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Vitamin B12: Main Image

Learn all about Vitamin B12

What is Vitamin B12

Vitamin B12 is a water-soluble vitamin needed for normal nerve cell activity, DNA replication, and production of the mood-affecting substance SAMe (S-adenosyl-L-methionine). Vitamin B12 acts with folic acid and vitamin B6 to control homocysteine levels. An excess of homocysteine is associated with an increased risk of heart disease, stroke, and potentially other diseases such as osteoporosis and Alzheimer’s disease.

How to Use It

Most people do not require vitamin B12 supplements. However, vegans should supplement with at least 2 to 3 mcg per day.

People with pernicious anemia are often treated with injections of vitamin B12. However, oral administration of 1,000 mcg per day can be used reliably as an alternative to vitamin B12 injections.

Absorption of vitamin B12 is reduced with increasing age. Some research suggests that elderly people may benefit from 10 to 25 mcg per day of vitamin B12. One study of elderly people with vitamin B12 deficiency suggested that as much as 500 to 1,000 mcg of vitamin B12 per day might be necessary to achieve optimal vitamin B12 status. Vitamin B12 status was measured in this study using a sensitive laboratory test (the plasma methylmalonic acid concentration).

When vitamin B12 is used for therapeutic purposes other than correcting a deficiency, injections are usually necessary to achieve results.

Sublingual forms of vitamin B12 are available, but there is no proof that they offer any advantage to oral supplements.

Where to Find It

Vitamin B12 is found in all foods of animal origin, including dairy, eggs, meat, poultry, and fish. According to one report, small, inconsistent amounts occur in seaweed (including nori and chlorella) and tempeh. Many researchers and healthcare professionals believe that people cannot rely on vegetarian sources to provide predictably sufficient quantities of vitamin B12. However, another study found substantial amounts of vitamin B12 in nori (at least 55 mcg per 100 grams of dry weight).

Possible Deficiencies

Vegans (vegetarians who also avoid dairy and eggs) frequently become deficient, though the process often takes many years. People with malabsorption conditions, including those with tapeworm infestation and those with bacterial overgrowth in the intestines, often suffer from vitamin B12 deficiency. Malabsorption of vitamin B12 can also result from pancreatic disease, the effects of gastrointestinal surgery, or various prescription drugs.

Side Effects

Oral vitamin B12 supplements are not generally associated with any side effects. Although quite rare, serious allergic reactions to injections of vitamin B12 (sometimes even life-threatening) have been reported. Whether these reactions are to the vitamin itself, or to preservatives or other substances in the injectable vitamin B12 solution, remains somewhat unclear. Most, but not all, injectable vitamin B12 contains preservatives.

In a double-blind trial, people with diabetes who also had with kidney disease received a daily placebo or 2.5 mg of folic acid, 1 mg of vitamin B12, and 25 mg of vitamin B6 for three years. Compared with the placebo, vitamin supplementation accelerated the decline in kidney function and increased the incidence of cardiovascular events (such as heart attacks) and heart disease-related deaths. Based on this study, diabetics with kidney disease should not take these vitamins without a doctor's supervision.

Pernicious anemia is a special form of vitamin B12 malabsorption due to impaired ability of certain cells in the stomach to make intrinsic factor—a substance needed for normal absorption of vitamin B12. By definition, all people with pernicious anemia are vitamin B12-deficient. They require either vitamin B12 injections or oral supplementation with very high levels (1000 mcg per day) of vitamin B12.

Older people with urinary incontinence and hearing loss have been reported to be at increased risk of B12 deficiency.

Infection with Helicobacter pylori, a common cause of gastritis and ulcers, has been shown to cause or contribute to adult vitamin B12 deficiency. H. pylori has this effect by damaging cells in the stomach that make hydrochloric acid—which is needed for normal absorption of vitamin B12. In one trial, H. pylori was detected in 56% of people with anemia due to vitamin B12 deficiency. Successful eradication of H. pylori led to improved blood levels of B12 in 40% of those infected. Other studies have also suggested a link between H. pylori infection and vitamin B12 deficiency. Elimination of H. pylori infection does not always improve vitamin B12 status. People with H. pylori infections should have vitamin B12 status monitored.

In a preliminary report, 47% of people with tinnitus and related disorders were found to have vitamin B12 deficiencies that may be helped by supplementation.

HIV-infected patients often have low blood levels of vitamin B12.

A disproportionately high amount of people with psychiatric disorders are deficient in B12. Significant vitamin B12 deficiency is associated with a doubled risk of severe depression, according to a study of physically disabled older women.

A preliminary study found that postmenopausal women who were in the lowest one-fifth of vitamin B12 consumption had an increased risk of developing breast cancer.

Although blood levels of vitamin B12 may be higher in alcoholics, actual body stores of vitamin B12 in the tissues (such as the liver) of alcoholics are frequently deficient.

Low blood levels of vitamin B12 are sometimes seen in pregnant women; however, this does not always indicate a vitamin B12 deficiency. The help of a healthcare professional is needed to determine when a true vitamin B12 deficiency exists in pregnant women with low blood levels of the vitamin.

Hydroxocobalamin (a form of vitamin B12) has been recognized for more than 40 years as an effective antidote to cyanide poisoning. It is currently being used in France for that purpose. Because of its safety, hydroxocobalamin is considered by some researchers to be an ideal treatment for cyanide poisoning.

  • Reliable and relatively consistent scientific data showing a substantial health benefit.
  • Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
  • For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.

For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.

Vitamin B12 has been used in connection with the following health conditions:

Used for AmountWhy
Anemia and Vitamin B12 Deficiency
600 to 1,000 mcg daily 3 stars[3 stars] Taking vitamin B12 may help prevent and treat anemia. Deficiencies of iron, vitamin B12, and folic acid are the most common nutritional causes of anemia.
Depression and Vitamin B12 Deficiency
See a doctor for evaluation3 stars[3 stars] Taking vitamin B12 can help counteract deficiencies related to depression.
High Homocysteine
(Folic Acid, Vitamin B6)
400 to 1,000 mcg of folic acid daily, 10 to 50 mg of vitamin B6 daily, and 50 to 300 mcg of vitamin B12 daily3 stars[3 stars] Vitamin B6, folic acid, and vitamin B12 all play a role in converting homocysteine to other substances within the body and have consistently lowered homocysteine levels in trials.
Vitamin B12 Deficiency
Consult a qualified healthcare practitioner3 stars[3 stars] Vitamin B12, often given as an initial injection and then orally, may correct a deficiency.
Age-Related Cognitive Decline and Vitamin B12 Deficiency
Consult a qualified healthcare practitioner2 stars[2 stars] Improved brain function among seniors has been observed after correcting vitamin B12 deficiency with injections, but oral vitamin B12 has not been studied for ARCD. People with ARCD should be tested for vitamin B12 deficiency.
Bell’s Palsy
Consult a qualified healthcare practitioner2 stars[2 stars] Vitamin B12 injections have been shown to be beneficial for people with Bell’s palsy.
Celiac Disease
(Vitamin B6, Folic Acid)
3 mg vitamin B6, 0.8 mg folic acid, and 0.5 mg vitamin B12 2 stars[2 stars] Daily supplementation with a combination of vitamin B6 (3 mg), folic acid (0.8 mg), and vitamin B12 (0.5 mg) have been shown to help relieve depression in people with celiac disease.
Chronic Fatigue Syndrome
Consult a qualified healthcare practitioner2 stars[2 stars] Vitamin B12 deficiency may cause fatigue, but B12 injections have been reported benefits even without deficiency. A doctor should evaluate deficiency and whether B12 injections may help.
Indigestion and Vitamin B12 Deficiency, Delayed Gastric Emptying, and Helicobacter Pylori Infection
1,000 mcg daily2 stars[2 stars] Vitamin B12 may be beneficial for people with delayed emptying of the stomach in association with Helicobacter pylori infection and low blood levels of vitamin B12.
Low Back Pain
(Vitamin B1, Vitamin B6)
Take under medical supervision: 50 to 100 mg each of vitamins B1 and B6, and 250 to 500 mcg of vitamin B12, all taken three times per day2 stars[2 stars] A combination of vitamin B1, vitamin B6, and vitamin B12 may prevent a common type of back pain linked to vertebral syndromes and may reduce the need for anti-inflammatory medications.
Macular Degeneration
(Vitamin B6, Folic Acid)
2.5 mg folic acid, 50 mg vitamin B6, and 1 mg vitamin B12 2 stars[2 stars] In a double-blind study of female health professionals who had cardiovascular disease or risk factors, daily supplementation with folic acid, vitamin B6, and vitamin B12 significantly decreased age-related macular degeneration.
Male Infertility
1,500 mcg daily2 stars[2 stars] Vitamin B12 is needed to maintain fertility. Vitamin B12 injections have been shown to increase sperm counts. Men
Migraine Headache
1 mg daily2 stars[2 stars] In a preliminary trial, vitamin B12 reduced the frequency of migraine attacks by at least 50% in 10 of 19 people with recurrent migraines.
Osteoporosis and High Homocysteine
1,500 mcg with 5 mg of folic acid daily2 stars[2 stars] Homocystinuria, a condition associated with high homocysteine levels, frequently causes osteoporosis. By lowering homocysteine levels, vitamin B12 may help prevent osteoporosis.
Schizophrenia and High Homocysteine
(Folic Acid, Vitamin B6)
Take folic acid (2 mg), vitamin B6 (25 mg), and vitamin B12 (400 mcg) daily2 stars[2 stars] People with schizophrenia who have high homocysteine levels may improve symptoms by supplementing with folic acid, vitamin B6, and vitamin B12.
Sickle Cell Anemia and Vitamin B12 Deficiency
Consult a qualified healthcare practitioner2 stars[2 stars] People with sickle cell anemia may be deficient in vitamin B12. Intramuscular vitamin B12 injections improved symptoms for patients in one study.
Thalassemia and Vitamin B12 Deficiency
If deficient: 300 to1,000 mcg daily2 stars[2 stars] Some studies have found people with thalassemia to be frequently deficient in vitamin B12, supplementing with the vitamin may help.
Type 2 Diabetes and Diabetic Neuropathy
Consult a qualified healthcare practitioner2 stars[2 stars] Vitamin B12 is needed for normal nerve cell function, and supplementing with it may improve symptoms of diabetic neuropathy.
Type 2 Diabetes and Diabetic Neuropathy
(Vitamin B1)
Refer to label instructions 2 stars[2 stars] Taking vitamin B1 combined with vitamin B12 may improve symptoms of diabetic neuropathy.
Urinary Incontinence
(if deficient )

See a doctor to test for deficiency

2 stars[2 stars] Vitamin B12 deficency can cause urinary incontinence that may be corrected with supplementation.
Vitiligo
Refer to label instructions 2 stars[2 stars] Studies have shown vitamin B12 to be effective at skin repigmentation in people with vitiligo.
Age-Related Cognitive Decline
(Vitamin B6, Folic Acid)
Refer to label instructions 1 star[1 star]

In a study of women with cardiovascular disease or related risk factors, supplementing daily with folic acid, vitamin B6, and vitamin B12 appeared to prevent age-related cognitive decline in those with low dietary intake.

Alzheimer’s Disease
Refer to label instructions 1 star[1 star] Some researchers feel Alzheimer’s disease may be related to vitamin B12 deficiency.
Asthma
Refer to label instructions 1 star[1 star] In some people, asthma symptoms can be triggered by ingesting sulfites, a food additive. Pretreatment with a large amount of vitamin B12 reduced some children’s asthmatic reaction to sulfites in one trial.
Atherosclerosis
Refer to label instructions 1 star[1 star] Blood levels of the amino acid homocysteine have been linked to atherosclerosis and heart disease in most research. Taking vitamin B12 may help lower homocysteine levels.
Bipolar Disorder
Refer to label instructions 1 star[1 star] Vitamin B12 deficiency has been associated with both mania and depression. In one study, these symptoms cleared after treatment with B12 injections.
Bursitis
Refer to label instructions 1 star[1 star] Vitamin B12 injections have been shown to relieve symptoms of acute shoulder bursitis and decrease the amount of calcification in some cases.
Canker Sores
3 to 1,000 mcg daily 1 star[1 star] Recurrent canker sores might be related to vitamin B12 deficiency, but research has shown that even without deficiency supplementing this vitamin may be beneficial.
Crohn’s Disease
Refer to label instructions 1 star[1 star] Vitamin B12 is needed to repair intestinal cells damaged by Crohn’s disease. Supplementation may offset some of the deficiency caused by Crohn’s-related malabsorption.
Dermatitis Herpetiformis and Vitamin B12 Deficiency
Refer to label instructions 1 star[1 star] Supplementing with vitamin B12 can counteract the nutrient deficiency that often occurs as a result of malabsorption.
Down’s Syndrome
Refer to label instructions 1 star[1 star] People with Down’s syndrome may be deficient in vitamin B12 and may benefit from supplementation.
Heart Attack
Refer to label instructions 1 star[1 star] Taking vitamin B12 may reduce blood levels of homocysteine. High homocysteine levels have been linked to an increased heart attack risk.
Hepatitis
Refer to label instructions 1 star[1 star] Vitamin B12 (with or without folic acid) has been reported in trials from the 1950s to help some people with hepatitis.
HIV and AIDS Support
Refer to label instructions 1 star[1 star] In HIV-positive people with B-vitamin deficiency, B vitamins appear to delay progression to and death from AIDS.
Hives
Refer to label instructions 1 star[1 star] Vitamin B12 injections have been reported to reduce the severity of acute hives and the frequency and severity of outbreaks in chronic cases.
Immune Function
Refer to label instructions 1 star[1 star] A deficiency of vitamin B12 has been associated with decreased immune function. Restoring vitamin B12 levels may improve levels of immune cells.
Insomnia
Refer to label instructions 1 star[1 star] In two small preliminary trials, people with insomnia resulting from disorders of the sleep-wake rhythm improved after supplementing with vitamin B12.
Lung Cancer
Refer to label instructions 1 star[1 star] Together, folic acid and vitamin B12 help cells replicate normally. In one trial, smokers with precancerous lung changes who were given folic acid and vitamin B12 saw a significant reversal of their condition.
Pain
Refer to label instructions 1 star[1 star] Vitamin B12 appears to have pain-killing properties. In people with vertebral pain syndromes, injections of massive amounts of vitamin B12 have reportedly relieved pain.
Phenylketonuria and Vitamin B12 Deficiency
Refer to label instructions 1 star[1 star] Vitamin B12 is found almost exclusively in foods of animal origin, which are restricted on the PKU diet. Supplementing with vitamin B12 may correct a deficiency.
Pre- and Post-Surgery Health
Refer to label instructions 1 star[1 star] In one trial, a combination of vitamins B1, B6, and B12 before and after surgery prevented post-surgical reductions in immune activity.
Retinopathy
Refer to label instructions 1 star[1 star] In one study, adding vitamin B12 to the insulin injections of children with diabetic retinopathy helped relieve symptoms.
Schizophrenia
Refer to label instructions 1 star[1 star] People with schizophrenia may have low vitamin B12 levels. Supplementing with the vitamin may correct an imbalance and improve symptoms.
Shingles and Postherpetic Neuralgia
Refer to label instructions 1 star[1 star] Vitamin B12 injections may relieve the symptoms of postherpetic neuralgia.
Stroke and High Homocysteine
Refer to label instructions 1 star[1 star] Elevated blood levels of homocysteine have been linked to stroke risk in most studies. Supplementing with vitamin B12 may lower homocysteine levels and reduce stroke risk.
Tinnitus
Refer to label instructions 1 star[1 star] Vitamin B12 injections may help reduce the severity of tinnitus in people who are deficient in the vitamin.
Type 1 Diabetes
Refer to label instructions 1 star[1 star] Supplementing with vitamin B12 may improve symptoms of diabetic neuropathy.
Vitamin B12 Deficiency in People with Low Stomach Acid
(Multivitamin)
Refer to label instructions 1 star[1 star] For people who have inadequate absorption of vitamin B12 due to low stomach acid, taking a multivitamin–mineral supplement can help correct a deficiency.


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Copyright © 2011 Aisle7.

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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2013.

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