The recommended daily allowance for vitamin B-12 for healthy adults age 19 to 30 years old is 2.4 micrograms per day. It's known as the energy vitamin because it helps boost your metabolism and energy in the body. Vitamin B-12 also balances the nervous system, helps prevent depression, improves moods, and also protects against cancer. It also helps you form healthy hair, skin, and nails and is essential for cell division and blood formation, which helps prevent anemia. Vitamin B-12 is very important for pregnant or lactating women and infants and children. Since it's only found in mainly animal products, strict vegetarians and vegans also want to make sure that they're getting enough vitamin B-12. If you fall into any of these categories, definitely consider taking a vitamin B supplement.