A Gut Microbe That Heals the Gut Is Dying Off

L. reuteri is fading from the microbiome even as we discover more of its benefits

Not many people have L. reuteri bacteria in their gut anymore, which might explain the rise in small intestinal bacterial infections. Shutterstock

Donna Schwenk’s kitchen is overflowing with bacteria. That comes as no surprise after more than two decades of culturing food for healing—first as a personal mission to heal her baby, and now for her business.

Still, she was a bit reluctant to try out a new bacteria. Afterall, her health was in tip-top shape, and her business, Cultured Food Life, was growing. The author of three bestselling books and a podcast host, Ms. Schwenk had her hands full with her courses teaching others the ins and outs of how to make their own fermentation labs at home.

She reluctantly began culturing yogurt with a new bacterial strain—Limosilactobacillus (formerly Lactobacillus) reuteri—at the encouragement of Dr. William Davis, a cardiologist and author of several books including “Super Gut.” Dr. Davis also asked her to eat it daily for a year.

“It blew my mind. I thought I was really smart. I thought I knew everything,” Ms. Schwenk said. “They use L. reuteri to clean fermentation vats because it’s so strong.”

She said the human gut is also a fermentation vat of sorts because it nurtures the growth of many different bacteria, some of which may also need to be cleaned out. That’s where L. reuteri comes in.

“It will kill all the other [microbes] that don’t belong there, and it will thrive. That’s why it’s working so well for people, because in that upper gastro area, without L. reuteri, you start having problems if you get other bacteria in there,” Ms. Schwenk said.

She began to offer it to friends, including one who had chronic diarrhea and couldn’t leave the house. Relief from pain and embarrassment came in just a few days. Other testimonies included improved energy and mental health, less muscle fatigue, easier breathing, appetite suppression, and more.

A single bacterial species can have widespread effects in the gut by altering the entire community of microbes in the human microbiome—the total collection of bacteria, viruses, and fungi.

In the case of L. reuteri, it inhibits the growth of pathogenic species while remodeling the biome, benefits host immunity, and decreases the translocation of bacteria out of the gastrointestinal tract into the bloodstream or lymphatic system—believed to be a root cause of autoimmune disease.

L. Reuteri’s Origins

Discovered in 1962, L. reuteri colonizes human gastrointestinal tracts and can withstand a wide range of pH environments, making it a rare beneficial bacteria that can proliferate in the small intestine. Typically, bacterial overgrowth in the small intestine can lead to digestive problems, but that isn’t the case with L. reuteri. Back when it was discovered, L. reuteri was found in about 30 percent to 40 percent of the population. A Science Daily article in 2010 said its presence had shrunk to 10 percent to 20 percent by then. Dr. Davis and others claim its level is now at 4 percent.

As with many other bacteria that are disappearing from the human microbiome, L. reuteri’s extinction is connected to antibiotic overuse, glyphosate, emulsifiers in processed food, and stomach acid blockers. Dr. Davis told The Epoch Times that L. reuteri is quite susceptible to death by antibiotics.

“Even though reuteri is ubiquitous in mammals and in indigenous human population like New Guinea or in the Brazilian rainforest, almost nobody in the modern world has reuteri anymore because we’ve all killed it,” he said.

It’s believed that L. reuteri is conferred to infants from breastfeeding mothers. A 2008 study published in Microbial Ecology in Health and Disease looked at samples of breast milk from different regions to illustrate the differences between the bacterial makeup of breast milk by country. Breastfeeding translates to greater protection against childhood diseases such as asthma and obesity.

About half of the mothers from Japan and Sweden had L. reuteri in their milk. Mothers in South Africa, Israel, and Denmark had very low or undetectable levels. Urban and rural living didn’t appear to play a significant role, although the authors speculated that diet could be a factor. The Japanese diet, for instance, is high in functional, probiotic, and fermented foods.

A Stanford University study that compared diets high in fiber to those high in fermented foods lends credibility to the idea that eating foods rich in probiotics diversifies gut bacteria. Those randomly assigned to fermented food diets for 10 weeks more quickly expanded their microbiomes and also displayed decreases in molecular signs of inflammation associated with disease, according to the results published in 2021 in Cell.

L. Reuteri and Gut Infections

L. reuteri appears to have a bi-directional relationship between gut health and disease. Several studies have shown that L. reuteri’s antimicrobial properties are nature’s version of an antibiotic—capable of protecting the body from gut infections.

There are various strains of L. reuteri that undergo a metabolic process that produces lactic acid, acetic acid, ethanol, and/or reutericyclin. These metabolites have proven effective against pathogens including Escherichia coli, Clostridium difficile, Salmonella, and Helicobacter pylori (H. pylori), according to a 2018 Frontiers Microbiology review article.

H. pylori infections are a major cause of chronic gastritis and peptic ulcers, in addition to a risk factor for gastrointestinal (GI) cancers. L. reuteri supplementation is particularly effective at decreasing the bacterial load of H. pylori when both are competing for food and resources. Some studies have shown that L. reuteri has the potential to completely eradicate H. pylori.

The microbe is able to resist the acidic environment of the small intestine and adhere to intestinal epithelial cells, where it begins to regulate intestinal flora, enhance the mucosal barrier, regulate immune cells, improve antioxidant activity, and regulate the immune system of the host, according to a Frontiers Immunology review article published in August that explains L. reuteri’s mechanism of action.

L. reuteri has been successfully used in GI diseases such as colic—which can affect as many as 20 percent of newborns—and diarrhea. One way that this pathogenic antagonist does this is by secreting exopolysaccharide, which is able to form mucus that tightens junctions in the intestinal mucosal barrier and begins healing GI damage.

L. reuteri bacteria have the ability to produce mucus that helps intestinal barrier form tight junctions that can better keep pathogens and toxins from entering the blood stream.

The Rise of SIBO

It’s a logical theory that L. reuteri’s disappearance is linked to small intestinal bacterial overgrowth (SIBO), which makes its reintroduction to the GI tract a compelling alternative to harsh prescription antibiotics for the condition.

SIBO is the presence of excessive bacteria in the small intestine that cause symptoms such as abdominal pain, bloating, diarrhea, and sometimes malabsorption. Stomach acid and peristalsis (contractions that move food through the digestive tract) are protective mechanisms designed to protect the small intestine against excessive bacterial growth. Most nonspecific gastrointestinal complaints are now considered to be SIBO.

“The SIBO gets pushed back by this microbe. There’s a variety of ways to gauge that, including if you test,” Dr. Davis said.

Besides breath tests that measure the amount of hydrogen or methane that you breathe out, inflammatory markers, blood pressure, body mass index, triglycerides, and symptoms related to inflammatory bowel disease have been associated with SIBO and impacted by L. reuteri, he said.

Diseases Associated With L. Reuteri

Weak intestinal barriers—sometimes called “leaky gut”—have been implicated in a number of diseases, particularly autoimmune diseases. According to the 2018 Frontiers Microbiology review, many studies have shown that L. reuteri induces anti-inflammatory regulatory T cells, or Treg cells, which play a role in preventing autoimmunity, suppressing cytokine storms, and limiting chronic inflammatory diseases.

This makes L. reuteri a good candidate for disease prevention, as well as symptom management. “Indeed, the therapeutic potential of various L. reuteri strains has been studied in diverse diseases and the results are promising in many cases,” the study authors wrote. “The safety and tolerance of L. reuteri has been proven by the numerous clinical studies.”

Among studies with some interesting findings about L. reuteri are:

• Colon Cancer: Low levels of L. reuteri and reuterin levels are linked with colon cancer, according to research published in Cell in 2022. The study found that L. reuteri was protective against tumor formation in the colon, with reduced L. reuteri and reuterin levels found in mice and humans with colon cancer. In mice, both the bacteria and its metabolite were found to decrease tumor growth and prolong survival.
• Obesity and depression: One L. reuteri strain was shown in a 2023 Frontiers in Pharmacology study to alleviate depressive-like behaviors and obesity co-morbidities in mice. They experienced improved blood lipids and insulin resistance. The bacteria also reduced liver inflammation, tightened intestinal junctions, and alleviated dysbiosis, or the overall imbalance of gut microbes.
• Constipation: Use of L. reuteri for symptoms of gas, abdominal pain, bloating, and incomplete defecation led to better outcomes over a placebo in a double-blind trial published in 2017 in Beneficial Microbes.

Proceed With Caution

While this microbe is very promising, there are some caveats. First, there are many different strains of L. reuteri that appear to have specific applications.

Also, as the 2023 review article warned, host genetics and epigenetics—particularly diet—appear to diversify immune responses. Other issues of concern are dosing, how well studies are designed in terms of subjects and controls, the length of intervention, and the synergistic effect of multiple strains, which could be beneficial but potentially damaging.

“[M]ixed strains might get out of control due to the inconsistent reproduction speed of each strain, thus disturbing the balance and hindering the control of microecology,” the review article stated.

Weak strains were a concern for Dr. Davis, which is why he cultured the bacteria in yogurt using a supplement dose intended for newborns, which was the only one available when he began his investigations. Using flow cytometry, he was able to ferment and multiply the dose from 100 million to 300 billion.

Compared with other yogurts, it’s a bit harder to culture—requiring a sustained temperature of 100 degrees for 36 hours—and it appears that permanent gut colonization is unlikely, so it would have to be maintained through diet, Dr. Davis said. The microbe is getting a lot of attention, however, with studies in the PubMed database growing to more than 200 in 2022 from 21 studies in 2005.

“So far, every observation made in mice is proving true in humans, seen anecdotally and in clinical trials,” Dr. Davis said. “In other words, a lot of the modern phenomenon we’re seeing recede by recolonizing the upper intestine with reuteri.”

The only people who should be cautious with L. reuteri—or take reduced doses—are pregnant or menstruating women, and children, he said. That’s because when women go into labor, their oxytocin levels surge. Another way that L. reuteri is believed to work is by increasing production of oxytocin, the so-called “love” hormone that facilitates bonding, although the mechanism of action isn’t well understood.