#1 Pharmacist Recommended Vitamin & Supplement Brand USP Verified Dietary Supplement Antioxidant Support Helps Support the Immune System No Color Added No Artificial Flavors No Added Preservatives Gluten Free USP has tested and verified ingredients potency and manufacturing process. USP sets official standards for dietary supplements. Lend your immune system a helping hand and help neutralize free radicals in the body. *Based on Pharmacy Times Survey of pharmacists recommending Letter Vitamin Supplements.