21st Century Vitamin C Supplement 1000 mg Prolonged Release Tablets helps boost your immune system for longer. This Vitamin C supplement contains 1000mg of Vitamin C per serving, which is gradually released in your body over time to assist strengthen your immune system and antioxidant levels. Vitamin C is an antioxidant ingredient that helps to build and promote immunity by removing toxins from the body also prevents or reduces cell damage produced by free radicals, so preventing disease. Free radicals may increase the risk of inflammation and other health problems.