Vitamin B12

Although this vitamin is plentiful in most people’s diets, after the age of 50 some people are less able to absorb it from food. Supplements are usually recommended, because even mild deficiencies may increase the risk of heart disease, depression, and possibly Alzheimer’s.

What it is

Also known as cobalamine, vitamin B12 was the last vitamin to be discovered. In the late 1940s, it was identified as the substance in calf’s liver that cured pernicious anaemia, a potentially fatal type of anaemia primarily affecting older adults. Vitamin B12 is the only B-vitamin the body stores in large amounts, mostly in the liver. The body absorbs B12 through a very complicated process. Digestive enzymes in the presence of enough stomach acid separate B12 from the protein in foods. The vitamin then binds with a substance called intrinsic factor (a protein produced by cells in the stomach lining) before being carried to the small intestine, where it is absorbed. Low levels of stomach acid, an inadequate amount of intrinsic factor (both of which occur with age) and inflammation of the small intestine can lead to deficiencies. However, because the body has good reserves of B12, it can take several years for a shortfall to develop.

What it does

Vitamin B12 is essential for cell replication, particularly red blood cells. It maintains the protective sheath around nerves (myelin), helps to convert food to energy, and plays a critical role in the production of DNA and RNA, the genetic material in cells.


Moderately high blood levels of homocysteine, a amino-acid-like substance, have been linked to an increased risk of heart disease. Working with folic acid, vitamin B12 helps the body to process homocysteine and so may lower that risk. Because of its beneficial effects on the nerves, vitamin B12 may help to prevent a number of neurological disorders, as well as the numbness and tingling often associated with diabetes. It may also be helpful in treating depression.

Additional benefits

Research shows that low levels of vitamin B12 are common in peopl with Alzheimer’s disease. Whether this deficiency is a contributing factor to the disease or a result of it is not known. The nutrient does, however, keep the immune system healthy. Some studies suggest that it lengthens the amount of time between infection with the HIV virus and the development of AIDS. Other research indicates that adequate B12 intake improves immune responses in older people. With its beneficial effect on nerves, vitamin B12 may lessen ringing in the ears (tinnitus). As a component on myelin, it is valuable in treating multiple sclerosis, a disease that involves the destruction of this nerve covering. And throught its role in cell replication, B12 may improve symptoms of rosacea.

Common uses

  • Prevents a form of anaemia.
  • Helps reduce depression.
  • Relieves nerve pain, numbness and tingling.
  • Lowers the risk of heart disease.
  • May improve multiple sclerosis and tinnitus.


  • Tablet.
  • Capsule.

How much you need

The RDI for vitamin B12 is 2 mcg a day for adults. But many experts recommend that you get 100-400 mcg. Vitamin B12 supplementation is very important for older people and vegans (who eat no animal products).

If you get too little: Symptoms of a vitamin B12 deficiency include fatigue, depression, numbness and tingling in the extremities caused by nerve damage, muscle weakness, confusion and memory loss. Dementia and pernicious anaemia can develop; both are reversible if caught early. The level of B12 in the blood decreases with age. People with ulcers, Crohn’s disease or other gastrointestinal disorders are at risk, as are those taking prescription medication for epilepsy (seizures), chronic heartburn or gout. Excessive alcohol also hinders absorption of vitamin B12.

If you get too much: Excess vitamin B12 is readily excreted in urine. There are no known adverse effects from a high intake of vitamin B12.

How to take it


A general dose of 1000 mcg of vitamin B12 a day is useful for heart disease prevention, pernicious anaemia, numbness and tingling, tinnitus, multiple sclerosis and rosacea. If you’re deficient in B12, higher doses may be needed. If you don’t produce enough intrinsic factor, B12 shots or a prescription nasal spray may be necessary; ask your doctor.

Guidelines for use

Take vitamin B12 once a day, preferably in the morning, along with at least 400 mcg of folic acid. Most multivitamins contain at least the RDI of vitamin B12 and folic acid; B-complex supplements have higher amounts. For larger, therapeutic amounts, look for a supplement with just vitamin B12 or B12 with folic acid. Using a sublingual (under the tongue) form enhances absorption.

Other sources

Animal foods are the primary source of B12. These include organ meats (particularly liver), brewer’s yeast, oysters, sardines and other fish, eggs, meat and cheese. Some breakfast cereals are fortified with this vitamin as well.


If you take vitamin B12 supplement, you must also have a folic acid supplement: a high intake of one can mask a deficiency of the other.

Reminder: If you have a medical or psychiatric condition, talk to your doctor before taking supplements.