I usually use my vitamins and supplements long before the 'use by' date, but I found a out-dated bottle of bulk Good And Natural vitamin C (Ascorbic Acid) 5000 mg.per tsp. and wondered if it was any good?
If it was stored out of the light and heat then it may still have some activity left.
Hv, Is ascorbic acid a good form of vitamin C? I agree it's best to get vit. C from food or herbs.
The synthetic ascorbic acid is actually pretty unstable and is quickly broken down by light, heat and moisture. Natural sources of vitamin C tend to be stronger and a lot more stable. Camu camu is an exception. Natural vitamin C sources also contain the synergistic bioflavonoids. Therefore I prefer food or herbal sources of vitamin C.
Does it depend on the product if it is stable after the 'use by ' date?
Pretty much. Some vitamins are more stable than others. Minerals and amino acids though are stable so multis will still have some benefits even well after their expiration.
Could you give us guidelines for out-dated vitamins and supplements? How long is OK?
See above, it all depends on the ingredients.