What are CFUs in probiotics, and how many do you really need?

Probiotics are regularly in the spotlight. This is undoubtedly good for public health, but it also means there’s an incredible range of options to choose from.

So, if you’re trying to figure out what’s best for your gut, it can feel a little overwhelming.

In this article, we’ll focus on one factor you might consider when choosing a probiotic supplement: colony-forming units, or CFUs.

Below, we explain what CFUs are, how much they matter, and what other factors you might want to look out for.

What are CFUs in probiotics?

A CFU is a unit of measurement. It shows the estimated number of friendly bacteria that are viable and able to multiply in a probiotic supplement. 

Why do we count colonies rather than individual bacteria? It’s essentially a quirk of history: when microbiology was a new field, it was challenging to see individual bacteria through the microscopes of the day, let alone count thousands of them.

So instead, scientists allowed bacteria to grow in petri dishes. Live, active bacteria replicate quickly, forming colonies, which microbiologists could count much more easily. And so, CFUs were born.

In general, CFUs are counted in billions, and you might see CFUs ranging from 2–75 billion on probiotic supplement labels. 

Sometimes, these figures are provided in more mathematical terms. This is what they mean:

• 1 x 10⁸ CFUs = 1 billion (1 billion has eight zeroes)

• 1 x 10⁹ CFUs = 1 billion (1 billion has nine zeroes)

• 1 x 10¹⁰ CFUs = 10 billion (10 billion has 10 zeroes)

Although a high CFU count seems positive (and it certainly can be), it’s not the only factor that matters when you’re looking for the right probiotic, as we’ll see.

Do more CFUs mean a better probiotic?

Having a higher CFU count doesn’t necessarily mean that a probiotic will be more effective for you.

More important than the number of bacteria is how many make it to your gut alive, what they do when they get there, and whether there’s scientific evidence that this type of bacteria can offer the health benefits you’re after.

Imagine you have a probiotic containing 10 trillion CFUs. If they all die in the highly acidic environment of your stomach, they won’t be as beneficial as 10 billion that reach your gut alive.

This is why Symprove have focused a great deal of scientific attention on ensuring that the microbes in their liquid solution can survive the journey. We’ll explain how this works later on.

The key message is that solely focusing on CFUs doesn’t guarantee you’ll get the best supplement. 

How many CFUs should a probiotic have?

Evidence suggests that to be effective, probiotics should contain between 10⁸ (100 million) and 10¹⁰ (10 billion) CFUs as a daily dose. Anything below 100 million could be considered a low-CFU probiotic.

Symprove has 10 billion CFUs per serving. Other products at the upper range contain 75 billion CFUs, and some even claim to reach 500 billion CFUs per serving.

Although the CFU count  is one metric to consider, it’s not the most important one when you’re selecting a probiotic. And in some situations, lower-CFU products are likely to be a better choice.

In most cases, the key factor is how many friendly bacteria make it to your gut alive.

CFUs vs strains: which should you pay attention to?

We’ve learned that the CFU count is one way to assess probiotics. Another consideration is how many different strains of bacteria are in the product.

Some probiotic supplements contain only one type of bacteria while others contain several. These are called single-strain or multi-strain probiotics.

The strains you want to take depend on the symptoms you’re tackling or the health benefits you’re looking for.

There’s evidence that different species of bacteria can work together, increasing their effectiveness. This so-called synergy is why a multi-strain probiotic with a moderate number of CFUs may be better in some instances. 

All of Symprove’s products contain four species of bacteria, each of which has been rigorously researched:

• Lactobacillus acidophilus

• Lactiplantibacillus plantarum

• Lacticaseibacillus rhamnosus

• Enterococcus faecium
  

These strains have been shown to benefit digestive and immune health.

Why delivery matters more than CFUs

As we touched on earlier, the number of CFUs in a product is less important than the number of bacteria that make it through your digestive tract alive. That’s why Symprove’s UK-based scientists have worked hard to design innovative ways to support these friendly bacteria on their perilous journey.

For instance, the microbes are kept alive in a water-based solution – they’re not freeze-dried. This means they can survive and thrive on the treacherous journey through your gastrointestinal tract, from gum to bum. 

Once they reach your colon, where most of your gut microbes live, these bacteria arrive ready for action and can get to work straight away. This is one reason why the product doesn’t need to overcompensate by having a higher CFU count. 

Additionally, Symprove’s in-house microbiologists designed and patented a method of precision fermentation. This process trains the microbes to weather the gastric storm, further increasing their chances of making it to your gut alive.

Research using a validated gut simulator model (known as SHIME) has shown that this innovative approach works and that Symprove’s live strains can survive the difficult environment of your stomach before setting up shop near the end of your intestines.

This model has been used to investigate the effects among different groups of people. 

Other factors to consider

Aside from the CFU count, your choice of species and the ability of the microbes to survive, there are other considerations when you’re choosing a probiotic supplement.

For instance, some contain gluten or ingredients that aren’t suitable for vegans or vegetarians.

Similarly, many people try to avoid certain ingredients in supplements, like artificial colours. This is why all of Symprove’s products are dairy-free, gluten-free, vegan-friendly and free from artificial colours. Also, when Symprove’s products were tested for histamine, none was present. 

Final thoughts: beyond the CFU number

Of course, the CFU count in a probiotic supplement is important to a certain degree. You want your probiotic to contain at least 100 million CFUs per serving. However, this measurement doesn’t tell the whole story.

More important is whether the probiotic strains of bacteria survive the journey to your gut, what they do when they get there and whether there’s scientific evidence of health benefits. That’s why Symprove have designed a multi-strain liquid solution that can survive that perilous journey.

Similarly, you want to choose a product that’s scientifically backed, which is why Symprove employs a team of microbiologists and continues to put its products to the test, publishing the results of their research in top-tier journals and continually innovating.

References

A four-strain probiotic exerts positive immunomodulatory effects by enhancing colonic butyrate production in vitro. International Journal of Pharmaceutics. (2019). Link.

Comparative survival of commercial probiotic formulations: Tests in biorelevant gastric fluids and real-time measurements using microcalorimetry. Beneficial Microbes. (2015). Link.

Influence of probiotic bacteria on gut microbiota composition and gut wall function in an in-vitro model in patients with Parkinson's disease. International Journal of Pharmaceutics: X. (2021). Link.

Multi-strain probiotics: Synergy among isolates enhances biological activities. Biology. (2020). Link.

Probiotics. (2025). Link.

Rebuilding the gut microbiota ecosystem. Environmental Research and Public Health. (2018). Link.

The simulator of the human intestinal microbial ecosystem. The Impact of Food Bioactives on Health: In Vitro and Ex Vivo Models. (2015). Link.