An indicator of the number of microorganisms in a sample that are alive and active, as measured through a new ‘flow cytometry’ technique involving fluorescent labelling of cell parts and exposure to a laser beam.

You might have seen the acronym ‘CFU’ on your probiotics label, but what’s AFU?

AFU stands for Active Fluorescent Units. It’s an additional measurement that offers us a more precise view of the number of living and active microorganisms in a sample. Through AFU we are able to calculate all viable cells, including ones that are efficacious but not necessarily culturable (and therefore would not be counted in a traditional plated CFU measurement).

We determine AFU using a technique called ‘flow cytometry’. This may sound complicated, but it’s really just a sophisticated use of light and data. During testing, individual cells are tagged with fluorescent ‘markers’ and counted by a laser as they pass through a tube.

It’s pretty lit.