A vitamin B12 deficiency is characterized by anemia, memory loss, neurological dysfunction, depression, irritability and, in rare cases, psychosis, according to Robert Oh, lead author of "Vitamin B12 Deficiency," which appeared in the "American Family Physician Journal." Deficiency of vitamin B12 may also increase the risk of stroke and heart attack. Because several foods in the standard American diet contain this vitamin, preventing vitamin B12 deficiency is simple for most people in the United States.
Add lean meats to your diet. Beef, calf liver and venison are sources of vitamin B12, according to the World's Healthiest Foods website. Several types of seafood, including shrimp, scallops and fish such as snapper, halibut and salmon, are also rich in this vitamin.
Include cereals fortified with vitamin B12, advises the Vegetarian Resource Group website. Check the nutrition labels on cereal boxes, because not all cereal manufacturers add the vitamin.
Add soy foods and beverages fortified with vitamin B12 to your diet. According to the Vegetarian Resource Group, several brands of soy milk and tofu are fortified with vitamin B12.
Consume dairy products and eggs. According to the World's Healthiest Foods website, eggs, cow's milk and yogurt are natural sources of vitamin B12.
Include meat substitutes fortified with vitamin B12 if you are a vegetarian or vegan, advises the Vegetarian Resource Group website. Some meat substitutes such as veggie burgers, tempeh, seitan and wheat gluten are fortified with vitamin B12.
Include foods rich in vitamin B6 in your diet, advises the World's Healthiest Foods website. Vitamin B6 is necessary for the proper absorption and storage of vitamin B12. Spinach, walnuts, poultry, avocados, bananas and brown rice are sources of vitamin B6, according to Dr. James F. Balch, author of "Prescription for Nutritional Healing."
Take a vitamin B12 supplement. A daily supplement of 5mcg to 10mcg is typically sufficient to meet the body's need for this vitamin, according to the Vegetarian Resource Group website.