Vitamins are chemical compounds that are needed in small amounts to support the functions of the body and therefore promote good health. Vitamin B-12, also known as cobalamin, is a water-soluble vitamin. The B-12 molecule is the largest of the vitamins and is used by every cell in the body.
Sources of B-12
Vitamin B-12 is synthesized by bacteria and is not made by either plants or animals. However, it is stored and used by plants and animals, so it can be obtained from plant and animal sources in the diet. Beef liver, fish such as salmon, fortified cereals and dairy products tend to be the best sources. Dietary supplements are available to be swallowed in pill form or used under the tongue. Prescription B-12 is also available for injection or intranasal use.
B-12 Absorption
Vitamin B-12 has a relatively complicated process of absorption. Acid and digestive enzymes in the stomach break down food to release vitamin B-12. Special proteins bind to B-12 and it is moved into the small intestine. The proteins are removed from B-12 and another protein called intrinsic factor binds to the vitamin. The B-12-intrinsic factor is taken up into the blood stream from the small intestine.
B-12 Deficiency
Vitamin B-12 is used for DNA synthesis and regulation, red blood cell formation, neurological functioning and fatty acid synthesis. According to "Robbins and Cotran Pathologic Basis of Disease" by Vinay Kumar, deficiency of vitamin B-12 leads to health problems. Pernicious anemia is a low red blood cell count from a B-12 deficiency that causes weakness, fatigue, depression and other problems. The nerves of the spinal cord can also be damaged, leading to difficulty walking and reduced sensation and feeling in the limbs. Gastrointestinal problems are also common.
Adverse Effects of B-12
Vitamin B-12 has a very low toxicity, but intake of this vitamin can exacerbate some underlying diseases. Treatment of certain forms of anemia can result in dangerously low potassium. Polycythemia vera is a condition in which the bone marrow produces too many red blood cells. If a person has an undiagnosed or mild polycythemia vera, it can be unmasked by vitamin B-12 administration. Also, in people with an inherited eye and neurological condition called Leber's disease, certain forms of B-12 can cause blindness.
References
- National Institutes of Health; Office of Dietary Supplements; Dietary Supplement Fact Sheet; Vitamin B12
- "Nutrition Concepts and Controversies"; Frances Sizer, Ellie Whitney; 11th Ed 2007
- "Lehninger Principles of Biochemistry"; David L. Nelson and Michael M. Cox; 4th Ed 2004
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar et al; 8th Ed 2009
Member Comments