What's the difference between prebiotics and probiotics?

Yes, it’s true – live-cultured yoghurt is a good source of probiotics. Image: iStock.

Even if you’ve never stepped foot in a supplements aisle, you’re probably familiar with the terms ‘probiotics‘ and ‘prebiotics’ — and quietly wondered how, or whether, they actually differ from one another. Or what they even do in the first place.

First things first: there is indeed a difference between probiotics and prebiotics. A few of them, actually.

“Prebiotics are selectively fermented ingredients that allow specific changes to the gastrointestinal microbial ecosystem that confer health benefits,” explains Dr Vincent Ho, clinical academic gastroenterologist to the University of Western Sydney’s School of Medicine.

“Probiotics, on the other hand, are defined as living microorganisms.”

These can be formulated into various products, including foods, drugs and dietary supplements; Dr Ho says the most common species of bacteria used as probiotics are Lactobacillus and Bifidobacterium.

However, they also occur naturally in certain foods. Live-cultured yoghurt is the one of the best-known foods containing probiotic strains, but they can also be found in miso soup, fermented veggies (think pickles, kimchi and sauerkraut), certain cheeses and kombucha.

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

Prebiotics occur naturally in foods like leeks, asparagus, wheat, oats and soybeans.

The main distinction between probiotics and prebiotics is how they behave when they reach your large intestine, or colon.

Prebiotics mainly consist of nonstarch polysaccharides and oligosaccharides, Dr Ho explains, which reach the large intestine unaffected by the digestive enzymes. There, they feed and promote the growth of bacteria that’s already residing in your gut microbiome.

“[Probiotics] on ingestion in sufficient amounts reach the intestine in an active state and can exert health effects,” Dr Ho says.

So you might be asking yourself if it's time to stock up on prebiotics and probiotics. It would seem many of us are doing so; the global probiotics market is reportedly valued at several millions of dollars. Many of the health claims surrounding the topic are unsubstantiated, but there is some evidence that prebiotics and probiotics can be useful in managing certain illnesses.

"A lot of myths abound about the benefits of prebiotics and probiotics for different human diseases. They simply cannot act as a panacea for a lot of medical conditions and it’s important to review the evidence carefully," Dr Ho says.

"In general the strongest evidence of benefit of pre- and probiotics is in diseases of the gut. This makes sense, as the effects of pre- and probiotics work directly in the gut initially before other bodily organs might become involved."

Dr Ho says certain probiotics have been shown to have some benefit in the treatment of acute infectious diarrhoea in children, and to be effective in increasing the eradication rates for Helicobacter pylori (a bacteria that can cause gastritis and peptic ulcers) when used with antibiotics. (Post continues after gallery.)

Probiotics have also been shown to be beneficial in the management of IBS, when compared with 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.

As for prebiotics, the prebiotic lactulose has been shown to be helpful in the treatment of a complication of chronic liver disease called hepatic encephalopathy. Interestingly, Dr Ho adds, a UK study found prebiotics may influence mental health in humans.

However, as Mother Jones reports, there is doubt among scientists and physicians as to the effects of probiotics supplements — mainly because there hasn't been a lot of rigorous clinical testing on them.

There's also the question of whether these manufactured products actually contain the amount of active organisms they claim to, and whether these bacteria are proven to survive the journey into the gut.

In 2006, the European Union introduced regulations 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.

Dr Ho explains that there is currently no legal definition for the term probiotic. In order for a commercial product to be classified as a 'probiotic', he says, it must satisfy five 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

Essentially, as with anything related to your health, it's wiser to consult with your doctor if you want to look at (and potentially enhance) your intake of prebiotics and probiotics.

Have you ever taken a probiotic or prebiotic? What was the reason?