Vitamin B12 is one of the eight vitamins that make up the B-complex. It is also known as cobalamin because it contains high levels of the metal ion cobalt. Like all B-vitamins, B12 is water-soluble. However, B12 differs from the other B-vitamins as it can be stored in the liver and kidneys for years.
Vitamin B12 works together with folic acid in the body to keep blood and nerve cells healthy and to synthesize and regulate DNA. Within the nervous system, vitamin B12 ensures healthy myelin sheaths, the fat-like coverings that surround nerve cells and help them receive and transmit signals.
Like all B-vitamins, cobalamin plays a role in energy production by working with enzymes to help metabolize carbohydrates, fats and proteins. Due to its role in energy metabolism, B12 is often used as a way to increase energy or endurance.
A special digestive secretion called intrinsic factor is required for the body to break down and absorb vitamin B12 in the small intestine. As a result, in conditions that involve intestinal disorders or malabsorption problems (e.g., celiac disease), a deficiency in B12 can occur. Vitamin B6 and folic acid are also important for vitamin B12 absorption. A high intake of folic acid can mask a vitamin B12 deficiency which if left undetected can cause neurological damage.
Cobalamin supplementation is used in treating conditions such as fatigue and Alzheimer’s disease, and to lower blood homocysteine levels. A high level of homocysteine in the blood is an independent risk factor for both Alzheimer’s and cardiovascular disease. However, at this time, there is no clear evidence that lowering homocysteine levels reduces the risk of developing either disease, and further study is needed.
Vital to produce healthy nerve and red blood cells
Enhances neural transmissions throughout the body
Helps with metabolism and energy production
Regulates proper DNA synthesis
No plant or animal can produce vitamin B12. Only bacteria, yeasts, molds and algae can manufacture this vitamin.
The B12 content of plants depends on their relationship to the environment. In plants that provide some B12, it is the microorganisms in the soil (bacteria, yeasts, molds, fungi) or roots that determine the amount of this nutrient in the plant food. Depending on these conditions, cultured and fermented bean products (tofu, miso, tamari), sea vegetables (kelp), algaes (blue-green algae) and yeasts (Brewer’s yeast) may contain significant sources of B12.
The B12 content of animals depends on their ability to store the vitamin. Given that B12 is stored in the liver and kidneys, it comes as no surprise that these animal products are the richest sources of this vitamin. Other good sources include eggs, meat, dairy, clams and fish like sardines and salmon.
Certain food products are fortified with B12 like breakfast cereals and soy but generally do not contain significant or reliable amounts of cobalamin.
Recommended Dietary Allowance
The Recommended Dietary Allowance (RDA) for cobalamin is 2.4 mcg for adults. A Tolerable Upper Intake Level for this B-vitamin has not been determined due to lack of data due to adverse events.
If you look on a nutritional supplement facts panel, you’ll notice the Amount Per Serving for vitamin B12 and the % Daily Values is at located at the top of the panel. The Amount Per Serving is based on the Reference Daily Intake (RDI) for this nutrient which is considered to be sufficient to meet the requirements of nearly all (97–98%) healthy individuals in each life-stage and sex group. The Reference Daily Intake for Vitamin B12 is 6 mcg which represents 100% of the Daily Values.
Because vitamin B12 is stored in the body deficiency is uncommon but can be more prevalent among vegetarians and the elderly who often have an inadequate intake of this nutrient. Therefore, dietary supplementation of vitamin B12 is recommended for these groups in particular.
The most common commercially available form of vitamin B12 supplements is cynocobalamin, an inactive form of the nutrient that the body converts into two active forms for use. While vitamin B12 is available as both oral and sublingual form, there is no indication that the sublingual form is better.
While it has become popular to receive vitamin B12 supplementation through injection, high oral doses of 1,000-2,000 mcg have been shown to be just as effective. Injection is typically used in those who have a deficiency caused by pernicious anemia and other malabsorption conditions.
Vitamin B12 is known to interact with certain medications such as the antibiotic Chloromycetin®, proton pump inhibitors like Prilosec® and histamine H2 receptor antagonists like Zantac® that are both used to treat peptic ulcers, and metformin medications like Fortamet® for diabetes.
Clinical Support Program, Recovery Support Program and Multi-Vitamin & Mineral are formulated with 405 mcg of vitamin B12. Not surprisingly, this vitamin is incorporated in the morning formulation of these program kits to enhance energy levels throughout the day. The morning packet of Anti-Aging Formula is also formulated with 270 mcg of B12.
Last updated July 1, 2018
David H. Rahm, M.D. is the founder and medical director of The Wellness Center, a medical clinic located in Long Beach, CA. Dr. Rahm is also president and medical director of VitaMedica. Dr. Rahm is one of a select group of conventional medical doctors who have education and expertise in functional medicine and nutritional science. Over the past 20 years, Dr. Rahm has published articles in the plastic surgery literature and educated physicians about the importance of good peri-operative nutrition.