Don't be fooled by bacteria's bad-boy image. While often associated with super-bugs and sickness, bacteria have a much friendlier face that's essential for excellent health.

There are more microbial cells than human cells in your body, and they have a close relationship to your health and metabolism – some scientists are even beginning to think of the body's resident microbes as a sort of organ, so it's likely you'll hear more about your "gut flora" and "microbiome" in the years to come.

Beneficial bacteria have been used as a starter culture for yoghurts and fermented dairy drinks for centuries, in fact, and are still in high consumer demand.

Probiotics and prebiotics: the good bugs

  • Probiotics are live microorganisms - such as bacteria, yeasts and fungi - which in adequate amounts may have health benefits. Studies have shown they can improve digestion, help protect against disease and enhance immune function. Strains of lactobacillus and bifidobacterium bacteria are the most commonly used probiotics as they can survive the passage to the gut. Probiotics are most widely available as dietary supplements in tablet, capsule and powder forms or as a component in yoghurts and fermented dairy drinks.
  • Prebiotics are non-digestible food ingredients that can increase the activity of select "good" bacteria. Prebiotics naturally occur in bananas, asparagus, leeks, onions, garlic, chicory and wholegrains like wheat, rye, barley and oats. Savvy marketers spruik their benefits in foods including breads and infant formulas. 

Get the bug balance right

In a healthy gut, there is a balance between beneficial bacteria and pathogenic or "bad" bacteria. Climate, ageing, food, stress, illness or infection and medications can disrupt this balance leading to an excess of "bad" bacteria leading to bloating, gas and constipation. While individual studies and anecdotal evidence suggest a wide range of uses, well-studied and accepted uses for probiotics are much fewer.

Probiotics may help prevent "traveller's tummy" and diarrhoea caused by antibiotics, and are used in the treatment of acute infectious diarrhoea. The lactobacillus rhamnosus GG and saccharomyces boulardii strains have been shown to be most effective for these conditions, but there are no formal clinical guidelines for probiotic use.

Accredited practising dietitian Milena Katz says that a person's gut bacteria are very individual – like a fingerprint – so there is no one-size-fits-all advice. Katz says it's a case of trial and error and advises patients with gut problems to try high-strength probiotic capsules over six weeks to see if symptoms improve.

For healthy people, probiotics aren't necessary, but Katz says probiotic foods such as yoghurt aren't going to hurt and are generally well tolerated. Probiotics are not advised for people with severe illnesses or who are immunocompromised.

Popular opinion

When CHOICE asked people about probiotic use, positive messages abounded:
  • "Yakult, every day. No ill effects. Actually think they are part of me beating Crohns."
  • Another said he used kefir (an eastern European probiotic drink) and "never had any ill effects, just the opposite in fact!"
  • One fan of a popular probiotic wrote: "It helps my partner who suffers with MS and often has problems with candida (a yeast) overload in his throat and a bloated tum."
  • Another commented: "I also have an irritable bowel and a bloated tummy at the best of times... It helps but has not solved the problem completely."

Bugs for babies

Strains of bifidobacteria and lactobacilli – along with other lactic acid bacteria – are found naturally in breast milk and thought to contribute to normal gut development and function. In newborns, bifidobacteria make up 95% of the gut's microbial population, but this decreases to 25% in adults.

Manufacturers such as Nutricia, which makes Aptamil infant and toddler formulas, add prebiotics to their products. Listed as galacto-oligosaccharides (GOS) and long chain polyfructose, Nutricia says these are "similar in form and function to the prebiotics found in breast milk" and "encourage the good bacteria in the digestive system to flourish, reducing the amount of harmful bacteria" and "assist in digestion and promote softer stools".

A report by the American Academy of Pediatrics said there may be some long-term benefit of prebiotics (such as oligosaccharides) for the prevention of atopic eczema and common infections in healthy infants, and while adding prebiotics to infant formulas wasn't shown to be harmful to healthy infants, more evidence was needed to support routine use.

Some claims shamed

Overseas, the European Food Safety Authority rejected all probiotic health claims, often citing insufficient evidence as the reason. In the US, the Federal Trade Commission (FTC) sought legal action against both Dannon (known as Danone in Australia) and Nestle over misleading claims made about their probiotic products. While not admitting any wrongdoing, Dannon agreed in 2010 to a US$21 million settlement and softened its claims about two products – DanActive and Activia.

When Danone launched Activia probiotic yoghurt in Australia, it boasted "17 published scientific studies on Activia". We found at the time that a study-summary on the Activia website referred to only 13, four of which weren't carried out on humans. Also beware the asterisked claims on products: if you were buying Activia to "help improve digestive comfort", the proviso was that you needed to eat at least two tubs a day.

Name that strain

The type of health benefit and amount of probiotics needed to achieve this benefit is strain-specific. According to the International Scientific Association for Probiotics and Prebiotics, a probiotic must be defined at strain level, yet in clinical studies, regulatory records and product advertising, this is often not the case.

When we hit stores for a product spot-check, we found many are marketed and sold at a genus (eg lactobacillus) or species level (lactobacillus casei).

Sounds legit...

Companies can also create an entirely new name for their probiotics such as the "Bifidus ProDigestis" in Nestlé's Ski Activ Digestion Yoghurt, or Danone Activa Yoghurt's "Bifidus ActiRegularis" complex. These trademarked creations appear aligned with the product's claimed health benefits while maintaining a "scientific" sound. While consumers commonly self-prescribe probiotics and most products are widely available without health-practitioner advice, product information available to consumers is often lacking.

Numbers matter

In Australia, probiotic products are considered either functional foods and regulated by Food Standards Australia New Zealand (FSANZ), or complementary medicine and regulated by the Therapeutic Goods Administration (TGA). Under the Food Standards Code, fermented milk beverages and yoghurts that claim to be probiotic must have a minimum of one million live bacteria per gram.

While complementary medicines must show the amount of an active ingredient, foods don't have to disclose the number of probiotic bacteria in a product, which makes it difficult for consumers to make an informed purchase decision. The number of probiotic bacteria should be maintained to the end of a product's shelf life to be of any health benefit. But stability testing isn't always undertaken by manufacturers and independent testing has shown some products have far fewer probiotics than they claim.

CHOICE verdict

CHOICE believes that health claims on food or complementary medicines should undergo pre-market assessment by the regulators to prevent manufacturers from making misleading or unsubstantiated claims. All probiotic products should name the probiotic bacteria to strain level and disclose the number of bacteria in the product to help consumers in their purchase decision.