Also called ester-C. A buffered form of vitamin C that incidentally provides small amounts of calcium. The ratio of C:Ca is about 10:1. This form is said to be more bioavailable, and may be good for people who can't take normal Vitamin C without gastric irritation. Evidently calcium ascorbate is a weak acid (that is, weaker than ascorbic acid), so it doesn't dump a lot of acidic material into the stomach at once.