Probiotics are often represented as a gut health essential, but scientists aren't so convinced.

Food and beverage marketing seems to have been taken over by probiotics. Probiotics have been hyped as a treatment for everything from diarrhoea to mental health conditions; sales of probiotics are expected to exceed $130 billion globally in 2026. 

Many consumers swear by probiotics, but there is little empirical evidence backing up their effectiveness for any particular health issue. While ongoing research into probiotics is promising, scientific evidence remains weak while marketing claims remain strong. 

Probiotics: What The Evidence Says

Probiotics are the “good bacteria”. They exist naturally in the gut lining as well as in supplements and food. In the body, probiotics make up the gut microbiome alongside trillions of other microbes. A healthy gut microbiome is emerging as important for overall health with impacts on digestion, immune function and metabolism.

Certain foods contain probiotics naturally, particularly fermented ones like kimchi, sauerkraut, yoghurt, and kefir.

For some digestive issues, there is some evidence that probiotics can be helpful. For example, probiotics have been used in  cases of some specific infections, lactose intolerance, and a form of irritable bowel syndrome (IBS) called pouchitis. Health benefits from the use of probiotics by healthy individuals currently has weak or nonexistent scientific evidence. As with the gut microbiome, probiotics are an emerging area of science, with a lot more to learn. 

The Gut Microbiome 

Most experts agree that adding probiotics to your diet isn’t harmful. But the hype may fool you into thinking you're eating a superfood - when you may not be.

Probiotics behave differently from person to person. One reason for this is because every individual has a different microbiome - a different makeup of microbe species in the gut. As a living ecosystem, introducing a new probiotic species to that ecosystem will have a different effect in each person.

There are lots of species of probiotics, such as Lactobacillus, Bifidobacterium, and Streptococcus thermophilus. Each species comprises of different strains, so the choice can be overwhelming. This is one reason the science remains unclear: every study tests a different probiotic, and there are no standardised tests. 

Coupled together, the science is muddled as there are several moving parts. 

What Makes a Good Probiotic?

As we've outlined, the science is inconclusive, not negative. Taking probiotics is unlikely to be harmful. If you would like to try probiotics, there are a few things to consider.

Many products we assume contain probiotics, like yoghurt, actually don't - the bacteria have been killed off during pasteurisation. Look out for products that have added live bacteria post-pasteurisation. Similarly, many kombuchas are actually fully pasteurised - particularly those sold at room temperature. 

In supplements, dosage is determined by what's called Colony Forming Units (CFUs). It's the measure of viable bacteria. Again, the amount needed is strain-specific; millions of CFUs on one strain can be more effective than billions of CFUs on another. 

Overall, before choosing a probiotic, it's worth seeking medical advice rather than trying to navigate the market on your own. 

So What Is Best for Gut Health?

Marketing hype is powerful. It shapes our associations. For many people "gut health" has become synonymous with "probiotics". But this is misleading. There's something else backed up by scientific evidence that is more powerful than probiotics - and that's fibre. 

Fibre is well-supported for both changing the environment within the gut, making it more favourable, while also feeding your existing probiotic microbe communities. 

Unlike probiotics, we're all dramatically under-consuming fibre. 

See our article on the 5 Benefits of Fibre That Should Convince You to Eat More of It