Vitamin B12

What is Vitamin B12?

Vitamin B12, which is also known as cobalamin, is one of the eight B vitamins. All B vitamins help the body to turn food into fuel, which is used to produce energy. These B vitamins help the body to burn fat and protein. B complex vitamins are needed for healthy skin, hair, eyes and liver. They also help the nervous system to work correctly.

All B vitamins are soluble in water, which means that the body does not store them. For this reason, it is important to receive a steady dose of B vitamins in the diet.

Vitamin B12 is a particularly important vitamin for maintaining healthy nerve cells, and it helps with the production of DNA and RNA. Vitamin B12 works in close partnership with vitamin B9, also known as folate or folic acid, in order to create red blood cells and help improve iron absorption in the body.

Folate and B12 work together to produce S-adenosylmethionine (SAMe). SAMe has a part to play in the immune system, maintains cell membranes and helps to produce and break down chemicals in the brain such as serotonin, melatonin and dopamine. It works together with vitamin B12 and folate (vitamin B9). A deficiency of either vitamin B12 or folate can reduce SAMe levels in the body.

Vitamins B12, B6 and B9 work together to control levels of the amino acid homocysteine. High homocysteine levels are associated with heart disease. However, researchers are not sure of whether homocysteine is a cause of heart disease or simply a marker which indicates that someone may have heart disease. More research is required to establish this.

Why is it important to analyse vitamin B12?

It is unusual for young people to suffer from vitamin B12 deficiency, but milder deficiencies are not uncommon in older people. This may be because they have less stomach acid, which the body needs to absorb B12. Low B12 levels can cause a range of different symptoms, including:

  • Fatigue
  • Respiratory distress
  • Diarrhoea
  • Nervousness
  • Numbness
  • Tingling in the fingers and toes
  • Severe B12 deficiency causes nerve damage

The people at the greatest risk of B12 deficiency include:

  • Vegans and vegetarians who do not eat dairy products or eggs, because vitamin B12 is found only in animal products
  • People with problems with absorbing nutrients on account of Crohn's disease, pancreatic disease, weight loss surgery, or medications
  • People with eating disorders
  • People with HIV
  • People with diabetes

If your diet includes meat, fish or shellfish, milk and other dairy products, you should be able to meet the recommended daily intake without taking a vitamin B12 supplement. Vegetarians who eat no animal products should take a vitamin B12 supplement with water. Elderly people may need larger amounts of vitamin B12 than younger people as the body's ability to absorb vitamin B12 from the diet declines with age. If you are considering taking a B12 supplement, ask your healthcare provider to help you decide on the right dose for you and make sure you undergo regular blood tests to check that you are getting the right amount of vitamin B12.

Vitamin B12 is found only in animal foods. Good dietary sources include:

  • Fish
  • Shellfish
  • Dairy products
  • Offal, particularly liver and kidneys
  • Eggs
  • Beef
  • Pork

Folic acid (vitamin B9), particularly taken in high doses, can mask the symptoms of a vitamin B12 deficiency. The hazard with this is that without symptoms, you may have a B12 deficiency and be unaware of it, with the accompanying risk of developing nerve damage, for example.

Many studies indicate that people with high levels of the amino acid homocysteine run almost twice the risk of developing coronary heart disease and 2.5 times the risk of stroke than people with normal levels. B complex vitamins, in particular vitamins B9, B6 and B12, can help to reduce the homocysteine level. However, researchers do not know whether high homocysteine is actually the definitive cause of heart disease.

People who are worried about heart disease should attempt to consume B vitamins from healthy foods. However, in some cases doctors may recommend taking B vitamins in order to reduce the homocysteine level. If you are worried about heart disease, ask your doctor whether a vitamin B supplement would be right for you.

Although there is no proof that vitamin B12 reduces the risk of breast cancer, population studies have shown that women who consume more folate (B9) in their diet have less risk of breast cancer. Vitamin B12 works with folate in the body, so this may help to reduce the risk of breast cancer. Another pilot study proposes that postmenopausal women with the lowest quantities of B12 in the diet also had an increased risk of breast cancer.

Studies indicate that vitamin B12 supplements can improve sperm quality and the ability of sperm to swim. This requires more research.

High levels of Vitamin B12

High levels are seen in people undergoing vitamin B12 treatment. Very high levels can be seen for a fairly long time following an injection of a sustained action drug. High levels are also seen in people with myeloproliferative conditions, particularly in cases of chronic myeloid leukaemia, liver damage and kidney failure.

Low levels of Vitamin B12

Low levels are seen in patients with an intrinsic factor deficiency (pernicious anaemia), ventricular resection, cancer of the stomach, terminal ileitis, malabsorption and transcobalamin deficiency, and in vegetarians.


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