Probiotics are one of the fastest growing sectors of the supplement market, and with so much research becoming available, it can be confusing to know how to select the best probiotic strain for you. For your convenience, we put the common questions people will ask (see below).

Probiotic supplements containing more than one strain of bacteria are commonly referred to as multi-strain supplements. Generally speaking, a multi-strain probiotic can be a good option as an everyday supplement to support gut health. Most high-quality, multi-strain probiotics contain around 5 or 6 different strains, but why not 10 or 15 strains? In theory, you would think that the more strains and higher number of bacteria a supplement has, the better, but this is not necessarily the case.

Dr. Lynne McFarland from the University of Seattle has authored over 150 peer-reviews, and has concluded from current data that adding more strains doesn't always lead to better outcomes for all illnesses1. But, she also acknowledges that the benefits of multi-strain mixtures may include broader range of effects. There are clearly pros and cons for both single and multi-strain probiotics – the former being more stable, the latter having the potential to offer more benefits, dependent on the strains used and condition being targeted.

The quality of the probiotics strains used is by far the most important factor to consider when selecting the right supplement, and looking at the available clinical trials behind the strains will help you to select the right strain (or strains) for you.

One concern people often have is whether their digestive system will become ‘lazy’ if they take probiotics every day. But, rest assured, probiotics are not thought to be like laxatives which can cause the gut to become 'lazy' and reliant on them in order to function. There is no current research to suggest the body becomes dependent on probiotics.

Taking too many probiotics or 'overdosing' on good bacteria is an extremely difficult thing to do. The human gut is home to roughly 40 trillion microbes. Most supplements on the market contain between 30~70 billion microorganisms per dose (depending on the product). Yogurt typically contain only 1 to 10 million per gram of bacteria. Given that the gut microbiome naturally contains in the region of 40 trillion microbes, the number of bacteria is much greater than the amount eaten, so it is easy to see why taking probiotic supplements (even at a high dose) poses us little risk.

There is absolutely no harm in taking probiotics in the long term. 

Probiotics are some of the safest natural supplements available, and have very few contraindications. There are a few groups of people who it is recommend exercise a degree of caution when they are considering supplementation with live cultures, an example of which is people who are immune-supressed (or taking immune suppressive medication), and people with dark blood in their stools. Under these circumstances, it would be wise to seek the advice of a doctor before considering probiotic supplementation.

The COVID-19 pandemic has been the driving force behind many clinical research studies over the past year. As the global scientific community races to better understand the virus, in order to slow its spread, every plausable angle has been examined. Amongst the research have been several studies examining a possible link between the SARS-CoV-2 virus and the gut microbiome. 

One published clinical study, which received worldwide press coverage has established a link between the composition of the gut microbiome and symptom severity in COVID-19 infection2. Once the link was established between the COVID-19 virus and the health of the gut microbiome, it logically called into question whether probiotics might have a part to play in the clinical picture. 

In April 2021, the British Medical Journal published the results of an observational longitudinal study3. The study considers the impact of taking various nutritional supplements including probiotics on the risk of testing positive for COVID-19. In total, 1.4 million users of the ZOE COVID Symptom Study App were included. A reduction in risk was found in those study participants taking probiotics. Probiotics were associated with the lowest risk of testing positive for the COVID-19 virus.

Although it remains to be confirmed that probiotics can help against COVID-19, it can be acknowledged that maintaining a healthy gut microbiome plays an important role in normal immune function.