The real deal with probiotics

September 12, 2018

One of the main questions surrounding probiotics is: what really reaches the gut?

It’s fairly simple to determine how much probiotic bacteria is in a food or supplement (at least at the time of manufacture), but how many microbes take hold in the gut and become part of the microbiome?

Immunologist Eran Elinav of the Weizmann Institute of Science attempted to find this out. He did so by directly sampling volunteers’ microbiome using endoscopies and colonoscopies.

As part of the study, 15 healthy volunteers were selected and chosen to receive either a commercially-available supplement or a placebo for a period of four weeks.

The supplement’s 11 strains comprised the four major Gram-positive bacterial genera typically used in off-the-shelf probiotics: namely Lactobacillus, Bifidobacterium, Lactococcus, and Streptococcus. The supplement contained 5 billion colony-forming units.

In half of the probiotic group, the supplemental bacteria are shown to basically pass right through them: going in one end and out the other.

In the remainder, the bacteria lingered before eventually being crowded out by highly competitive existing microbes. This according to colonoscopy and enteroscopy analysis conducted weeks after the introduction of probiotic consumption.

As well as humans, the researchers tested the effects of probiotic supplements on the intestines of mice. Interestingly, they found that “gut probiotics colonisation in supplemented GF (germ-free) mice increased by 10-fold, 5-fold, 20-fold, and 50-fold in the UGI lumen, UGI mucosa, LGI mucosa and LGI lumen.”

Trillions of bacteria make homes in our guts and everyone has a different mix of microbial inhabitants.

Dr. Elinav says it is bad to expect an off-the-shelf probiotic to work for everyone.

“And in that sense just buying probiotics at the supermarket without any tailoring, without any adjustment to the host, at least in part of the population, is quite useless,” he adds.

The research group studied the impact of probiotics after a course of antibiotics, which wipe out both good and bad bacteria.

Their trial on 46 people, published in the journal Cell, showed it led to delays in the normal healthy bacteria re-establishing themselves.

Dr. Elinav added, “Contrary to the current dogma that probiotics are harmless and benefit everyone, these results reveal a new potential adverse side effect of probiotic use with antibiotics that might even bring long-term consequences.”

There have been some proven benefits of probiotics, notably in protecting premature babies from necrotising enterocolitis.

There remains great optimism within science that understanding the complex relationship between the microbial and human parts of our body will lead to new treatments.

However, Dr. Trevor Lawley, a microbiome researcher at the Sanger Institute, said he was not surprised by the findings.

According to him, probiotics have been around for a long time and they’re coming under more scrutiny.

“These are very innovative studies, but they are preliminary findings that need replicating.The gut has a natural property to stop colonisation, as it usually blocks pathogens, and that is something we have to outmanoeuvre.”