How to Choose a Probiotic Supplement: Strains & CFUs

How to Choose a Probiotic Supplement: Strains, CFUs & What to Look For

Choosing a probiotic supplement can be surprisingly confusing.

Walk into a health-food shop or search online and you’ll find products containing different strains, different combinations of microorganisms, dramatically different CFU counts and a wide range of prices.

Some products contain one strain. Others contain a dozen or more.

Some promise billions of live microorganisms. Others advertise much larger numbers.

And many make broad claims about digestion, immunity, gut health and general wellbeing.

So how do you decide which product, if any, makes sense for you?

The most important principle is this:

Don’t choose a probiotic simply because it has the most strains, the highest CFU number or the biggest marketing claims.

The useful question is whether the specific microorganism or strain, dose and intended use are supported by evidence.

This guide explains what to look for on a probiotic label, what CFUs mean, why strains matter, how storage and expiry dates affect a product, and when it makes sense to speak with a healthcare professional before taking one.

Do you actually need a probiotic supplement?

Before comparing products, ask a more basic question:

Do you have a reason for taking one?

There is no universal recommendation that healthy people should take a probiotic supplement. Evidence varies considerably depending on the probiotic, the health condition being studied and the person taking it.

Some probiotic preparations have been studied for particular purposes, including antibiotic-associated diarrhoea and certain gastrointestinal conditions. But evidence for many other advertised uses remains uncertain.

That means buying a probiotic “for general gut health” isn’t necessarily the same as choosing a product for a specific, evidence-supported purpose.

If you are considering a probiotic for a particular health problem, it is sensible to discuss the decision with a healthcare professional and ask him or her, how to choose a probiotic supplement?

What exactly is a probiotic?

A probiotic is a live microorganism that, when administered in adequate amounts, confers a health benefit on the host.

Probiotics can include bacteria and certain yeasts.

Common groups include Lactobacillus and Bifidobacterium, although the naming of probiotic bacteria has changed considerably in recent years and individual products may use newer genus names.

The important point is that “probiotic” is not simply another word for “good bacteria.”

A microorganism qualifies as a probiotic because a health benefit has been demonstrated for the relevant microorganism under defined conditions.

The three-part name you should look for

One of the most useful things on a probiotic label is the microorganism’s identification.

It is commonly expressed as:

Genus → species → strain

For example, a product might identify a microorganism by its genus and species followed by a strain designation.

Why does the strain matter?

Because two microorganisms belonging to the same species can have different properties and may have different evidence behind them.

This means that seeing the word Lactobacillus or Bifidobacterium on the label is not enough information to tell you whether the product is appropriate for a particular purpose.

The strain is often much more informative than the headline marketing claim.

Why strain-specific evidence matters

Suppose research shows that one particular probiotic strain has been studied for a specific condition.

That does not automatically mean:

every strain of the same species works in the same way;
every product containing that species will have the same effect;
a product containing several unrelated strains will necessarily work better.

The World Gastroenterology Organisation recommends linking probiotic health benefits as closely as possible to specific strains or combinations of strains at the doses that have been studied.

This is one of the most important ideas to understand when comparing products.

What does CFU mean?

CFU stands for colony-forming units.

It is a way of expressing the number of viable microorganisms in a probiotic product.

You may see labels advertising:

1 billion CFU
10 billion CFU
50 billion CFU
100 billion CFU

It is easy to assume that a larger number must mean a better product.

It doesn’t.

The NIH Office of Dietary Supplements notes that higher CFU counts alone do not necessarily mean greater health benefits. The potential benefit depends on both the specific microorganisms or strains and the amount provided.

So don’t choose a probiotic based solely on the biggest number printed on the front of the bottle.

Should you choose the highest CFU product?

Generally, no.

A useful question is:

What CFU amount has actually been studied for the microorganism and purpose I’m interested in?

Different probiotic products can contain very different amounts, and effective amounts vary between microorganisms and uses.

The right dose is therefore not necessarily the largest dose available.

A product with 100 billion CFU is not automatically superior to one containing 10 billion CFU.

Look at when the CFUs are guaranteed

There is another detail that can easily be missed.

A label may state the number of CFUs:

at manufacture

through the expiry/use-by date

Those statements are not equivalent.

The number of viable microorganisms can decline over time. The NIH Office of Dietary Supplements notes that some experts recommend looking for products that state the CFU count that will be present through the expiry or use-by date rather than only the number present at manufacture.

That makes the label much more useful.

Check the expiry or use-by date

How to Choose a Probiotic Supplement

Probiotic microorganisms are living organisms, so viability matters.

When comparing products, check:

Expiry or use-by date

and read the manufacturer’s storage instructions.

A product that needs refrigeration should be stored appropriately. Some products are designed to remain stable at room temperature.

Don’t assume that all probiotic supplements need to be refrigerated.

The manufacturer should tell you how the product should be stored.

Check the storage instructions

Look for information such as:

Refrigerate after opening
Keep refrigerated
Store at room temperature
Keep away from heat and moisture
Do not freeze

Follow the manufacturer’s instructions rather than assuming that one storage method applies to every probiotic.

If a product requires refrigeration and spends a long time in a hot environment, its viability may be affected.

Does more than one strain mean a better probiotic?

Not necessarily.

Multi-strain products can be useful in some circumstances, and some research has specifically studied combinations of microorganisms.

But more strains does not automatically mean more benefit.

A product containing ten strains is not automatically better than a product containing one well-studied strain.

The key question is whether the particular combination has evidence for the intended use.

This is one area where the old “more is better” approach to probiotics needs to be left behind.

What should you look for on the label?

A useful probiotic label should give you enough information to identify what you are actually buying.

Look for:

Genus, species and strain

You should be able to identify the microorganisms rather than seeing only a vague claim such as “proprietary probiotic blend.”

CFU count

Look for the number of colony-forming units provided per serving.

Expiry or use-by information

Make sure the product is within date.

Storage instructions

Follow the manufacturer’s directions.

Serving information

Check how much the manufacturer considers one serving and whether the stated CFU count applies to that serving.

Additional ingredients

Look at the complete Supplement Facts or ingredients panel, especially if you have allergies, intolerances or dietary restrictions.

Evidence for the intended use

This is the most important point.

A beautifully designed label does not prove that the product will provide the benefit you are looking for.

Be cautious with “proprietary blends”

A proprietary blend may tell you the overall amount of a mixture without clearly identifying how much of each individual microorganism is included.

That can make it harder to compare the product with research studies.

Where practical, a transparent label that identifies the specific microorganisms, strain designations and CFU amounts is easier to evaluate.

Don’t choose a product simply because it is expensive

Price is not a substitute for evidence.

A more expensive probiotic may contain more strains, a higher CFU number, a particular delivery system or additional ingredients.

None of those features automatically proves that it will work better for you.

Compare the details on the label and the evidence for the intended use rather than assuming price equals quality.

Don’t be distracted by dramatic health claims

Be wary of products that appear to promise a long list of benefits.

Claims that a single probiotic can:

“detox” the body
cure digestive disorders
eliminate inflammation
prevent disease
dramatically boost immunity
solve multiple unrelated health problems

should be treated very cautiously.

Research into probiotics is active and promising in some areas, but the evidence is much more specific than many marketing messages suggest.

What does the evidence say about probiotics?

Research has investigated probiotics for many different health conditions.

Some areas have encouraging evidence, but results vary according to the probiotic used.

For example, some probiotic preparations have been studied for:

antibiotic-associated diarrhoea;
certain gastrointestinal conditions;
constipation;
ulcerative colitis;
irritable bowel syndrome;
some forms of eczema;
other specific health problems.

That doesn’t mean a generic probiotic supplement will help with each of these conditions.

In many cases, researchers still do not know which probiotic is most useful, at what dose, for how long, or which people are most likely to benefit.

This is why matching the product to the intended purpose matters.

What if you’re taking antibiotics?

This is one of the reasons people commonly consider probiotics.

Some probiotic preparations have been studied for the prevention of antibiotic-associated diarrhoea, with evidence of benefit for some people and some preparations.

However, results vary by probiotic, population and circumstances.

If you are considering taking a probiotic alongside antibiotics, particularly if you have other health conditions or take multiple medications, ask a healthcare professional about the specific product and your circumstances.

What if you have digestive symptoms?

Bloating, constipation, diarrhoea and abdominal discomfort can have many different causes.

It can be tempting to buy a probiotic and hope that it solves the problem.

Sometimes a particular probiotic may help a particular symptom or condition.

But persistent, severe or unexplained digestive symptoms deserve proper assessment rather than repeated experimentation with supplements.

A supplement should not delay diagnosis or appropriate treatment.

Probiotics and fermented foods are not the same thing

If you prefer to get live microorganisms from food, you may already eat foods such as:

yoghurt
kefir
kimchi
sauerkraut
miso
tempeh
kombucha

These can be perfectly reasonable foods to include in a varied diet.

But remember:

Not every fermented food is a probiotic food with a demonstrated health benefit.

And even when a food contains live microorganisms, that does not necessarily mean the microorganisms have been studied for the particular health effect you are looking for.

Can food be a better choice than supplements?

How to Choose a Probiotic Supplement

That depends on what you are trying to achieve.

For general nutrition, whole and minimally processed foods provide a much wider range of nutrients and dietary components than a single supplement.

Fermented foods can be part of a varied diet.

A probiotic supplement is a different proposition: it provides a deliberately selected microorganism or combination of microorganisms at a defined dose.

If you are considering a supplement for a particular health purpose, the relevant evidence should guide the decision.

How long should you take a probiotic?

There is no single answer that applies to every probiotic.

Duration depends on:

the microorganism;
the dose;
the intended use;
the research that supports the product;
and the individual taking it.

Avoid assuming that “longer” automatically means “better.”

Some uses have been studied over particular time periods, while long-term effects are less well understood for many products.

When should you speak to a healthcare professional?

You should consider professional advice before taking a probiotic supplement if you:

have a serious underlying health condition;
have a weakened immune system;
are seriously ill;
are taking multiple medications;
are considering a probiotic for a significant or persistent medical problem;
are pregnant or breastfeeding and are unsure whether a particular product is appropriate;
are choosing a probiotic for a child.

Particular caution is warranted in premature infants and people who are seriously ill or immunocompromised, because serious infections associated with probiotics have been reported.

What if a probiotic doesn’t work?

Don’t automatically assume that you need a stronger product.

If a probiotic doesn’t produce the result you expected, consider:

Was the intended use supported by evidence?

Was the specific strain studied for that purpose?

Was the dose appropriate?

Was the product stored correctly?

Was there another reason for the symptoms?

The answer may simply be that the probiotic isn’t effective for that particular problem.

A simple probiotic-buying checklist

Before purchasing, ask:

1. Why am I taking it?

Be specific about the purpose.

2. Which microorganism or strain is in it?

Look beyond the word “probiotic”.

3. What CFU dose am I getting?

Don’t assume the highest number is best.

4. When is that CFU count guaranteed?

Prefer clear expiry/use-by information.

5. How should it be stored?

Follow the manufacturer’s instructions.

6. Has this specific product, strain or combination been studied for my intended use?

This is the most important question.

7. Do I need professional advice first?

Especially if you have an underlying health condition or take medications.

The bottom line

Choosing a probiotic isn’t about finding the bottle with the biggest number on the front.

It’s about understanding what you’re buying and why you’re buying it.

Look for:

A clearly identified microorganism or strain

A transparent CFU count

Clear expiry and storage information

Evidence that relates to the intended use

And remember:

More strains don’t automatically mean better.

More CFUs don’t automatically mean better.

A higher price doesn’t automatically mean better.

The best probiotic is not necessarily the one with the longest label or the most impressive marketing.

It’s the one whose specific microorganism, dose and intended use make sense in light of the evidence.

Frequently Asked Questions

What is the most important thing to look for in a probiotic?

Look for the specific microorganism or strain and evidence supporting its use for the purpose you have in mind. The number of strains and CFUs alone does not tell you whether a product is effective.

Are more probiotic strains better?

Not automatically. Some multi-strain products have been studied successfully, but benefits depend on the particular microorganisms and their doses.

What does CFU mean?

CFU means colony-forming units. It is a measure of viable microorganisms in the product.

Is a higher CFU probiotic better?

Not necessarily. Higher CFU counts alone do not guarantee greater health benefits.

Should I choose a probiotic with billions of CFUs?

Don’t choose solely on the number. Consider the microorganism or strain, intended use and evidence for the dose.

Do probiotic supplements need to be refrigerated?

Not always. Storage requirements vary between products, so follow the manufacturer’s instructions.

Is a probiotic that lists many strains better?

Not necessarily. A product with several strains is not automatically better than one containing a single well-studied strain.

Should I take probiotics every day?

There is no universal rule. How often and how long to use a probiotic depends on the product and intended purpose.

Can I take probiotics with antibiotics?

Some probiotic preparations have been studied alongside antibiotics, particularly for antibiotic-associated diarrhoea. Ask a healthcare professional about the specific product and your circumstances.

Are probiotics safe?

They are generally well tolerated by healthy people, but they are not risk-free for everyone. People who are seriously ill or immunocompromised may face greater risks.

Can probiotics cure digestive problems?

No general cure claim is justified. Some specific probiotic preparations may help with specific conditions, but effects vary.

This article is for general information and should not be considered medical advice. If you have a health condition, take medication, or are considering probiotics for a specific medical problem, speak with an appropriate healthcare professional.

Check out our other articles on probiotics:
Probiotics: Benefits, Foods, Supplements & What the Evidence Says and Probiotic Foods

Choosing Probiotic Supplements