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vitamin B-12

What high-vitamin B-12 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 B-12 foods?

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

Excellent sources of vitamin B-12 include calf's liver and snapper.

Description

What is vitamin B-12?

Vitamin B-12 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 B-12 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 B-12 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 B-12, and the exclusive source of this vitamin appears to be tiny microorganisms like bacteria, yeasts, molds, and algae.

Like most vitamins, B-12 can occur in a variety of forms and can take on a variety of names. Names for B-12 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 B-12 cannot gain access to the rest of the body where it is needed.

How it Functions

What is the function of vitamin B-12?

Forming red blood cells

Perhaps the most well-known function of B-12 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 B-12, 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 B-12 itself, but by a lack of intrinsic factor -- the stomach-made protein required for the absorption of B-12.

Developing nerve cells

A second major function of B-12, 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 B-12 is deficient. Although the vitamin plays an indirect role in this process, supplementation of B-12 has been shown to be effective in relieving pain and other symptoms in a variety of nervous system disorders.

Other roles for vitamin B-12

Protein -- the component of food required for growth and repair of cells -- depends upon B-12 for proper cycling through the body. Many of protein's key components, called amino acids, become unavailable for use in the absence of B-12. Since one of the steps in carbohydrate and fat processing requires B-12 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 B-12?

Although B-12 is not the only nutrient deficiency that can contribute to occurrence of the following symptoms, B-12 deficiency should be considered as a possible underlying factor whenever any of the symptoms listed below are present.
Symptoms potentially associated with vitamin B-12 deficiency:

dandruff nervousness
decreased blood clotting numbness in feet
decreased reflexes paleness
depression red tongue
difficulty swallowing sore tongue
fatigue tingling in feet
heart palpitations weakness
memory problems weak pulse
menstrual problems

Toxicity Symptoms

What are toxicity symptoms for vitamin B-12?

No toxicity levels have been reported for vitamin B-12, 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 B-12.

While not a consideration in the daily diet or in everyday supplementation of B-12, it should be noted that in the case of some medical therapies involving injection of B-12, allergic reactions have been reported.

Impact of Cooking, Storage and Processing

How do cooking, storage, or processing affect vitamin B-12?

When derived from animal foods, vitamin B-12 is fairly well preserved under most cooking conditions. For example, about 70% of the vitamin B-12 present in beef is retained after broiling for 45 minutes at 350 Fahrenheit. Similarly, about 70% of B-12 is still present after cow's milk is boiled for 2-5 minutes. Retention of vitamin B-12 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 B-12?

B-12 and the stomach

Stomach problems can contribute to a B-12 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 B-12 absorption called intrinsic factor (IF). Without IF, B-12 cannot be absorbed from the gastrointestinal tract into the body's cells.

A second way for stomach problems to create B-12 deficiency is through inadequate secretion of stomach acids. Lack of stomach acids (a condition called called hypochlorhydria) gets in the way of B-12 absorption since most B-12 in food is attached to proteins in the food, and stomach acids are necessary to release the B-12 from these proteins.

The above stomach problems that can contribute to B-12 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.

B-12 and vegetarianism

The ability of a strict vegetarian diet to supply adequate amounts of B-12 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 B-12.

In humans, these stores may last for twenty years or longer. Given this potential for storage, a daily requirement for B-12 is regarded as highly unlikely.

A second school of thought, however, points to the unreliability of plants as sources of B-12. 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 B-12 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 B-12, depending upon the bacteria, molds, and fungi used to produce them. The B-12 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 B-12 content is not required. In general, tofus, tempehs, and sea vegetables tend to be more consistent sources of B-12 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 B-12 in a strict vegetarian diet.

Drug-Nutrient Interactions

What medications affect vitamin B-12?

Categories of drugs that can diminish the body's supply of vitamin B-12 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.

CATEGORY NAME OF MEDICATION
Antibiotics Kantrex (kanamycin)
Neomycin
Anticancer Drugs Methotrexate
Anticonvulsants Dilantin (phenytoin)
Mysoline (primidone)
Phenobarbitol
Antigout Drugs Colbenamid (colchicine)
Colchicine
Antihypertensives Aldomet (methyldopa)
AntiParkinson's Larodopa (levodopa)
Antipsychotics Thorazine (chlorpromazine)
Antituberculosis
Drugs
INH (isoniazid)
Birth Control
Pills
Ovulen (ethynodiol diacetate)
Ovral (ethinyl estradiol)
Ortho-Novum (norethindrone ethinyl estradiol)
Cholesterol-Lowering
Drugs
Cholestyramine
Atromid (clofibrate)
Potassium
Replacements
K-Lor (potassium chloride)
Micro-K
Slow-K

Nutrient Interactions

How do other nutrients interact with vitamin B-12?

Vitamin B6 is required for proper absorption of vitamin B-12, and deficiency of vitamin B6 has been shown to impair B-12 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 B-12 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 B-12?

Vitamin B-12 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 B-12 are found in dietary supplements?

Cyanocobalamin is the form of B-12 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 B-12 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 B-12 like cobamamide may be less preferable for supplementation.

On a drop-for-drop basis, sublingual (under-the-tongue) forms of B-12 deliver more of the vitamin into your bloodstream than tablet or intranasal (inhaled through the nose) versions.

Food Sources

Introduction to Nutrient Rating System Chart

The following chart shows the foods which are either excellent, very good or good sources of this nutrient. Next to each food name you will find the following information: the serving size of the food; the number of calories in one serving; DV% (percent daily value) of the nutrient contained in one serving; the nutrient density rating; and the food's World's Healthiest Foods Rating. Not all of our Daily Value standards are obtained from the FDA. In most instances, we used FDA Daily Values when available because they are widely recognized and apply to both men and women. However, when unavailable, we've used other science-based research to establish nutritional standards. Underneath the chart is a table that summarizes how the ratings were devised. Read more about our Nutrient Rating System.

Foods Ranked as quality sources of:
vitamin B12 (cobalamin)
Food Serving
Size
Cals Amount
(mcg)
DV
(%)
Nutrient
Density
World's
Healthiest
Foods Rating
Liver, Calf 4 oz-wt 187.1 41.39 689.8 66.4 excellent
Snapper, Baked 4 oz-wt 145.2 3.97 66.2 8.2 excellent
Venison 4 oz-wt 179.2 3.60 60.0 6.0 very good
Shrimp, MixedSpecies, Steamed, Boiled 4 oz-wt 112.3 1.69 28.2 4.5 very good
Scallops, Baked, Broiled 4 oz-wt 151.7 2.00 33.3 4.0 very good
Chinook Salmon Fillet-Baked/Broiled 4 oz-wt 261.9 3.25 54.2 3.7 very good
Beef Tenderloin, Lean Broiled 4 oz-wt 240.4 2.92 48.7 3.6 very good
Lamb, Loin, Roasted 4 oz-wt 229.1 2.45 40.8 3.2 good
Cod, Pacific, Fillet, Baked, Broiled 4 oz-wt 119.1 1.18 19.7 3.0 good
Halibut, Baked/Broiled 4 oz-wt 158.8 1.55 25.8 2.9 good
Yogurt, Cow Milk, Low Fat 1 cup 155.1 1.38 23.0 2.7 good
Milk, Cow, 2% 1 cup 121.2 0.89 14.8 2.2 good
Egg, Hen, Whole, Boiled 1 each 68.2 0.49 8.2 2.2 good
World's Healthiest
Foods Rating
Rule
excellent DV>=75% OR Density>=7.6 AND DV>=10%
very good DV>=50% OR Density>=3.4 AND DV>=5%
good DV>=25% OR Density>=1.5 AND DV>=2.5%

Public Health Recommendations

What are current public health recommendations for vitamin B-12?

The Recommended Dietary Allowances for vitamin B-12 set in 1998 by the National Academy of Sciences are as follows:

  • 0-6 months: 400 picograms
  • 6-12 months: 500 picograms
  • 1-3 years: 900 picograms
  • 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

References

  • Areekul S, Pattanamatum S, et al. The source and content of vitamin B12 in the tempehs. J Med Assoc Thai 1990 Mar 73(3):152-156.
  • Carmel R. Cobalamin, the stomach, and aging. Am J Clin Nutr 1997 Oct 66(4):750-759.
  • Clementz GL, Schade SG. The spectrum of vitamin B12 deficiency. Am Fam Physician, 1990 Jan 41(1):150-162.
  • Davis, RE. Clinical chemistry of vitamin B12. Adv Clin Chem 1984 24:163-216.
  • Delpre G, Stark P, and Niv Y. Sublingual therapy for cobalamin deficiency as an alternative to oral and parenteral cobalamin supplementation. Lancet 1999 Aug 28 354(9180):740-741.
  • Fennema OR (Ed.). Food chemistry. Second edition. Marcel Dekker, New York, 1985.
  • Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995.
  • Herbert V, Jacob E, Wong K-T, et al. Destruction of vitamin B12 by vitamin C (letter). Am J Clin Nutr 30:297.
  • Lovblad K, Ramelli G, et al. Retardation of myelination due to dietary vitamin B12 deficiency: cranial MRI findings. Pediatr Radiol 1997 Feb 27(2):155-158.
  • Machlin LJ and Langseth L. 1988. Vitamin-vitamin interactions. In: Bodwell CE and Erdman JW (Eds). Nutrient interactions. Marcel Dekker, New York, p297.
  • Machlin LJ and Langseth L. 1988. Vitamin-vitamin interactions. In: Bodwell CE and Erdman JW (Eds). Nutrient interactions. Marcel Dekker, New York, p296.
  • Machlin LJ and Langseth L. 1988. Vitamin-vitamin interactions. In: Bodwell CE and Erdman JW (Eds). Nutrient interactions. Marcel Dekker, New York, p301.
  • Plaut GW, Smith CM, Alworth WL. Biosynthesis of water-soluble vitamins. Ann Rev Biochem 1974 43:899-922.
  • Spalla C, Grein A, et al. Microbial production of vitamin B12. 1997, Chapter 15 in: Bickel H and Schultz Y (Eds), Digestion and absorption of nutrients, Int J Vit and Nutr Res, Sup 25, Hans Huber Pub, Bern, pp257-284.
  • Sutterlin MW, Bussen SS, Rieger L et al. Serum folate and Vitamin B12 levels in women using modern oral contraceptives (OC) containing 20 microg ethinyl estradiol. Eur J Obstet Gynecol Reprod Biol 2003 Mar 26;107(1):57-61.

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This page was updated on: 2004-11-21 12:15:42

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