Fuel Your Foundation. Perform At Your Peak. We power health and peak performance in athletes who demand the most from themselves, their sport and their nutrition.*. Klean is Clean. Klean Athlete products are GMO-free and formulated without wheat, gluten, or artificial coloring, flavoring or sweeteners. Every product is third party certified by NSF International's NSF Certified for Sport program, to help athletes, coaches and trainers make more informed decisions when choosing sports supplements.