02/12/2025
Probiotics are measured in more than one way, and it makes a big difference in how you understand their effectiveness.
CFU, or colony-forming units, tells you how many bacterial cells can grow on and make what’s called a colony (or a family, so to speak). It’s a common industry standard, but it may not account for how many of those cells survive the journey, through months of storage, shipping, and finally, through your stomach acid. Plus, it may not accurately estimate the number of viable cells, since clumps of live bacteria can grow into one colony.
AFU, or active fluorescent units, takes it a step further. This measure uses advanced techniques to count how many living, metabolically active cells are still viable and ready to get to work in your gut. Think of it as the difference between counting seeds in a packet (CFU) versus knowing how many will actually sprout and grow into healthy plants (AFU).
By focusing on AFU, you get a clearer picture of what’s alive, active, and capable of supporting your microbiome, right where it matters.
