There are over 400 species of bacteria in your belly right now that can be the key to health or disease. The genomes of the bacteria and viruses of the human gut alone are thought to encode 3.3 million genes.
Published in The Journal of Alternative and Complementary Medicine, the study reviewed the results of seven previous studies which tested for symptoms in over 300 healthy volunteers both before and after supplementation with a probiotic.
Researchers from Griffith University in Queensland, Australia, wrote: "Interest in the gut-brain axis and emerging evidence that the intestinal microbiota can influence central nervous system function has led to the hypothesis that probiotic supplementation can have a positive effect on mood and psychological symptoms such as depression and anxiety.
"Although several human clinical trials have investigated this, results have been inconsistent. Therefore, a systematic review and meta-analytic approach was chosen to examine if probiotic consumption has an effect on psychological symptoms."
Studies published before July 2016 that were randomized and placebo controlled, and measured preclinical psychological symptoms of depression, anxiety, and perceived stress in healthy volunteers pre and post supplementation with a probiotic were included.
Seven studies met the inclusion criteria and provided data for nine comparisons.
"The meta-analysis showed that supplementation with probiotics resulted in a statistically significant improvement in psychological symptoms (standardized mean difference 0.34; 95% confidence interval 0.07-0.61, Z=2.49) compared with placebo," they wrote.
"These results show that probiotic consumption may have a positive effect on psychological symptoms of depression, anxiety, and perceived stress in healthy human volunteers."
According to lead author Dr Natalie Colson, more studies need to be conducted to determine if the consumption of probiotics could also assist with symptoms of diagnosed clinical depression.
"The research into the relationship between the gut and the brain is reasonably new however we are now starting to better understand this 'gut brain axis'.
"We don't know yet how far this could be used in the treatment of depression, however the gut microbiome presents as a potential target for the treatment of cognitive and mood disorders.
"But it does appear that generally healthy people who are going through stressful periods could certainly benefit from adding probiotics to their diet."
Further studies may allow for the development of novel probiotic treatment strategies for gastrointestinal-related disorders that are associated with impaired communication between the gut and brain, said Dr Colson.
2. Probiotics May Treat Anxiety and Depression
6 SURPRISING FACTS ABOUT MICROBES IN YOUR GUT
1. What's in Your Gut May Affect the Size of Your Gut
Need to lose weight? Why not try changing your gut bacteria? New research published in the journal Science suggests that the microbes in your gut may play a role in obesity. A probiotic supplement of exceptional quality and effectiveness that contains at least 10 billion CPU (colony-forming units) of several human strains of "friendly" intestinal micro-flora can actively prevent weight gain.
Scientists have been exploring the connection between gut bacteria and chemicals in the brain for years. New research adds more weight to the theory that researchers call "the microbiome--gut--brain axis."
Research published in Proceedings of the National Academy of Science shows that mice fed the bacterium Lactobacillus rhamnosus showed fewer symptoms of anxiety and depression. Researchers theorize that this is because L. rhamnosus acts on the central gamma-aminobutyric acid (GABA) system, which helps regulate emotional behavior.
L. rhamnosus, which is available as a commercial probiotic supplement, has also been linked to the prevention of diarrhea, atopic dermatitis, and respiratory tract infections.
3. The More Bacteria the Better
While bacteria on the outside of your body can cause serious infections, the bacteria inside your body can protect against it. Studies have shown that animals without gut bacteria are more susceptible to serious infections.
Bacteria found naturally inside your gut have a protective barrier effect against other living organisms that enter your body. They help the body prevent harmful bacteria from rapidly growing in your stomach, which could spell disaster for your bowels.
To do this, they develop a give-and-take relationship with your body.
"The host actively provides a nutrient that the bacterium needs, and the bacterium actively indicates how much it needs to the host," according to research published in The Lancet.
4. Gut Bacteria Pass from Mother to Child in Breast Milk
It's common knowledge that a mother's milk can help beef up a baby's immune system. New research indicates that the protective effects of gut bacteria can be transferred from mother to baby during breastfeeding.
Work published in Environmental Microbiology shows that important gut bacteria travels from mother to child through breast milk to colonize a child's own gut, helping his or her immune system to mature.
5. Lack of Gut Diversity Is Linked to Allergies
Too few bacteria in the gut can throw the immune system off balance and make it go haywire with hay fever.
Researchers in Copenhagen reviewed the medical records and stool samples of 411 infants. They found that those who didn't have diverse colonies of gut bacteria were more likely to develop allergies.
But before you throw your gut bacteria a proliferation party, know that they aren't always beneficial.
6. Gut Bacteria Can Hurt Your Liver
Your liver gets 70 percent of its blood flow from your intestines, so it's natural they would share more than just oxygenated blood.
Italian researchers found that between 20 and 75 percent of patients with chronic fatty liver disease--the kind not associated with alcoholism--also had an overgrowth of gut bacteria. Some believe that the transfer of gut bacteria to the liver could be responsible for chronic liver disease.
How Do Probiotics Work
Probiotics work in many different ways by their production of antimicrobial substances (organic acids, hydrogen peroxide, and bacteriocins) that inhibit pathogen adhesion and degrade toxins produced by microbial invaders. Probiotics resist colonization by competing for binding sites as well as for nutrients with pathogens. In other words, they crowd out pathogens like candida and harmful E. Coli.
Probiotics secrete various proteins that stimulate the immune system both locally and throughout the body, boost intestinal brush border enzyme activity and increase secretory-IgA (a family of antibodies lining mucous membranes). Enzymes like lactase, sucrase, maltase, alpha-glucosidase, and alkaline phosphatase are enhanced by probiotics. Cholesterol and triglyceride blood levels are metabolized and lowered by healthy probiotic populations. Probiotics are able to resist translocation, defined as the passage of pathogens from the GI tract to extraintestinal sites such as the mesenteric lymph node (MLN), spleen, liver, kidneys, and blood.
Cultured dairy products like yogurt, acidophilus milk, buttermilk, sour cream, cottage cheese and kefir are the best known food sources of friendly bacteria. Equally effective probiotic food sources include cultured/fermented vegetables (cabbage, turnips, eggplant, cucumbers, onions, squash, and carrots). Other, lesser known or used food sources of probiotics are sauerkraut and sourdough breads. Ideally, one could get a good supply of probiotics from one or more of these diverse foodstuffs. If dietary sources are not easily available, supplemental probiotic powders and capsules are good alternatives. Choose a brand that has at least 3 different strains of friendly bacteria and between 6 -- 15 billion live organisms.