Your baby resembles a tadpole more than a human, but is growing fast. The circulatory system is beginning to form, and the tiny heart will start to beat this week. Your baby is the size of a sesame seed. Read about your pregnancy at 5 weeks.
Stores of B12 can last for up to a year. Foods high in Vitamin B12 include shellfish, liver, fish, crab, fortified soy products (tofu, soymilk), fortified cereals, red meat, low fat dairy, cheese, and eggs.
What are the best food sources? Vitamin B12 is found naturally in animal-based foods, such as meat, fish, poultry, eggs and dairy foods. Particularly rich sources of vitamin B12 include shellfish, herring, sardines, trout and some game meats.