Vitamin B-12 is a water soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins and the most complex. It is normally involved in the metabolism of every cell in the body, especially affecting DNA synthesis and regulation, but also fatty acid synthesis and energy production.
Vitamin B12 cannot be made by plants or animals as only bacteria, yeast, molds and algae have the enzymes required for its formation. It is naturally found in meat (especially liver), shellfish, milk and eggs. Animals must obtain it directly or indirectly from bacteria. Since plants do not provide B-12 to humans, vegans, who eat only plant based foods, may need to get their B-12 from supplements or foods fortified in B-12. A normally functioning stomach, pancreas and small intestines are required for B-12 absorption. Stomach acids free B-12 from food allowing it to bind to certain proteins unique to the stomach (Intrinsic Factor), enabling receptors in the small intestines to take it in. The body stores enough B-12 in the liver to last several years, so deficiency occurs from lack of food sources or poor absorption of the vitamin from food. Vitamins B-6 and E are also required for B-12 absorption, so persons deficient in B-12 may also be lacking in these nutrients.
Many common drugs and dietary supplements can interfere with the absorption of B-12. These include:
Alcohol, antibiotics, some antibiotics, Pepcid, Zantac, Prilosec, (and other anti-acid medications), Metformin, nicotine, Dilantin, HIV medications, folic acid, and potassium supplements
B-12 deficiency may present as the following symptoms:
Anemia, GI symptoms, neurological symptoms, change in mental status, confusion, depression, constipation, fatigue, muscle weakness, numbness and tingling in the hands and feet, shortness of breath, or sore mouth and tongue
A severe deficiency may cause irreversible nerve damage. Large doses of folic acid will correct the anemia of B-12 deficiency but not prevent or correct the nerve damage caused by the deficiency and should not be used to treat anemia until the cause is known. A deficiency not corrected by food may need to be treated with oral supplementation or injections. If minimal or no response noted, a medical evaluation should be conducted.
B-12 deficiency may be caused by Celiac and Crohn’s diseases (or other malabsorption syndromes), damage to the liver, pancreas or stomach, diet, medications, or parasites, as well as other situations.
Many research studies are looking at connections between B-12 deficiency and heart disease, breast cancer, Alzheimer’s disease and depression.
No toxicity levels have ever been reported and there are no known cases of toxic amounts being consumed. Allergic reactions can occur with injections. Vitamin B-12 is preserved with most cooking methods when the vitamin is derived from animal/fish sources.
Foods highest in Vitamin B-12: