Vitamin B12 supports red blood cells, nerve health, and DNA production, with adults needing about 2.4 micrograms daily. Shellfish like clams, oysters, and mussels are the richest sources, while dairy, ...

Even if you have a balanced diet, you might not be getting enough vitamin B12. The reason? B12 is found almost exclusively in animal foods. For instance, beef is a top source of B12. Just one 4-ounce ...