Probiotics — Bacterial Strains Matter

There are literally billions of different strains of bacteria that can inhabit the human body. This fact alone makes a massive impact on choosing a probiotic supplement that can actually be effective. Understanding how these beneficial bacteria are classified may seem complicated at first (hopefully this article will simplify it!) but it’s critical to making an informed choice.

Unfortunately, many manufacturers count on the fact that many consumers don’t understand this information. Because it allows them to market probiotic supplements that are not nearly as beneficial as they could be.

How Bacteria Are Classified

Stick with us for a minute… we’ll get past the boring part as quickly as possible.

Going back to your High School science classes, all living things are classified into groups so they can be identified, named and studied. This is called Taxonomy. Life is divided into Domains, which are divided into Kingdoms, which are divided… etc. Here’s a chart of how Taxonomy currently breaks down all Life forms for handy reference:

“Bacteria” is actually a Domain, the highest classification of living things.^[1] So it’s not surprising that there are millions – perhaps even billions – of species of bacteria.

Fortunately, we don’t have to know about all of them. There are 5 relevant Genera (Genus groups) of bacteria that have been studied in relation to the human intestinal tract and probiotics.^[2] Further, only certain Species out of those Genera have been studied. This narrows our focus quite a bit.

Probiotic Species Are Not Interchangeable

To put this in perspective, let’s look at how this works for people. There are various races of humans. For most of history those races were divided into countries. Within countries we had tribes. Within tribes we had villages. Within villages we had families. Within families we had households. Within households we had individual people.

Now, two children may be born into the same household. So they share all of the other classifications all the way back up to “human.” Let’s say one of the children – we’ll call him Bob -. grows up and the village discovers Bob is the best darn hunter the whole tribe has ever seen. Nobody’s gonna go hungry with Bob around.

Until the day Bob gets sick. Well, OK. Bob has a brother named Bill. They are nearly identical, grew up in the same house and all. Surely they’re practically interchangeable. So the village sends Bill out to hunt in Bob’s place. But Bill is not Bob, and he is really, really bad at hunting. The village isn’t getting any meat as long as they’re using Bill as their hunter.

Bill is good at other things, but he can’t hunt like Bob.

Strains of bacteria are just like Bill and Bob. Lactobacillus Acidophillus (Genus Lactobacillus, Species Acidophillus,) has been thoroughly studied.^[3] Lactobacillus Curvatus does not have the same scientific backing.^[4]

The bottom line is that not every strain of “good” bacteria makes for a good probiotic supplement. You have to make sure you’re getting strains in your supplement that have actually been studied, and actually found to benefit humans. Otherwise you might be sending a Bill out to hunt when you need a Bob.

Different Species Live In Different Places

Going back to our human example, a household lives in a particular place. As children, Bob and Bill lived in the same hut – you wouldn’t find Bob sleeping every night over at Tom’s hut because Tom’s parent’s aren’t his parent’s.

And here’s where this becomes relevant to your Probiotic supplement search: Each Genus populates a different area of the human intestinaltract.^[5] Even more specifically, different species (sometimes called strains) of bacteria prefer to live in different areas of your digestive system.^[6]

If a village wants to have huts in every area, it has to have enough households to cover that much space. If you want to cover your entire digestive system with beneficial bacteria, you want to get enough different strains to cover that much intestine.

So the next thing you want to think about when choosing a probiotic supplement is to look for one with strains from all 5 relevant Genera. Because you want to ensure that your entire system is covered, not just one small area.

The 5 Relevant Genera Of Probiotics

So as mentioned above, there are 5 Genera of probiotic bacteria that have been studied specifically for their effect on the human intestinal tract. Each of these 5 Genera “like” a different area of that digestive system. So finding a supplement with each of these is a good start.

These Genera are:

Lactobacillus^[7]
Bifidobacterium^[8]
Lactococcus^[9]
Streptococcus^[10]
Saccharomyces^[11]

The Specific Strains You’re Looking For

This will not be an exhaustive list, and it will continue to be updated.

Specific strains of probiotics that have been studied and found to have benefits to humans include:

Lactobacillus

L. Adidophilus is possibly one of the most studied strains in existence. It produces lactase,^[12] the enzyme that breaks down the sugar in milk, and which is not naturally produced by those with lactose intolerance. It has been shown beneficial against diarrhea^[13] , and combats pathogens in the digestive tract.^[14] It also has been found to relieve symptoms of Irritable Bowel Syndrome^[15] and help increase immune responses.^[16]
L. Casei promotes recovery from diarrhea^[17] , strengthens immunity^[18] ^[19] , and may help deter the recurrence of certain types of bladder cancer.^[20]
L. Rhamnosus enhances immunity^[21] , “significantly alters vaginal flora,”^[22] (in other words, it was found to deter pathogens in the vagina which can lead to infections), and can help protect against urinary tract infections.^[23]
L. Brevis plays an important role in the synthesis of Vitamin D and Vitamin K.^[24]
L. Plantarum helps combat irritable bowel syndrome,^[25] has antifungal properties,^[26] and acts as a barrier in the gut to help prevent pathogens from being absorbed.^[27]
L. Salivarius has “antiinfective properties”^[28] and can help cleanse the colon, combating diverticulitis pockets.^[29]

Bifidobacterium

B. Bifidum “significantly alleviates irritable bowel syndrome”^[30] and boosts immune system response.^[31]
B. Lactis enhances the immune system^[32] and can reduce the severity if E. Coli.^[33]
B. Longum can improve lactose digestion,^[34] helps reduce inflammation in Ulcerative Colitis patients,^[35] and alleviate some allergy symptoms.^[36]

Lactococcus

L. Lactis has shown promise in combating Inflammatory Bowel Disease and Colitis.^[37]

Streptococcus

S. Thermophilus supports immune health ^[38] and can help combat diarrhea.^[39]

Saccharomyces

S. Boulardii may help with symptoms of Crohn’s disease^[40] , ulcerative colitis^[41] , or Inflammatory Bowel Disease.^[42]

The Bottom Line

The bottom line when choosing a probiotic supplement is to choose one with multiple strains from multiple genera. Additionally, strains on the list above will ensure that the product you’re taking includes strains that have actually been studied and found to provide some benefit to humans.

For more information on choosing a Probiotic supplement, see our Probiotic Supplement Recommendations