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vitamin B12

What high-vitamin B12 foods can do for you:

  • support production of red blood cells and prevent anemia
  • allow nerve cells to develop properly
  • help your cells metabolize protein, carbohydrate, and fat

What events can indicate a need for more high-vitamin B12 foods?

  • red or sore tongue
  • tingling or numbness in feet
  • nervousness
  • heart palpitations
  • depression
  • memory problems

Excellent sources of vitamin B12 include calf's liver and snapper.

Nutrient Chart

For serving size for specific foods, see Nutrient Rating Chart below at the bottom of this page.


What is vitamin B12?

Vitamin B12 is one of the most controversial members of the vitamin family collectively referred to as the "B-complex" vitamins. Although the full chemical structure of B12 was not identified until the 1960s, two Nobel Prizes have already been awarded for research involving this vitamin. The first of these Nobel Prizes, awarded in 1934, involved the discovery that a food (liver, a very rich source of B12) could be used to treat a particular type of anemia (inability of the bloodstream to carry oxygen) called pernicious anemia. The second came thirty years later when chemists figured out the exact structure of this important vitamin.

Vitamin B12 is unusual with respect to its origins. While most vitamins can be made by a wide variety of plants and specific animals, no plant or animal has been shown capable of producing B12, and the exclusive source of this vitamin appears to be tiny microorganisms like bacteria, yeasts, molds, and algae.

Like most vitamins, B12 can occur in a variety of forms and can take on a variety of names. Names for B12 include: cobrynamide, cobinamide, cobamide, cobalamin, hydroxcobalamin, aquocobalamin, nitrotocobalamin, and cyanocobalamin. Each of these designations contains a form of the word "cobalt," since cobalt is the mineral found in the center of the vitamin.

B-12 is also unusual in that it is dependent upon a second substance, called intrinsic factor, to make its way from the "GI" tract (gastrointestinal tract--the stomach and intestines) into the rest of the body. Without intrinsic factor, which is a unique protein made in the stomach, vitamin B12 cannot gain access to the rest of the body where it is needed.

How it Functions

What is the function of vitamin B12?

Forming red blood cells

Perhaps the most well-known function of B12 involves its role in the development of red blood cells. As red blood cells mature, they require information provided by molecules of DNA. (DNA, or deoxyribose nucleic acid, is the substance in the nucleus of our cells which contains genetic information.) Without B12, synthesis of DNA becomes defective, and so does the information needed for red blood cell formation. The cells become oversized and poorly shaped, and begin to function ineffectively, a condition called pernicious anemia. More often than not, pernicious anemia isn't caused by a lack of B12 itself, but by a lack of intrinsic factor -- the stomach-made protein required for the absorption of B12.

Developing nerve cells

A second major function of B12, less clearly understood than the first, involves its participation in the development of nerve cells. A coating which encloses the nerves -- called the myelin sheath -- forms less successfully whenever B12 is deficient. Although the vitamin plays an indirect role in this process, supplementation of B12 has been shown to be effective in relieving pain and other symptoms in a variety of nervous system disorders.

Other roles for vitamin B12

Protein -- the component of food required for growth and repair of cells -- depends upon B12 for proper cycling through the body. Many of protein's key components, called amino acids, become unavailable for use in the absence of B12. Since one of the steps in carbohydrate and fat processing requires B12 for its completion, insufficiency of the vitamin can also affect the movement of carbohydrates and fats through the body.

Deficiency Symptoms

What are deficiency symptoms for vitamin B12?

Although B12 is not the only nutrient deficiency that can contribute to occurrence of the following symptoms, B12 deficiency should be considered as a possible underlying factor whenever any of the symptoms listed below are present.

Symptoms potentially associated with vitamin B12 deficiency:

decreased blood clottingnumbness in feet
decreased reflexespaleness
depressionred tongue
difficulty swallowingsore tongue
fatiguetingling in feet
heart palpitationsweakness
memory problemsweak pulse
menstrual problems

Toxicity Symptoms

What are toxicity symptoms for vitamin B12?

No toxicity levels have been reported for vitamin B12, and no toxicity symptoms have been identified in scientific research studies. Even long-term studies, in which subjects have taken 1,000 micrograms of the vitamin on a daily basis for five years, have revealed no toxicity effects.

When the National Academy of Sciences established its current Tolerable Upper Intake Levels (ULs) for the B complex vitamins in 1998, it did not establish a Tolerable Upper level for vitamin B12.

While not a consideration in the daily diet or in everyday supplementation of B12, it should be noted that in the case of some medical therapies involving injection of B12, allergic reactions have been reported.

Impact of Cooking, Storage and Processing

How do cooking, storage, or processing affect vitamin B12?

When derived from animal foods, vitamin B12 is fairly well preserved under most cooking conditions. For example, about 70% of the vitamin B12 present in beef is retained after broiling for 45 minutes at 350ยบ Fahrenheit. Similarly, about 70% of B12 is still present after cow's milk is boiled for 2-5 minutes. Retention of vitamin B12 in plant-based foods like tempeh, a fermented food made from soy, has not been well researched.

Factors that Affect Function

What factors might contribute to a deficiency of B12?

B-12 and the stomach

Stomach problems can contribute to a B12 deficiency in two ways.

First, irritation and inflammation of the stomach can prevent the stomach cells from functioning properly. When functioning improperly, the cells may stop producing a substance required for B12 absorption called intrinsic factor (IF). Without IF, B12 cannot be absorbed from the gastrointestinal tract into the body's cells.

A second way for stomach problems to create B12 deficiency is through inadequate secretion of stomach acids. Lack of stomach acids (a condition called called hypochlorhydria) gets in the way of B12 absorption since most B12 in food is attached to proteins in the food, and stomach acids are necessary to release the B12 from these proteins.

The above stomach problems that can contribute to B12 deficiency have a wide variety of causes. These causes include abuse of over-the-counter antacids, abuse of prescription medicines used to control stomach acidity, and stomach ulcers (also called gastric ulcers), which may themselves be due to infection with the bacteria, helicobacter pylori.

B12 and vegetarianism

The ability of a strict vegetarian diet to supply adequate amounts of B12 remains controversial, despite increasing evidence in support of vegetarianism and its nutritional adequacy. The controversy is fueled by two somewhat divergent schools of thought. One school emphasizes the fact that most animals, including humans, are capable of storing long-term supplies of B12.

In humans, these stores may last for twenty years or longer. Given this potential for storage, a daily requirement for B12 is regarded as highly unlikely.

A second school of thought, however, points to the unreliability of plants as sources of B12. For strict vegetarians who eat no animal products whatsoever, this unreliability may pose a problem. Since no plant is capable of making B-12, the amount of B12 in plant food depends upon the relationship of the plant to soil and root-level microorganisms (bacteria, yeasts, molds, and fungi) which make the vitamin. Cultured and fermented bean products like tofu, tempeh, miso, tamari and shoyu may or may not contain significant amounts of B12, depending upon the bacteria, molds, and fungi used to produce them. The B12 content of sea vegetables also varies according to the distribution of microorganisms in the surrounding sea environment.

Unfortunately, reliable nutrient analyses are often unavailable for consumers of these products, and labeling for B12 content is not required. In general, tofus, tempehs, and sea vegetables tend to be more consistent sources of B12 than misos, tamaris, and shoyus. Depending upon the medium in which they are grown, brewer's and nutritional yeast can also be significant sources of B12 in a strict vegetarian diet.

Drug-Nutrient Interactions

What medications affect vitamin B12?

Categories of drugs that can diminish the body's supply of vitamin B12 include antibiotics, anticancer medications, anticonvulsants, anti-gout medications, antihypertensives, antiParkinson's medications, antipsychotics, antituberculosis medications, birth control pills, cholesterol-lowering drugs, and potassium replacements. Examples of specific medications in each category are listed below.

AntibioticsKantrex (kanamycin)Neomycin
Anticancer DrugsMethotrexate
AnticonvulsantsDilantin (phenytoin)Mysoline (primidone)Phenobarbitol
Antigout DrugsColbenamid (colchicine)Colchicine
AntihypertensivesAldomet (methyldopa)
AntiParkinson'sLarodopa (levodopa)
AntipsychoticsThorazine (chlorpromazine)
AntituberculosisDrugsINH (isoniazid)
Birth ControlPillsOvulen (ethynodiol diacetate)Ovral (ethinyl estradiol)Ortho-Novum (norethindrone ethinyl estradiol)
Cholesterol-LoweringDrugsCholestyramineAtromid (clofibrate)
PotassiumReplacementsK-Lor (potassium chloride)Micro-KSlow-K

Nutrient Interactions

How do other nutrients interact with vitamin B12?

Vitamin B6 is required for proper absorption of vitamin B12, and deficiency of vitamin B6 has been shown to impair B12 absorption in animal studies.

Conversion of vitamin B12 from its non-active into its biologically active form requires the presence of vitamin E. Individuals at risk for vitamin E deficiency may show signs of vitamin B12 deficiency as well.

Contrary to research from the mid 1970s, supplemental doses of vitamin C above the 500 milligram level do not appear to compromise B12 function.

Excessive intake of folic acid can mask B-12 deficiencies, and individuals at risk for vitamin B12 deficiency who are also taking folic acid in supplement form should consult with their healthcare practitioner.

Health Conditions

What health conditions require special emphasis on vitamin B12?

Vitamin B12 may help in the prevention and/or treatment of the following health conditions:

  • Alcoholism
  • Anemia (Pernicious)
  • Arthritis (Rheumatoid)
  • Asthma (Bronchial)
  • Atherosclerosis
  • Cancer
  • Celiac Disease
  • Crohn's Disease
  • Dermatitis (Seborrheic)
  • Epstein-Barr Virus
  • Fatigue
  • Leukemia
  • Lupus
  • Multiple Sclerosis
  • Neuropathies/Neuromuscular degeneration

Form in Dietary Supplements

What forms of vitamin B12 are found in dietary supplements?

Cyanocobalamin is the form of B12 most commonly found in vitamin supplements. However, this form of the vitamin is only found in the laboratory, where a cyanide molecule is added to the vitamin to help stabilize it in tablet or capsule form. Once inside of the body, the cyanide portion is broken off and the vitamin is activated. While no suggestion has been made as to increased risk

of cyanide poisoning through the use of B12 in this form, some healthcare professionals prefer the hydroxycobalamin or dibencozide forms of the vitamin which do not contain the cyanide molecule and are naturally-occurring.

Since the cobalamin forms of the vitamin are the only ones known with certainty to play an active role in the body, alternative forms of B12 like cobamamide may be less preferable for supplementation.

On a drop-for-drop basis, sublingual (under-the-tongue) forms of B12 deliver more of the vitamin into your bloodstream than tablet or intranasal (inhaled through the nose) versions.

Food Sources

What foods provide vitamin B12?

Since vitamin B12 cannot be made by any animals or plants, the B12 content of animals and plants depends on their ability to store the vitamin and their relationship to microorganisms (like bacteria in the soil). Because of their greater ability to store vitamin B12, animals contain more of the vitamin than plants. Excellent sources of vitamin B12 are therefore limited to animal foods. These foods include snapper and calf's liver. Very good sources of vitamin B12 include venison, shrimp, scallops, salmon, and beef. Within the plant world, sea plants (like kelp), algaes (like blue-green algae), yeasts (like brewer's yeast), and fermented plant foods (like tempeh, miso, or tofu) are the most commonly consumed food sources of vitamin B12, although none of these plant foods can be counted on to be a consistently excellent or very good source of the vitamin.


Introduction to Nutrient Rating System Chart

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the World's Healthiest Foods that are either an excellent, very good, or good source of vitamin B12 (cobalamin). Next to each food name, you'll find the serving size we used to calculate the food's nutrient composition, the calories contained in the serving, the amount of vitamin B12 (cobalamin) contained in one serving size of the food, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.

World's Healthiest Foods ranked as quality sources of:
vitamin B12 (cobalamin)
Foods Rating
Calf's liver, braised4 oz-wt187.141.39689.866.4excellent
Sardines3.25 oz can191.48.22137.012.9excellent
Snapper, baked/broiled4 oz-wt145.23.9766.28.2excellent
Venison4 oz-wt179.23.6060.06.0very good
Shrimp, steamed/boiled4 oz-wt112.31.6928.24.5very good
Scallops, baked/broiled4 oz-wt151.72.0033.34.0very good
Salmon, chinook, baked/broiled4 oz-wt261.93.2554.23.7very good
Beef tenderloin, lean, broiled4 oz-wt240.42.9248.73.6very good
Lamb loin, roasted4 oz-wt229.12.4540.83.2good
Cod, baked/broiled4 oz-wt119.11.1819.73.0good
Halibut, baked/broiled4 oz-wt158.81.5525.82.9good
Yogurt, low-fat1 cup155.11.3823.02.7good
Cow's milk, 2%1 cup121.20.8914.82.2good
Egg, whole, boiled1 each68.20.498.22.2good
World's Healthiest
Foods Rating
very goodDV>=50%ORDensity>=3.4ANDDV>=5%

Public Health Recommendations

What are current public health recommendations for vitamin B12?

The most recent Recommended Dietary Allowances (RDAs) for vitamin B12 were set in 1998 by the National Academy of Sciences. The RDAs were established for all persons 1 year of age and older. For infants under the age of 1 year, Adequate Intake (AI) levels were set. These AI and RDA guidelines are as follows:

  • 0-6 months: 400 nanograms
  • 6-12 months: 500 nanograms
  • 1-3 years: 900 nanograms
  • 4-8 years: 1.2 micrograms
  • males 9-13 years: 1.8 micrograms
  • males 14 years and older: 2.4 micrograms
  • females 9-13 years: 1.8 micrograms
  • females 14 years and older: 2.4 micrograms
  • Pregnant females of any age: 2.6 micrograms
  • Lactating females of any age: 2.8 micrograms


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