Thanks to the ever-increasing prevalence of probiotic foods and supplements — not to mention cutesy ad campaigns featuring bouncing, smiling blobs of bacteria — ‘probiotics’ has joined the ranks of popular health buzzwords.

There are countless claims about the health benefits of probiotics; they’re often said to improve digestion, promote resistance to illness, provide relief from gastro, and many more.

However, a new study from the University of Copenhagen has concluded products marked ‘probiotic’ aren’t necessarily the silver health bullet they’re cracked up to be.

Researchers reviewed seven small, randomised control trials, which investigated the impact of probiotic products — commonly taking the form of capsules, milk drinks, yoghurts or sachets — on the gut bacteria of healthy people. The findings, published in Genome Medicine, suggest there was little effect.

“While there is some evidence from previous reviews that probiotic interventions may benefit those with disease-associated imbalances of the gut microbiota, there is little evidence of an effect in healthy individuals,” lead researcher Oluf Pederson notes.

If you're already healthy, probiotics mightn't do much for your gut. (Image: iStock)

In other words, putting your money towards a gym membership or adding some more leafy greens in your shopping trolley is probably going to be more useful for your health.

If you're sitting there thinking, 'This is all well and good, but what even is a probiotic?', we can help.

Probiotics are often referred to as "good" or "friendly" bacteria, but it's not quite that simplistic. "They are defined as live microorganisms that confer a health benefit on the host when administered in adequate amounts," explains Dr Vincent Ho, clinical academic gastroenterologist to the University of Western Sydney’s School of Medicine.

This is not to be confused with prebiotics, which Dr Ho defines as “selectively fermented ingredients that allow specific changes to the gastrointestinal microbial ecosystem that confer health benefits."

While probiotics occur naturally in certain foods, like live-cultured yoghurt (the natural kind), miso soup, kombucha and fermented vegetables, they can also be formulated into various products. The most common species of bacteria used as probiotics are Lactobacillus and Bifidobacterium.

Watch: Magdalena Roze shares five things you should know about making kombucha. (Post continues after video.)

Interestingly, there's no legal definition for the term "probiotic". However, in order for a commercial product to be classified as such, Dr Ho explains it must satisfy the following criteria:

1) Alive
2) Specified by a particular strain
3) Present in adequate amounts through to the end of shelf-life
4) Demonstrated to be effective in controlled human trials
5) Safe for the intended purpose

Meeting these stipulations isn't necessarily straightforward. In fact, the European Union introduced regulations in 2006 that effectively banned the use of the terms 'prebiotic' and 'probiotic' on packaging, because the products using them had no solid proof of their supposed benefits.

While the University of Copenhagen study indicates probiotics don't necessarily benefit already healthy people — with more research required — there are a lot of claims floating around about the effect they can have on various diseases and health conditions.

Live-cultured yoghurt is one of the most common food sources of probiotics. (Image: iStock)

Dr Ho says many of these are unsubstantiated. "[Probiotics] simply cannot act as a panacea for a lot of medical conditions and it’s important to review the evidence carefully," he explains.

The strongest evidence of any health benefit linked to probiotics is in diseases of the gut, he adds. "This makes sense, as the effects of pre- and probiotics work directly in the gut initially before other bodily organs might become involved."

The impact of probiotics in the management of irritable bowel syndrome (IBS) is one benefit that's been examined by researchers.

"A number of studies have shown significant benefits with probiotics compared to placebo. A reduction in abdominal bloating and flatulence is consistently shown in studies and some strains can help to minimise abdominal discomfort," Dr Ho says.

He adds that two strains, Saccharomyces cerevisiae and Lactobacillus rhamnosus, have also been shown to reduce the severity and duration of acute infectious diarrhoea in children when administered orally. (Post continues after gallery.)

Furthermore, certain probiotics have been shown to be effective in increasing the eradication rates of a type of bacteria that can lead to gastritis and peptic ulcers when used in combination with antibiotics.

"While the evidence is more robust for diseases that directly affect the gut, both pre- and probiotics are being currently studied in disease conditions as varied as atopic dermatitis, pancreatitis, fatty liver, obesity and in the critically ill patient in intensive care," Dr Ho says.

In sum? Don't rush to the nearest supermarket, stock up on anything that mentions 'probiotic' on its label and expect a miracle.

As with anything related to your health, attempting to self-medicate — or in this case, dramatically increasing your intake of probiotics — shouldn't be your first step. Always consult with a doctor if you have any concerns or questions.

Do you buy 'probiotic' products? Why?

Featured image: iStock.