Over recent years there has been a surge in products containing live cultures of ‘good bacteria’, or ‘probiotics’, that claim to aid digestion, ease intestinal problems and keep your gut microbiota (the microbial population that lives in your gut) balanced and healthy. But are these probiotics as good for you as they seem?
In fact, there is actually little evidence to support the claim that the ‘friendly bacteria’ contained in probiotic drinks, yoghurts and supplements have any effect on healthy people. A group of Danish researchers from the Novo Nordisk Foundation Centre for Basic Metabolic Research, University of Copenhagen, recently reviewed the results of seven randomised controlled trials of probiotic products and supplements on the faecal microbiota of health adults and found little evidence of change.
Reviewing trial results of various probiotic products including biscuits, milk-based drinks, sachets and capsules, the team investigated their effects on the overall composition of faecal microbiota including the number of species present and the distribution of species with a population, and compared findings with those taking a placebo.
Lead author Professor Oluf Pederson said that although previous studies have shown that some probiotic interventions may help people with diseases that cause imbalances in the gut, there was “no convincing evidence […] for consistent effect of examined probiotics on faecal microbiota composition in healthy adults” and indicated the need for much larger, carefully designed and conducted clinical trials.
On the other hand, there is some evidence to suggest that probiotic therapy can benefit people with irritable bowel syndrome (IBS). In addition, people taking antibiotics for a prolonged period of time may disrupt the balance of good and bad bacteria in the gut so may be advised to take probiotics during their course, and for several weeks afterwards, in order to replenish their gut microbiota.
Even though taking probiotics may be helpful in these situations, it is advisable to discuss your options with your doctor or dietician, who may take a stool sample to determine which probiotic would be most beneficial for you. This is because what is deemed as a ‘healthy microbiota’ is not the same for all people, and what may be good for one person may not be so good for another. Therefore, although taking certain probiotics may be helpful to one individual, they could actually be harmful to someone else. It is important to have a healthy balance, but this balance needs to be specific to your individual system.
A recent study by PhD student Amy Wallis and co-author Dr Michelle Ball, both of Victoria University, suggested gender-specific differences related to the gut bacteria in patients with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Using faecal microbial data and self-reports from 274 patients with ME/CFS, Wallis and colleagues found sex-specific interactions between certain bacteria of the phylum Firmicutes and ME/CFS symptoms. For example, high levels of Streptococcus bacteria in the gut related to increased symptoms in men with CFS, yet decreased symptoms in women.
“This and other results with Lactobacillus bacteria show that caution is needed when using probiotics as, in some cases, it could do more harm than good,” Wallis added.
Further research is still required to determine the cause of these sex-specific differences, although Wallis suggests that they may be linked to how hormones and the microbiota affect the immune system. In the mean time, these results show the need for caution in probiotic use.
The lack of evidence of a genuine cause and effect relationship has caused Europe to put in place strict regulations which include banning the term ‘probiotic’ on packaging for products that contain live cultures of ‘good bacteria’, highlighting the need for further research into whether probiotics do have health benefits. Currently the Food Standards Australia and New Zealand (FSANZ) do still allow the term probiotic to be used on packaging, however they have adopted a new framework for regulation.
An additional issue with ‘probiotic’ packaging is that many products don’t specify how many bacteria they contain, and even if they do, this is only relevant at the time of packaging, as storage, light, air and moisture can all affect the bacteria and there is no way to determine how many are still alive by the time you consume the product. Likewise, specific scientific research is often over-generalised, advertising probiotic bacteria at the species level rather than the specific strain or using made up names that sound ‘scientific’ yet continue to brand their product.
Although it is true that maintaining a healthy gut microbiota is important for overall health, probiotics may not be the answer. Generally speaking, the best way for healthy adults to improve their gut health is to have a varied, balanced diet that is high in fibre. In addition, prebiotics (non-digestible food ingredients that promote the growth of beneficial microorganisms in the intestines) have been suggested to be a better choice than probiotics as they act as food for the good bacteria already present inside your gut, improving the balance, rather than adding new bacteria to the microbiota. If you must take probiotics, generally probiotic-rich whole foods are recommended over supplements due to the added nutritional benefits such as the high levels of calcium found in yoghurt.