# Probiotic doses - comparing CFU measurements

I have a probiotic that says it has 8 billion CFU (colony forming units) per capsule.

I'm reading a paper on this same probiotic that discusses a study where the participants took 11.8 log CFU per day.

How do I compare these two dosages? How many CFU is `11.8 log`?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1198254/

The study group members (8 males and 4 females) took three probiotic containing capsules (8.4 log CFU per capsule) two times daily (the daily dose 9.2 log CFU) during three weeks.

So, the study protocol says the active group took 6 capsules a day.

The question says that the retail version of this capsule says it contains 8 billion CFU per capsule. So, without knowing the weight of the bacteria in the capsule, it's not possible to do a direct comparison as bacteria are normally counted as the ability to form colonies per g, or per ml of the bacterium. And then because these figures are very high, they are changed to a log base 10.

• er, in my quote from the study? Oct 21 '17 at 21:21
• Don't understand, that quote is from the study. Oct 21 '17 at 21:21
• In the study it said 8.4 log CFU per capsule, the capsule OP was referring to has 8 billion CFU per capsule. Are those values the same? This is what I'm asking. Otherwise the six capsules a day might not really help OP if they come in different size. I don't really now what 8.4 log means mathematically. logarithm base ten of 8.4? That would be less than one CFU... Oct 21 '17 at 21:26
• The retail capsules should say CFU/g or CFU/ml or log CFU instead of just CFU so can't be sure. But I assumed that the company makes only the one size which I used for my answer. See technologyinscience.blogspot.com/2011/11/… Oct 21 '17 at 22:41
• Thanks for clarifying that. Maybe include it in your answer? (You already have my +1, otherwise I‘d upvote again) Oct 21 '17 at 22:43