How do probiotics affect mood? – Nevada Today

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Probiotics are live microorganisms or “good bacteria” that have health benefits when consumed. A closely related term is ‘prebiotics,’ defined as food ingredients that promote growth or activity of beneficial microorganisms. Probiotics and prebiotics are part of the discussion regarding an exciting area of research of microbiomes, a community of microorganisms that inhabits a particular environment. The human microbiome refers to a collection of microorganisms living in or on the human body – e.g., on the skin, gums and teeth and in the genital tract and the gut. We are on the cutting edge of illuminating the complex and symbiotic relationship between the microbiome and a healthy human host.

Probiotics and prebiotics help in the balance of good and bad bacteria. The hundreds of kinds of bacteria in your gut are essential to your good health, and antibiotics, the food you eat, a variety of environmental factors and even stress can disrupt the balance between good and bad bacteria. When your gut bacteria are out of sync with more bad bacteria, a condition called dysbiosis occurs, where normally dominating bacteria species are underrepresented and harmful species fill the void. Associated illnesses with dysbiosis include periodontal disease, inflammatory bowel disease, colitis, obesity, cancer and neurological issues, such as mood changes.

We have known about a brain-to-gut connection for some time. Gut bacteria may be affecting our eating decisions by way of the vegus nerve, a connection of 100 million nerve cells from the digestive tract to the base of the brain. The gut bacteria, along with neighboring intestinal cells, communicate with branches of the nervous system: the enteric nervous system, nerves that surround the entire gastrointestinal tract. This elaborate nerve system is so sophisticated that it’s been referred to as the body’s second brain. Gut microbes may influence our mood through alteration of neural signals in the vegus nerve via taste receptors, perhaps releasing toxins to make us feel bad and good. We know that certain strains of bad bacteria can increase anxious behavior, and clinical trials have found that drinking probiotics, specifically Lactobacillus casei, will improve mood. Adding health-promoting bacteria through probiotic treatment reduces the anxiety levels caused by inflammation and infection, which can be key factors in stress and the way the body responds to it.

Historically, the role of antibiotics has been a life-saving gift of science to keep bacterial infection in check; however, there are concerns that antibiotic treatments could have marked effects on beneficial gut bacteria resulting in an increase by opportunistic bad bacteria. For example, elderly individuals treated for pneumonia by antibiotics may be prone to opposing mood changes; such as, feeling your surroundings aren’t real, sad empty feelings, irritability, nervousness; whereby, prompt intervention with probiotics can correct such issues.

The effect of the microbiome on brain are profound and complex and the subject of intense research. The symbiotic and dysbiosis relationship make this area of research poised to become one of the most fascinating and eventful of innovative therapy for medicine and neuroscience.


Stanley Omaye Portrait

Stanley T. Omaye is a professor of nutrition and toxicology in the Department of Agriculture, Nutrition and Veterinary Sciences at the University of Nevada, Reno. He is also the director of the Environmental Science & Health graduate program. His research interests include nutrition and aging, environmental health and pollutants, food safety, nutritional quality of food and more.


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