Thought I'd report back from my google scholar search... Seems like calcium ascorbate is considered a very safe supplement,
with high bio-availability and good for bone health. Used topically, it' said to moisturize better than ascorbic acid. Maybe I'll
take some of it as a supplement during the winter after all!
In case anyone's interested, I found that it dissolves more easily than ascorbic acid when making skin serum and it does seem to moisturize better.
Being a more stable form of vit c means it should keep better but also makes it less acidic, so it doesn't have the same exfoliating effect as ascorbic acid.
A mixture of the two forms would probably be optimal..