* Dietary Supplement * NSF Certified for Sport You’re a competitor so you’ve heard the phrase, “gut check.” In this case, we’re literally talking about your gut. Your intestinal tract. Klean Probiotic balances bacteria in your gut so that the nutrients you need to perform can be properly absorbed into your bloodstream. Not only that, since strenuous exercise can suppress the immune system, Klean Probiotic is also formulated to help support your body’s immune response.