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Cultures for GI Health

Colony forming units

When comparing probiotic supplements, you should always check the label for two things: the probiotic strains (there are many and they all have specific functions) and the number of CFUs the supplement contains. It is generally recommended that probiotics with at least 5-10 billion CFUs are indicated for daily use. But what does that mean?

Microbiologists have recently confirmed that all of us have somewhere in the order of 40 trillion bacterial cells in our bodies. CFU stands for colony-forming units, indicating how many live and active microbes are in a sample. Saying that a probiotic has 5 billion CFUs means that there are potentially 5 billion living microbes that can divide and multiply to contribute to the colony.

Why count cfus?

Probiotic manufacturers use the CFU designation to indicate the efficacy of their products. With simple logic, one would assume that more CFUs means better. However, there are a number of factors that are important to understand when looking at a CFU count.

How the supplement was manufactured, shipped and stored can have a big impact on whether or not the live cultures will survive the journey to your digestive tract.

The FDA is considering alternative methods of measuring the strength of probiotics but CFU is the only approved method of standardization in the industry.

counting cfus

How Much Is Too Much?

If some probiotic is good, more must be better, right? Wrong!

Ingesting a probiotic with a very high CFU count may cause a temporary immune reaction. A controlled number of new bacteria can be integrated into the intestinal ecosystem with ease, but a large influx of new strains can overwhelm the digestive tract and tax the body, creating undesirable side effects.

Diarrhea, bloating, gas and nausea are indications that the change in the gut is too quick. If you experience these symptoms, reduce the frequency of use or switch to a lower CFU product.

Shelf-Stable vs Living Cultures

Many probiotic supplements require refrigeration during their useful life. Others claim to be shelf-stable. Most bacteria are sensitive to temperature and moisture. Extreme heat can kill the organisms. In shelf-stable, freeze-dried products moisture can reactivate the cultures before they are in a hospitable environment. 

Consumer Labs has found that many probiotics sold do not contain the stated amount of CFUs. So buying a probiotic can be a little bit of a gamble. The fact is, even shelf-stable probiotics cannot survive extreme temperatures. Learn as much as you can about the manufacturing, shipping and storing process as you can before buying.

Shelf-stable probiotics are convenient but it is important to understand the factors that can create problematic temperature fluctuations. Most bacteria cannot survive extremely hot temperatures. Learn as much as you can about the manufacturing, shipping, and storing process as you can before buying.

Temperature Matters

Microorganisms are living things that need certain conditions to survive. One of the important factors is the ambient temperature. Most bacteria cannot survive temperatures outside of the range of 40℉ to 140℉.

When purchasing a probiotic with a label that says refrigerate, although it is not simple, try to confirm that the store has kept it refrigerated. Online shopping is probably more reliable, since it can be shipped overnight or with refrigerated shipping.

The instructions on many shelf-stable probiotic supplements make confusing statements. Many say do not exceed a certain temperature or refrigeration can extend shelf life. Those words suggest that refrigeration is preferable and recommended despite the label.


Shelf-stable probiotics are shipped with other non-perishable goods, which has no controlled standards. Transportation may include long periods sitting on loading docks with no temperature control.

The USDA requires that shelf-stable products be able to be stored at room temperature safely. Room temperature is generally accepted to be between 68 and 72 degrees Fahrenheit.

Manufacturers of quality shelf-stable probiotics use packaging and other methods to protect the cultures in transit.

When buying probiotics pay attention to the expiration date. Look to see if there is a guarantee. Once you get the product, be sure to follow the manufacturer’s recommendations. If you are not sure, refrigerate. Use a probiotic in blister pack or container, immediately upon removing it from its packaging.

How to Preserve Living Cultures

Given the money we spend on probiotics, it makes sense to handle the supplements so that they maintain their potency for as long as possible.

Some tips to keep in mind to prolong the cell life are:

  • Follow the manufacturer’s recommendations
  • Make sure to refrigerate after opening or at all times, if the probiotic is not shelf-stable
  • Try not to expose the probiotics to extreme temperatures
  • Us a probiotic in a blister pack, if possible
  • Make sure to seal your probiotic bottle tight after each use
  • Don’t handle the supplements and then put them back in the bottle, this may introduce moisture into the bottle from your hands

The Benefits of multi-strain probiotics

In nature, there are no completely isolated creatures. Like most living things, it turns out that our microbial friends thrive in an ecosphere of many organisms. Our gut has a collection of commensal, symbiotic, and pathogenic strains, that co-exist in harmony. Each performs its role and the process keeps rolling along.

When the balance is upset, the beneficial organisms have to compete with the pathogenic and commensal strains for energy. Supplementing the diet with a single strain may help but is just as likely to create further imbalance.

Without the presence of its neighbors, the culture cannot fully perform its functions. Selecting a probiotic with multiple complementary strains may improve the efficacy of the supplement.

The Promise of Synbiotics

Some companies have found ways to ship probiotics with prebiotic included. This provides “food” for the active cultures. Researchers refer to these supplements as synbiotics

Initial research findings seem to suggest that there may be significant benefits to pairing the right prebiotic with a probiotic strain. Finding a probiotic that ships with prebiotics may help extend the shelf life of your supplement as well as maximize the number of organisms that actually reach the intestines.


This is a selection of the most frequently asked questions about CFUs.

A higher CFU count is useful if there is a possibility of losing part of the culture in transport.

Under medical guidance, a high CFU count may be useful in the treatment of specific diseases. For daily use, the recommended CFU strength is 5 – 10 bn.

There are different with different quality issues. Shelf-stable probiotics will have a more limited variety of bacterial strains because of temperature sensitivity.

Both types of probiotics have potential control issues with shipping.

Shelf-stable products generally need to be maintained at temperatures between 68 and 72 degrees (room temperature) Fahrenheit unless the package states otherwise. Extreme heat is lethal to many bacterial strains.

On the other hand, refrigerated supplements need cool temperatures. But there is no guarantee that the shippers and vendors have not left the packages sitting out too long.


Kavita. R. Pandey, Suresh. R. Naik, and Babu. V. Vakil

Probiotics, prebiotics and synbiotics- a review

Jul 22 2015

Paulina Markowiak and Katarzyna Śliżewska

Effects of Probiotics, Prebiotics, and Synbiotics on Human Health

Sep 9 2017

Anthea Levi

Are Synbiotics the New Probiotics?: Synbiotics are set to be the next buzzy nutrition trend. Here’s what to know before you consider taking them.

May 2 2018


The information on this website is NOT medical advice. It is not intended to diagnose, treat, cure, or prevent any disease. Before making any changes please seek advice from a medical professional.

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