Nutrients - Vitamin B12

Vitamin B12

Overview

All B vitamins are water-soluble, meaning that the body does not store them. Vitamin B12, also called cobalamin, is one of 8 B vitamins. It is important to know that all B vitamins help the body convert food (carbohydrates) into fuel (glucose), which is used to produce energy. These B vitamins, commonly referred to as B complex vitamins, also help the body use fats and protein. B complex vitamins are also used for healthy skin, hair, eyes, and liver. They help the nervous system function properly.

Vitamin B12 is an especially important vitamin for maintaining healthy nerve cells, and it helps in the production of DNA and RNA, the body's genetic material. Vitamin B12 also works closely with vitamin B9, also called folate or folic acid, to help make red blood cells and to help iron work better in the body. Folate and B12 work together to produce S-adenosylmethionine (SAMe), a compound involved in immune function and mood.

Vitamins B12, B6, and B9 work together to control blood levels of the amino acid homocysteine. High levels of homocysteine are associated with heart disease. However, researchers aren't sure whether homocysteine is a cause of heart disease or just a marker that indicates someone may have heart disease.

It' s rare for young people to be deficient in vitamin B12, but it' s not uncommon for older people to be mildly deficient. That may be because their diets are not as healthy or because they have less stomach acid, which the body needs to absorb B12. Low levels of B12 can cause a range of symptoms including fatigue, shortness of breath, diarrhea, nervousness, numbness, or tingling sensation in the fingers and toes. Severe deficiency of B12 causes nerve damage.

Others at risk for B12 deficiency include:

1. Vegans, vegetarians who also don't eat dairy or eggs -- vitamin B12 is found only in animal products

2. People with problems absorbing nutrients, due to conditions such as Crohn's disease, pancreatic disease, and people who have had weight loss surgery

3. People who are infected with Helicobacter pylori, an organism in the intestines that can cause an ulcer. H. pylori damages stomach cells that make intrinsic factor, a substance the body needs to absorb B12

4. People with an eating disorder

5. People with HIV

6. The elderly

Folic acid (vitamin B9), especially when taken in high doses, can mask the symptoms of a vitamin B12 deficiency. The danger is that without symptoms, someone with a vitamin B12 deficiency may not know it, and could run the risk of developing nerve damage. Anyone planning to take more than 800 mcg of folic acid should talk to their doctor first, to make sure they do not have a B12 deficiency.

Vitamin B12
Vitamin B12 is bound to protein in food. The activity of hydrochloric acid and gastric protease in the stomach releases vitamin B12 from its protein.  Once it is released, vitamin B12 begins to work quickly. It is important for the formation of red blood cells, neurological function, and DNA synthesis. It also supports the digestive system in keeping glucose levels stable.

A simple blood test can determine the level of B12 in the body. Adults who have a value below 170 to 250 pg/ml are considered deficient in the vitamin. An elevated blood homocysteine level or elevated methylmalconic acid level may also suggest a B12 deficiency.

Tests

Vitamin B12 and folate are ordered to detect deficiencies and to help diagnose the cause of certain anemias. One type of associated anemia is pernicious anemia, an autoimmune disease that affects the absorption of B12. This megaloblastic anemia occurs when the body produces antibodies against the gastric parietal cells or the intrinsic factor, resulting in B12 malabsorption.

Folate, B12, and an assortment of other tests may be ordered to help evaluate the general health and nutritional status of a person with signs of significant malnutrition or dietary malabsorption. This may include people with alcoholism, other liver diseases, gastric cancer, and those with malabsorption conditions such as celiac disease, tropical sprue, Crohn’s disease, inflammatory bowel disease, and cystic fibrosis.

B12 and folate may also be ordered to aid in diagnosis when an individual presents with an altered mental state or other behavioral changes, especially in the elderly. B12 may be ordered with folate, by itself, or with other screening laboratory tests (antinuclear antibody, CRP, rheumatoid factor, CBC and chemistry blood tests) to help establish reasons why a person shows symptoms of neuropathy.

In those treated for known B12 and folate deficiencies, these tests will be ordered occasionally to monitor the effectiveness of treatment. This is especially true in those who cannot properly absorb B12 and/or folate and must have lifelong treatment.

Recommended Daily Allowance

If you are considering taking a B12 supplement, ask your health care provider to help you determine the right dose for you.

Daily recommendations for dietary vitamin B12 are listed below.

Pediatric

 Newborns - 6 months: 0.4 mcg (adequate intake)

 Infants 6 months - 1 year: 0.5 mcg (adequate intake)

 Children 1 - 3 years: 0.9 mcg (RDA)

 Children 4 - 8 years: 1.2 mcg (RDA)

 Children 9 - 13 years: 1.8 mcg (RDA)

 Teens 14 - 18 years: 2.4 mcg (RDA)

Adult

 19 years and older: 2.4 mcg (RDA)*

 Pregnant women: 2.6 mcg (RDA)

 Breastfeeding women: 2.8 mcg (RDA)

*Because 10 - 30% of older people may not absorb B12 from food very well, people over 50 should meet their daily requirement through either foods fortified with vitamin B12 or a supplement containing B12.

Cautions

If the B12 deficiency is not remedied, permanent nerve damage can occur. Neuropathy is a common problem for people with diabetes, who experience pain, tingling, and numbness in their arms, hands, legs, and feet, resulting in sores.

Vitamin B12 is an especially important vitamin for maintaining healthy nerve cells, and it helps in the production of DNA and RNA, the body's genetic material. Vitamin B12 also works closely with vitamin B9, also called folate or folic acid, to help make red blood cells and to help iron work better in the body.

Food Sources

Vitamin B12 is found only in animal foods. Liver, sardines, and salmon rank highest, with liver running away with it. Kidney, eggs, beef, and pork are also good sources. There are no vegetarian sources. Supplements include - Methylcobalamin is probably the best.

Precautions

One large study found that women who took 1,000 mcg of vitamin B12 along with 2500 mcg of folic acid and 500 mg of vitamin B6 daily reduced their risk of developing AMD, an eye disease that can cause loss of vision.

Fatigue is one of the symptoms of a vitamin B12 deficiency. One preliminary study indicated that people with chronic fatigue syndrome might benefit from B12 injections, although more research is needed to know for sure.

Although there is no evidence that vitamin B12 alone reduces the risk of breast cancer, population studies have shown that women who get more folate in their diet have lower risk of breast cancer. Vitamin B12 works with folate in the body, so it may help contribute to a lesser risk. Another preliminary study suggested that postmenopausal women who had the lowest amounts of B12 in their diet had an increased risk for breast cancer.

Studies suggest that vitamin B12 supplements may improve sperm counts and sperm mobility. However, the studies were of poor quality. Better studies are needed to see whether B12 has any real effect.

Possible Interactions

If you are currently being treated with any of the following medications, you should not use vitamin B12 supplements without first talking to your health care provider.

Medications that reduce levels of B12 in the body include:

Anti-seizure medications -- including phenytoin (Dilantin), phenobarbital, primidone (Mysoline)

Chemotherapy medications -- particularly methotrexate

Colchicine -- used to treat gout

Bile acid sequestrants -- used to lower cholesterol; include colestipol (Colestid), cholestyramine (Questran), and colsevelam (Welchol)

H2 blockers -- used to reduce stomach acid; include cimetidine (Tagamet), famotidine (Pepcid AC), ranitidine (Zantac)

Metformin (Glucophage) -- medication taken for diabetes

Proton pump inhibitors -- used to reduce stomach acid; include esomeprazole (Nexium), lansprazole (Prevacid), omeprazole (Prilosec), and rabeprazole (Aciphex)

Antibiotics, Tetracycline -- Vitamin B12 should not be taken at the same time as tetracycline because it interferes with the absorption and effectiveness of this medication. Vitamin B12 should be taken at different times of the day from tetracycline. All vitamin B complex supplements act in this way and should be taken at different times from tetracycline. In addition, long-term use of antibiotics can lower vitamin B levels in the body, particularly B2, B9, B12, and vitamin H (biotin), which is considered part of the B complex vitamins.