What are Probiotics?

Probiotics, also known as 'live cultures', are microorganisms often found naturally in the body and which can also be taken in supplement form. Probiotics are usually, but not always, strains (types) of bacteria, which confer various health benefits in the body.


The term ‘probiotics’ is used to describe the beneficial live micro-organisms that, when administered in adequate amounts, positively influence human health. Examples of probiotic microorganisms include probiotic bacteria such as Lactobacillus acidophilus or Bifidobacterium infantis

Where do probiotics come from?

Every friendly bacteria strain is unique, and this is also true of their origins. Saccharomyces boulardii, for example, is actually a yeast, and was originally derived from the lychee fruit. Bifidobacterium lactis HN019, on the other hand, was first extracted from a yoghurt source. Many strains of friendly bacteria are known as 'human strains', this means they were initially isolated from healthy digestive tracts of humans and are natural residents of the gut! This doesn't, however, mean they are extracted from humans for commercial use or that probiotics you may take are directly taken from that source. In fact, the original strains are stored in microbiology 'banks' and future generations are cultured by scientists in laboratories.

What is a probiotic 'strain'?

Many people (healthcare professionals included) misunderstand the definition of a 'strain'. The term ‘strain’ refers to a biological variety within a species; a species in turn, exists within a genus. A strain is just a specific type of bacteria, in the same way that a Golden Retriever is a specific type of dog. Different manufacturers use different strains. Although these may be of the same species and genera; meaning that one acidophilus supplement is not equal to another acidophilus supplement. It is hence best to choose a probiotic supplement that uses robust, well-researched strains.

Bacterial Naming Convention Explained

The naming of probiotic strains can take some getting used to, so we've tried to explain it here as simply as possible, as it is so important. The strain name can tell you all about the research and mode of action behind the friendly bacteria.

The name Lactobacillus acidophilus Rosell-52 tells you the name of the genus (Lactobacillus), the species (acidophilus), and the strain (Rosell-52) of the probiotics.

Many of our strain names include 'Rosell' as they originated from, and have been rigorously tested by, the leading firm in the field, Institut Rosell.

For further clarification on the difference between a genus, a species and a strain.

Which are the best strains?

When selecting the optimum probiotic supplement, it is important to consider the viability and efficacy of the strains themselves. The strains must be alive at the time of consumption, and must survive the stomach acidity in order to reach the intestines. The Optibac strains undergo numerous in-vitro tests documenting their viability at room temperature, and to survive the acidic stomach environment and bile salts.

Probiotics are all individual, and different strains have different modes of action in the body. Therefore, the best live probiotic supplement for you might not be the best for somebody else. In general, however, there are a few good ways to tell if a strain is high quality:

  • It should be guaranteed to reach the gut alive
  • It should be well-researched
  • It should have been featured in gold standard human clinical trials and not just in-vitro tests

Generally, the best strains tend to be the most well-researched, so look out for those with plenty of clinical trials investigating them.

Are probiotics the same thing as dairy or yoghurt?

Not quite. Yoghurts will always contain probiotic bacteria (to different extents, according to various factors including pasteurisation, whether or not probiotics have been added for nutritional value, and so on), and interestingly, it is these live bacterial cultures which help to convert milk into yoghurt in the first place. However probiotic bacteria can also be found in other foods such as sauerkraut, and they may be extracted from dairy and cultivated and multiplied to make a probiotic supplement.

Are probiotics always bacterial?

They are often bacterial, but not always. It is also possible to have active cultures of beneficial yeasts, for example Saccharomyces boulardii.

Optibac probiotic strains

At Optibac we specialise entirely in probiotics and all of our products contain various types of live or active probiotic strains. We use different strains for different groups of people and for different reasons. We aim to offer each of our customers a specific supplement to suit their individual needs. When it comes to probiotics, it is not a question of 'one-size-fits-all'! Our range has something for everyone - find which one is right for you.

Bifidobacterium bifidum Rosell-71
Well-researched and proven to survive to reach the gut alive and adhere to the gut lining. Find this strain in Every Day, Babies & Children and One Week Flat.

Bifidobacterium breve Rosell-70
Well-researched and proven to survive to reach the gut alive and adhere to the gut lining. Find this strain in Every Day.

Bifidobacterium infantis Rosell-33
Clinically trialled and shown to survive and reach the guts of children alive. Find this strain in Babies & Children.

Bifidobacterium lactis BB-12®
Thought to be the world's most well-researched strain of the entire Bifidobacteria genus. Find this strain in Bifido & Fibre.

Bifidobacterium lactis Bl-04
Extensively researched and often trialled with B. lactis Bi-07 and L. acidophilus NCFM®. Find this strain in Every Day EXTRA  and Every Day MAX.

Bifidobacterium lactis Bi-07
Clinically researched and proven to survive and reach the gut alive, alone or in combination. Find this strain in Every Day EXTRA.

Bifidobacterium lactis HN019
rom the incredibly well-researched Bifidobacterium genus, HN019 was originally isolated from a yoghurt source. Find this strain in Every Day MAX.

Bifidobacterium longum Rosell-175
Well-researched and proven to survive to reach the gut alive and adhere to the gut lining. Find this strain in Every Day

Lactobacillus acidophilus NCFM®
The most well-researched strain of L. acidophilus in the world. Find this strain in Every Day EXTRA and Every Day MAX.

Lactobacillus acidophilus Rosell-52
Often trialled with L. rhamnosus Rosell-11, this strain is well-researched and proven to reach the gut alive even during antibiotics. Find this strain in Every DayBabies & Children.

Lactobacillus casei Rosell-215
Well-researched and proven to survive to reach the gut alive and adhere to the gut lining. Find this strain in One Week Flat.

Lactobacillus paracasei CASEI 431®
One of the most well-researched strains of Lactobacillus; described in over 80 scientific publications, and tested on thousands of people in over 20 clinical trials. Find this strain in Immune Support.

Lactobacillus paracasei Lpc-37
Well-researched and proven to survive to reach the gut alive and adhere to the gut lining. Find this strain in Every Day EXTRA.

Lactobacillus reuteri RC-14®and Lactobacillus rhamnosus GR-1®
Extensively researched and proven to reach the intimate area; mostly trialled as a pair, in 26 trials and in over 2,500 women. Find these strains in For Women.

Lactobacillus rhamnosus Rosell-11
This strain has been trialled with L. acidophilus Rosell-52 alongside antibiotics. Find this strain in Every Day.

Lactococcus lactis Rosell-1058
Well-researched and proven to survive to reach the gut alive and adhere to the gut lining. Find this strain in Every Day and One Week Flat.

Saccharomyces boulardii
Actually a transient yeast, S. boulardii boasts international acclaim and was introduced to the UK and Ireland by Optibac. Find this strain in Saccharomyces Boulardii.


In conclusion, it is very important to look at friendly bacteria on a strain-specific level, rather than only the genus and species of microorganism in question. To find out more about the Optibac range, take a look at the shop, or 'Why Optibac?'