Patented ascorbate complex bound with calcium carbonate. Recommended to help support healthy immune system. Naturally processed in purified water without the use of alcohol or acetone solvents. This makes Ester-C a more readily available, readily absorbed form of vitamin C. Ester-C, a well-known antioxidant, has been shown to aid in reducing joint cartilage degeneration and decreases susceptibility to infections. Up to 4 times more metabolic activity than ascorbic acid. Non-acidic and gentler on the stomach.