As the name suggests, soil-based Bacillus organisms are found in the dirt. Some experts warn that SBOs can compete with our resident gut bacteria and become pathogenic. But studies suggest that, for most people, specific, well-researched categories of soil-based probiotics are harmless.
“The safety of all probiotics has been well documented, given you’re using a formula that’s been tested to ensure it meets its label claims,” says Ruscio.
“Customer awareness around soil-based probiotics is in its infancy, and just like any supplement, the efficacy and safety is controversial,” says Morra, adding that she uses SBOs in her clinical practice and hasn’t observed any negative effects.
But it’s a risky approach for people with compromised immunity, she adds. The spore-forming nature of SBOs means they may proliferate and become pathogenic.
For people in reasonably good health, studied strains of soil-based probiotics should be well tolerated. As with any probiotic, discontinue its use if you experience negative reactions, like bloating, gas, or constipation, that last longer than a few days.