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Vitamin B12 in a nutshell:
Vitamin B12 is involved in brain and neuron health, helping create the myelin sheaths that surround neurons.  It’s also involved in creation of DNA and red blood cells.  Deficiency leads to pernicious anemia.  Vitamin B12 is also involved in turning used folic acid back into active folic acid.

Best source of Vitamin B12 for Juicers
Vitamin B12 is not really found in high concentrations in plants products.  You can get your daily dose easily by eating clams, mackerel, salmon, octopus etc, but not so easily from fruit and vegetables.  It can also be found in some fermented soy-based products like Tofu.  If you are a vegan, it may help to take B12 supplements.

Alternative Names: Vitamin B12; cobalamin.

What Is Vitamin B12?

Vitamin B12 is a nutrient that is difficult—although not impossible—to obtain from a vegan diet. Vitamin B12 deficiency develops over a period of years, but once this vitamin is finally depleted, symptoms may be life-threatening.

Vitamin B12 is a water-soluble vitamin. As its name suggests, vitamin B12 incorporates the rare earth mineral cobalt into its structure. It exists as a group of “vitamers” that the body can convert from one form to another, but the basic structure of the vitamin is built by bacteria and algae.

Humans get their vitamin B12 either by consuming certain fermented foods or certain kinds of algae, or by eating animals that consumed these bacteria or algae (or that consumed other animals that consumed the original source of B12).

The kind of vitamin B12 you get from food is a compound called hydroxocobalamin. As a dry powder, it is intensely red due to the presence of cobalt. It occurs in such minute traces in food that it is just as likely to be found in a white food as a red food or food of any other color.

This is not the form of vitamin B12 the human body uses. It's one of the vitamers of B12 that the body can use to make the vitamin it actually uses.

The kind of vitamin B12 you get in a nutritional supplement is a compound called cyanocobalamin. The cyano- in the name refers to the addition of a cyanide group (yes, the poisonous kind of cyanide) during the manufacturing process. The human body cannot use cyanocobalamin directly, but it can remove the cyanide to make methylcobalamin, which it can use as a cofactor for various enzymes.

Almost all the world's supply of synthetic vitamin B12 is made by a single company in France. It's possible to make vitamin B12 through a purely chemical process, but since there are over 40 steps in the chemical process, the French manufacturer and other manufacturers of synthetic vitamin B12 begin by fermenting sugars with bacteria.

The bacteria that are used in the fermentation process are in the same family that cause acne, Propionibacterium. The boards of medicines of the member countries of the EU, HealthCanada, and the US Food and Drug Administration all approve the use of Propionibacteria to produce vitamin B12, because they do not release any toxins as they make hydroxocobalamin.

Many consumers find this concern ironic since the next step in the manufacturing process is to take the same chemical found in food and treat it with cyanide so it will last longer in a bottle on the shelf. The acne bacteria produce the hydroxocobalamin vitamer. The manufacturers then make a liquid solution of hydroxocobalamin and water and run it through a mixture of charcoal and sodium cyanide. The “pre-B12” absorbs the cyanide and becomes stable for addition to animal feeds and nutritional supplements.

As you might imagine, some consumers object to using nutritional supplements made by adding cyanide to a food chemical. Anywhere in the world except the United States, if your doctor gives you a B12 shot, you are likely to get hydroxocobalamin, the cyanide-free vitamer of B12. In the United States, you will get a shot of cyanocobalamin, the cyanide-treated form of B12 that is also used in cattle and chicken feed.

The total amount of vitamin B12 the human body can store is 2 to 5 milligrams. About half of the body's B12 is bound to cholesterol in the liver. It releases about 0.1% of its B12 every day into the bile that carries excess fat and cholesterol to the intestines. Bile may or may not be reabsorbed into the body, so a portion of that 0.1% of 50% of the body's vitamin B12 is returned to the liver.

It usually takes several years for vitamin B12 deficiency symptoms to show up, although B12 may be depleted much more quickly in infants.

What Does Vitamin B12 Do in the Human Body?

Every cell in the human body uses vitamin B12. It plays an important role in creating DNA, and also in regulating energy production. This vitamin is also critical for manufacturing useful fatty acids.

The unusual thing about vitamin B12, however, is that since one of its most critical tasks is helping regenerate folic acid (vitamin B9), getting enough folic acid can mask vitamin B12 deficiency. The interrelationships are a little hard to follow but here is the absolute basics of what you need to know.

There are only two types of cellular processes in the human body that absolutely require vitamin B12 and can't be accomplished with folic acid. One group of essential cellular reactions that require B12 is a group of cellular processes known as the methylmalonyl-coenzyme A mutase reactions. They are usually referred to as MUT reactions after the name of the gene involved.

MUT reactions absolutely require vitamin B12. They are necessary for maintaining the myelin that protects nerves in the central nervous system and neurons in the brain. In other words, if you don't have vitamin B12, eventually you will have problems with your brain and nerves.

Another essential function of vitamin B12 is regulating homocysteine. This chemical builds up as the body uses the amino acids cysteine and methionine. Homocysteine is an irritant chemical that dissolves collagen in the linings of blood vessels and joints. It's not possible to lower high homocysteine without vitamin B12.

However, high homocysteine is just half of the problem.

If you are familiar with natural health, you probably already know that homocysteine causes inflammation and another chemical called S-adenosylmethionine, or SAM-e, relieves it. SAM-e also interacts with DNA through a process called methylation, which can turn off cancer-causing genes and turn on cancer-protective genes.

There is a critical relationship between the harmful homocysteine and the helpful SAM-e. The body makes SAM-e out of homocysteine with the help of an enzyme called methionine synthase, which depends on vitamin B12.

Vitamin B12 is also well known for its role in creating DNA for red blood cells. Vitamin B12 deficiency used to be associated with a condition known as pernicious anemia, in which failures to create the right kind of DNA led to the production of misshapen and and fragile red blood cells that failed to carry adequate amounts of oxygen to tissues through the bloodstream.

Vitamin B12's role in the creation of DNA for red blood cells is converting “used” folic acid back into “active” folic acid. If you take large amounts of folic acid, it's not strictly necessary to take vitamin B12 to remedy anemia. However, a tiny amount of vitamin B12 makes a large amount of folic acid unnecessary in this vital function of the human body.

What Happens When We Don't Get Enough Vitamin B12?

The most common complication of not getting enough vitamin B12 is high homocysteine levels. Because many other factors also affect inflammation, high homocysteine levels may or may not cause obvious symptoms.

Only the highest levels of homocysteine cause specific symptoms such as strokes or heart attacks, usually occurring when people are in their 20's or 30's. Only about 1 in 200,000 people ever develops homocysteine levels that are this high. Symptoms of extreme high homocysteine include a drooping of the lens of the eye and serious intellectual deficiencies before the heart attacks or strokes occur.

At the other end of the spectrum, science really does not know whether mild levels of vitamin B12 deficiency might interfere with the process of methylation, which can be very important in cancer prevention. At this time, doctors do not know exactly how much vitamin B12 may be needed to provide methyl groups for DNA and prevent cancer.

Doctors do know, however, about two relatively common B12 deficiency diseases, megaloblastic anemia and neurologic symptoms of B12 deficiency.

Megaloblastic anemia. The most commonly treated B12-deficiency disease is megaloblastic anemia. Vitamin B12 regenerates folic acid that is used to make enzymes that enable baby blood cells to make DNA. If either vitamin B12 or folic acid is deficient, the process of creating new DNA may not keep up with the creation of other parts of the cells.

The result is the creation of large, misshapen red blood cells that don't have enough hemoglobin to carry enough oxygen to all the body's tissues. Megaloblastic anemia can be treated with folic acid, but there still may be a risk of neurological problems if supplementation does not include B12.

Neurologic symptoms of B12 deficiency. The most serious symptoms of vitamin B12 deficiency appear in the nervous system. There may be peripheral neuropathy, the failure of nerves in the hands and feet that result in sensations of numbness, tingling, and burning. There can be memory loss, disorientation, trouble walking, mood swings, or dementia. Fortunately, only about 25% of people who develop megaloblastic anemia also develop peripheral neuropathy, problems with walking, or dementia.

Vitamin B12 deficiency may also cause redness and soreness of the tongue and lining of the mouth and chronic stomach upset.

Are You at Risk for Vitamin B12 Deficiency?

Most kinds of vitamin deficiency are relatively rare. Vitamin B12 deficiency is very common, especially in individuals who have passed the age of 60.

Infection-related B12 deficiencies. At some time after the age of 60, about 1 in 3 adults will develop infection-related vitamin B12 deficiency. Bacterial infections that cause peptic or duodenal ulcers interfere with the stomach's ability to release vitamin B12 from food or the small intestine's ability to receive it. A condition called small intestine bacterial overgrowth (SIBO) can literally coat the small intestine so vitamin B12 and other nutrients cannot get in.

As soon as the infections are successfully treated, however, normal absorption of vitamin B12 resumes. If peptic ulcer disease, duodenal ulcers, or SIBO are treated within a year, there are usually no problems from the short-term deficiency.

Absorption-related B12 deficiencies. About 1 in 10 adults over the age of 60 has absorption-related vitamin B12 deficiency. This is because the digestive tract usually is less able to release and absorb vitamin B12 as people age.

Most of the B12 provided by the diet is found in meat, dairy products, and fish. If the stomach does not make enough acid, it cannot release B12 from the proteins that bind it. Once the proteins in food are broken down by stomach acid, the B12 is attached to different proteins made by the stomach that carry it to the small intestine.

These proteins deliver the B12 digested in the stomach to specialized receptors in the small intestine. These receptors can only absorb B12 in an alkaline environment. If the pancreas cannot release enough calcium into the small intestine to keep its content alkaline, vitamin B12 is not absorbed.

Pernicious anemia. About 1 in 50 adults over the age of 60 has a condition known as pernicious anemia. This condition is caused by an autoimmune disease that destroys the acid-producing cells lining the stomach. The stomach cannot digest proteins to release vitamin B12. Even worse, pernicious anemia stops the production of intrinsic factor, which is needed to carry B12 to the small intestine. People who have pernicious anemia cannot absorb the B12 in either food or supplements.

Vitamin B12 deficiency can also occur at any age as a result of drug abuse or drug treatment.

• Aminosalicylic acid is a compound similar to aspirin that relieves inflammation in ulcerative colitis and Crohn's disease. Taking aminosalicylic acid preparations such as 4-aminosaliclic acid or PAS can begin to cause vitamin B12 deficiency in just a month.
• The AIDS drug AZT (zidovudine), which is also marketed as Combivir and Retrovir, can cause low B12 levels, but consult with your physician before taking supplemental B12.
• Binge drinking of alcohol can interfere with the stomach's ability to make the intrinsic factor that carries B12 to the small intestine for absorption.
• Chloramphenicol (marketed as Chloromycetin) is a broad-spectrum antibiotic. It may interfere with the ability of vitamin B12 to reach the bone marrow where red blood cells are made.
• Cholestyramine (Questran) and colestipol (Colestid) lower cholesterol levels by keeping the liver from reabsorbing bile salts, which also carry a small amount of vitamin B12. They do not cause B12 deficiency, but they can aggravate it.
• H2-receptor antagonists such as Axid (nizatidine), Pepcid (famotidine), Tagamet (cimetidine), and Zantac (ranitidine) for heartburn and gastroesophageal disease (GERD) reduce the release of stomach acids so that less B12 is released from food.
• High doses of colchicine for gout, more than 1900 mg a day, can interfere with absorption of B12 and other nutrients. Smaller doses do not seem to have any detrimental effect.
• Metformin (Glucophage) is the world's most commonly prescribed medication for type 2 diabetes. It can lower both folic acid and vitamin B12 levels, causing high homocysteine levels and, in rare cases when it is taken for 5 years or more, megaloblastic anemia. The way metformin interferes with vitamin B12 absorption is by causing the pancreas to use calcium to release insulin, so taking calcium supplements usually corrects the problem with B12 absorption. It is still necessary to take supplemental folic acid.
• Neomycin antibiotic taken in high doses can interfere with B12 absorption.
• Nitrous oxide, used as an anesthetic for dental procedures, can destroy B12 in the nerves.
• Oral contraceptives usually lower B12 levels but usually do not cause deficiency.
• “Poppers” oxidize vitamin B12 into a form that the body cannot use. Users of this recreational drug need at least to take vitamin B12 supplements on a daily basis.
• Phenytoin (Dilantin) for seizure disorders and migraines interferes with the ability to the small intestine to absorb both B12 and folic acid.
• Potassium chloride supplements can interfere with the ability of the small intestine to absorb vitamin B12. If you need to take supplemental potassium, use potassium citrate, which does not interfere with B12 absorption as severely.
• Proton-pump inhibitors such as Aciphex (rabeprazole), Prevacid (lansoprazole), Prilosec (omeprazole), and Protonix (pantoprazole) reduce production of stomach acid and interfere with the release of B12 from digested food.

Antibiotics usually actually improve vitamin B12 levels by removing bacteria from the lining of the small intestine that could block the absorption of B12 from intrinsic factor. They are not used to treat vitamin B12 deficiency, however.

How to Make Sure You Get Enough Vitamin B12

Unlike requirements for most vitamins, vitamin B12 requirements increase with age. If you are 50 or older, you need 2.4 micrograms (0.0024 milligrams) of vitamin B12 every day, and to be sure that you get it, you should take a supplement. Breastfeeding mothers and pregnant women need even more B12, 2.8 micrograms per day and 2.6 micrograms per day, respectively. They also benefit from B12 supplements.

Adults age 19 through 49 also need 2.4 micrograms of B12 every day, but it is safe for them to get it from food. Teens aged 14 through 18 need 2.4 micrograms per day, tweens aged 8 to 13 need 1.8 micrograms per day, children aged 4 to 7 need 1.2 micrograms per day, and infants and toddlers need 1.0 micrograms per day or less.

It's not hard for most of us to get a lot more B12 than the 2 to 5 micrograms our bodies can absorb in a single day.

• A 3-1/2 oz/100 gram serving of clams contains 99 micrograms of vitamin B12.
• A 3-1/2 oz/100 gram serving of most kinds of liver contains 70 to 93 micrograms of vitamin B12.
• A 3-1/2 oz/100 gram serving of oysters or octopus contains 29 to 35 micrograms of vitamin B12.
• A 3-1/2 oz/100 gram serving of Braunschweiger (liver sausage) contains 20 micrograms of vitamin B12.
• A 3-1/2 oz/100 gram serving of Kellogg's Complete or General Mills TOTAL cereal contains 20 micrograms of vitamin B12.
• A 3-1/2 oz/100 gram serving of salmon or mackerel contains 17 micrograms of vitamin B12.
• A 3-1/2 oz/100 gram serving of almost any other meat contains at least 2 micrograms of vitamin B12.

Most people who eat meat every day get more than enough vitamin B12. For them, the problem is not getting enough B12 in the diet, it is making sure it is absorbed.

Vegans, however, have a different problem. Plant foods don't contain vitamin B12. At one time it was thought that spirulina, which is a terrific source of most minerals, vitamins, essential fatty acids, and essential amino acids, was also a good source of vitamin B12. Better analytical methods revealed that spirulina actually binds vitamin B12 in a form that cannot be released in the human digestive tract. Spirulina will not give vegans the B12 they need.

For most of human history, vegans got their B12 from tiny insects in grains and vegetables. Now that food is processed under sanitary conditions, vitamin B12 is a real problem for vegans unless they take supplemental vitamin B12. The Vegan Society, the Vegetarian Resource Group, and the Physicians Committee for Responsible Medicine all recommend that vegans take a vitamin B12 supplement once a week to prevent deficiency. You can get tiny amounts of vitamin B12 from fermented foods such as sauerkraut and pickles, but not enough for all your body's needs.

Also, if you take any of the medications mentioned earlier in this article, a weekly B12 supplement (usually 1000 micrograms) is a must.

Using Vitamin B12 to Support Recovery from Diseases

Many health conditions respond well to vitamin B12 supplements taken by mouth. The cyanocobalamin form of B12 is cheaper, but the cyanide-free methylcobalamin or hydroxocobalmin are not a whole lot more expensive. Vitamin B12 supplementation is used to support recovery from:

• Bell's palsy. This nerve condition affecting one side of the face often resolves much faster with methylcobalamin supplements are taken.
• Cancer and rheumatoid arthritis. These conditions are often treated with methotrexate, a drug that works by depriving cancer cells of folic acid. If you are not getting this drug for leukemia or lymphoma, taking vitamin B12 may help prevent anemia and neutropenia, serious complications of chemotherapy. Talk about any supplements you take with your oncologist first.
• Diabetic neuropathy. This common complication in diabetics who are unable to control their blood sugar levels sometimes responds to B12 supplementation over a period of about 3 months. The effects are variable, but diabetics often report reduced pain, numbness, and burning in the extremities and fewer falls.
• Heart rate variability. Rapid pulse followed by slow pulse without any obvious relationship to stress or exercise can result from a kind of diabetic neuropathy of the vagus nerve, which acts as a natural pacemaker for both the heart and digestive tract. Diabetics who have heart rate variability often respond to B12 treatment.
• Male infertility. Both sperm count and sperm motility sometimes increase after correcting B12 deficiency.
• Sleep disturbances. Vitamin B12 is necessary for the pineal gland to make melatonin. Supplemental B12 may be helpful for people who have trouble getting to sleep, especially during the winter months.

How much B12 should you take? Usually a single 1000-microgram capsule once a week is enough. Diabetics may take up to 500 micrograms three times a day.

It's best to take vitamin B12 with food, and even better if you eat a bitter food (which stimulates the secretion of gastric juices) such as a salad at the beginning of the meal. Calcium supplements usually interfere with nutrient absorption, but they are helpful when taken at the same time as B12. Vitamin C supplements usually increase nutrient absorption, but they should not be taken at the same time as B12. It's especially helpful to take your B12 with milk or a calcium supplement if you take the diabetes drug metformin (Glucophage).

What about B12 injections?

Vitamin B12 injections are generally something you should never attempt on your own, even if you have access to injectable B12.

Sometimes giving people with megaloblastic anemia B12 injections results in a condition called hypokalemia, drawing too much potassium out of the bloodstream, resulting in severe muscle fatigue. Vitamin B12 injections have been known to trigger attacks of gout. You are extremely unlike to encounter these complications if you use a supplement you take by mouth, but any use of vitamin B12 injections should be supervised by a doctor.

On rare occasions, taking vitamin B12 injections can unmask a condition known as polycythemia, in which the body makes too many red blood cells.

Is There a Danger In the Cyanide-Treated Form of B12 Supplements?

Most people don't experience any problems using vitamin B12 supplements made with the addition of cyanide because the amounts of B12 in the supplement are measured in millionths of a gram and the amounts of cyanide released from the supplement are also measured in millionths of a gram. There is one exception to this general rule.

Smokers are exposed to cyanide from tobacco smoke. Their bodies may not be able to process additional cyanide released from synthetic B12. There is even a condition called tobacco amblyopia, damage to the optic nerve caused by the toxins released by tobacco smoke that causes double vision.

This condition is made worse by taking vitamin B12 supplements made with cyanide. It is not made worse by taking the much more expensive supplements made with hydroxocobalamin. This form of B12 actually absorbs cyanide released into the bloodstream by cigarette or cigar smoke.