From yogurt and other fermented foods to fresh fruits and vegetables, many everyday foods contain live microbes.And while humans have been eating these safe and potentially beneficial bacteria in their diets for thousands of years, living microbes have received far less attention than other components of the diet.With growing global awareness of the importance of gut health, many people believe that ingesting live microbes promotes good health, but until now, experts have been unable to come up with guidelines on how many microbes we should consume each day.

A team of seven interdisciplinary scientists recently published an editorial in The Journal of Nutrition.They explained that so far there is very little evidence of a link between living microbes and human health, highlighting specific gaps in studies and developing plans to quantify the relationship between living microbial consumption and population health outcomes.

In this review, the authors outline why this scientific research is worth the effort.The challenge is that past microbial consumption in the population is poorly documented.Dietary intake is often misreported in current nutrition studies;And the complex biology of the digestive tract, which makes it difficult to discover the mechanisms of microbial health benefits.

Co-author Dr Mary Ellen Sanders, executive science officer at the International Association for Probiotics and Prebiotics Sciences (ISAPP), said: "People often hear that they should continue to add 'good microbes' to their gut microbiotics.But it's important to build scientific evidence for the idea, not just assume it's true.Our paper calls on scientists around the world to start building the evidence base in a rigorous way."

The publication builds on a panel at the ISAPP 2019 annual meeting in Belgium, which aimed to explore evidence that living microbes in general - not just bacterial strains with a special status for probiotics - make up an important part of the human diet.