Science 

Probiotic Strains and Their Functions

July 13, 2020 6 min read

Assortment of probiotic pills on a blue background

You may already be familiar with what probiotics are and the many health benefits that are associated with them, which you can also read more abouthere. It is common, though, to still have some questions or confusion about how to choose the best supplement for you. This blog will help teach you how to read and interpret a probiotic supplement label and will review the functions and purpose of the many different probiotic names and strains that are often listed so that you can gain more insight and confidence in choosing the right product for you.

What are probiotic strains?

A probiotic strain refers to the specific type of bacteria present in a supplement. You may have seen names likelactobacillus orbifidobacterium, which are broad categories (genera) of probiotic bacteria. There are many many different species and strains within each of those probiotic genera, and each serves a different purpose.

The probiotic strain is what determines the bacteria's role and effect in the body. For example, some work more on the immune system, while others have a greater impact on the digestive tract. This is why paying attention to the strain type can make a big difference when treating or trying to prevent any sort of health ailment.

How to interpret a probiotic label

Looking at the label of a probiotic supplement can be intimidating and confusing. Rather than seeing words you recognize and numbers in grams or percentages, you’ll find a list of scientific and difficult to pronounce names of bacteria. If you don’t know what to look for, it can seem like it's not worth your time to read or pay attention to.

However, what is listed on a probiotic panel can help you tell the difference between a quality probiotic and one that may not be worth spending your money on.

Table of different probiotic strains

Here’s an example using the strain Lactobacillus casei (Lc-11):

  • “Lactobacillus” is referring to the broader category of the bacteria, known as thegenus. The genus can be thought of as the strain’s extended family and there are many different bacteria strains within each genus. Note that the genus is often abbreviated by the first letter, so this may be written asL. casei (Lc-11)in some instances.
  • “Casei” refers to thespecies of bacteria, which can be thought of as closer family members.Different species of probiotics have different abilities and serve different purposes.
  • “Lc-11” refers to the specificstrain, which as mentioned, makes a big difference in the function of the probiotic. The strain will always be listed as a combination of letters and numbers, and gives the most unique identification of the bacteria type.

Not all probiotic manufacturers will list the type of strain on a label. This can be a red flag when selecting what product to buy since it would leave off a vital piece of information. Not all types ofLactobacillus casei, for example, function equally, so listing the strain can help consumers know which probiotic may work best for them and what they are trying to accomplish with their health.

What different probiotic strains do

In order to understand the various probiotic strains, it can be helpful to break them down according to the genus and species they belong to. Becauselactobacillus andbifidobacterium strains are among the most common genera, some of the benefits of various strains within each of those are highlighted below.

Benefits of lactobacillus strains:

  • Lactobacillus plantarum: Strains from this category have been shown to have protective effects against invasion of pathogens in human cells. It has been studied and used in the medical fields for the treatment of various conditions including Alzheimers, obesity, diabetes, cancer, Parkinson’s disease, hypertension and more(1). Its strains have also been shown to help improve immune responses.
  • Lactobacillus acidophilus: This is probably the most widely used and studied probiotic species. Its strains are common ingredients or byproducts of fermented milk like kefir and yogurt, and may help support digestive health, specifically for people who experience negative symptoms of lactose intolerance(2).L. acidophilus strains have been shown to inhibit the growth of harmful bacteria and provide improvements in blood sugar and lipid levels(3).One of the longest studied and most proven strains ofL. acidophilus is DDS-1, which has been shown to support a strong immune system and treat conditions like atopic dermatitis and acute respiratory infections when used in combination with theBifidobacterium lactis species(4) (5).
  • Lactobacillus gasseri: This strain has been studied for its role in managing obesity, including its ability to help reduce fat mass, body mass index, waist and hip circumference(6). It may be an ingredient in probiotics that are geared towardsweight management.
  • Lactobacillus rhamnosus:Strains from this species have been shown to help treat and reduce the risk of infectious and antibiotic-associated diarrhea in both children and adults, as well as supporting weight management(7).
  • Lactobacillus reuteri: In children and infants,L. reuteri is beneficial in the prevention and/or treatment of many conditions including diarrhea, abdominal pain, atopic dermatitis, allergies, feeding intolerance and infant colic. It has also been studied for its ability to reduce negative gut symptoms and even reverse leaky gut syndrome, with promising results(8). Because the benefits ofL. reuteri are strain-specific, it may be best to combine different strains to reap the most beneficial effects.

Benefits of bifidobacterium strains:

  • Bifidobacterium bifidum: Research shows it may help reduce symptoms of IBS(9). Other roles and benefitsB. bifidum include helping to optimize immunity and preventing eczema in babies born to pregnant women who took it in supplement form in combination withB. lactis andL. acidophilus strains(10).
  • Bifidobacterium longum:Strains of this species have been researched and shown to help reduce gastrointestinal symptoms, support immune function and protect against infectious diseases by stabilizing and promoting balance in the gut microbiome(11). It also helps with proper digestion of carbohydrates to help prevent and/or treat symptoms of maldigestion(12).
  • Bifidobacterium lactis:Scientific studies have proven thatB. Lactisstrains can play a role in enhancing immunity, fighting tumor growth, improving digestion and lowering cholesterol(13).
  • Bifidobacterium infantis: Strains from this species can help relieve symptoms of IBS, including abdominal pain, gas and bloating(14). It has also been shown to help reduce inflammation in both gastrointestinal and non-gastrointestinal conditions such as psoriasis and chronic fatigue syndrome(15). Other studies demonstrate the ability of B. infantis to support the microbiome of breastfed infants and prevent immune-related diseases(16).
  • Bifidobacterium breve: Strains in this species haveantimicrobial activity against harmful human pathogens, and it has been closely studied for its role in the treatment and prevention of pediatric conditions.B. breve has been shown to play a positive role in treating gut disorders including diarrhea and infant colic as well as celiac disease, obesity, allergies and brain disorders. In addition,B. breveis also used for the prevention of side effects in preterm infants as well as during antibiotic treatments or chemotherapy(17).

In addition to paying attention to the genus, species and strain of a probiotic, it is also helpful to know the CFU count. This refers to the number of Colony-Forming Units (organisms) that are in the product. The higher the number, the better chance the organisms have of surviving the journey through the gut, so more is usually better when it comes to CFU’s. Some probiotics contain as many as60 billion CFU’s.

In summary

There is a lot involved when it comes to probiotics, and understanding what to look for when buying a supplement is important to make sure you reap the most benefits. While all probiotics support a healthy balance of gut bacteria, various species and strains serve more targeted, unique purposes that aren’t limited to the gastrointestinal tract alone. High quality, pure probiotic supplements are considered safe by research and believed to be unlikely to cause harm. Keep in mind that the optimal dose of probiotics depends on the strain and product, so it's always a good idea to work alongside a healthcare practitioner when selecting, and to chooseproducts that come fromtrusted brands. It is also recommended to always check the labels of probiotic supplements for recommended storage conditions and expiration dates.

Joanna Foley - Contributing Writer, Physician's Choice