There is a growing body of research indicating that there is a relationship between the brain, the gut and its natural population of friendly bacteria. Based on past studies in rodents, a team of researchers from the University College Cork wanted to test the effects of probiotics on the behavior of mice.

The scientists fed the probiotic species L. rhamnosus to mice in the team's laboratory. After a few weeks, these animals behaved in a more relaxed manner and produced lower levels of the stress hormone cortisone when compared to subjects that were given placebos. These results suggest that there is a way to treat the brain directly through the gut without being mediated by the immune system or hormones, a finding that can lead to new therapies, as reported Oct. 31 in the newsletter Food, Nutrition & Science.

"Our data show that the relationship between the gut and the brain is through the vagus nerve, which is one of the main regulators of how the brain is able to sense what is going on in the rest of the body," said author John Cryan.

Further research is needed to see how humans might react to this probiotic species, which is not commercially available.

The product rating agency states that probiotics are beneficial bacteria that can improve digestive problems, may lower cholesterol and can potentially strengthen the immune system.

Since many yogurts claim to be rich with probiotics, Consumer Reports tested many major brands to uncover the truth. The analysis included popular brands of strawberry yogurt such as Dannon, Yoplait and Stonyfield.

"It turns out that all the yogurts we tested, whether they were labeled probiotic or not, had high levels of bacteria that were good for you," said John Santa of Consumer Reports, quoted by the news source.

Although many of the yogurts contained healthy ingredients, some were very high in sugar.

"Several products we looked at contained about 25 grams of sugar per serving," said Linda Greene, a tester for Consumer Reports. "That's equal to about six teaspoons of sugar!"

"Prebiotics are a specialized soluble fiber," said industry insider Brenda Watson, adding that "as a soluble fiber, prebiotics break down in the digestive tract to perform a specific function instead of passing through relatively intact as insoluble fiber does.”

Watson emphasized that both fibers are beneficial, and that prebiotics help feed probiotic bacteria in the intestines.

"This nutrient works with probiotic cultures to inhibit the growth of harmful bacteria that cause digestive upset, irritable bowel, gas, irregularity and bloating," said Watson.

The relationship between probiotics and prebiotics is called a symbiotic interaction.

In addition to boosting digestive health, probiotics are also believed to improve cardiovascular function and enhance the immune system. 

Although it may seem counterintuitive, some bacteria may help promote good health. Strains of these beneficial microorganisms are called probiotics and are often found in food products, such as yogurt.

However, with many people seeking multi-tasking foods, some manufacturers label items with complex terms that may fool unwitting consumers into thinking that the products they buy contain top-of-the-line probiotics. A recent article published in Men’s Health provides several tips on how individuals can seek out snacks that may provide actual health benefits.

Becoming familiar with bacteria names may help consumers sort through a grocery aisle stocked with numerous probiotics, the publication explains. Individuals should look for products that provide the genus, strain and species of the bacteria, since there is often more research available on the health-boosting qualities of specific probiotics, the magazine suggests.

The news provider warns that yogurts containing only L. bulgaricus and S. thermophilus may not be the best option for people who want their probiotics to do more than enhance lactose digestion, since these bacteria primarily provide flavor.

Probiotics are sometimes referred to as "good bacteria" that replace harmful varieties in the gut that sometimes lead to digestive health problems. The Mayo Clinic explains that healthy bacteria are naturally present in the gut, but probiotics help increase the amount of these microorganisms.

A recent study published in the journal BioEssays indicated that some probiotic strains may support psychological health as well as good digestive function.

The researchers explained that probiotic intestinal microbiota may help transport neurochemicals back and forth between the brain and the gut through the bloodstream.

"There is already evidence to suggest that the connection between gut microbes and the nervous system represents a viable route for influencing neurological function," said lead researcher Mark Lyte.

He hypothesized that lactobacilli and bifidobacteria in the gut provide a pathway for neurochemicals to be picked up into the bloodstream. Lyte cited a study conducted on laboratory rodents that indicated a similar process occurred in mice.

The researchers collected results from several previous studies, one of which indicated that walking at a brisk pace for 30 minutes per day was associated with healthy brain function in older adults.

Another group of scientists who measured participants' activity energy expenditure over the course of five years found that subjects with the highest expenditures were less likely to report poor cognitive health when they were in their late 70s.

"Various biologic mechanisms may explain the positive relation between physical activity and cognitive health. The mechanisms by which physical activity is related to late-life cognition are likely to be multifactorial," the study's authors wrote.

The National Institutes of Health recommends that adults engage in at least 150 minutes of moderate intensity physical activity each week in order to sustain good overall well-being.

The study's results showed that the protein p40 was effective in treating colitis, a condition marked by inflammation in the colon. The researchers explained that the molecule promotes intestinal epithelial cell growth and function, and also helps reduce inflammatory responses that sometimes kill healthy cells.

They said that that process is important because some species of gut bacteria aid in the digestion of certain substances, produce vitamins and promote a healthy intestinal microbial balance. When this system goes awry, it may result in chronic issues with colon health.

The study's findings indicated that oral administration of p40 thwarted intestinal injury and acute colitis in three different mouse models of intestinal inflammation.

Although these benefits have not been tested on humans, these findings may support evidence that probiotics can promote good colon and digestive health.

Recently, a new study published in the Journal of Clinical Investigation indicated that these healthful strains of bacteria may be able to protect against one specific digestive health condition called ulcerative colitis, which is caused by inflammation of the intestinal cells.

The researchers used laboratory rodents to demonstrate that the delivery of a probiotic bacteria–derived soluble protein, called p40, to the colon was effective in protecting these mice from developing colitis.

"We hypothesize that p40 may have direct effects on macrophages and/or lymphocytes to regulate immune responses during inflammation," said the study's authors.

According to the National Digestive Diseases Information Clearinghouse, as many as 70 million Americans have a digestive disease and more than 600,000 have been diagnosed with ulcerative colitis. Individuals who have this condition may experience decreased joint health, fatigue or anemia.

The news provider explained that between 2 and 3 percent of all women regularly experience these types of infections, which are commonly caused by an imbalance of the vaginal bacteria Lactobacillus crispatus.

"The problem with UTIs we are facing is antibiotic resistance. So, there is a push to develop non-antibiotic methods to prevent and treat infections," lead researcher Thomas M. Hooton told the news source.

In order to help prevent the recurrence of UTIs among 100 female participants, the researchers gave half of the subjects probiotic vaginal suppositories, while the other subjects received placebo treatments, the news outlet explained.

The study's results showed that only seven women in the test group experienced UTIs during the experiment period, compared to 13 of the participants who took fake probiotics.

The National Institutes of Health (NIH) notes that some symptoms of UTIs include frequent or painful urination, fever and exhaustion.

NextFoods, the producer of GoodBelly probiotic beverages, recently announced a new line of probiotic drinks that are vegan-friendly and safe for people who have dairy allergies.

The new selections will include GoodBelly Coconut Water, SuperGreen Live and Straightshot. The products contain the probiotic strain Lp299v, which can allow good bacteria to pass through stomach acid and access an individual's digestive system, where the microbes can multiply and promote digestive health, according to NextFoods.

A Michigan ABC News affiliate, WJRT-TV, recently reported that probiotics found both in food products and naturally in the intestines can help individuals stave off flu symptoms by fighting infectious bacteria.

The source recommended several other probiotic sources, including yogurt, buttermilk, sauerkraut and Japanese miso soup.

Taking simple steps to improve food choices may help people experience better long-term health.

Probiotic supplements may be a good option for aging adults who are susceptible to weakened immune systems and who can sometimes lack proper nutrition in their diets.