Healthy Science/ Probiotics: How Many Billion CFU do I Need to Maintain Daily Digestive Health?

Probiotics: How Many Billion CFU do I Need to Maintain Daily Digestive Health?

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  • The right dose of probiotics will depend on several factors—most notably, an individual’s purpose for taking probiotics
  • A daily dose of 10-20 billion CFU is advisable for individuals seeking everyday immune and digestive support
  • For some health indications, higher doses of probiotics may have a greater clinical benefit than lower doses

What Dose Should I Take?

A push towards using natural methods to maintain digestive health in recent years has led to an increased interest in probiotics—live microorganisms which confer health benefits when consumed in adequate amounts, often for immune and digestive health.1 Probiotics are thought to exert beneficial effects by supporting protective barriers, enhancing immune responses, and rebalancing the microbial community by displacing potentially pathogenic bacteria.24

Upon learning of probiotic benefits, people often want to know what constitutes as an “adequate” amount? However, because there are so many different probiotic organisms and variables to consider when making recommendations (e.g., dosage, delivery methods, number of strains, etc.) it is difficult to generalize one optimal dose as “adequate” for providing probiotic effects for everyone.5,6

Consequently, the answer to “what dose should I take?” will ultimately depend on an individual’s purpose for taking probiotics.

Colony Forming Units

Probiotic dosage is expressed in CFU, or colony forming units. This estimates the number of live microbes capable of forming colonies in laboratory testing. CFU is determined in the laboratory because it tells you the viability of the bacteria before they’re exposed to the GI tract.1 Supplemental probiotics come in a wide range of CFUs—from the high millions to as many as 200 billion.

The International Scientific Association of Probiotics and Prebiotics (ISAPP) does not assign a specific amount to their definition of “probiotic”; however, other national health agencies require a minimum of one billion CFU to be labeled as probiotic.1 Thus, ISAPP considers a total daily dose of one billion CFU to be the minimum effective amount, unless clinical research demonstrates otherwise.1

Balancing the Intestinal Ecosystem

Although the vast majority of existing clinical trials indicate that probiotic doses of 10-20 billion CFU per day are sufficient for maintaining immune and digestive health, research studies examining the dose-response of larger CFUs and products featuring CFUs of 50 to 100 billion are becoming increasingly common.6,7 While it may be tempting to assume that a larger CFU automatically translates to greater probiotic benefits, this is not necessarily the case for every individual or health indication.8,9

One of the mechanisms of probiotic therapy is restoration of intestinal balance by replacing harmful microbes with more favorable ones. Because not everyone needs very large amounts of probiotic bacteria to achieve this, regularly providing the body with a moderate infusion of high-quality bacteria may represent a more biologically meaningful approach to health maintenance than overwhelming the gut microbiota ecosystem with more bacteria than is needed.

Thus, for individuals in relatively good health, a daily dose of 10-20 billion CFU is likely sufficient for supporting everyday immune and digestive support. 

Different CFUs for Different Needs

As with most supplements and drugs, there is a large dose range over which probiotics are clinically effective, and higher dosages may be advisable for certain individuals and health conditions.1012 For example, research suggests that supplementing with a high CFU may be beneficial for people who’ve experienced a significant alteration to their gut microbiome due to illness, use of antibiotics, or other lifestyle factors.5,13

Adding to the complexity of dosing, research studies show that different health conditions can respond differently to different probiotic strains and dosages. For some health conditions, a lower dose may work as well or even better than a higher dose, whereas for other health conditions, higher amounts (50 billion+ CFU) are necessary to provide a clinical effect.7,10,1418 More and better studies investigating the dose-response relation of probiotics for different health conditions can further inform our understanding of optimal dosing. 

Survivability and Stability

CFU is not the only variable in the probiotic dosage equation. The survivability of a probiotic product’s strains and the methods used to provide stability and enhance survival within the digestive system are just as important as the number of viable bacteria it provides.19,20 After all, probiotic bacteria can’t displace pathogens if they don’t survive. For a deeper dive into variables affecting probiotic survivability, check out “Probiotics 101: Everything you need to know”.


  • It is difficult to define an “adequate” CFU for achieving probiotic effects because there are so many different probiotic organisms and variables affecting probiotic efficacy.5,6
  • The number of CFU a person needs will ultimately depend on their purpose for taking probiotics. 
  • While most studies show that 10-20 million CFU are adequate for probiotic benefits, larger CFUs may be more suitable for individuals requiring significant support and/or seeking relief from certain health conditions.7,10,1418
  • Individuals looking to start a probiotic regimen should speak with a medical professional about what CFU and strains to look for. 
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