Digestive complaints are widespread. According to the National GI Survey, more than 60 percent of people in the U.S. report at least one gastrointestinal (GI) symptom each week—everything from heartburn and acid reflux to abdominal pain, bloating or constipation. Researchers are finding evidence that links the gut or microbiome—home to trillions of bacteria—with overall health and, in the case of an unhealthy gut, some diseases. New studies are even revealing that poor gut health is associated with worse outcomes in COVID-19. In a word, the gut is the foundation of health.
The problem with many gut symptoms lies with what we eat and how we have shifted from hunter-gatherer eating to a largely processed Western diet, says Christopher Lowry, Ph.D., a professor of integrative physiology and a probiotics researcher at the University of Colorado Boulder. “There is a hypothesis that states that inflammatory conditions are driven by reduced exposure to environmental microorganisms that we were commonly exposed to in our ancestral past,” Lowry explains. “Administration of these bacteria is then a matter of simply replacing something that we lost due to the transition from a hunter-gatherer or rural, agrarian existence to a modern urban environment.”
Lowry’s team, which focuses on probiotics and mental health, developed a vaccine made from a soil-derived bacterium that helped prevent a PTSD-like syndrome when tested on mice. “We are in awe that this bacterium, which is about one one-millionth of a meter long (one micron), can have such powerful stress-resilience effects,” says Lowry. “These studies are exciting because they point toward a future when probiotics, i.e., live microorganisms, when administered in adequate amounts, confer a health benefit on the host and may be used in a targeted way.”
To support the gut microbiome, Lowry says, “The first-line approach should be a diet rich in vegetables, fruits, nuts, seeds and healthy fats, like olive oil. The American Gut Project has highlighted how persons who report consuming, on average, more plants (30 plus) each week have a more diverse gut microbiome, which is thought to reflect a healthy gut microbiome ecosystem.” Probiotics also support a healthy brain-gut axis by actively inducing anti-inflammatory responses, Lowry says. Here’s a look at some of the strongest research. »
STRAINS
There are numerous probiotic strains. Each strain has a different effect in the body. You will see the strain names on food or supplement labels, combined with the species name. For example, the Bifidobacterium or Lactobacillus species are often abbreviated as B. or L.
Mental Health
Findings: Lowry conducted a randomized, double-blind, placebo-controlled trial that found that a probiotic called Lactobacillus reuteri reduced C-reactive protein, a measure of inflammation, and stress reactivity in veterans. It is becoming clear that inappropriate inflammation is a risk factor for anxiety, depression and PTSD, Lowry says.
Strains that help: L. acidophilus, L. casei and B. bifidum for depression, and L. casei for anxiety.
TRY: Nutrition Now PB8: 10 Probiotic Strains
GI Health
Findings: Evidence is particularly strong for probiotics and improving conditions such as diarrhea, constipation and inflammatory bowel disease, says Lowry.
Strains that help: Lactobacillus and Bifidobacterium
Metabolic Health
Findings: A 2020 meta-analysis found that probiotics improve body mass index, blood pressure, glucose metabolism and cholesterol levels in obesity, which also has links with inflammation, says Lowry.
Strains that help: L. rhamnosus, plantarum, gasseri and paracasei