Vampires

Vampires (also called The Cold Ones) are the primary supernatural creatures of the Twilight universe. They are immortals who feed and survive on the blood of humans or animals. Vampires are one of the three known supernatural species in the Twilight series after shape-shifters and werewolves.

Diet
Blood is the only component of a vampire's diet; failing to drink blood (whether human or animal) for an extended period of time will physically and mentally weaken a vampire. The longer a vampire abstains from blood, the more likely the vampire will lose their rationality and mental faculties until they give into their thirst, because their throats are described to be in burning torment which will get worse the longer they lack blood in their systems. Animal blood is less appealing to vampires though it still gives them nutritions, and a vampire that feeds on human blood is fractionally stronger than another vampire the same size that feeds on animal blood. Vampires that live on animal blood are referred to as "vegetarians". On occasion, the appeal of human blood can be so enticing that a vegetarian vampire will lose his/her control, especially if their self-control is weak. When they drink blood that smells very appetizing, their throat starts to "burn" and all they will think about is their thirst, and thus loses all sense of self. To a vegetarian, carnivores' blood is more appetizing than herbivores, though still not quite as good as humans.

Newborns
Newborn or newborn vampire is the term for a vampire that has been transformed for less than one year. On average, a newborn's physical strength, senses and speed greatly surpass that of an older vampire because they still have their own blood lingering in their tissues. As time passes, however, the venom in them will consume that blood, and the newborn's physical capabilities and thirst will slowly diminish until it reaches that of a normal vampire, by the end of its first year.