Probiotics CFU: What It Is and What to Look for When Buying a Probiotic

Putting it simply, CFU or Colony Forming Unit is the measurement used to determine the amount of good bacteria and yeasts contained in probiotics. A CFU is a viable bacteria or yeast that is able to reproduce, thus forming further groups of the same bacteria or yeasts. Biologists use the term CFU to denote the number of live and active organisms in a laboratory sample as opposed to the total of all bacteria in a sample including those that are dead or inactive. Therefore only those bacteria which are viable can be classed as probiotics.

Manufacturing of Probiotics

The bacteria and yeasts are usually manufactured in a raw material form by companies who then sell and ship these to packaging and marketing companies who then produce the supplements you see for sale in the shops. If the product is produced by a reputable manufacturer the package will contain a comprehensive label giving all the information you need to know. Without correct and thorough labelling you will be unable to make an informed decision about whether or not to purchase the product; it’s always important to read the label to make sure that you have the right information.

How Much CFU Should a Probiotic Contain?

probioticsUnfortunately there isn’t enough information available to recommend the minimum concentration of CFUs to ensure a beneficial effect in humans as the required studies have not yet been completed. Research has shown that different strains have varying abilities to colonise and grow in the gastro intestinal tract, therefore the efficiency is likely to be strain dependent. However, despite this, guidelines for daily and weekly doses of probiotics have been issued which recommend a minimum of 1 x 108 CFU/ml or CFU/g.


When you purchase a probiotic supplement, whether that’s in the form of tablets or capsules you will see the CFU/per tablet or capsule detailed on the product label. If the instructions recommend that you take more than one tablet or capsule as the dosage, the CFU listed may relate to the serving size rather than per capsule/tablet.

Most powdered probiotics will also have a recommended serving size (unless they are individually packaged portions), together with the CFU contained in that quantity. Dosages can be listed either as per teaspoon or as CFU per gram or millilitre depending on how the product is packaged. These measurements indicate how many viable microbes are contained in a certain measurement.  You may need to multiply this measurement by the number of grams or millilitres you need to take in order to get the total number of CFU in your serving size.

Most reputable supplement companies and branded probiotics available on the market will state the number of colony forming units on their product packaging.  There are two ways to do this, either by stating the number of CFUs at the time the product was manufactured or the number of CFUs expected to remain viable at the time of the expiration date of the product.   If the label merely states the number of CFUs without any reference to manufacture or expiration date then you have no way of knowing how many CFUs will be viable when you take the probiotic and whether you are actually getting the number of microbes stated on the label.

Products which only give the total number of good bacteria by weight rather than CFUs make it very difficult to accurately compare them against other similar products and it’s likely that they don’t contain enough of the culture to make them effective.  You should also be aware that sometimes supplement manufacturers may not test the CFU of the raw material before it’s packaged, meaning that the CFU number on the label may relate to the that which was in the raw material rather than the quantity that’s in the product itself.

The Effects of Transportation and Storage On CFUs

Despite providing information regarding the quantity of CFUs contained in the product on the label, there are several ways in which the CFU content listed can decrease.  For example, the amount of live microbes in the raw material can die before you ever get to take it if:

  • The raw material wasn’t transported to the manufacturer in cool low-humidity conditions.
  • The product manufacturer neglected to store the raw material in cool, low-humidity conditions.
  • The product manufacturer didn’t use a temperature and humidity controlled environment to package the raw material.
  • The packaged product wasn’t transported to the supplier in the right conditions.
  • The supplier didn’t keep the product at the correct temperature and humidity prior to sale.
  • You, the purchaser, didn’t store the product according to the instruction, for example leaving it at room temperature rather than putting it in the fridge.

Note:  some probiotics such as those containing yeasts do not require refrigeration. Another reason why you should always check the labels to make sure you have the correct information.