What Really Happens to Your Body When You Start Taking Probiotics

Probiotics, good-for-you bacteria best known for their connection to healthy digestion, naturally occur in plenty of foods — often the fermented kinds, including kimchi, miso and yogurt. They also come in the form of dietary supplements, and some food brands have taken to adding them to their products (these days, you can even find probiotic ice cream!).

Whether probiotics in food or supplemental form is better is still up for debate; certain conditions seem to benefit from food-based probiotics, but this isn't always the case.

A December 2010 study in the ​International Journal of Food Microbiology​ examined human saliva and fecal samples after participants consumed either yogurt (a great source of probiotics) or probiotic pills and found that both options provided the body with comparable amounts of microorganisms.

Probiotics get their good reputation for benefiting gut health, but they can potentially support the entire body, according to the Cleveland Clinic. While probiotics are naturally part of the human system, increasing your intake — through food or supplements — can be a good way to improve your health.

"Although more research is needed to understand the exact impact of the gut microbiome when it comes to heart health, we now know our gut affects more than digestion."

And sure, while there's still a lot of work to be done around these beneficial bacteria, a multitude of studies answer the question, what do probiotics do? Here's a rundown.

You may have heard of the gut-brain connection, a term used to describe the link between our microbiota and our brains. While the research is still in its early phases, emerging studies suggest that probiotics can have a beneficial effect on mental health.

An August 2017 study in the journal ​Gastroenterology​ found 64 percent of participants with irritable bowel syndrome (IBS) and mild-to-moderate anxiety and/or depression who took a probiotic supplement every day for six weeks reported decreased depression symptoms during that time.

Just 32 percent of people taking an inactive placebo showed similar results. The study also showed, with MRI examinations, that those taking the probiotic had greater changes in the parts of the brain that deal with mood. The findings suggest that probiotics can have antidepressive properties, the researchers note.

A March 2016 study in ​Nutrition​ observed that participants who took a specific cocktail of probiotics — a mixture of three ​Lactobacillus​ and ​Bifidobacteria​ strains — over eight weeks experienced significantly reduced symptoms of depression.

While some supplement studies appear promising, not all indicate that probiotics are a mood-boosting panacea. Dietary interventions, such as a low-FODMAP diet, can trump probiotic supplements for managing anxiety, per a May 2019 review of 21 studies in ​General Psychiatry.​

A small June 2018 study in ​Clinical and Translational Gastroenterology​ found a possible connection between brain fogginess and probiotic use. Taking probiotics can lead to a possible increase in small intestinal bacterial overgrowth (SIBO) and D-lactic acidosis, which can result in disorienting brain fog.

There isn't much science on what happens to the brain after taking probiotics for a short period of time, but research has seen positive, more immediate effects of taking the bacteria, as you'll learn as you read on.

There's a lot of promise around probiotics' benefits for digestive health. "Probiotics can balance out intestinal microflora and potentially mediate bloat, diarrhea or constipation," Monica Auslander Moreno, RD, LDN, nutrition consultant for RSP Nutrition, tells LIVESTRONG.com.

Probiotics can help prevent diarrhea associated with antibiotics and periodontal disease and help induce or maintain ulcerative colitis remission, per the National Institutes of Health (NIH).

Taking probiotics may provide the body with more good-for-you bacteria, which can help restore balance in the gut, per a June 2018 study in the ​BMJ​. Probiotics may be especially helpful in preventing diarrhea for people taking antibiotics and those with Clostridioides difficile (C. Diff), according to the Cleveland Clinic.

What's more, probiotics have the potential to ease constipation, per a January 2010 ​Word Journal of Gastroenterology​ study.

Unfortunately, on the immediate side of things, taking probiotic supplements might bring about side effects like diarrhea, gas and bloating. These various tummy-related side effects are the result of the sudden increase of bacteria in the digestive system; for most people, they should subside within a few days, per the Cleveland Clinic.

There's evidence that probiotics may give your heart the cleanup it's been throbbing for.

For people with high cholesterol, certain strains of probiotics, like ​Lactobacilli​, may help prevent the production of cholesterol and break down the excess that already exists. ​Lactobacillus​ probiotics significantly reduced total cholesterol as well as LDL cholesterol (the bad kind) levels in a June 2017 study review in ​PLOS One​.

Probiotics may also have a positive effect on blood pressure. People who drank a beverage containing the probiotic ​L. plantarum​ every day for six weeks saw a significant reduction in blood pressure levels, while the control groups' levels remained unchanged, per a small December 2002 study in the ​American Journal of Clinical Nutrition.​

There's a lot more to learn about the effect of probiotics on the heart. "Although more research is needed to understand the exact impact of the gut microbiome when it comes to heart health, we now know our gut affects more than digestion," Brittany Modell, RD, founder of Brittany Modell Nutrition and Wellness, tells LIVESTRONG.com.

"We know probiotics can help with gut health, which can ultimately help with heart health."

The findings around probiotics and weight are a little muddy, but certain probiotics may be a useful tool for weight loss and reducing belly fat.

A strain called ​Lactobacillus gasseri​ may slow down dietary fat absorption and, instead, increase the amount of fat excreted by the body, per a March 2015 study published in ​Lipids in Health and Disease​.

Eating yogurt with the probiotic ​Lactobacillus fermentum​ or ​Lactobacillus amylovorus​ is linked to lowering body fat by three to four percent over a six-week period, per a January 2013 study in ​Journal of Functional Foods.​ Similarly, an April 2014 study in the ​British Journal of Nutrition​ observed that women with obesity who took ​Lactobacillus rhamnosus​ supplements lost more weight than the control group over three months.

While probiotics for weight loss may seem auspicious, certain strains of probiotics, namely, ​Lactobacillus acidophilus​, are linked to promoting weight gain, per an August 2012 ​Microbial Pathogenesis​ study.

This discovery further supports the fact that more research on individual probiotic strains is necessary for understanding probiotics' effects on our health.

Our mouths are no stranger to bacteria, but adding more of the good kind seems to have some payoff. Research suggests that probiotics may help kick bad breath to the curb.

Oral probiotics, including ​streptococcus salivarius​ strains K12 and M18, are linked to combating the growth of bacteria that's associated with halitosis, per the University of Connecticut. After one week of using probiotic lozenges, 85 percent of study participants showed a reduction in volatile sulfur compounds associated with bad breath.

Stinky smells aren't the only mouth-related condition that probiotics may be able to tackle. An October 2009 pilot study in ​Clinical Periodontology​ tested the effect of drinking probiotic milk daily for eight weeks and found that those who drank probiotics saw a decrease in gum inflammation.

A 2006 ​Swedish Dental Journal​ study, in which participants were given a certain dose of probiotics or placebo, found that those given the highest probiotics dosage showed the greatest reduction in gingivitis symptoms over a two-week period.