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Are probiotics worth it?
$63 billion. That’s the estimated amount people spend worldwide on probiotics in 2021. That includes sales of supplements, yogurt, and other food products. Probiotics are living microorganisms often referred to as "friendly bacteria" or "good bacteria". But does the science justify the money spent on probiotics? Are there clear health benefits from taking probiotics?
In theory, probiotics restore diversity to a person’s gut microbiome, which helps regulate the immune system and reduce inflammation. But consumer protection agencies have repeatedly slapped down companies for making unproven health claims about their products. Meanwhile wellness bloggers the world over tout probiotics as the cure for any number of ailments. And what about for already healthy people, are probiotics worth it?
That's where Metafact comes in. Each month we investigate a topic asking many independent experts to review the evidence. In 2019 we asked more than 30 gut experts to share the facts on Probiotics. There is wide interest from readers on this topic - so this month we asked our probiotics expert to let us know if anything has changed. Here's the updated review.
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Probiotics are not needed for a healthy microbiome
The science is uncertain, but taking probiotics probably won't harm you
Different probiotics companies use different strains of bacteria, so it's difficult for science to deliver a verdict on whether they carry health benefits
There's some evidence to suggest probiotics help in treatment of certain digestive ailments, but plenty of experts express doubt
Probiotics will never replace a good fiber-rich diet. To help you, read our expert summary on fiber here
2001: The year in which 'probiotic' was formally defined by the World Health Organisation
25%: Proportion of people who have used probiotics in past 6 months
$63,100,000,000: Global market for probiotics in 2021
42%: Proportion of probiotic market consumed in Asia-Pacific
$133,920,000,000: Global market predicted for probiotics by 2030
23%: Proportion of websites that make probiotic health claims that are supported by substantiated scientific evidence
20%: Number of online probiotics claims not supported by any scientific evidence
54%: Proportion of parents who use non-professional sources (the internet or family members) to prescribe probiotic supplements to their children
The ‘Magic’ Yoghurt
For hundreds of years, people have been consuming foods that are supposed to promote good digestive health, but the modern science around probiotics is typically traced back to a guy named Élie Metchnikoff. An immunologist and Nobel laureate, Metchnikoff theorized in the early 1900s that a person’s health could be improved by introducing good bacteria to the gut’s microbiome via yogurt. His ideas languished for a time, but they began to gain steam in the 1990s, when the modern probiotics industry was born.
As a 2013 article in the journal Frontiers in Public Health recalled, “Metchnikoff’s concepts laid the foundation” for the science, but that same article notes that Metchnikoff’s work has spawned plenty of fringe medical theories about the role the gut plays in any number of ailments, both real and imagined. Let's dive deeper with independent gut experts to get the facts...
Do probiotics make it past the stomach?
In order for probiotics to be most beneficial, they must be able to make it to the gastrointestinal tract. There are two related questions we needed to verify. The first: Do probiotics actually make it past the stomach? Some experts have cast doubt as to whether the bacteria in probiotics supplements can survive the acids found in the stomach.
The second question? If they do make it to the intestines, do probiotics organisms spend any meaningful amount of time there?
Let’s start with the first question. All of our experts agreed that probiotics do make it past the stomach. But the time of day when you take the probiotic can help in determining how much of the bacteria navigates all the way through your digestive tract. “Although the pH of the gut is generally considered to be highly acidic (i.e., pH<3.5-5), studies have shown that following a meal, the pH of the stomach can rise to a range of 4.0 – 6.0,” noted Case Western Reserve University Professor Mahmoud Ghannoum. “Approximately two hours after eating, the pH then returns to pre-ingestion levels.” What does that mean? “This indicates that taking your probiotic after a meal makes sense since the acidity will decrease.”
So probiotic microorganisms do make it to the gut, but do they stay there for very long? Highly unlikely. “Actually, it is quite difficult to get new strains to establish in a healthy bacterial gut community,” wrote Technical University of Denmark Professor Tine Licht. “Which is a good thing because it means that the healthy community is robust and difficult to alter.” Indeed!
How long can you expect the probiotics to remain in your gut? Dr. Ashok Kumar Pattanaik’s research found “that the probiotic-effects disappears within a fortnight of its withdrawal from the diet.” The most common bacteria found in probiotics are lactobacilli and bifidobacteria, and Dr Philippe Langella, an expert from Institut National de la Recherche Agronomique, estimated that they “could persist in the gut between 2-3 days for lactobacilli and 5-7 days for bifidobacteria.”
That’s not to say there aren’t specific cases where probiotics could colonize the gut for a longer period. Dr Toni Gabaldon, an expert from the Institute for Research in Biomedicine in Barcelona, explained that, in cases where there's "already low diversity or an unbalanced ecosystem," the probiotic has a better chance to "colonize the niche." For example, a patient could experience lower bacteria diversity after taking antibiotics. Which leads us to our next set of questions...
Are probiotics necessary for a healthy microbiome?
All of us are colonised with a diverse and complex array of microbes with whom we have established a strong symbiotic relationship. Over 95% of all microbes found on the human body can be found in the gut. There has been an explosion of commercially available probiotic products claiming to boost your gut health and support a healthy microbiome.
Yet in order to have a meaningful impact on the host, probiotics must establish themselves within the gastrointestinal environment, a process called colonisation. Most probiotics have only been shown to transiently colonise the gut, meaning that when you stop taking them, their [presumed] effects disappear. Beyond that, the challenge is that scientists don't really know what a "healthy" microbiome is, let alone understand how transient probiotics may impact the host in a meaningful way.
Professor Emma Allen-Vercoe from the University of Guelph, explains that "scientists are still working to determine what defines a 'healthy' microbiome", noting that many factors contribute to an individual's microbiome composition, so much so that each person's microbiome is unique.
Experts suggest there isn't a single probiotic that will be the cure all to microbiome-related diseases or the promoter of eternal health. Probiotics are only likely to represent one of many aspects that contribute to health and disease. "Taking probiotics without addressing lifestyle issues is not enough" highlights Professor Mahmoud Ghannoum, noting that factors such as sleep, exercise, stress and diet all impact the composition of the microbiome and must also be addressed to support a healthy gut.
While there may be debate around the use of probiotics for the treatment of certain diseases, the expert consensus is clear for healthy individuals: probiotics are not needed to support a healthy gut microbiome. Instead, eating a fiber-rich diet is what gut experts recommend to maintain a healthy microbiome.
Are probiotics helpful for digestive conditions?
While there are plenty of people who take probiotics year-round, it shouldn’t be surprising that many turn to the supplements whenever they’re suffering from digestive issues. Is there scientific evidence that probiotics actually help with these ailments?
Let’s start with IBS, short for irritable bowel syndrome, which can cause a mixture of diarrhea and constipation. “Repeated studies have failed to find any convincing differences in the gut microbiota compared to the healthy population” notes Professor Emma Allen-Vercoe, an expert from University of Guelph. Part of the problem, she writes, is that doctors still don’t completely understand the cause of IBS, so it’s impossible to determine what bacteria, if any, would help in treating it.
Others weren’t so polite in their assessment of claims that probiotics can help treat IBS. “This literature is a pile of garbage,” wrote Tom MacDonald, a professor of immunology at Queen Mary University of London. “IBS comes in two forms, constipation and diarrhea ... It has no reliable readouts apart from symptom scores and there is a huge placebo rate in trials.”
So why does he think some studies show a positive impact for IBS patients? “It is because there are a bunch of gastroenterologists who make a living out of IBS and who review each others’ papers and invite each other to meetings. There is also a big problem that different studies use different probiotic bacteria or combinations, so to do a meta-analysis you need to stick to the same probiotic, but frequently, dosing is different between studies.”
What about attempts to recolonize the gut after antibiotics treatment? Here, our experts were more mixed in their assessments. Dr Hannah Wardill, an expert from University of Adelaide, argued that “studies have been largely supportive of probiotic use after antibiotics,” but most of them don’t “differentiate between dead and alive bacteria, nor does it assess the functional aspects of the microbiome. As such, the results simply show that there is a greater presence of microbes in the stool.”
Kate Secombe, an expert who’s also from University of Adelaide, pointed to a study suggesting that probiotics can actually hinder the gut from recolonizing with healthy bacteria after antibiotics treatment. “So overall, the jury is still out on this,” she concluded. “But if you are otherwise healthy, you may be best off letting your microbiome restore itself, helped along with a varied diet including lots of fiber.”
Should healthy people take probiotics?
So we’ve addressed the role probiotics can play in treating several ailments. But what if you have a pretty normal digestive system. Should you still take probiotics? Is it safe to take them?
Most of our experts agreed that, at worst, probiotics are mostly harmless and will pass through you without any negative effects. Dr Hannah Wardill, the expert from University of Adelaide, pointed out two studies regarding this subject. The first, from the European Journal of Clinical Nutrition “reported higher levels of ‘good bacteria’ in the participants' guts, but this was not associated with any tangible health benefit.” In fact, as soon as the participants stopped taking their probiotics, the "beneficial" effects on the microbiome vanished.
The second study, published in Cell, found that healthy people who are given probiotics actually see their gut bacteria suffer. “Again not surprising,” wrote Wardill. “Often probiotics are recommended to people after they have antibiotics to help restore their gut flora, but this study actually showed that probiotics slowed down or delayed restoration of their gut bacteria!” The researchers found that it’s actually more beneficial to administer a fecal transplant of healthy stool (ideally taken from the patient prior to the antibiotics regiment).
Dr Mansel Griffiths, an expert from University of Guelph, noted that several probiotics studies with pigs showed positive health effects, but other experts wondered why you’d want to introduce new microorganisms into a healthy ecosystem. “As long as the host is already healthy and the gut microbiota is already in a homeostatic state, there's no need as such to introduce a foreign bacterium (even if it has been found to be beneficial for some people) into your already healthy gut,” wrote Dr Ravinder Nagpal, a research fellow at Wake Forest School of Medicine.
Several of our experts pointed out that, whatever your position is on probiotics, they can’t serve as a stand-in for a healthy lifestyle. “Taking probiotics without addressing lifestyles (e.g. stress, exercise, sleep) issues is not enough,” wrote Case Western Reserve University’s Mahmoud Ghannoum. “Thus, I recommend that you address these issues and eat a nutritionally balanced diet that is low glycemic, rich in fiber, and low in sugar.”
Is Kombucha and other fermented foods 'probiotic'? Under the scientific definition, unlikely. Many manufacturers make misleading labels on foods.
Are probiotics harmless? Mostly. But if you have a health condition, consult your physician.
Do probiotics affect mental health?Uncertain. Encouraging results from animal studies, not yet conclusive in humans.
Is there evidence that probiotics are good for general health? Negative. Evidence so far weak.
Do probiotics help treat colic in babies?Jury is still out on this.
Do probiotics help premature babies?Yes. Demonstrated in multiple randomised controlled trials.
Can probiotics improve your mood?Uncertain..
Do probiotics help mothers and infants?
"While probiotics are a multi billion dollar industry, there is little evidence to show that supplementing infants provides any health benefits. We conducted an observational study where 35 of 86 participating mothers self-administered probiotics during breastfeeding, as well as directly to their infants. The primary objective was to determine if probiotic exposure influenced the infants’ fecal microbiome with the secondary objective to assess associated changes to the mothers’ breast milk immunity and infant health.
Analysis of infant fecal microbiome throughout the first 6 months of life revealed that probiotics were associated with higher abundances of Bifidobacterium at week 1 only. Short-chain fatty acid production and predicted metagenomic functions of the microbial communities were not altered.
While probiotics did not alter breast milk immune markers, fecal sIgA responses were higher among probiotic supplemented infants. Surprisingly, this was not associated with better health outcomes, as the probiotic cohort had higher incidences of mucosal-associated illnesses as toddlers. This retrospective clinical comparison suggests that probiotic exposure during infancy has limited effects on gut microbial composition yet is associated with increased infection later in life.
These correlative findings caution against probiotic supplementation during infancy until rigorous controlled follow up studies determining their safety and efficacy have occurred."
Candice Quin, expert in gastroenterology from University of British Columbia