Here’s the dirt on spore forming bacteria - aka soil-based probiotics 

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Learn whether probiotics with spore forming organisms are right for you and your family - and if yes, the best route to introduce them into your digestive health regimen.

Plant Based Probiotics

Eat dirt? Or maybe some of the microbes in it?

There’s been a lot of recent discussion surrounding spore forming bacteria that are used in some probiotic supplements. As spore forming bacteria are still in their infancy in terms of scientific research, people want to know…

Are they truly effective?

And if yes, which strains are safe to consume?

To start, spore forming bacteria are microbial strains that are formed from spores. Some people call them "soil bacteria" or "homeostatic soil organisms (HSOs)" because spore forming bacteria can be found in the dirt from the ground!

Spore forming bacteria can also germinate inside the digestive tracts of humans and animals.

Research indicates spore forming bacteria may provide myriad health benefits, such as helping with diarrhea, food digestion, vaginal health and inflammation, to name a few.* They may even help other probiotic bacteria take hold in the digestive tract, and increase their effectiveness.*

Spore forming bacteria have also been praised for their “hardiness,” meaning that such supplements don’t require refrigeration.

Jordan Rubin put soil-based probiotics on the map several years ago, after he healed his severe Crohn’s by adjusting to a real food diet and supplementing with spore forming bacteria. He then went on to found Garden of Life and sell the first soil based probiotics to the masses.

The duality with spore forming probiotic supplements 

But here’s the rub - many of the commercially available, spore forming probiotics on the market right now have:

  • More than 20 different spore forming strains - many of which have not undergone extensive safety studies,
  • And/or unwanted ingredients and allergens.

So some people have great results with the commercially available soil-based probiotics, while others experience digestive issues or negative reactions.

As we touched on above, there’s a distinct duality with soil-based organisms due to their durability. Because soil-based bacteria have the ability to form spores, they’re said to be more durable than other probiotic strains. They can withstand changes in temperature and moisture; and they can survive stomach acid to take hold in the intestines - fast. As digestive author Jini Patel-Thompson writes:

“To summarize the research briefly, soil organisms (SO) are spore formers, so they make good competitors for yeast, fungus, and other pathogens. This is why so many people taking soil organisms will initially experience very favorable results. However these spores are extremely difficult to kill, surviving sterilants, disinfectants, acceleration forces, heat, pressure, radiation and many antibiotics. Strong antibiotics — like Vancomycin — can suppress certain spores.”

This is precisely why people who are immunocompromised should not take supplements with spore forming bacteria and the reason they should only be used on a short-term basis.

Here’s where we’re coming from with Primal Soil

We believe the benefits of spore forming bacteria can be achieved with our line of Organic 3 non-spore forming probiotics (e.g. GutPro, etc). At the same time, we wanted to develop a spore forming probiotic supplement that’s tried and true - to help people avoid taking numerous untested, potentially risky soil strains and/or being exposed to potential allergens.* No one wants to be a guinea pig when it comes to digestive health!

Thus, Primal Soil™ - a super clean formula that contains two clinically proven, spore forming probiotic strains of bacteria:

Bacillus coagulans and Bacillus subtilis.

These strains:

  • Are clinically proven to help with diarrhea, digestive comfort, cholesterol health, inflammation and immune strength.*
  • Are DNA tested for genetic identity, potency and purity.
  • Are proven generally safe to use.1 2  To date, there are no known cases of children or adults, who have diarrhea but are otherwise healthy, developing bacterial infections from these two Bacillus bacteria.*
  • Produce short-chain fatty acids to support the mucosa.*

Just as important, you won’t find untested spore forming strains in Primal Soil™!

It’s also free of common allergens. This means no milk/casein, eggs, fish, shellfish, wheat/gluten, peanuts, tree nuts, yeast or soy in your Primal Soil™ capsules.

Why only two spore forming strains in Primal Soil

Because less really is more when it comes to soil-based strains.

Too often, manufacturers do not use DNA testing for purity. That means spore forming bacteria can be contaminated with other microbes that could be harmful. And again, many strains endorsed as "helpful probiotic bacteria" have not been properly researched.

We wanted to make sure that what we offered you was proven to be safe and effective.*

So we pored through the research and carefully chose two strains that had solid safety records and extensive scientific records of providing health benefits to humans.

Soil-based probiotics with companion probiotics 

If you’re looking for a clean, spore forming probiotic supplement, the Bacillus coagulans and Bacillus subtilis in Primal Soil™ may be all you need.*

But please keep in mind, given that the spore forming organisms in Primal Soil™ are transient bacteria (meaning not your own body’s permanent flora), they are not meant for long-term use. We recommend taking Primal Soil™ for no longer than two months at a time.

Here’s some quick background…

Our ancestors were very likely were exposed to soil bacteria by eating fresh fruits and vegetables grown from rich, healthy soil in which these organisms were present. This way, they inadvertently consumed bacteria. And that was a good thing… unlike our current hyper sanitary environment, that encourages scrubbing hands squeaky clean and toxic chemical disinfectants.

But back in the day, nobody was ingesting mega doses of soil bacteria. For instance, one capsule of a spore forming probiotic would have much higher potency than a carrot from the garden.

This is why your primary probiotic shouldn’t be spore forming. Instead, your daily probiotic should contain human strains of bacteria (such as lactobacillus bifidus bacteria that naturally occurs in the human digestive tract), as those are more suitable for every day, ongoing use.

So if you’re considering Primal Soil™, here’s what we recommend…

If you've used probiotics in the past and are at more advanced stage of digestive healing, our Primal Gut™ probiotic is a great, everyday supplement.* In fact, we created it to be a companion to Primal Soil™!

Primal Gut™ is our most comprehensive formula, and is appropriate for those who are looking to introduce a wider variety of blended bacteria to their regimen. We've carefully calibrated the amount of each strain to maximize the health benefits and minimize negative digestive reactions.*

How to take Primal Soil™ and Primal Gut together? 

The Primal Soil™ can be taken in tandem with Primal Gut™ - but only in one-to two-month cycles.

Taking the two supplements together is beneficial, as Primal Soil™ produces short-chain fatty acids other probiotic bacteria love, increasing the effectiveness of other probiotics.*

You can start with Primal Gut™ and slowly build up to your optimal dose, as guided by a qualified healthcare professional (ideally who is familiar with digestive health).

Once you’ve been on the optimal dose of Primal Gut™ for two weeks, you can can add a capsule of Primal Soil™. The Primal Soil™ can be taken at the same time as Primal Gut™, or separately. We always recommend that our probiotics be taken with meals.

Maybe eating dirt - or some of the microbes in it - may not be such a bad idea after all...especially if you do it strategically.


Please note that while Primal Soil has been extensively tested and proven safe for adults,* it not be used if you are critically ill or immunocompromised. 


*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.


1 Lefevre M et al. Safety assessment of Bacillus subtilis CU1 for use as a probiotic in humans.Regul Toxicol Pharmacol. 2017 Feb;83:54-65. 

2 Endres JR et al. Safety assessment of a proprietary preparation of a novel Probiotic, Bacillus coagulans, as a food ingredient. Food and Chemical Toxicology. 2009;47(6):1231-1238.

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