There are two classes of vitamin: water-soluble and fat-soluble. A water-soluble vitamin is typically not stored; your kidneys filter out and excrete the excess. The water-soluble vitamins are the B and C vitamins. However, although it is a water-soluble vitamin, B-12 is stored by the body. Hydrochloric acid in the stomach releases B-12 from protein during digestion. Once released, B-12 combines with a substance called intrinsic factor and is then absorbed into the bloodstream.
Storage
Instead of filtering and excreting excess vitamin B-12 like other water-soluble vitamins, your body stores B-12 in your liver. In fact, your liver stores enough to sustain your needs for approximately 3 to 5 years, even if you no longer consume B-12.
Function
Vitamin B-12 assists in a variety of functions inside your body. Primarily, it is responsible for cellular formation and DNA replication. It helps form red blood cells and allows your nervous system to function properly. Its involvement in the production of methionine is very important. Vitamin B-12 binds with methionine synthase and L-methylmalonyl-CoA mutase, which transfers homocysteine to methionine. Methionine helps form DNA, RNA, hormones and proteins.
Deficiency
Deficiency of vitamin B-12 is quite rare since your liver stores it. Deficiency usually occurs due to problems with absorbency. Vegetarians and vegans are at high risk for vitamin B12 deficiency because it is found mainly in animal-based foods. Signs and symptoms of a deficiency include fatigue, constipation, weakness, decreased appetite and weight loss. Megaloblastic anemia can also occur. This is a serious condition marked by abnormally large red blood cells, which means your cells cannot get the oxygen they need. A vitamin B-12 deficiency can be treated with an injection of the vitamin, which allows it to bypass absorption.
Recommendations
The recommended daily vitamin B-12 intake varies according to age. Infants up to 6 months old need 0.4 micrograms. From ages 7 months to 1-year old, babies need 0.5 micrograms. From ages 1 to 3, children need 1.2 micrograms and from ages 4 to 8, they need 1.2 micrograms. Ages 9 to 13 need 1.8 micrograms and from 14 years and on, you need to consume 2.4 micrograms. Dietary sources of vitamin B-12 include meat and fortified grain products. Examples are cereal, milk, eggs, ham, fish and beef. Before increasing your dietary intake of any vitamins or adding supplements, seek out the guidance of your physician. He will let you know the right course of action for your condition.
References
- "Nutrition"; Paul Insel, Don Ross, Kimberley McMahon, Melissa Bernstein; 2011
- Merck Manuals Online Medical Library; Vitamin B12; Larry E. Johnson, MD, PhD; April 2007
- Office of Dietary Supplements: Dietary Suplements Fact Sheet: Vitamin B 12
- MayoClinic.com; Vitamin B 12; April 1, 2011
- PubMed Health; Megaloblastic Anemia; January 31, 2010
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