General Practice 2022

Vitamin B12: what is it for and why it can be high or low

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Vitamin B12: what is it for and why it can be high or low
Vitamin B12: what is it for and why it can be high or low

Vitamin B12 is a B-complex vitamin present mainly in foods of animal origin, such as eggs, milk and dairy products, meat, fish and chicken, being essential for the formation of blood cells, preventing megaloblastic anemia, a disease caused by vitamin B12 deficiency.

In addition, vitamin B12 is also essential for the development and maintenance of central nervous system functions, and for the metabolism of proteins and carbohydrates in food, helping to maintain a good physical and mental disposition.

Vitamin B12 is also found in fortified foods, or supplements, which can be in the form of capsules, tablets, drops or injectable form, being indicated only in cases of vitamin deficiency. Understand how to treat vitamin B12 deficiency.

What is vitamin B12 for

Adequate intake of vitamin B12 helps in the performance of some functions in the body, including:

  1. Help maintain heart he alth, as adequate levels of vitamin B12 in the body can prevent blood levels of homocysteine ​​from increasing, an amino acid that in large amounts, is related to cardiovascular diseases;
  2. Avoid megaloblastic anemia, as vitamin B12 participates in the formation of blood cells, helping to transport oxygen and nutrients to the cells. Understand what it is and how to treat megaloblastic anemia;
  3. Improve physical and mental disposition, as vitamin B12 helps in the metabolism of carbohydrates, helping to maintain energy in the body;
  4. Maintain the he alth of neurons, as vitamin B12 participates in the formation and maintenance of the functions of the cells of the central nervous system.

However, in order to obtain the benefits of this vitamin, it is important to maintain a regular intake of foods that are sources of vitamin B12, as well as maintaining a balanced diet and exercising regularly.

Where to find vitamin B12

Vitamin B12 is found mainly in foods of animal origin, such as milk and dairy products, meat, liver, chicken, fish, seafood and eggs. See a list of the main foods rich in vitamin B12.

However, although they do not naturally contain vitamin B12, some foods of plant origin, such as breakfast cereals, vegetable milks and brewer's yeast, can be enriched with this vitamin, being interesting options for those who follow a he althy lifestyle. vegetarian food.

Recommended Daily Intake

The recommended amount of vitamin B12 intake varies by age, as indicated in the following table:


Recommended Daily Intake (mcg)

From 0 to 6 months

0, 4 mcg

From 6 to 12 months

0, 5 mcg

1 to 3 years old

0, 9 mcg

3 to 8 years old

1, 2 mcg

9 to 13 years old

1, 8 mcg

Men and women over 14 years old

2, 4 mcg

Also, pregnant women need to consume 2.6 mcg of vitamin B12 per day. The recommended intake for breastfeeding women is 2.8 mcg of vitamin B12 per day.

When to take vitamin B12 supplements

Vitamin B12 supplements may be necessary when the intake of foods that source this vitamin is low, such as in strict vegetarian diets, or in situations where the body cannot absorb the vitamin, such as in cases of stomach surgery.

Supplementation with vitamin B12 in the form of pills, liquids or injectables should always be prescribed by a doctor or nutritionist, after evaluating the levels of the vitamin in the body, which is done through a blood test or urine.

See nutritionist Tatiana Zanin for some tips on foods and vitamin B12 supplements:

When vitamin B12 gets high or low

Some situations, such as diet, surgery or the use of some medications, can change the levels of vitamin B12 in the body, which can be verified by performing blood tests, such as the dosage of vitamin B12, urine and the evaluation of the signs and symptoms presented by the person.

Vitamin B12 low

Vitamin B12 may be low in people who do not eat meat, fish, eggs or dairy. Low levels of vitamin B12 can also occur in people with pernicious anemia, an autoimmune disease that decreases the production of intrinsic factor in the stomach, a key substance for absorbing vitamin B12.

Vitamin B12 levels can also be low in the body of the elderly and in those who have undergone gastric or intestinal reduction surgery, as these people have lower production of intrinsic factor. Those who have Crohn's disease or celiac disease, which are conditions that cause frequent diarrhea, may also have low levels of vitamin B12 in the body.

In addition, the use of medications that block or neutralize the production of stomach acids, or that decrease the production of beneficial bacteria in the stomach and intestines, such as omeprazole and antibiotics, can also decrease vitamin B12 levels, which can cause symptoms such as numbness in the hands and feet and headache. Learn about other symptoms and see how to treat low vitamin B12.

High Vitamin B12

High vitamin B12 in the body is a very rare condition, as the body normally eliminates excess vitamin B12 through urine or sweat, even when taking supplements with high doses of this vitamin.

However, increased levels of vitamin B12 in the body can indicate the presence of some diseases, such as cirrhosis, hepatitis, polycythemia vera or some types of cancer, such as chronic myeloid leukemia. In these cases, it is advisable to go through a consultation with a doctor so that the causes can be evaluated and the appropriate treatment is recommended.

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