most animals - both Carnivores and Herbivores - can synthesize their own Vitamin C.

Humans are one of the few species who can't - we need Vit C in the diet.

Carnivores deny this because it complicates their propaganda ...

but with added synthetic Vitamin C ( Ascorbic Acid is so cheap it is a popular for cleaning swimming pools for example ) Carnivore becomes viable.

5 years worth of Vitamin C bought as bulk Ascorbic Acid is less than $20.

If you have money it's better to only buy 1 year's worth as it will slightly degrade overtime depending on how you store it.  5 years is pushing it in terms of shelf life.