Functions

Vitamin B12’s functions include the following:

• Assisting in the production of neurotransmitters, which are chemicals that regulate sleep, pain, and mood
• 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. People who do not have enough stomach acid (such as those taking strong acid-neutralizing medications) may not be able to separate B12 from food. People with this problem, however, absorb B12 supplements without difficulty.

Two proteins are also 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 may occur in mid- to late-life. Severely reduced levels of IF lead to a condition called pernicious anemia. People with pernicious anemia have trouble absorbing B12 supplements and may need either very high doses or injections.

Symptoms of vitamin B12 deficiency include the following:

• Fatigue
• Numbness and tingling of the arms or legs
• Difficulty walking
• Sore tongue
• Loss of appetite
• Constipation
• Memory loss
• Disorientation
• Moodiness

Vitamin B12 Toxicity

Vitamin B12 has a 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

Vitamin B12 can be found in animal products, such as fish, meat, poultry, eggs, and milk. Some foods high in vitamin B12 include:

• Clams
• Beef liver
• Trout
• Salmon
• Tuna fish
• Haddock
• Yogurt
• Fortified breakfast cereals

Health Implications

Tips For Increasing Your Vitamin B12 Intake:

Here are tips 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 barbecue 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 sliced fresh fruit or crunchy granola.
• Skewer large shrimp with mushrooms, tomatoes, onion, and zucchini. Brush on a marinade and toss on the barbecue.
• If you take a multivitamin/mineral supplement, make sure that it contains B12.