Vitamin B12 is crucial to the human body, which needs it to produce new DNA, red blood cells, proteins, hormones and lipids (fats). Vitamin B12 is also key to the health of nerves. Vitamin B12 is part of the vitamin B complex, which includes thiamin, niacin, vitamin B6, folate and vitamin B12. Each of these vitamins has its “own unique role in the body, but most B vitamins have a role in helping your body’s cells to produce energy,” said Heather Mangieri, a spokeswoman for the Academy of Nutrition and Dietetics and owner of Nutrition Checkup in Pittsburgh. The typical American diet meets or exceeds the daily recommended amount of vitamin B12. However, vitamin B12 deficiency remains a common problem in the United States because it can be affected by other factors, like age and digestion. Seniors, vegans and pregnant women are especially prone to vitamin B12 deficiency. People may not realize vitamin B12 is missing from their diets because the liver can store a 5-year supply in reserve.