What are CFUs and AFUs?

Quality over quantity is the motto for some, but you don’t always have to choose between the two and compromise. High quality and proper quantity is ideal. But making sure you are aware of and understand the correct measurements of quality and quantity is the first step to analyzing the best option between products. Probiotic quality and proper quantity are predicated upon efficacy proven through human clinical trials and research.

Bacteria Quantification

Accurately quantifying a probiotic’s bacteria is understandably important as the quantity heavily affects the efficacy of the probiotic. Oftentimes probiotic products will be dosed at levels shown to have a beneficial effect in human clinical trials and research. Although probiotics may be marketed at these efficacious levels the customer does not always receive the proven levels due to improper storage, manufacturing, and/or shipping which leads to bacteria degradation and bacteria death. When you use a probiotic the most important quantity is the number of viable bacteria at the moment of use. Simply measuring or guessing the amount of viable bacteria in a probiotic based off of weight is insufficient and inaccurate. Common ways to accurately count current probiotics is in terms of CFUs and AFUs.


LYVECAP STRONG does not compromise, it delivers top quality with proper quantity. 

Colony Forming Units (CFUs)

Colony Forming Units or CFUs is the method of plating bacteria and then counting the number of resulting colonies after a period of time allowed for growth. CFUs are a common way to enumerate the bacteria in probiotics as it is the industry standard traditional method of counting bacteria in the scientific community. CFUs give insight as to the number of bacteria present and able to grow. But, one of the fallbacks of using CFUs is its inability to count 100% of viable bacteria. Using CFUs to measure bacteria means viable but not culturable bacteria are not counted, the reason being that lab conditions can be less favorable than conditions in the gut. So with CFUs an underestimate of viable bacteria is more likely than an overestimate, which can account for bacteria degradation and bacteria death.

Active Fluorescent Units (AFUs)

Active Fluorescent Units or AFUs (sometimes referred to as TFUs or Total Fluorescence Units) is the method of counting bacteria using flow cytometry, which entails tagging bacteria with fluorescent ‘markers’ then enumerating the living bacteria. Enumerating probiotics in terms of AFUs is a more recently developed than enumerating probiotics in terms of CFUs. While CFUs remains the industry standard, enumeration in AFUs offer a quicker way to count bacteria as it can take less than an hour whereas enumeration in CFUs can take between 48-72 hours.

Takeaway: Counting probiotic bacteria in CFUs or AFUs enables probiotic products to match serving size to dosing proven to be effective. 


In terms of quantifying bacteria, choosing a probiotic based on its use of CFUs or AFUs is relatively unimportant. More important is the count of bacteria regardless of whether it is in CFUs or AFUs. Of course the quantity of bacteria in a probiotic only matters if the probiotic blend at said quantity has proven to be effective in human clinical trials and research. When it comes to choosing a probiotic you do not need to compromise between quality and proper quantity, you should have both for true efficacy.

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