What is Acidophilus?

Acidophilus is a species of good bacteria, within the Lactobacillus genus. There are many different strains (types) of acidophilus, including Lactobacillus acidophilus NCFM®, perhaps the most researched strain of acidophilus in the world. Find out more about acidophilus in this FAQ.

When you mention friendly bacteria, acidophilus is often the first name that springs to mind. 'Acidophilus' has become synonymous with live cultures and many people just ask for an 'acidophilus supplement' when choosing a friendly bacteria supplement. However, it is important to note that acidophilus is just one of many different species of good bacteria. It's even more important to understand that within each species, there are many different strains, all with unique properties. 

Read more about the difference between species and strains, or read on to find out everything you need to know about acidophilus bacteria and supplements.

Acidophilus taxonomy diagram
Taxonomy diagram

What is 'acidophilus'?

Acidophilus is a species of bacteria from the Lactobacillus genus: its full name is written as Lactobacillus acidophilus, sometimes abbreviated to L. acidophilus. It is a naturally occurring bacteria found in the gut, mouth and vagina and has been incredibly well-researched in studies focusing on a number of different areas of health. Due to its numerous health benefits L. acidophilus is commonly found in live cultures supplements, such as our own.

Within the acidophilus ‘species’, there are a large number of specific ‘strains’ (types). One example is Lactobacillus acidophilus NCFM®, which is perhaps one of the most widely researched strains of bacteria in the world, and certainly the most extensively researched strain of L. acidophilus.

You can find this strain in our Every Day EXTRA and Every Day MAX. Other L. acidophilus superstars include Lactobacillus acidophilus Rosell-52 (in our Every Day, For travelling abroad and For Those On Antibiotics), Lactobacillus acidophilus La-05®, and Lactobacillus acidophilus La-14®   (in our Pregnancy).

Key fact:

Acidophilus is a species of bacteria that sits within the Lactobacillus genus. Within the species, there are many different individual ‘strains’.

Acidophilus under microscope
L. acidophilus under microscope

Are all strains of L. acidophilus the same?

All strains of L. acidophilus are part of a genus (or ‘family’) of lactic-acid-producing bacteria called Lactobacillus. Strains from this genus tend to be the most widely used in live cultures supplements due to their versatile nature. But not all strains within the L. acidophilus species have the same properties, so when looking at live cultures supplements, it is best to compare them at strain level, as opposed to merely species or genus level.

Key fact:

Different strains within the same species have different modes of action in the body, so it is important to find the strain that is most suitable for you.

Healthcare practitioners can find out more about L. acidophilus on the Probiotics Database, on the Probiotic Professionals site.

What is acidophilus used for?

Lactobacillus acidophilus is a species of lactic acid-producing bacteria. Once they have colonised the gut, they prefer to use carbohydrates and sugars such as lactose as their fermentation substrate. This means that they break down these sugars as they pass through our intestine, which is why they are often used by those with lactose intolerances. People with lactose intolerance lack sufficient digestive enzymes to digest lactose (a sugar found in milk and dairy products) but strains of L. acidophilus bacteria can help to break lactose down into a more digestible form. L. acidophilus strains produce lactic and acetic acids as a by-product of fermentation. These acids lower the pH of the intestines, discouraging the over-growth of bad bacteria, known as pathogens, and encouraging the growth of ‘good’ or ‘friendly’ bacteria in the gut. In this way acidophilus is beneficial in maintaining a healthy balance of gut flora.

Beyond these characteristics, which are common to all bacteria within the acidophilus species, most of the known benefits of L. acidophilus are found at ‘strain’ level. For example, Lactobacillus acidophilus NCFM® has very different characteristics and health benefits to Lactobacillus acidophilus La-14®.

Key fact:

When choosing the best acidophilus supplement for your needs, look at the L. acidophilus strains which have been researched for the specific health condition or symptom you wish to support. 

How do I find the best acidophilus?

This really depends on what is meant by ‘best’! In terms of suitability, it’s a case of finding the right strain to suit you, and your own specific health requirements, which can involve some research.

  • Firstly, it should have sufficient scientific evidence to support its safety and ability to survive in the gut.
  • Secondly, opt for ‘quality over quantity’. Don’t be drawn in solely by huge billion counts of a supplement. Higher billions do not necessarily equal higher product quality – it’s much more important to get the most researched strains, even if they’re in lower quantities. It’s definitely a case of ‘quality over quantity’ when it comes to friendly bacteria supplements.
  • Lastly, check the product has a 'time of expiry' guarantee as opposed to a 'time of manufacture' guarantee, as this means the product strength is guaranteed until the supplement goes out of date, rather than just at the time of manufacture (as numbers decrease after this point).

One of the most highly researched strains of acidophilus is Lactobacillus acidophilus NCFM®, which can be found in our supplements Every Day EXTRA and Every Day MAX, both of which satisfy the above mentioned product quality criteria.

Key fact:

Do your homework before buying an L. acidophilus supplement. Choose one containing high quality, well-researched strains which meet your own individual health needs, whilst also satisfying the above quality criteria.

How much acidophilus should I take?

This question is a little tricky to answer, as different health symptoms require not only different strains of acidophilus, but potentially different acidophilus dosages. As a general rule I would advise following the clinical trial data as closely as possible. So, if a double-blind, placebo-controlled clinical trial shows efficacy for supporting a condition or symptom that is of relevance to you, I would recommend taking as close to the same daily dosage that was used in the trial as you can. Wherever possible our acidophilus supplements are formulated in this way too, using data and dosage information from the most efficacious clinical trials.

Live cultures come in different ‘formats’: you can choose from acidophilus powders, acidophilus tablets, acidophilus capsules and even acidophilus in liquid format. The majority of products on the market are in capsule format, as these are generally found to be easier to swallow than tablets, and have better shelf-stability, and less risk of contamination than loose powders (powders portioned in to individual sachets also avoid the risks associated with loose powders).

Some manufacturers of live cultures use enterically coated capsules, which are said to protect the bacteria inside them from the harsh acidic conditions of the stomach. We however, use robust strains of friendly bacteria that are known to survive at a low pH anyway, so we have no need for enteric coating. This means that our capsules can be opened, and the contents sprinkled on to food or drinks (so long as they are not hot or too acidic) with no loss to product integrity. Even if you open up our acidophilus capsule in this way, you can still be sure that the bacteria will survive and you are getting the full dose. You may like to read the following FAQ: Can I open live cultures capsules?

Key fact:

Different conditions may require different doses, where possible take a similar CFU (billions) count to that used in clinical trials relating to your specific health condition.

Are there any side effects from taking acidophilus?

In general live cultures, including those from the acidophilus species, have very few side effects. The majority of people do not experience any negative symptoms from taking an acidophilus supplement. However, everybody is different, and therefore everyone reacts to things differently.

With the introduction of any new live cultures supplement, some people may initially experience mild digestive symptoms, such as: bloating or excess gas. In most cases these symptoms do not last for longer than a few days, and are simply the result of a shift in microbial population and diversity. Mild acidophilus side-effects can simply be a sign that changes are taking place within the eco-system of their gut. 

Whilst mild symptoms may be bothersome, they are for the most part, a positive sign that the ‘friendly’ bacteria are doing their ‘job’, crowding out pathogenic strains of bacteria and competing for space on the gut wall lining.

However, if any side effect is troubling you, or lasts for longer than described, I would always recommend stopping taking the product and contacting the manufacturer for advice. It could be other ingredients in the product that are causing issues, such as a prebiotic fibre. Or, it could just be that the strain of acidophilus is not compatible with your individual microbiome at that time. Always listen to your own body, and respect its uniqueness.

Read our FAQ ‘Do live cultures have side effects?’ to find out more.

Key fact:

L. acidophilus may occasionally cause mild abdominal discomfort and/or bloating in some people, but this typically only lasts for a few days and indicates that the bacteria are reaching the gut. If symptoms persist speak to the manufacturer for advice.

How long does acidophilus take to work?

This is a question that everyone wants to know the answer to, but frustratingly there is no ‘one size fits all’ here either! With everyone’s microbiome being as unique to them as their fingerprint, it is impossible to know for certain how long it will take to feel the benefits of taking acidophilus supplements.

We receive wonderful feedback and product reviews from our customers. For some people our supplements have an almost instant effect, whereas for others it can take several weeks or more. It depends partly on the state of a persons’ health to start with and also their compliance with taking the product. Diet, lifestyle and any medications being taken are other factors to consider. In general, I would advise patience. The benefits are well worth it, and your health will thank you for it in the longer term.

Key fact:

Everybody responds differently, and at different speeds, when starting a new live cultures supplement. Don’t be disappointed if results take a little while, they will be worth it in the longer term.

Shop for acidophilus.

You may also like to read: What is L. helveticus?

For further research in to L.acidophilus and specific strains within this species healthcare professionals might like to take a look at The Probiotics Database.

Authors: Dr Aisling Dwyer MB BCh BAO (Medicine, Surgery and Obstetrics), MSc (Personalised Nutrition)​, Dr Kate Stephens PhD Food and Microbial Sciences; Gut Microbiology (University of Reading), BSc Medical Microbiology