Vitamin B12 (Cobalamin) Supplement Uses, Benefits, Dosages & Side Effects

Vitamin B12 (cobalamin) is an essential nutrient that is involved in energy metabolism, neurological health and the production of red blood cells.

As a dietary supplement, it is sometimes used to support energy levels, athletic performance, cognitive function, mood balance, sleep, and eye health.

This vitamin is generally found in animal products, such as fish, meat, chicken, milk, and eggs. It does not naturally occur in plant-based foods which is why vegans and vegetarians often must take a Vitamin B12 supplement to avoid a deficiency.

According to the NHANES survey, between 1.5% to 15% of the general population is deficient in this vitamin. Deficiencies are more common in people who are older or who have intestinal disorders that affect the absorption of this vitamin from foods.

If you are deficient in Vitamin B12, you may experience symptoms including muscle weakness, fatigue, memory dysfunction, low appetite, weight loss, constipation, changes in mood or numbness and tingling in the extremities.

This article will discuss how vitamin B12 works in the body, its uses and benefits for health, deficiency issues, foods that contain this compound, and safety and side effects.

Cobalamin

Vitamin 12 Supplement

Energy

Brain Health

Blood Cells

How It Works:

• Involved in energy production
• Supports healthy nerves and blood cells
• Involved in detoxification pathways

Dosage:

Between 1,000 - 5,000 mcg per serving

Safety:

Rated Likely Safe

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What is Vitamin B12?

Vitamin B12 is one of the vitamins that make up the B vitamin complex of compounds. There are eight B vitamins in total, and all are known to induce similar biological effects. [1, 2]

Like the other B vitamins, vitamin B12 is water-soluble. However, unlike the other B-complex vitamins, this vitamin is stored in the body in large amounts.

Vitamin B12 contains cobalt, and is sometimes referred to as cobalamin (also spelled cobalamine). It is an essential micronutrient because humans cannot produce it endogenously (within the body).

It has to come from foods we eat, or from taking a dietary supplement that contains it. Cobalamin is commonly found in supplement formulations that contain other B-complex members, especially vitamins B6 (pyridoxine) and B9 (folate).

According to the Mayo Clinic (MC), vitamin B12 is important for converting carbohydrates into glucose to use in energy production, DNA synthesis, amino acid synthesis, proper neurological function, and red blood cell production. [1]

It also is required as a cofactor for the enzyme methionine synthase, which is responsible for catalyzing the conversion of homocysteine to the amino acid methionine. This amino is used to make S-adenosylmethionine, which has a wide range of roles in the body.

B12 is also a cofactor for the enzyme L-methylmalonyl-CoA mutase which is involved in fat and protein metabolism as well as hemoglobin (red blood cell) synthesis.

How Does Vitamin B12 Work Inside the Body?

The Natural Medicines Comprehensive Database (NMCD) states that vitamin B12 exists in several forms, namely methylcobalamin and hydroxocobalamin. It is produced by certain microorganisms and can also be found in some animal-based foods like meat and eggs.

A synthetic lab-produced form of vitamin B12 is called cyanocobalamin, which is a compound of cobalamin and a cyano group.

According to Dr. Josh Axe, cobalamin is necessary for various bodily functions and offers many health benefits including aiding in digestion, contributing to cardiovascular health, enhancing nervous system function, facilitating energy production, and maintaining nerve function. [4]

The NMCD reports that cobalamin is needed for processes including production of nucleoproteins, cell reproduction, biosynthesis of myelin (protein/phospholipid compound that protects nerve fibers), and normal erythropoiesis (red blood cell production). [3]

The National Institutes of Health (NIH) state that vitamin B12 is a universal methyl donor in the body. [1]

Methylation is the process in which one compound “donates” a methyl group to another compound. A methyl group is a carbon atom that has 3 hydrogen atoms attached to it (CH3).

Methylation is necessary for many important biochemical processes in the body, including the biosynthesis of more than 100 hormones and neurotransmitters, DNA production and metabolism, and the metabolism of lipids and proteins.

According to the NIH several years worth of cobalamin is stored in the liver. Because of this, deficiency of this nutrient is rare in healthy people who consume animal products.

In developed where the average diet is based on a wide variety of food choices, the majority of people are able to obtain adequate amounts of this vitamin from food sources. [2]

However, individuals who are vegan or vegetarian and avoid products enriched with cobalamin often have a deficiency in this vitamin. The National Health and Nutrition Examination Survey (NHANES) estimates that deficiency affects between 1.5% and 15% of the general population.

According to the MC low vitamin B12 levels are most likely in those with HIV/AIDS, severe alcoholics, vegetarians/vegans, and the elderly. [1]

A deficiency may also result from gastrointestinal problems that can cause impaired nutrient absorption from foods consumed.

The Mayo Clinic states that vitamin B12 is bound to proteins in foods. Stomach acid detaches cobalamin from those proteins during the digestion process.

Subsequently, it gets combined with a glycoprotein called gastric intrinsic factor (GIF) so that it can be incorporated into the bloodstream. [2]

If the intestines cannot effectively absorb cobalamin, a condition called pernicious anemia can result. Pernicious anemia is marked by insufficient production of erythrocytes (red blood cells). [3]

Vitamin B12 Uses and Health Benefits

The NMCD states that there are dozens of well-researched uses for vitamin B12 supplements. Conditions that people use this vitamin for include:

• Age related macular degeneration (AMD)
• Alzheimer’s disease
• Atherosclerosis (hardening of the arteries)
• Breast, cervical, colorectal, and lung cancer
• Cardiovascular disease
• Diabetic neuropathy (nerve damage causing pain and/or numbness)
• Hyperhomocysteinemia
• Liver and kidney disease
• Lou Gehrig’s disease (amyotrophic sclerosis)
• Mental disorders including depression and schizophrenia [4]

Other uses for cobalamin listed by the NMCD include improving energy, male fertility, osteoporosis, memory loss, cognitive function, and mood enhancement.

The NMCD has rated vitamin B12 as Effective for preventing and treating vitamin B12 deficiency and for Imerslund-Grasbeck disease (genetic disorder causing malabsorption of this vitamin).

The NCMD has rated cobalamin as Likely Effective for cyanide poisoning and hyperhomocysteinemia. It is rated Possibly Effective for AMD, and postherpetic neuralgia.

Vitamin B12 has been studied for a wide range of additional uses. However, more research is needed to determine effectiveness for these uses.

Injectable vitamin B12 formulations are approved by the FDA as prescription medications for the treatment of cobalamin deficiency.

All other forms of this product are considered dietary supplements and have not been approved as drugs to prevent or treat medical conditions.

Vitamin B12 for Energy Synthesis

B-complex vitamins work together to help the body break down food into energy. Sugar (glucose) from foods is then used to produce the main energy source used in our cells: adenosine triphosphate (ATP). [3]

One of the roles of B12 in the body is as a cofactor for an enzyme called L-methylmalonyl-CoA mutase. This enzyme is responsible for catalyzing the conversion of L-methylmalonyl-CoA to succinyl-CoA, an important step in the Krebs cycle.

This reaction is necessary to produce energy from fat (lipid) and protein molecules. Not having enough B12 in the body can impair the ability to efficiently break down fats and protein into energy.

Vitamin B12 is also important for the transportation of oxygen throughout the body. It is involved in the production of hemoglobin which carries oxygen from the lungs through the body in red blood cells.

Because vitamin B12 is important in energy synthesis, low levels of this and other B-complex vitamins often results in fatigue and weakness. [3] This condition is sometimes referred to as megaloblastic anemia.

There is a clear connection between endogenous cobalamin and ATP synthesis. However, it is not yet known whether supplementing with additional Vitamin B12 in people who do not have a deficiency can boost energy levels.

This supplement is commonly promoted for energy enhancement, athletic performance, muscle strength and stamina. It is also commonly included in energy drink formations at high dosages.

More research is needed to determine whether it is effective for fatigue, boosting energy levels or as an ergogenic aid for enhancing physical performance. Some studies have been conducted, but more clinical trials are needed to evaluate efficacy.

Cognitive Function and Neurological Health

Cobalamin is important for maintaining nerve health and facilitating efficient nerve-to-nerve signaling. [2] It is purported to have memory-supporting properties and is being studied for its effects on neurodegenerative diseases.

Being deficient in Vitamin B12 and Folate (Vitamin B9) can result in neuropsychiatric disturbances including depression, dementia, and damaged myelin sheaths causing impaired nerve signal conduction. [4]

It is hypothesized that increased vitamin B12 consumption may protect the brain and nervous system from damage and support cognitive functioning. While this vitamin does exhibit some neuroprotective properties, more research is needed to determine efficacy in human subjects.

It is being studied for its effects on reducing the risk of developing conditions marked by cognitive decline like dementia and Alzheimer’s disease. [4]

One preliminary study found that taking oral vitamin B12, vitamin B6, and folic acid (synthetic vitamin B9) daily for two years slowed brain atrophy in elderly patients in areas of the brain associated with Alzheimer’s disease and cognitive decline. [3]

However, more research is needed to determine its therapeutic efficacy for conditions involving age-related memory loss. It has not been approved as a drug for the prevention or treatment of Alzheimer’s disease.

Dr. Axe says that cobalamin helps to ensure proper functioning in the nervous system, which in turn may help to balance the mood. He states that a well-regulated nervous system is less likely to cause mood disorders like anxiousness and depression. [4]

Vitamin B12 works with vitamin B9 (folate) to produce SAMe (S-adenosylmethionine) in the human body. SAMe is important for neurological function, particularly regulating mood and the adaptive stress responses. [2]

In research cobalamin has been shown to be important for cognitive processes like concentrating, processing, learning, and remembering.

Because of this, some research is addressing if and how it might be used for attention deficit disorder (ADD) and attention-deficit hyperactivity disorder (ADHD).

B-complex vitamins are also required for producing brain chemicals called neurotransmitters that are involved in memory, thinking, mood regulation, behavior control and more.

Some of the neurotransmitters that are influenced by the B family of vitamins include serotonin, dopamine, and norepinephrine (noradrenaline).

According to Dr. Axe, these neurotransmitters are involved in regulating focus and mood, resulting in greater physical and mental energy. [4]

One pilot study found that twice weekly intramuscular injections of hydroxocobalamin helped improve happiness and general well-being of patients with fatigue or tiredness.

More research is still needed to determine the therapeutic efficacy of vitamin B12 for any cognitive disorders. Some studies have demonstrated nootropic benefits, but further research is required to validate preliminary results.

Cardiovascular Health

Vitamin B12 is required to regulate the levels of an amino acid metabolite called homocysteine in the blood. Homocysteine is a naturally occurring byproduct of the methylation of the amino acid methionine.

When homocysteine builds up in the bloodstream, it can cause damage to the inside of blood vessels.

The damaged surfaces of the inner linings (endothelium) of the blood vessels encourages the formation of arterial plaque.

As low-density lipoprotein (LDL) cholesterol, triglycerides, and other fatty acids accumulate inside arteries, less blood can pass through them. [2]

This decreases the effective diameter of blood vessels, creating more work for the heart muscle and affecting blood pressure. These plaque formations can lead to a condition called atherosclerosis, commonly referred to as “clogged arteries”.

High homocysteine levels (hyperhomocysteinemia) are associated with increased risk for atherosclerosis, coronary artery disease, and heart disease. [2]

Elevated homocysteine is also associated with increased risk for ischemic stroke and nerve damage (neuropathy) in the central nervous system (CNS) and peripheral nervous system (PNS). [2]

Multiple clinical trials have shown that cobalamin together with folic acid (and sometimes vitamin B6) can reduce levels of homocysteine in the blood. Taking vitamin B12 alone has had limited effects on homocysteine levels.

Additionally, it is still not known if elevated homocysteine levels are a cause of vascular disease or if levels become elevated because of vascular disease. It is still unclear at this point if lowering homocysteine levels reduces cardiovascular disease and deaths.

While some studies have shown promising results, there has not been enough reliable evidence from clinical trials to rate the efficacy of vitamin B12 in atherosclerosis, heart disease, hypertension, or related conditions. More clinical research is still needed. [3]

Vitamin B12 Deficiency

Vitamin B12 deficiency is rare in most people who consume animal products in the diet. The body naturally stores large amounts of this compound in the body, primarily in the liver.

The Linus Pauling Institute (LPI) states that average body stores in humans can exceed 2500 micrograms (mcg) of B12, and that only 2.4 mcg/day is needed to maintain a healthy cobalamin status.

Because such small amounts are needed daily and body stores can be so large, deficiency symptoms can take months to years to manifest. [3]

The LPI states that when deficiency does occur, it is likely to be caused by an inability to absorb available B12, not because it is not available. This could be caused by various possible conditions involving the stomach, pancreas and/or small intestines. [5]

Elderly people are at a higher risk of deficiency because of impaired intestinal absorption rates.

Another cause of deficiency can be due to certain dietary choices, namely being a vegetarian or a vegan.

The University of Maryland Medical Center (UMM) states that those who do not eat meat, dairy products, or eggs are more likely to develop cobalamin deficiency because the vitamin is not found naturally in plant-based foods.

According to the UMM, vitamin B12 deficiency can cause an array of symptoms including fatigue, nervousness, diarrhea, shortness of breath, and/or numbness/tingling in the extremities. Severe cases of cobalamin deficiency can cause permanent damage to nerves. [6]

The LPI states that taking high doses of folic acid, the synthetic form of vitamin B9, can mask the symptoms of vitamin B12 deficiency. This could cause symptoms to go unnoticed and unaddressed, possibly leading to nerve damage.

According to the LPI, anyone planning to take 800 mcg/day or more of folic acid should consult with their doctors first to ensure they do not have a B12 deficiency.

Vitamin B12 Food Sources

The Mayo Clinic states that vitamin B12 is found in animal-based foods including organ meats like liver, muscle meats, eggs, dairy products, and certain fish and shellfish. [1]

Cobalamin is only found naturally in animal-based foods and not in plant-based foods. This vitamin is produced by micro-organisms in the gut of animals.

Vegetarians who consume dairy products and eggs can get their vitamin B12 from sources such as eggs, milk, cottage cheese, and yogurts.

Some plant-based foods are fortified with cobalamin such as some plant/nut milks, some breakfast cereals, and nutritional yeast products. These can be a source of this vitamin for vegans who consume no animal products.

The UMM states that the elderly may need to consume more of this nutrient than younger adults because the ability to absorb it decreases with age in most people. [1]

When possible, it is recommended to choose animal-based foods that are organic, grass-fed, and non-GMO.

Vitamin B12 Supplements

When possible it is often recommended to obtain vitamin B12 from food sources. However, due to various reasons this is not always possible. In these cases, supplementation may be useful or necessary.

The UMM reports that this vitamin is available as individual vitamin B12 supplements and as part of multivitamins that normally contain balanced amounts of all eight B-complex compounds.

Cobalamin is available as an intranasal spray as well as in tablets, capsules, lozenges, liquid drops, chewable gummies, and soft gels.

Vitamin B12 is most often labeled as either cyanocobalamin or hydroxocobalamin in dietary supplements. It may also be sold in the form of methylcobalamin, which may have some advantages over other forms of this vitamin.

Cobalamin supplements come in a large variety of dosages including 500 mcg, 1000 mcg, 2000 mcg, and 5000 mcg formulations. Supplements containing 1000 mcg are some of the most commonly available.

UMM recommends that all people considering using a vitamin B12 supplement, or a multivitamin B-complex supplement, consult with their healthcare providers to discuss the best doses for their needs.

Vitamin B12 Dosage

The Mayo Clinic reports the following RDAs (recommended daily allowances) for vitamin B12:

• 2.8 micrograms daily (mcg/day) for women who are breastfeeding
• 2.6 mcg/day for pregnant women
• 2.4 mcg/day for all others over 14 years of age
• 1.8 mcg/day for children between 9 and 13 years
• 1.2 mcg/day for children between 3 and 8 years
• 0.9 mcg/day for children between 1 and 3 years
• 0.5 mcg/day for infants between 6 and 12 months
• 0.4 mcg/day for infants between 0 and 65 months [1]

It has been estimated that between 10-30% of older people do not efficiently absorb food-bound cobalamin. In the elderly, eating fortified foods or taking a supplement daily of between 25 and 100 mcg has been used to maintain a healthy B12 status. [3]

When used as a dietary supplement, dosages are typically much higher than the RDA values. Supplement dosages typically range from 500 mcg up to 5000 mcg, with 1000 mcg supplements being common.

In research studies, dosages are typically higher than RDA values as well. Various dosages that have been studied include:

• 1 mg per day for age-related macular degeneration
• 0.5 mg per day plus vitamin B6 and B9 for Alzheimer’s disease
• 100 mcg per day plus other vitamins for atherosclerosis
• 400-500 mcg per day for hyperhomocysteinemia
• 400 mcg with 2 mg folic acid daily for schizophrenia [3]

If you are interested in taking a cobalamin supplement than it is recommended that you speak to your doctor. They will be able to determine the best dosage for your needs.

Safety and Side Effects

The Natural Medicines Comprehensive Database has rated vitamin B12 supplements as Likely Safe even in large doses when used orally, topically, intramuscularly, or intranasally and appropriately.

In pregnant and nursing women, cobalamin is rated as Likely Safe when used orally in amounts that do not exceed the RDA. There is insufficient data available to rate the safety of larger amounts in these groups.

According to the NMCD, even large doses of vitamin B12 do not usually cause serious side effects when administered either orally or intramuscularly. [3]

In rare cases cobalamin can cause itching, diarrhea, and/or a vascular skin reaction called urticaria. It may also cause thrombosis, feelings of whole-body swelling, and/or anaphylaxis. [3]

When applied topically, vitamin B12 seems well-tolerated in most for up to 12 consecutive weeks. [3]

Vitamin B12 Interactions

The Mayo Clinic states that cobalamin may interact with certain types of medications, supplements, and some herbs.

The MC says to seek medical advice before using vitamin B12 supplements with:

• ACE (angiotensin converting enzyme) inhibitors commonly used for high blood pressure
• Agents like colchicine used for cancer, gout and bone loss
• Agents that affect blood production
• Agents that affect the nervous system
• Anticonvulsant agents used for seizures
• Bile acid sequestrants
• Proton pump inhibitors and H2 blockers used for stomach/intestinal disorders

The Mayo Clinic further advises caution when using this vitamin with anti-Alzheimer’s agents, alcohol, metformin, nicotine, nitrous oxide, birth control pills and medications used for cardiovascular disease. [1]

According to the NMCD, supplemental cobalamin should not be taken with Chloramphenicol as it can affect red blood cell production.

The NMCD also states that caution should be exercised when taking it in conjunction with either potassium or vitamin C (ascorbic acid). Potassium supplements can decrease cobalamin absorption in some people. Preliminary evidence suggests that vitamin C destroys this vitamin in the gut.

Vitamin B12 is an important micronutrient that is vital to health for various reasons. All people considering the use of this supplement are advised to consult with their doctors first to determine whether it is appropriate for them.

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