How Vitamin B12 Works


Vitamin B12 acts differently than other vitamins. A substance called intrinsic factor, made in the stomach, must be present in the intestinal tract in significant amounts to allow for the absorption of vitamin B12. This factor combines with the vitamin B12 that is released from food during digestion. People who don't have intrinsic factor eventually show symptoms of a vitamin B12 deficiency -- a condition called pernicious anemia. This article will explain how B12 was discovered, which foods have it, how much is needed and why those who are deficient must take large doses of supplements.
  • What Is Vitamin B12?

    Why would eating liver cure anemia? That question set scientists on the road to the discovery of one of the most complex and unique vitamins. It turns out that vitamin B12 must be present for new cells to form, and it can only be made by bacteria, which is why foods from animals tend to have a lot of it. Find out the details on this page, along with some other good sources for those of you (OK, all of you) who don't much care for liver.

  • Benefits of Vitamin B12

    Vitamin B12 is used effectively in diseases that afflict the young and old alike. It is used to treat asthma and has shown promise against HIV. In the elderly, it can help reverse a slowdown in mental function -- and even seems to hinder Alzheimer's if the disease is caught early enough. Learn about the medicinal uses of vitamin B12 on this page.

  • Vitamin B12 Deficiency

    Because the American diet is rich in animal foods, most of us get plenty of vitamin B12. In fact, the main groups of people at risk for B12 deficiency are vegans (strict vegetarians) and people whose stomachs produce less acid as they age. Some people are also born without the intrinsic factor needed to absorb B12. This page will tell you how muh B12 you need and cover the scenarios in which people don't get enough.

  • Vitamin B12 Supplements

    A lack of vitamin B12 usually results from the body's inability to absorb it, not from a dietary deficiency. That means that people who don't have enough must take large quantities of supplements, far more than they would actually need, so that enough of the vitamin will "stick" in the body. Find out how much of a supplement you would need on this page.
Vitamin B12 is just one of the many vitamins that are part of a healthy diet. Check out the following links to learn more:
  • Folate is necessary for healthy growth, because it makes DNA and RNA. Learn how it manufactures cells at How Folate Works.
  • Vitamin A plays an essential role in eyesight. Learn how it helps us to see, even in the dark, at How Vitamin A Works.
  • Found mostly in protein, Vitamin B3 keeps us strong. How Vitamin B3 Works explains what happens if you don't get enough of it.
  • Vitamin B6 is effective against more than 100 ailments. How Vitamin B6 Works will explain the details and tell you how to get enough in your diet.
  • Everyone knows Vitamin C fights the common cold. Learn how it does the trick at How Vitamin C Works.
  • To learn about the many vitamins in our diet, how much you should be eating, and where to find them, go to our general Vitamins page.
  • To find the lowest prices on B vitamin supplements, click here.
This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.

What Is Vitamin B12

Vitamin B12, also called cyanocobalamin or cobalamin, is unique. It differs from other vitamins, even from others of the B complex, in many ways. It has a chemical structure much more complex than that of any other vitamin. It's the only vitamin to contain an inorganic element (the mineral cobalt) as an integral part of its makeup. And only microorganisms and bacteria can make vitamin B12 -- plants and animals can't.

The pursuit of vitamin B12 began in 1926, when two investigators found that patients who ate almost a pound of raw liver a day were effectively relieved of pernicious anemia. Scientists correctly speculated that liver contained a substance that prevents the disorder, but they wondered why victims of pernicious anemia needed it in such large quantities.

William Castle suggested that liver contained an anti-pernicious anemia (APA) factor. He also believed that people who had the disease lacked a factor intrinsically necessary to use the APA factor. By eating about a pound of liver a day, these people could counteract the lack of the intrinsic factor and absorb the APA factor they needed.

Oysters and other animal foods are good sources of vitamin B12.
© 2007 Publications International, Ltd.
Oysters and clams are surpassed only by liver as good sources of vitamin B12.

For the next 20 years, scientists searched for the APA factor. Progress was slow until 1948, when testing began on an experimental "animal" -- the microorganism Lactobacillus lactis. Instead of testing liver extracts on people, researchers tested them on the microorganisms. Since these microorganisms reproduce so quickly, many generations could be tested in a short period of time.

In less than a year, two research groups -- one in England and one in the United States -- both managed to isolate the APA factor -- pure vitamin B12.

Vitamin B12 is essential to cells because it's needed to assist folate in making DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), which carry and transmit genetic information for every living cell. This information tells a cell how to function and must be passed along each time a cell divides.

Rapidly dividing cells need a continuous supply of vitamin B12 and folate. Vitamin B12 plays a central role in folate metabolism. It releases free folate from its bound form so it can be absorbed, and it helps in the transportation and storage of folate.

A deficiency of vitamin B12 can create a folate deficiency even when dietary intake of folate is adequate. That is why a deficiency of either vitamin causes a similar type of anemia.

Vitamin B12 functions in the production of a material called myelin, which covers and protects nerve fibers. Without enough B12, the myelin sheath does not form properly or stay healthy. As a result, nerve transmission suffers, and people experience irreversible nerve damage.

It's a slow and insidious process that can ultimately end in death. Pernicious (anemia) in fact means, "leading to death."

Vitamin B12 is found mostly in animal foods, such as dairy products, eggs, liver, meat, clams, oysters, sardines, and salmon. Fermented bean products, such as tempeh, contain some vitamin B12. Manufacturers also add vitamin B12 to some cereal products.

Food Quantity Vitamin B12
Liver (beef) 3 1/2 ounces
70.4
Clams, canned 1/2 cup
24.7
Liver (chicken)
3 1/2 ounces
19.2
Oysters, raw 3 1/2 ounces
19
Sardines
3 1/2 ounces
8.7
Product 19 cereal 1 cup 6
Liverwurst 2 slices 4.8
Salmon, canned 3 1/2 ounces 4.3
Grape-Nuts cereal 1/2 cup 3
Hamburger 3 ounces 2.3
Tuna, canned in water 3 1/2 ounces 2.2
Lamb 3 1/2 ounces 2.1
Haddock 3 1/2 ounces
1.7
Beef steak 3 ounces 1.6
Veal, lean 3 1/2 ounces 1.4
Yogurt, low-fat 8 ounces 1.4
Flounder 3 1/2 ounces 1.2

Bacteria in the intestines make some vitamin B12, but far less than the amount needed daily.

B12 has shown promise against diseases from asthma to AIDS to Alzheimer's. Find out how it's used on the next page.

Vitamin B12 is just one of the many vitamins that are part of a healthy diet. Check out the following links to learn more:
  • Folate is necessary for healthy growth, because it makes DNA and RNA. Learn how it manufactures cells at How Folate Works.
  • When teamed with other B vitamins, B2 helps in metabolism. Find out what it does at How Vitamin B2 Works.
  • Relax; you'll find the stress-busting Vitamin B5 in every food you eat. Learn about it at How Vitamin B5 Works.
  • Your body can make its own Vitamin D if you get enough sunshine. Learn the details at How Vitamin D Works.
  • Vitamin E is an antioxidant, which keeps the blood clean. Separate truth from fiction at How Vitamin E Works.
  • To learn about the many vitamins in our diet, how much you should be eating, and where to find them, go to our general Vitamins page.
  • If you're looking for the best prices on B vitamins, click here.
This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.

Benefits of Vitamin B12

Vitamin B12 has health benefits for young and old alike, and everyone in between. It combats asthma in children, has shown promise against HIV in adults, and has helped the elderly who find their minds aren't as sharp as they used to be.

Older adults who notice a decline in mental function, even the emergence of Alzheimer's disease, need to get on the B12 bandwagon. Experts have found that when mental symptoms are treated with vitamin B12 within six months of onset, many of the symptoms disappear or mental clarity improves.

As you get older, vitamin B12 can reverse mental slowdowns or just help you get a good night's sleep.
© 2007 Publications International, Ltd.
As you get older, vitamin B12
can reverse mental slowdowns
or just help you get a good night's sleep.

Vitamin B12 may also help alleviate depression in the elderly by working with a compound that helps to make serotonin, the neurotransmitter responsible for a calm feeling of well being.

B12 also plays a role in melatonin production. Melatonin is the hormone responsible for letting you get a good night's sleep. As we age, the body is less efficient at making this hormone. B12 supplementation has helped some older adults sleep better.

On the opposite end of the life spectrum, children who have asthma may benefit from vitamin B12 as well. Weekly injections of 1,000 mcg or daily oral supplements of 1 to 3 mcg improved their condition and resulted in less shortness of breath.

AIDS patients typically have low levels of this vitamin. This can be used as an indicator that overall nutritional status is low and that attention needs to be given to intake of all nutrients. In the laboratory, vitamin B12, in any form, reduces replication of HIV. This is a hopeful treatment yet to be tested in humans.

Several studies show that B12 dramatically increases sperm counts in men whose counts are low. The vitamin also jump-starts sperm's action, increasing motility rates.

People with tinnitus, that constant ringing in the ears, are often deficient in vitamin B12. Supplementation diminishes the irritating ringing for some people.

Fortunately, most people get more than enough B12 in their daily diet. Find out the recommended daily allowance on the next page.

Vitamin B12 is just one of the many vitamins that are part of a healthy diet. Check out the following links to learn more:
  • Vitamin B1, or thiamin, is one of the essentil vitamins added back to "enriched" foods. Learn about it at How Vitamin B1 Works.
  • Found mostly in protein, Vitamin B3 keeps us strong. How Vitamin B3 Works explains what happens if you don't get enough of it.
  • Everyone knows Vitamin C fights the common cold. Learn how it does the trick at How Vitamin C Works.
  • Biotin aids in metabolism, turning food into energy. Learn more at How Biotin Works.
  • Vitamin K plays a vital role in blood clotting. Learn more at How Vitamin K Works.
  • To learn about the many vitamins in our diet, how much you should be eating, and where to find them, go to our general Vitamins page.
  • If you're looking for the best prices on B vitamins, click here.
This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.

Vitamin B12 Deficiency

The RDA for vitamin B12 is 2.4 micrograms (mcg) daily for adults, 2.6 mcg daily for pregnant women, and 2.8 mcg for women who are breast-feeding. The average American diet provides 7 to 30 mcg of the vitamin. Unlike other vitamins, vitamin B12 is stored in the liver, so these suggested amounts refer to an average daily intake over a span of days.

When the supply of vitamin B12 in the body is low, it slows down the production of red blood cells (causing anemia) and the cells that line the intestine. This is similar to what happens as a result of insufficient folate. But unlike folate deficiency, a lack of vitamin B12 can also cause serious damage to the nervous system. If the condition persists for a long time, the damage is irreversible.

An injection of B12 may be necessary for patients with pernicious anemia.
© 2007 Publications International, Ltd.
An injection of B12 may be necessary
for patients with pernicious anemia.

A deficiency of vitamin B12 caused by insufficient intake is not common. The average well-fed person has a supply of the vitamin stored in the liver that can last five years or longer. Dietary deficiency of vitamin B12 is seen only in strict vegetarians (vegans) who don't eat foods of animal origin -- not even milk or eggs.

Such a restricted diet is a particular problem for pregnant or breast-feeding women since the baby can develop a vitamin B12 deficiency even if the mother remains healthy. For this reason, vegan mothers should eat foods fortified with vitamin B12. Vegetarians who regularly eat eggs or drink milk usually get all the vitamin B12 they need.

Pernicious anemia is usually an inherited disease in which a deficiency of vitamin B12 occurs despite adequate amounts in the diet. People with this disease cannot produce intrinsic factor, the substance needed to absorb vitamin B12. They need to receive injections of vitamin B12 so the vitamin can bypass the stomach and intrinsic factor and enter the bloodstream directly.

Because intrinsic factor originates in the stomach, partial or total removal of the stomach reduces absorption of vitamin B12. Moreover, removal of the end of the small intestine (ileum) also creates a deficiency, because that's where absorption of the vitamin takes place. In these cases, pernicious anemia results from the surgery, not dietary deficiency.

Stomach acid frees vitamin B12 from the proteins it is bound to in foods, but for the one-third of adults who experience a decline in stomach acid as they age, this can be a problem. They risk a vitamin B12 deficiency later in life. If undetected, the problem can cause nerve damage. An unexplained unsteady gait and loss of coordination often signal this type of vitamin B12 deficiency.

Research around the world concludes that 10 to 12 percent of older adults are deficient in vitamin B12 to some degree. All agree that assessment of this nutrient is difficult because typical tests may not be sensitive enough and other nutrients and medications can interfere with results.

For those who don't have enough B12, huge amounts of supplements may be necessary. Find out why on the next page.

Vitamin B12 is just one of the many vitamins that are part of a healthy diet. Check out the following links to learn more:
  • Folate is necessary for healthy growth, because it makes DNA and RNA. Learn how it manufactures cells at How Folate Works.
  • When teamed with other B vitamins, B2 helps in metabolism. Find out what it does at How Vitamin B2 Works.
  • Vitamin B6 is effective against more than 100 ailments. How Vitamin B6 Works will explain the details and tell you how to get enough in your diet.
  • Vitamin A plays an essential role in eyesight. Learn how it helps us to see, even in the dark, at How Vitamin A Works.
  • Vitamin E is an antioxidant, which keeps the blood clean. Separate truth from fiction at How Vitamin E Works.
  • To learn about the many vitamins in our diet, how much you should be eating, and where to find them, go to our general Vitamins page.
  • If you're looking for the best prices on B vitamins, click here.
This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.

Vitamin B12 Supplements

Physicians usually treat pernicious anemia with an injection of anywhere from 50 to 100 mcg of vitamin B12 three times a week. These injections may need to continue throughout life. However, medical studies show that large amounts of active vitamin B12 can be absorbed, even without intrinsic factor.

Huge amounts of vitmain B12 are needed to offset deficiency.
© 2007 Publications International, Ltd.
Because B12 deficiency is usually the result of the body's inability to absorb it,
huge amounts are needed to offset this condition.

The form of vitamin B12 called methylcobalamin is the only active form sold in the United States. Cyanocobalamin, a more commonly available form, requires modification in the body, and even then, when used in studies, it is not always effective. Methylcobalamin, when given in very large doses, can be absorbed.

There are supplements that are meant to be taken under the tongue. Sublingual administration is thought to bypass the absorption problems related to the intrinsic factor by allowing the vitamin to be absorbed directly into the venous plexus -- the complex of blood vessels located in the floor of the mouth.
To find great prices on B vitamins, click here.

Huge amounts of the vitamin ensure that at least some of it gets absorbed, even without intrinsic factor; 1,000 mcg per day is a common recommendation, sometimes starting with 2,000 mcg per day for the first month. There are no reports of vitamin B12 causing toxicity or adverse effects even in these large amounts. In fact, it is often used as a placebo because of its assured non-toxicity.

As you can see, vitamin B12 just doesn't quite act the same as other vitamins. After reading this article, you'll be able to understand it better and its importance in your diet.

Vitamin B12 is just one of the many vitamins that are part of a healthy diet. Check out the following links to learn more:
  • Vitamin B1, or thiamin, is one of the essentil vitamins added back to "enriched" foods. Learn about it at How Vitamin B1 Works.
  • Relax; you'll find the stress-busting Vitamin B5 in every food you eat. Learn about it at How Vitamin B5 Works.
  • Biotin aids in metabolism, turning food into energy. Learn more at How Biotin Works.
  • Your body can make its own Vitamin D if you get enough sunshine. Learn the details at How Vitamin D Works.
  • Vitamin K plays a vital role in blood clotting. Learn more at How Vitamin K Works.
  • To learn about the many vitamins in our diet, how much you should be eating, and where to find them, go to our general Vitamins page.
  • If you're looking for the best prices on B vitamins, click here.
ABOUT THE AUTHOR

Jennifer Brett, N.D. is director of the
Acupuncture Institute for the University of Bridgeport, where she also serves on the faculty for the College of Naturopathic Medicine. A recognized leader in her field with an extensive background in treating a wide variety of disorders utilizing nutritional and botanical remedies, Dr. Brett has appeared on WABC TV (NYC) and on Good Morning America to discuss utilizing herbs for health.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.