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Are all probiotics equally good for your gut microbiome?

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The gut microbiome has become a key health focus, but not all yoghurts and probiotic supplements are born equally.

QUESTIONDo all commercially available yogurts contain probiotics? Are all probiotics equally good for your gut microbiome or are some more beneficial than others?

ANSWERThe health benefits of ingesting bacteria have been known for centuries. Fermented milk, for instance, is an age-old remedy for an upset stomach.

Now, after several decades of over-eager disinfection and bacteria-avoidance, we’re seemingly rediscovering how gut bacteria boost health. But relating that to what we eat is an inexact science, and product labelling is often not much of a guide.

First up, probiotics are a subset of microorganisms, and yogurt starter cultures are not necessarily probiotics, says the Ministry for Primary Industries.  In fact, the starter cultures for yogurt are not commonly probiotics.

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If a label claims a yogurt “contains probiotics”, that constitutes a nutrition content claim. The label should also state the specific strain of probiotic used and the average quantity of that strain in colony forming units (CFUs).

At this point, it’s worth explaining the bacteria naming convention. Otherwise, any discussion of the benefits or otherwise of probiotics is like saying, “Eating food is good for us”. Yes, but which food?

So, Lactobacillus rhamnosus GG, for instance, is from the genus lactobacillus and species rhamnosus and the strain is GG. Some yogurt labels list the genus and species of bacteria the product contains, but don’t say the exact strain, nor the CFUs per serving, which is important information.

Despite widespread use of probiotic supplements, drinks and probiotic-containing yogurt, there is no evidence to suggest that randomly taking a probiotic-containing product is going to provide health benefits.

In fact, recent findings from two studies investigating the effect of an 11-strain probiotic supplement on the human gut revealed that many people’s digestive tracts prevent standard probiotics from successfully colonising them and there was considerable individual variation in how they affect the gut microflora. They also found that taking probiotics to counterbalance antibiotics could delay the return of normal gut bacteria to their original state.

Many strains of probiotic have been studied but it has been difficult to show a universal, consistent, positive cause-and-effect relationship for any single strain. And even if a particular strain was linked to a positive health effect, we would need to ensure the yogurt or food we consumed had a big enough dose of that probiotic.

Certain strains of probiotics have been linked to specific health benefits, including reducing the severity and duration of antibiotic-associated diarrhoea, eczema associated with cow’s milk allergy, respiratory tract infections, infant colic, bacterial vaginosis and urinary tract infections.

A Canadian study compared the prevalence and dosage of probiotic strains in the country’s food supply with dosages used in clinical trials and found the tested dosages were up to 25 times higher than that found in a serving of most foods.

Considering the wide range of probiotic species, strains and dosages, and how they interact with our individual gut microbiome, it is difficult to work out the health effect any particular one will have on us.

The only permitted health claim in New Zealand is for live yogurt starter cultures containing 108 CFU/gram of Lactobacillus delbrueckii, subspecies bulgaricus and streptococcus thermophilus, which improves lactose digestion.

Otherwise, go ahead and enjoy the taste of your probiotic yogurt – it may or may not be benefiting your gut microflora and health.

This article was first published in the September 29, 2018 issue of the New Zealand Listener.