his product is a potent blend of many vitamins, minerals and known antioxidants. This naturally pleasant tasting beverage is great to maintain our health and boost energy. The key word is "complex". Ester-C Complex is a combination of ascorbic acid (natural Vitamin C) and Calcium Ascorbate, which ultimately yields 500 total mg of Vitamin C. It is complexed with Calcium Ascorbate and other metabolites for greater absorption and faster utilization by your body. So the total complex is 625mg of Ester-C Complex, which yields 500mg of natural Vitamin C as ascorbic acid. Calcium Ascorbate is a buffered salt (mineral) form of the water-soluble antioxidant Vitamin C (ascorbic acid). Calcium is reacted with ascorbic acid to buffer the acidic nature of this vitamin, making it more gentle for the special needs of those who may have a sensitive gastrointestinal tract. The pH of this buffered mineral Ascorbate is approximately 6.8-7.4 as compared to ascorbic acid that is about a pH of 2.5. Calcium Ascorbate provides approximately 10% elemental calcium.