Vitamin B12, which is also called cobalamin, is a water-soluble vitamin that is found naturally in some foods and added to others. The vitamin is also available in nutrition supplements. B12 is the only water-soluble vitamin that can be stored in the body, primarily the liver, according to "Nutrition and You" by Joan Salge Blake.
Absorption
In order for vitamin B12 to be properly absorbed, a protein called intrinsic factor must be present in the stomach. Intrinsic factor binds to vitamin B12, which allows the small intestine to absorb it. Without intrinsic factor, vitamin B12 cannot be absorbed, regardless of how much of the vitamin is consumed.
Functions
Vitamin B12 is essential for proper neurological function and formation of red blood cells, according to the Office of Dietary Supplements. Vitamin B12 also is required to take certain fatty acids and amino acids and synthesize them to create the DNA that is located in the nucleus of the body cells.
Daily Needs
The daily references intake for vitamin B12 is 2.4 mcg for both adult males and females. Pregnant or lactating women have slightly increased needs and are recommended to consume 2.6 and 2.8 mcg, respectively. Blake notes that on average, American adults are consuming 4 mcg daily, which is well over the body's needs.
Food Sources
Naturally occurring vitamin B12 can be found in the highest concentrations in animal sources, such as meat, fish, poultry and dairy products. Liver, which contains 48 mcg per serving, is the highest food source of natural vitamin B12. Synthetic vitamin B12 can be found in fortified cereals and soy milk. Vitamin B12 is usually not present in plant products, so vegetarians and vegans are often at an increased risk of developing deficiencies.
Deficiency and Anemia
Most Americans consume plenty of vitamin B12, therefore, deficiency is rare. When deficiency does occur, it can cause a variety of symptoms, including fatigue, weakness, constipation, lack of appetite and weight loss. A lack of B12 can also lead to nerve damage, which presents as abnormal sensations, such as numbness and tingling in the hands and feet, according to the Office of Dietary Supplements.
A vitamin B12 deficiency can progress to a condition called megaloblastic anemia, which is characterized by a lack of red blood cells. When the blood does not contain enough red blood cells, oxygen cannot be properly delivered to the body tissues. This can result in a number of symptoms, including fatigue, weakness and shortness of breath.
References
- Office of Dietary Supplements: Vitamin B12
- "Nutrition and You"; Joan Salge Blake; 2007
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