Do probiotics really work?

Dr Michael Mosley and other experts share what science really says - and whether food or supplements are the best options.

Michale Mosley investigates probiotics in Trust Me I'm A Doctor

Dr Michael Mosley puts fermented foods to the test. Source: BBC Worldwide

Globally, each year we spend more than $39 billion on probiotics. But is popping pills and powders or eating yoghurt really going to help with weight control, mood and digestion, or treating your allergies? And just what are probiotics, anyway? 

If you've ever been on a course of antibiotics or been unwell for some time, you may have been advised to take probiotics. These, along with prebiotics, are added – and promoted – in many everyday foods, such as yoghurt or fermented dairy drinks, and other products such as and , and are also available as a tablet, capsule or powder. All promise to help balance your gut health.
Cabbage kimchi
Korean kimchi is one of many traditional fermented foods. Source: Murdoch Books
Around the world, more than (A$39 billion) is spent on probiotics every year, even though there’s still not extensive research to support the health benefit claims. While an increasing number of studies are examining how our gut bacteria influence every aspect of our health, there is still so much we don't know about our inner eco-system. However, research during the past few years suggests that probiotics may , help children suffering from , boost, promote , aid , reduce caused by antibiotics (such as diarrhoea), treat , and even clear .

What are probiotics (and prebiotics)

“Probiotics are live organisms that have been proven by research to have a health benefit,” Accredited Practising Dietitian Charlene Grosse tells SBS. “And a prebiotic is a food substance that specifically promotes the growth of good bacteria in our bowel.”

While we're conditioned to think of bacteria as negative or harmful, and something to banish from our body, good bacteria and other microorganisms . The microorganisms in probiotics products are the as, or quite similar to, the microorganisms that normally live in our bodies (of which there are 100 trillion). 

“Probiotics are essentially supposed to work in the opposite way to antibiotics,” says Dr Saleyha Ahsan, one of the hosts of Trust Me I’m a Doctor, which takes a look at probiotics in the show’s most recent season. “Instead of killing harmful bacteria, it’s claimed they add new beneficial bacteria to the complex swamp of microbes that already live in our intestines.”

An expensive waste of money?

The question researchers, and the Food Standards Australia and New Zealand () has, is whether taking a supplement of probiotics or eating food which boasts it as an ingredient, can do our bodies any good. After all, before the bacteria in a probiotic product can change our gut for the better, ”they have to survive the perilous journey through the acid bath that is our stomach and set up home in the intestines”, Ahsan explains.  

But not all probiotics are created equal, nor does everybody respond in the same way to probiotics. “While one type of probiotic, such as Lactobacillus, may help prevent ill health, another type of the same probiotic may be useless or may do more harm than good,” Victoria University's  tells SBS. “A generic probiotic is not suitable for everyone, because the reasons for imbalance are highly individual,” she says. “Ultimately, people need to gain an understanding of their own gut health and this can be achieved by working their doctor and providing a simple stool sample."

Ball's also found that probiotics act differently between men and women, which means it's not as simple as taking a one-size-fits-all supplement to restore your gut health.
Ultimately, people need to gain understanding of their own gut health and this can be achieved by working their doctor and providing a simple stool sample.
Dr Margaret Morris, Professor and Head of Pharmacology at the School of Medical Sciences, University of New South Wales, who is currently working on the link between the gut and cognitive health, agrees that more research needs to be done. Morris' , which indicate that eating an unhealthy diet leads to poor gut bacteria, which can be linked to changes in cognitive ability (or function) may go a long way to exploring some of the effects of gut microbiota on the brain. “What we do know, is that if you have been eating poorly, drinking excessive levels of alcohol, or taking antibiotics, you'll have a disruption of the balance of good and bad bacteria in your gut,” she says. “When your bacteria is in balance, your body is healthy and your immune system is strong. If it's lacking, you're more likely to have poor memory recall, disrupted sleep patterns, low mood and other health issues.”

Another reason to ensure your bacteria is balanced is the effect it has on your weight. “When an obese person diets, the balance of their gut organisms shift towards that of a lean person,” she says of her recent . “Some obese people try to redress their bacterial imbalance by consuming probiotics, but unless you know which bacteria you're lacking, they may not do much good.”

Real food may be the best bet

“Our gut make up is determined to some extent by genes, lifestyle, history of disease and current diet,” says Dr Morris. “Based on recent laboratory research, it seems that eating prebiotic-rich and high fibre foods and cutting out sugar, saturated fats and alcohol for at least 20 consecutive weeks is, right now, a good way to properly balance your gut bacteria. It was also found that enriching the diet with flavones was effective.”

Dietitian Charlene Grosse recommends including prebiotic foods in your diet - to provide fuel for the good bacteria in your bowel - that also happen to include flavones. “These include onion, garlic, inulin, wheat, Jerusalem artichoke, chicory and bananas.” And if you want to add fermented foods to help encourage good bacteria, add, “yoghurt, kefir, kombucha, miso soup, sauerkraut and tempeh,” she says.

All of these, when made using traditional methods, can be rich in helpful bacteria.
In the first episode of Trust Me, I'm a Doctor season 6, Dr Michael Mosley and Dr Saleyha Ahsan examine whether eating taking a supplement, consuming a fermented dairy drink or eating foods high in insulin is better at encouraging a healthier gut flora and whether commercially-produced or alternative probiotics are better.
Dr Saleyha Ahsan with volunteers from an experiment on probiotics
Dr Saleyha Ahsan with volunteers from an experiment on probiotics. Source: BBC Worldwide
As Mosley explains, we’re all familiar with the idea of fermentation being used to make products such as beer, but before the invention of refrigeration, it was also widely used to preserve food. Today, it’s becoming more popular again as people embrace making their own fermented foods, such as sauerkraut (fermented cabbage), kimchi (Korean fermented vegetables), kefir (a fermented dairy drink) and kombucha (fermented tea). 

The that homemade fermented foods have higher levels of probiotics than commercial varieties. This is because the experiment concluded, some commercial varieties are subjected to pasteurisation after preparation to ensure their safety and extend their shelf life, which can kill off the bacteria, whereas that wouldn't be the case for the homemade varieties.

“For general good gut health, and to acquire a range of helpful bacteria, fermented foods are an excellent way forward, “ Mosley concludes. “And our tests suggest you’ll find more of these helpful bacteria in traditionally made fermented foods.”

If you do want to make your own probiotics, follow a recipe (fermentation and storage times and temperatures are important), and ensure that your hands and cooking utensils are clean.

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SBS Food is a 24/7 foodie channel for all Australians, with a focus on simple, authentic and everyday food inspiration from cultures everywhere. NSW stream only.
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7 min read
Published 24 February 2017 1:25pm
Updated 4 February 2020 4:04pm
By Charmaine Yabsley


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