Whole food vitamins and minerals come from whole foods, such as fruits, vegetables and herbs. This whole food type of vitamin or mineral is much preferred by the body over its synthetic counterpart, due to its better recognition and utilization. For proper absorption by a carnivore, whole foods need to be broken down to mimic the pre-digestion that takes place in the gut of a prey.
Herbivores possess an enzyme, which carnivores do not, called cellulase. This allows them to break down the cell walls of plants in order to access the vitamins and minerals. Thus, the dog must eat the rabbit who pre-digested the carrot in order to assimilate Vitamin A.
This is why in a home-prepared raw diet or a commercial raw diet the veggies should be blended and some (cruciferous) should be steamed or cooked and blended to mimic nature, and aid in the breakdown process for your carnivore.
Also, in the wild, predators forage. They eat plants to aid digestion, stimulate the immune system and even to treat illnesses. The Native Americans observed wild animals to learn which plants to eat. I believe sometimes our indoor dogs and cats know which outdoor plants they need to consume in order to provide a lacking vitamin or mineral, or which will cause them to vomit if they feel nauseous or need to purge a hairball. However, sometimes, they don't know. Perhaps the grass they seek is unavailable. They may routinely make a bad choice and vomit grass every time they go outside and eat it. Repetitive vomiting is damaging to the esophagus. This would be a situation in which you would want to intervene and prevent your pet from consuming that particular plant material. Generally the cat grasses that you purchase in the grocery store are appropriate and enjoyed by many cats. This and catnip are an intermittent luxury.
There are commercial supplements which can fulfill this need. The Standard Process line, Mediherb, Animal Essentials Organic Green Alternative, Mercola Spirugreen, Pet Kelp and Cranimals are a few examples of quality whole supplements that we stock to fulfill this important category and to fill in nutritional gaps in your pet's nutrition. Always introduce new foods gradually and think of these as functional spices. A little goes a long way! Mix it up a little. You can vary and alternate these depending on the nutritional issue that you are managing.