Vitamin C is ascorbic acid which is commonly found in fruit and vegetables especially citrus fruits. It is an essential vitamin for humans and cannot be manufactured in the body so it has to be provided through our diets and the food we each.
Ascorbic acid as the name suggests is acidic and when dissolved in water has a PH of 5. Ascorbic acid is available naturally in its pure form and also combined with minerals such as calcium ascorbate.
Calcium ascorbate has a PH of 7.4 when dissolved in water which means it is very slightly alkali. Calcium ascorbate is simple to produce, calcium carbonate is mixed with ascorbic acid in solution under controlled conditions, the solution is then dried leaving pure calcium ascorbate crystals.
Many companies have started to use calcium ascorbate if their food supplements due to its lower acid content which users often find to be easier to digest and gentle in the stomach.
Care needs to be taken to ensure fully reacted calcium ascorbate is requested as a short cut is it to simply blend dry calcium carbonate with ascorbic acid, however this does not give the required buffering effect.
There are branded and generic forms of buffered Vitamin C the most popular being Ester C, which is backed by extensive clinical research.
Nutritional Biochemist, Industry consultant on supplements