stress plays in their lives. Driven by negative views on the political climate, survey respondents reported feeling significant stress due to inflation, fear of not having enough money to care for their basic needs, and concerns for personal safety. More than one in four respondents said they couldn’t function normally due to the impact of stress. Notably, the report highlights the fact that many of the stressors are out of the individuals’ control. Yet, there are many mental health–promoting factors that can be controlled, including engaging in exercise, getting enough sleep, developing a positive support system, and maintaining a healthful diet. Can manipulating the gut microbiota also help?
The Gut-Brain Axis
Research has shown a clear connection between the gut and the brain, referred to as the gut-brain axis. The gut-brain axis describes the bidirectional communication that occurs between the gut microbiota and the brain via the central and enteric nervous systems, sympathetic and parasympathetic nervous systems, and neuroendocrine and neuroimmune pathways.2 The bidirectional communication of the gut-brain axis means the brain can impact the gut, and the gut can influence the brain. How these messages are delivered between the gut and the brain isn’t fully understood, but vitamins metabolized by bacteria in the gut, neurotransmitters, and neuroactive microbial metabolites, such as short-chain fatty acids, all play a part.2
Of course, food provides energy for the brain and nutrients for hormone production. And nutrients help preserve brain function as people age. Specific nutrients and compounds, including omega-3 fatty acids, magnesium, GABA, and L-theanine, all have been associated with improved mood.3 Using food and, if needed, the right kind of supplementation to influence the composition of good bacteria in the gut also appear to be important opportunities to support good mental health.
What’s more, it’s known that changes in the microbiome are associated with immune health, weight, and mental health.4 With regard to mental health, research has shown there are differences in the gut microbiome between people who have major depressive disorder and those who don’t.5 Since stress and anxiety have been on the rise, so have prescriptions for antidepressants.6 While some of these medications are indicated to treat depression and anxiety, they aren’t always effective and often come with unwanted side effects.6 Importantly, some medications used to treat depression and anxiety, as well as other ubiquitous drugs prescribed for other conditions, such as metformin, proton pump inhibitors, and laxatives, are associated with undesirable changes in the gut microbiota.7 The more drugs one individual takes, the stronger the impact on the gut.
Role of Probiotics
Since mood is influenced by a variety of factors, treatment for mood disorders is complex and requires a multifaceted approach. In addition to pharmacotherapies, dietary interventions and possibly including probiotics may be an affordable and effective part of the treatment plan without significant side effects. However, research on the efficacy of probiotics associated with improved mood in human subjects is limited.
A 2021 review by Bear and colleagues, published in Microorganisms, says that research on the connection between the microbiome and mood has been conducted mostly in animals.8 Few studies, and even fewer controlled trials, have been conducted in humans. Still, what researchers know about this connection is encouraging and should spur innovation and further studies, particularly since treatments for mood disorders come with limited success.
Research in humans suggests that probiotics may play a part in managing mood in individuals who don’t experience clinically diagnosed mood disorders. In a study of 38 healthy individuals, daily probiotic supplementation with a probiotic mixture (Lactobacillus fermentum LF16, L rhamnosus LR06, L plantarum LP01, and Bifidobacterium longum BL04) resulted in better sleep and improvements in mood.9 A 2019 randomized, double-blinded, placebo-controlled study showed that supplementation with Lactobacillus plantarum DR7 reduced stress and anxiety in adult subjects after eight to 12 weeks of use.10 The subjects also reported improved cognitive and memory function.
The US Probiotic Guide lists only three products on the market in the United States with research supporting their potential to improve mood: Calm Biotic, InnovixLabs Mood Probiotic, and Yakult brands, which are indicated with Level II evidence along with the disclaimer that the products aren’t a suitable substitute for standard treatment.11
What About Prebiotics?
Some experts believe a diet rich in prebiotics also may play a role in improving mood. Kara Landau, APD/AN, known as “The Prebiotic Dietitian,” and founder of Gut Feeling–Gut Health Product Development + Certification, a voluntary certification program for products designated as prebiotic, describes a gut-healthy diet as one “made up of prebiotic rich ingredients, [including] foods that contain prebiotic fibers and resistant starches, as well as polyphenolic compounds.” To increase prebiotics in the diet, she recommends Jerusalem artichokes, chicory root, asparagus, onions, green bananas, green banana flour, resistant potato starch, roasted and then cooled potatoes, whole grains, raw oats (ie, overnight oats), legumes, and lentils. Prebiotics provide the fuel for the good microbes in foods and dietary supplements. In fact, probiotics use prebiotics to produce metabolites such as short-chain fatty acids, which are known to be associated with better mood.
Putting It Into Practice
At the 2022 Food & Nutrition Conference & Expo™, Hannah D. Holscher, PhD, RD, an associate professor of nutrition and research at the University of Illinois, presented on the dietary and microbial connections to mood and cognition.12 Holscher emphasized that research on the association between the microbiota and mood in humans is limited. However, she recommends practitioners encourage clients and patients to eat a diverse diet with plenty of colorful foods. The diet can include culturally appropriate foods that improve diet quality, as well as fermentable fibers and prebiotics. Research measuring the Mediterranean diet score and the Alternative Healthy Eating Index found that the diets of people with depression and anxiety tended to be poorer in quality.13
With regard to probiotic supplementation, Holscher says it’s important to be selective, recognizing that impacts are strain-specific and dose-dependent with limited human evidence.
Since Lactobacillus strains are the most well-studied in the literature for influencing mood, one conservative approach may be to start clients with foods containing lactobacillus bacteria in increasing amounts, along with a diet Holscher describes. Once that has been achieved, dietitians can monitor clients for improvement and adjust as needed. If a supplement is determined to be appropriate, consider using those cited in the US Probiotic Guide, possibly with the addition of prebiotics. Clients should follow the regimen for eight weeks or more before determining its efficacy. Supplements and diet shouldn’t be used in place of medical management of major depressive disorder or anxiety.
The growing field of nutritional psychiatry and the emergence of psychobiotics, a term referring to beneficial bacteria that influence bacteria-brain relationships, reflect the opportunities for using food and probiotics to improve mental health.2 Diet is an essential part of supporting good mental health, as the food people eat also can impact their mind and mood. Dietitians should leverage the current research on dietary interventions that support gut health, consider probiotic supplementation where evidence supports it, and work with local mental health professionals to provide referrals when necessary.
However, helping clients and patients optimize their diet first is key. Supplementation with probiotics and prebiotics can be part of an effort to help clients feel better physically and mentally. A holistic, multidisciplinary approach will help clients get appropriate treatment that’s more effective with fewer side effects and greater benefits.
— Sherry Coleman Collins, MS, RDN, LD, is president of Southern Fried Nutrition Services in Atlanta, specializing in food allergies, digestive disorders, and nutrition communications. Visit her on Twitter, Instagram, and Facebook @DietitianSherry.
1. Stress in America 2022: concerned for the future, beset by inflation. American Psychological Association website. https://www.apa.org/news/press/releases/stress/2022/concerned-future-inflation. Accessed October 19, 2022.
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11. Clinical guide to probiotic products available in USA: applications, dosage forms and clinical evidence to date – 2022 edition. AEProbio website. http://www.usprobioticguide.com/PBCIntroduction.html?utm_source=intro_pg&utm_medium
=civ&utm_campaign=USA_CHART. Accessed October 28, 2022.
12. Holscher H. Dietary and microbial connections to mood and cognition. Presented at: Food & Nutrition Conference & Expo™; October 2022; Orlando, Florida.
13. Gibson-Smith D, Bot M, Brouwer IA, Visser M, Penninx BWJH. Diet quality in persons with and without depressive and anxiety disorders. J Psychiatr Res. 2018;106:1-7.