Battle of the bacteria: Probiotics ward off pathogens and protect against infections

23 Aug 2024 --- Getting a daily dose of probiotics with at least one billion live “good” bacteria will keep upper respiratory infections and stress at bay. We catch up with Dr. Olaf Larsen, senior manager of science at Yakult Nederland and assistant professor of One Health Innovation at VU Amsterdam, who shares insights about how the quality of the gut microbiota has definitive protective effects on the body.

“There was a very nice paper a few years ago on probiotics that showed that the quality of the gut microbiota is directly related to the outcome of disease, in this case, an infection with SARS-CoV-2, the virus causing COVID-19. People with relatively good quality, in general, had a very mild course of disease and full recovery — no problems,” Larsen tells Nutrition Insight.

“Whereas people that were totally on the other end of the spectrum with low-quality gut microbiota are often associated with all kinds of morbidities like obesity and metabolic syndrome and end up more often in intensive care or maybe even died because of the infection.”

Respiratory tract infections

In endurance sports, consuming probiotics can mean the difference between an average performance and a winning one, as upper respiratory tract infections or inflammation often develop.

In addition, accidentally drinking water when swimming in a river containing possible pathogenic microorganisms, like during the Olympic Games, may also increase the probability of developing gastrointestinal problems.

“There are nice results on probiotic consumption for endurance athletes to prevent upper respiratory tract infections. While this may not seem a big deal — merely a common cold — it could prevent you from winning. The clinical trial showed that the chances that you will develop an upper respiratory tract infection when you take probiotics are significantly lower,” Larsen explains.

“Doing sports is good for your health, but very intense sports influence the state of your immune system. Excessive exercise, like that for endurance athletes, may compromise the immune system, leading to a higher probability of developing upper respiratory tract infections. Marathon or triathlon athletes may have a higher chance of having such a compromised immune system, simply because the activity burdens the body.”

Larsen notes: “If you want to take probiotics, you should do this on a daily basis for an extended period of time. These microorganisms are still considered as ‘strangers’ by the body, so they will leave the body. They will not stay in the gastrointestinal tract and colonize. In order to ensure that your gastrointestinal tract has the probiotics constantly, you have to take them on a daily basis.”

Gastrointestinal complaints like diarrhea may also be prevented by taking probiotics. “For example, when you travel to countries where the hygiene is less optimal than in most parts of the Western world. You may eat contaminated foods or contaminated drinks that contain some pathogenic bacteria and then you could develop diarrhea, for example.”

“The whole idea of taking probiotics is to fill your gastrointestinal tract with many good beneficial bacteria, so they compete with the bacteria in the drinking water or the foods,” says Larsen.

Probiotics can also be taken with an antibiotic course to reduce the probability of developing diarrhea, a common side effect of antibiotic usage. Ideally, one should start taking the probiotics a few days before and continue for up to two weeks after that.

Bona fide probioticsDaily probiotic consumption significantly reduces the chance of developing upper respiratory tract infections.

The WHO has defined bona fide probiotics. Larsen underscores: “There are a few criteria for good probiotics. First of all, the microorganisms should be alive in a preparation or in the foodstuff.”

“Quite often, they’re not alive and dead. They should have a minimal dosage of one billion per portion and you need to have clinical data — scientific literature showing the potential health benefit of this specific product.”

“Scientifically, a credible probiotic contains at least one billion microorganisms that are still alive, and nowadays, this is already higher, two, three, maybe five. Some products like ours contain 20 billion.”

“Another very important thing is that the probiotics have to be determined based on the strain level,” he continues. “It’s the smallest, most detailed classification level of a microorganism. You often see so-called probiotics that state that they ‘contain Lactobacillus.’ That can be anything.”

Larsen notes that a good probiotic product will state the bacteria up to the smallest classification level, for example, Lacticaseibacillus paracasei strain Shirota. The designation “Shirota” refers to the strain.

“It is important that the strain is known because you cannot automatically say that another Lactobacillus will do the same thing because it’s different. In the end, you need the information about what strain is in your product.”

“A clinical trial that’s been published showing the health effect of this particular strain makes it credible. But ultimately, you do not want information only on the health effects of the particular strain. You want to have information on the health effects of the particular strain in a specific product,” he says.

That is because the product characteristics may influence the health benefit of the specific strain. For example, the health effect may be dependent on the strain residing in a milk product or a powder product.

Legislation hurdles

Larsen points out that the current EU regulations on probiotics complicate the assessment process for consumers, who must evaluate the quantity, clinical information and content of the probiotic product.

“Currently, it’s not allowed to publish a particular health effect on it because EFSA (European Food Safety Authority) rejected the health claim dossiers for all dedicated probiotic products in the EU.”

A simple way to identify whether an individual’s gut microbiota is a match for a specific probiotic is to keep a diary highlighting the exact complaints and the effects of the product on the body daily. The probiotic should be consumed for about eight weeks. If the particular probiotic product has not had a positive impact, one can switch to another one and try that instead.

In 2023, experts from Yakult Europe and the Netherlands sat down with Nutrition Insight to explain the modern research perspective on the gut microbiome, microorganisms and their role in overall health. Most proclaimed probiotics on the market today do not reveal how many live bacteria are in the supplements nor provide the scientific literature to verify the health benefits.

In addition, four substantial microbiome R&D projects have been launched in the European region: Holomicrobiome, MicroHealth, Fermented Foods and DeVenir. Yakult Europe, which has significant stakes in all the projects, granted Nutrition Insight an in-depth interview about the purpose, drive and objective of its futuristic initiatives, which aim to make dietary microbes an official food category.

Further, Yakult Europe hosted thought leaders to present emerging research findings on the link between gut health and its effect on mental health. In the last 30 years, there has been a steep upward trend in rising cases of depression and anxiety in Western countries. Researchers have connected the upward trend and the gut microbiome’s role in preventing these mental and mood disorders to avoid “catastrophic collapse.”

By Inga de Jong

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