Dietary Supplement. Essential Nutrients* With Rapid-Uptake Fast-C™ & NAC. Antioxidant, detox & immune support*. Clinically proven rapid absorption. No upset stomach, no heartburn Whether you are taking vitamin C for antioxidant protection, detoxification, or immune support, amplify its effects with Advasorb™ Vitamin C. Combining Fast-C™ - a unique, rapidly absorbed, and better retained form of vitamin C - with N-acetyl cysteine , this potent formula delivers: Antioxidant Protection: Vitamin C and NAC are both antioxidants t.