Vitamin B12
Recommended Intake
Vitamin B12 Deficiency
Vitamin B12 Toxicity
Major Food Sources
Health Considerations
Tips for Increasing Your Vitamin B12 Intake

Vitamin B12, also called cobalamin, is a water-soluble vitamin. Water-soluble vitamins are stored in the body in very limited amounts, and are excreted through the urine. Therefore, it is a good idea to have them in your daily diet. Vitamin B12, the most complex of the vitamins, contains the metal ion cobalt in its structure.

Vitamin B12's functions include:

• aiding in the conversion of homocysteine to methionine; elevated blood levels of homocysteine have been associated with an increased risk of heart attack
• assisting in the production of neurotransmitters, which are chemicals that regulate sleep, pain, and mood
• playing a role in carbohydrate, protein, and fat metabolism
• enabling proper DNA replication
• helping catalyze the reaction that produces succinyl-CoA, a chemical required for the synthesis of hemoglobin
• making red blood cells and preventing anemia

Recommended Intake:

Vitamin B12 Deficiency
Most diets provide adequate B12; deficiency is often a result of absorption problems. In the stomach's acidic environment and through the action of the enzyme pepsin, vitamin B12 is released from food. Two proteins are important for the vitamin's absorption and transport: intrinsic factor (IF) and R proteins. A B12 deficiency can result if there are any problems with pepsin, IF, or R proteins. Reduced secretion of IF is often a problem in mid- to late-life.

Symptoms of vitamin B12 deficiency include:

• pernicious or megaloblastic anemia
• numbness and tingling of the arms or legs
• difficulty walking
• fatigue
• sore tongue
• loss of appetite
• constipation
• memory loss
• disorientation
• moodiness
• damage to the myelin sheath, the protective covering around nerves
• dementia

The following populations may be at risk for vitamin B12 deficiency and may require a supplement:

• People with pernicious anemia. This condition occurs when there is an absence of intrinsic factor. A person who has pernicious anemia will need to be monitored by a physician and take lifelong supplemental vitamin B12.
• Older adults. The incidence of B12 deficiency among the elderly may be as high as 15 percent. A multivitamin may not contain enough B12 to compensate; talk with your health care provider about what your specific needs are for supplementation.
• People with gastrointestinal (GI) disorders. GI disorders, like celiac disease, Crohn's disease, or GI surgery, can lead to malabsoprtion of B12.
• Strict vegetarians. B12 is generally not present in plant foods; it is found only in animal products. Vegetarians who consume no animal products may need to supplement with B12. Fortified cereal can be a good source of vitamin B12 for a vegetarian.
• People who consume excessive amounts of alcohol. Alcoholics tend to have diets lacking in several essential nutrients, including B12.

Vitamin B12 Toxicity
Vitamin B12 has a very low potential for toxicity. The tolerable upper intake level (UL) for vitamin B12 from dietary sources and supplements combined has not been determined. This does not mean that there is no potential for adverse effects resulting from high intakes. Because data is limited, caution should be used when supplementing.

No symptoms of vitamin B12 toxicity have been reported.

Major Food Sources

Health Considerations

• Folate supplementation and B12 deficiency

  Megaloblastic anemia can occur as a result of either a folate deficiency or a vitamin B12 deficiency. Supplementing with folate can correct this anemia. But, it will not correct the B12 deficiency. Permanent nerve damage can result if a B12 deficiency is left untreated. If you have megaloblastic anemia, talk with your doctor about assessing your B12 status as well as you folate status.

• Homocysteine, cardiovascular disease, and vitamin B12

  Homocysteine is an amino acid. While most amino acids found in the body are building blocks of protein or muscle, homocysteine is not a component of protein. It is formed as an intermediate step in the production of another amino acid, methionine. The conversion of homocysteine to methionine requires a number of vitamins, including folate, B6, and B12. A deficiency of any one of these vitamins can cause the level of homocysteine in the blood to rise, which may damage coronary arteries or make it easier for blood clotting cells to clump together and form a clot. This can increase your risk of heart attack or stroke.

Tips for Increasing Your Vitamin B12 Intake
To help increase your intake of vitamin B12:

• Rub a little olive oil, squeeze a bit of fresh lemon, and crack some black pepper and salt on a fresh piece of salmon. Grill on the barbeque or broil it in the oven.
• Have a bowl of fortified, high-fiber breakfast cereal in the morning.
• Mix canned tuna with some olive oil, white beans, and salt and pepper. Enjoy with some whole wheat crackers.
• For an afternoon snack, try a cup of yogurt. Jazz it up with some cut fresh fruit or crunchy granola.
• Skewer large shrimp with mushrooms, tomatoes, onion, and zucchini. Brush on a marinade and toss on the barbeque.
• If you take a multivitamin/mineral supplement, make sure that it contains B12.