Not All Vitamins Are Created Equal | What Is Bioavailability?

When it comes to vitamins plants and animals use different forms of certain vitamins:

• Plants do not produce Vitamin  A, retinol and instead rely on provitamin A or plant vitamin A beta-carotene or other types of carotenoids. Beta-carotene is very poorly absorbed compared to retinol and must be converted into retinol in the body
• Plants only produce vitamin K1, animals require mostly K2. K1 can be converted into K2, but again only in small quantities (not enough to satisfy our needs).
• Plants use vitamin D2 while animals use D3
• Plants do not produce Vitamin B12 and are not good sources for the other B vitamins with a few exceptions

On the bright side, plants specifically fruits are one of the best sources of vitamin C. Vitamin C is found in relatively smaller quantities in organ meats like liver and heart, but fruits and juices are one of the best dietary sources of Vitamin C.

Last, but not least plants are often densely packed with Vitamin E, but this is a double-edged sword. Vitamin E requirements are increased the more polyunsaturated fat that are contained in any living organism in order to keep the polyunsaturated fats from oxidizing (vitamin E is a potent antioxidant). So generally, the best sources of Vitamin E also contain large amounts of the polyunsaturated fats which kind of defeats the point of consuming them for their Vitamin E quantity.