Vitamin B12: what it is, benefits, where to find it, food

Have you heard of essential nutrients? They are those that our bodies are unable to produce, such as vitamins and some minerals. However, they are necessary for the body to perform various functions and maintain health.

These essential nutrients are ingested through food and have different concentrations in each product. Therefore, having a balanced and diversified meal is essential to consume the necessary substances.

Several nutritionists from food professionals argue that it is possible to find in food all the components necessary to maintain health, and supplementation (with multivitamins) is only indicated when there are deficiencies or problems with food absorption.

Vitamins are organic molecules that act in different functions in the body, allowing different chemical reactions to occur. Even if the human being needs small amounts of them (each type has a different average value), it is not always easy to ingest them, due to the poor quality of the meals.

Studies and surveys show that nutritional deficiencies are one of the biggest problems in the world. And this is not only the case in countries with low economic and social development or in families with lower purchasing power.

Even people who are supposed to eat well may be offering the body a poor quality and variety of nutrients and vitamins. In the latter case, the cause may be due to over-consumption of processed foods and fast foods, for example.

In fact, with the dietary changes that have occurred especially in recent years, the consumption of products that are low in nutrients has led to anemia, weakening of the immune system and obesity .


What is vitamin B12?

Among the nutrients that are most insufficient in the diet, is vitamin B12, which is an important component to maintain the balance and good health of the body. It is part of a group formed by 8 vitamins, called B complex .

Vitamin B12, also known as cobalamin or cyanocobalamin, is an essential micronutrient for the body and has water-soluble behavior (that is, it is capable of being diluted in water).

This means that it is essential for maintaining the healthy functioning of the body, but it cannot be produced naturally, so it must come from dietary sources.

As it is a micronutrient, the quantities that the organism needs are quite small (on average, 2.4mcg is necessary for adults).

In addition to the actions it performs in the body independently (such as the formation of red blood cells and maintenance of the nervous system), B12 is essential for other nutrients to act correctly, as is the case with vitamin B9 ( folic acid ).

Adequate consumption of B12 can help prevent heart disease, nervous system changes and participate in metabolic processes, obtaining energy for the body.

In the same way, improper intake (excessive or insufficient) can cause damage to health. The most well-known alteration is anemia due to lack of B12, but a low-vitamin diet (lacking vitamins) can cause other signs, such as changes in mood, tiredness and changes in metabolism.

In general, it is not difficult to find B12 source products, as the vitamin is present in meat, milk and eggs, as well as products that are industrially enriched with it (such as vegetable or even cow’s milk).

Although the food sources are of animal origin, the nutrient is actually synthesized by bacteria, therefore, foods of plant origin do not have vitamin B12.

The B vitamins

In 1911, researcher Casimir Funk was studying the properties and components of food and identified structures previously unknown. Initially, he called these substances vitamins, which comes from the Latin vita = something as vital, fundamental to life, and amine = derived from ammonia.

Some time later, it was realized that not all vitamins were derived from ammonia, but the name was already popular among scholars and remained so.

Currently, it is known that there are dozens of substances that our bodies need in small quantities, but only 13 of them are called vitamins, as they are considered the most important.

When they started to be isolated, these substances were named with a letter and the criterion was the order of discovery. However, some substances have changed category and lost their vitamin status (that’s why we don’t know vitamin F or G).

However, among them is a vitamin that is actually a group of vitamins: the B complex.

At the beginning of the studies, the researchers believed that it was just the same substance (vitamin B), but after some time the differences started to be noticed, as well as the different actions in the body. So it was necessary to differentiate these components.

The result was the B complex composed of 8 vitamins: thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folic acid (B9) and cyanocobalamin. B12).

In general, these vitamins participate in the breakdown of carbohydrates into glucose, assist in the breakdown of fats and proteins , act on gastric muscles and assist in the absorption of nutrients by the intestine.

Each performs specific functions and generates benefits to the body, but others are still able to work together, that is, helping each other in their organic actions (for example, B9 is only active in the body with the presence of B12).

Remember that, at the beginning, the different B-complex vitamins were confused with a single substance? This is because in addition to the similarity of molecular structures, they are also present in certain foods. For example, meats, vegetables, grains and milk.

Only B12 is present only in products of animal origin, being found in foods such as liver, eggs, meat (red and white) and in milk and dairy products.

How is vitamin B12 synthesized?

Although vitamin B12 is ingested through animal sources (meat, eggs and milk), it is produced by bacteria.

So why should we eat meat and milk, for example, to boost vitamin intake?

It is like thinking that the vitamin is not in the food, but only with it. Animals have these bacteria in the intestinal flora or obtain them when they eat contaminated food (such as pasture). The vitamin is processed by the intestine of the animal and deposited in the tissues. Thus, when the human being consumes the meat, he ends up ingesting the nutrient.

Plants, vegetables and fruits only have B12 if they are contaminated by bacteria, that is, they do not produce it.

We have the bacteria responsible for the production of B12 in the intestine too, however, the amount is very small and the location does not favor the absorption of the nutrient.

B12 inside the body

The main concentration of these bacteria is in the colon (central part of the large intestine), which is after the ileum, which is the final part of the small intestine. But it is precisely in the ileum that the absorption of nutrients occurs. That is, even if it produces some amount of vitamin B12, it is not able to be properly absorbed.

When food reaches the stomach, gastric juice and digestive enzymes separate B12 from proteins. A special enzyme, called the intrinsic factor, binds to the vitamin, providing a kind of protection against degradation (catabolism) until it reaches the intestinal region.

Upon reaching the small intestine, the intrinsic factor is released from B12, causing it to be absorbed and released into the bloodstream, where it will be transported to the cells of the body. In addition, the body is able to store between 3mg and 5mg, and it is in the liver that B12 is concentrated, which may represent between 60% and 90% of all body storage.

Up to half the amount of B12 ingested is not used by humans. In addition, at each meal, our body can only absorb up to 1.5mcg of B12. But take it easy, you don’t have to do a lot of calculations, since the daily average recommendation of the nutrient already foresees this reduction in absorption.

Between us and the animals, there are dietary differences, but also digestive differences. They usually feed on plants directly from the soil, which tend to be contaminated by bacteria.

The digestive tract of ruminants (such as cows) favors that nutrients are produced and absorbed in sufficient quantities for organic needs, due to the various digestive stages.

What is B12 for?

Cobalamin is essential for the proper functioning of cells, especially those in the nervous system, bone marrow and intestine. Among the actions of the vitamin in the body are:

Blood cell formation

There is a direct participation of B12 in the formation, maturation and repair of cells, including red blood cells.

Red blood cells, which are red blood cells, are greatly affected by the action of B12, as the vitamin assists in the correct division of blood cells, preventing them from becoming too large and fragile.

Since red blood cells are responsible for the transport of oxygen, if there are changes in its structure, oxygenation of tissues throughout the body can be compromised.

Helps in DNA repair

B12 indirectly participates in the structuring of DNA, as it acts as a coenzyme in this process. B12 deficiency generates changes in several processes of DNA synthesis, making cell division in the spinal cord difficult.

In pregnant women, B12 is even more necessary, as it is through maternal feeding that the baby will receive the necessary nutrients for its formation. The vitamin is necessary for the correct production of nucleic acid, which is DNA, reducing the risks of future problems.

Absorption and activation of vitamins

Cobalamin participates in the action of other components, such as the conversion of folic acid (vitamin B9) into a bioactive form (that is, capable of acting in the body). Therefore, without B12, the body begins to show folic acid deficiency.

Improves conditioning and gives more energy

In order for you to be able to perform your activities it is necessary that the organism has energy. And they don’t even have to be sports activities or wake up early to run a marathon. Simple activities, such as working, climbing a ladder and watching TV require energy.

If B12 is being ingested properly, your cells and muscle tissues will receive the necessary amount of oxygen (as it helps in the formation of the red blood cells that carry oxygen to the cells), preventing exaggerated tiredness.

In addition, B12 participates in the transformation of carbohydrates into glucose (ie energy). Without the vitamin, muscles have no energy to burn, making any small task exhausting and fatigue constant.

Therefore, B12 helps you to carry out daily activities and facilitates those who are planning to start more intense sports.

Helps metabolize nutrients

Vitamin B12 acts on the metabolism of nutrients such as carbohydrates, proteins and fats. Some studies suggest that weight gain is related to a lack of it, as the vitamin could stimulate metabolism and obtain (or expend) energy.

However, what is really known is that adequate levels of cobalamin help in the correct metabolization of nutrients, but high consumption (through supplementation, for example) does not guarantee results in weight reduction.

People who want to reduce weight can be helped indirectly: as cobalamin helps to give you more energy and prevent tiredness, you are able to do more physical activities and therefore spend more calories.

Assists in the circulatory system

As vitamin B12 helps in the regulation and reduction of cholesterol levels, the entire circulatory system is benefited, causing a reduction in the risks of hypertension and heart problems.

Increases good cholesterol (HDL)

People tend to pay more attention to food and exercise to prevent an increase in LDL (which is bad cholesterol). But HDL, which is good cholesterol, also deserves attention.

A study published in the medical journal Metabolism, Clinical and Experimental, points out that the B vitamins can favor the production of HDL in the liver and small intestine.

This favors the synthesis of vitamins and hormones, reduces the risk of the formation of fatty plaques in the arteries and, consequently, reduces the chances of a heart attack or stroke.

Healthier nervous system

It is observed that patients with Alzheimer’s disease have a higher prevalence of hypovitaminosis B12, suggesting that the nutrient may participate in the functioning of the nervous system.

Although studies on the relationship between Alzheimer’s and B12 are ongoing, it is already known that the vitamin protects neurons and can reduce neuronal degeneration.

Homocysteine ​​reduction

Homocysteine ​​is an amino acid produced after the digestion of some foods, such as red meat and dairy products.

After digestion, the amino acid is sent into the blood and, in large quantities, can increase the risk of clogging the arteries and accumulation of fatty plaques in the blood vessels (causing atherosclerosis ).

B12 assists in the correct metabolism of homocysteine, preventing it from being concentrated in the blood and, therefore, minimizing health risks.

Benefits of B12

Vitamin B12 has several functions and participates in different processes in the body, but in addition, it can have indirect actions on the body and on the well-being of the patient.

It is important to note that studies on the benefits of B12 do not offer unanimous results on all the actions and shares of the vitamin.

Below you will find some improvements that are possibly promoted by ingesting and supplementing B12.

Improves sleep

A study published by the neuropsychiatric center at Akita University School of Medicine suggests that B12 may help anyone who is struggling to sleep or stay asleep.

In addition to facilitating sleep induction (that is, it helps you and sleep), the correct rate of B12 improves its stability, so you wake up less during the night.

Stabilizes the mood

According to the website of Hospital Sírios Libanês, the lack of B12 can have a major impact on cognitive and mood functions. Therefore, restoring and maintaining rates can help with emotional stabilization, reducing or ameliorating symptoms of depression , anxiety , agitation, stress and avoiding sudden changes (for example, patients who go from euphoria to lethargy in a few hours).

Increases mood

In addition to being related to obtaining energy, vitamin B12 is an important component for the absorption of other nutrients, resulting in anemia.

To be more willing, the body must have access to all nutritional sources and be able to use them correctly. Therefore, supplementing B12 can provide more energy and disposition for daily activities.

Strengthens muscles

Those who practice physical activities, whether light or intense, need strong and conditioned muscles to cope with the exercise. B12 acts on the nervous system making communication with muscles more effective. That is, you will perform the physical movements more accurately, reducing the risk of injury and improving the results.

Assists in memory and concentration

Adequate cobalamin intake favors mental aspects related to reasoning, memory and concentration, in addition to reducing the damaging effects of stress on the brain and the risks of depression.

Improves immunity

Nutritional food and intake play an essential role in maintaining immunity and vitamin B12 participates in the synthesis of important substances to maintain health.

By increasing immunity, the risk of disease is reduced and, when they occur, recovery is more accelerated.

Benefit to fabrics

Have you noticed that your hair, nails and skin look less healthy or weakened? It may be lack of B12.

As the vitamin promotes the reproduction and replacement of cells, the body’s tissues are greatly benefited. The nails are strong and resistant, the hair has less fall and the skin is more resistant.

Male fertility

For men, B12 can improve the amount of sperm. Among the factors that can make fertilization difficult is the low quantity or quality of semen.

Protects the heart

B12 helps to minimize the risk of heart disease by reducing homocysteine.

But to have a healthy heart, it is necessary that proper habits are followed, such as the practice of physical activities. Remember that the vitamin also participates in the processes of obtaining energy? So you adopt a much healthier lifestyle for your heart.

However, there are studies that indicate that, although B12 decreases homocysteine ​​levels, the risks to the heart are not reduced, as suggested by the studies of the Heart Outcomes Prevention Evaluation (HOPE), published by the medical journal Journal of the Renin-Angiotensin -Aldosterone System.

It can reduce pain

In addition to stress, vitamin B12 can help control headache attacks, reducing or preventing headaches.

In addition, a study carried out in 2010 indicates that the vitamin has anesthetic effects, decreasing the pain in cases of low back pain, sciatica, trigeminal neuralgia, facial paralysis and optic neuritis.

In patients with pain due to external causes (such as fractures, burns and injuries), the vitamin decreases the reception and perception of pain, improving the recovery of the condition.

Reduces cancer risks

According to a study by the Linus Pauling Institute of Oregon State University, in the United States, B12 can decrease the risks of chromosome changes, causing less damage to DNA molecules. DNA changes are one of the factors that can cause cancer .

May favor (indirectly) weight reduction

There are studies that indicate the action of B12 in reducing weight or accelerating metabolism.

You may have heard about the relationship between nutrient and weight reduction through some recent diets released by celebrities, such as Madonna and Katy Perry, who adopt vitamin supplementation to compose meals or replace some foods.

However, other research shows that the nutrient only helps in the metabolism of fats and proteins, participating in digestion and obtaining energy. Therefore, ingesting higher doses than recommended or supplementing meals even with the appropriate rates, would not bring benefits (neither to the body, nor to weight loss).

Health and nutrition professionals indicate that there is no evidence that B12 is directly related to weight loss. It can improve mood and energy, favoring greater caloric expenditure, but it cannot be said that supplementing the vitamin will speed up metabolism to the point of causing weight reduction.

But, it is emphasized that, every weight loss process must be done with adjustments in the diet and practice of physical activities. So, having an adequate intake of all vitamins and nutrients promotes healthier weight reduction.

Good for the elderly

Research carried out by the Department of Physiology, Anatomy and Genetics at the University of Oxford, England, points out that the elderly who intensified their consumption of B12 in the long term had less brain damage due to age over the 2 years of the study.

B12 during pregnancy

The nutrients ingested by the pregnant woman are essential for the baby to form properly and be born healthy. B12, along with folate and iron, plays a key role in reducing the risk of miscarriage, premature birth and the formation of baby’s tissues.

Research from the University of Warwick, UK, points out that low B12 intake during pregnancy may increase the baby’s risk of developing type 2 diabetes and other metabolic diseases.

In 2016, the study analyzed blood, adipose and placental tissue samples from mothers and children. The results indicate that the lack of the vitamin may be linked to the baby’s leptin changes.

Leptin is responsible for the perception of satiety and, with its increase, the risks of insulin resistance are greater, causing type 2 diabetes (which may develop years later).

Ideally, women should monitor B12 levels before becoming pregnant and adjust their meals. During the 9 months, it is necessary to reinforce the intake of vitamin sources and carry out medical and nutritional monitoring, making supplementation or dietary adjustments according to the guidelines of the professionals.

B12 deficiency

The reference value of B12 is between 200pg / mL and 900pg / mL. However, the classifications of vitamin insufficiency vary widely according to each researcher or laboratory.

While there are studies that suggest a deficiency below 200pg / mL, others indicate that up to 500pg / mL can already be considered a low value.

The values ​​should then be evaluated with your doctor who will also consider the presence of symptoms and other nutritional deficiencies, checking the need to readjust the diet or start supplementation with B12.

It is estimated that about 40% of the world population has low amounts of B12. However, this deficiency does not always present symptoms and is often never diagnosed.

As with other nutritional deficiencies, the lack of the vitamin can cause damage to the body, hinder the proper functioning and cause health complications. It is worth mentioning that B12 stocks are, in general, durable, so even if there is no daily consumption of the vitamin, the organism’s rates can remain stable.

When performing blood tests, the reference values ​​generally used by laboratories are:

  • Severe deficiency : below 150 pg / mL;
  • Deficiency : between 150pg / mL and 200pg / mL
  • Possibility of deficiency : 200pg / mL and 300 pg / mL
  • Normal levels : between 300pg / mL and 900 pg / mL
  • Hypervitaminosis : above 1000pg / mL

Symptoms of lack of B12

The symptoms of low levels of B12 are widespread and do not always allow them to be associated with hypovitaminosis. But there are usually changes in mood (tiredness and weakness), neurological signs (numbness and tingling in the hands and legs), as well as anemia.

In general, the first signs can involve constant tiredness, mood swings, reduced immunity and inflammation of the mouth. If levels continue to drop, reaching severely low values, the body’s functions are affected, with a reduction in DNA synthesis and an increase in homocysteine ​​in the blood.

Other symptoms can occur, such as:

Psychological symptoms

Low B12 rates can impact emotional and nervous well-being, with:

  • Irritability;
  • Difficulty concentrating;
  • Memory changes;
  • Sudden changes in mood;
  • Depression and severe anxiety;
  • Lethargy;
  • Mental confusion;
  • Hallucinations.

Physical symptoms

The physical signs that the patient may present involve:

  • Drop in immunity (leaving the patient more prone to flu and infections);
  • Frequent tiredness, even without great efforts;
  • Weakening of nails and brittle hair;
  • Pallor;
  • Ulcerations in the mouth (small whitish wounds);
  • Inflammation in the mouth and stomach pain (due to gastrointestinal ulcers);
  • Megaloblastic anemia (increase in the volume of red blood cells);
  • Pains and tingles in the arms and legs;
  • Difficulty moving;
  • Dizziness and dizziness;
  • Heart attack;
  • Stroke;
  • Difficulty and reduced vision;
  • Urinary and fecal incontinence;
  • Fertility problems;

What can cause B12 deficiency?

When it is difficult to absorb the vitamin or the food is not able to meet the needs, the concentration of B12 in the body begins to be reduced.

The liver then releases the stored nutrient, replacing the substance so that the body’s functions are not affected. However, if there is no replacement through food, this stock will also be depleted, causing symptoms to begin to appear.

The manifestation of a lack of B12 may vary between each patient. Some may take up to 7 years for liver supplies to run out and symptoms to begin to appear.

One of the problems with B12 insufficiency is that the organism is inserted in a vicious cycle. That is, the lack of B12 causes symptoms (such as anemia) that interfere with the absorption of the vitamin itself, causing the condition to be even more aggravated.

Despite being a nutrient acquired through food, low intake of cobalamin is the smallest cause of deficiency, and the factors that most trigger the reduction of B12 are:

Nutrient absorption problems

When there are gastrointestinal changes that hinder the absorption of nutrients, B12 can be greatly affected.

For example, inflammation of the stomach or intestines can interfere with the correct degradation of nutrients, being quite common in the elderly and people who use alcohol and drugs, as they can trigger changes in the intestinal flora or gastric juice.

Atrophic gastritis

The gastritis atrophic reduces the production of an enzyme called intrinsic factor. The lack of this enzyme makes it difficult to transport B12 to the intestine, causing absorption inefficiency.

Patients with atrophic gastritis are more likely to develop pernicious anemia , which occurs when red blood cells (red blood cells) are not produced properly and die quickly, due to a lack of intrinsic factor.

In cases of gastric atrophy, there may be a facilitation for the reduction of cobalamin levels, but studies suggest that the atrophy of the stomach walls alone is not enough to cause B12 hypovitaminosis.

Pancreatic disorders

When there are changes in the functioning of the pancreas, there may be a decrease in the secretion of substances essential for the absorption of B12, preventing the correct use of the nutrient.

Zollinger-Ellison syndrome

The syndrome is characterized by the exaggerated stimulation of gastric juice secretion, which can cause severe ulcers, tumors in the stomach and changes in stomach acidity.

As there are changes in digestion, the absorption of B12 can be impaired in the intestine.

Increased growth of bacteria in the intestine

The high amount of bacteria in the intestine can also be the cause of B12 deficiency, especially in the elderly, where there is a high prevalence of the proliferation of bacteria in the intestinal region.

In this case, there may be a reduction in absorption or even causing B12 to be consumed by infectious agents.

Acquired immunodeficiency syndrome (AIDS)

Cobalamin is present in low levels in most of the patients with acquired immunodeficiency syndrome ( AIDS ), due to the possible failure in the absorption of the nutrient in the intestine region.

Surgical procedures

The patient who underwent bowel surgery may have impaired absorption due to changes in the organ’s structure. In addition, gastric surgeries (such as stomach reduction) can interfere with the production of intrinsic factor and impair the transport and absorption of cobalamin.

Hereditary disorders

Uncommon, hereditary disorders can cause B12 malabsorption, including congenital transcobalamin II deficiency or failures in cobalamin absorption.

Use of some medications

There are drugs that can cause B12 deficiency through malabsorption, such as metformin (used to control diabetes) and stomach acid reducers (such as omeprazole and ranitidine ).

Vegan or low B12 diets

Although cobalamin deficiency is little associated with eating habits, it is still possible that this is the cause of hypovitaminosis, especially in vegan diets (as they are free from all products of animal origin).

How much B12 should we consume?

The consumption of B12 is determined through a somewhat complex account, as our body has a limited absorption of the vitamin at each meal. That is, even if you take a large dosage, about 1.5mcg can be absorbed.

In general, our intestines need to carry 1mcg of vitamin B12 into the blood for the day to supply cellular needs. However, it is not enough to consume this amount through food, as the body can absorb an average of 50% of what is consumed.

That is, if you drink 2 glasses of milk with 2mgc of B12, only 1mcg will be used.

The ideal average values, then, are double the need of the organism (1mcg) and another safety margin. To facilitate the bill, the consumption indications already make that bill. The suggested values ​​of B12 for each age are:

  • 0 to 6 months : 0.4mcg / day;
  • 6 to 12 months : 0.5mcg / day;
  • 1 to 3 years : 0.9mcg / day;
  • 4 to 8 years : 1.2mcg / day;
  • 9 to 13 years : 1.8mcg / day;
  • Above 14 years : 2.4mcg / day;
  • Pregnant women : 2.6mcg / day;
  • Lactating : 2.8mcg / day.

Groups of risk

Some factors can favor B12 deficiency, such as:


Although age, in itself, does not cause a lack of vitamin cobalamin, it is estimated that approximately 60% of people over 60 have low levels of B12.

The most likely factor for this prevalence is that aging usually causes changes in gastric secretions or changes in the intestinal tract, making it difficult or reducing the absorption of the nutrient.

In addition, if the person has not eaten a balanced diet during his life, it is possible that the stocks of B12 have been depleted over the years and the signs begin to manifest.

Changes in diet, lifestyle and quality of meals caused by age (such as avoiding food due to difficulty in chewing) may favor hypovitaminosis.

People with pernicious anemia

Patients with pernicious anemia tend to have B12 deficiency due to the lack of intrinsic factor, which is essential for the transport of the nutrient to the intestine.

Vegans and Vegetarians

Due to a more restricted diet, people who adopt vegan or vegetarian diets may be deficient in B12. About 40% of these patients have lower levels of the nutrient.

Pregnant and Lactating

During pregnancy, it is necessary that the woman’s nutrition is well balanced and all the necessary nutrients are ingested. In addition to improving the mother’s well-being, this favors the proper formation of the baby, avoiding health risks.

Breastfeeding mothers also need to pay attention to the nutrients ingested, as it is through maternal feeding that the baby will receive the nutrients and strengthen the immune system.

Use of some medications

Patients who make continuous use of drugs that regulate the acidity of the stomach may have their enzymes and stomach substances modified, interfering with the transport and metabolism of nutrients.

In addition, the use of antibiotics can alter the intestinal flora and hinder the correct absorption of cobalamin. The use of omeprazole , H2 blockers, cholestyramine , colchicine and neomycin may alter absorption.

Tests to check B12

Tests to measure B12 concentrations are not always part of people’s routine, being ordered only when the patient notices the symptoms.

When B12 anemia is suspected or insufficient absorption, complete blood count , vitamin B12, iron and folic acid tests may be ordered.

These tests are carried out through the traditional collection of blood or urine and may point out cases of anemia due to B12 or other types, such as anemia due to lack of iron.

Blood count

The test is ideal for assessing the amount and size of red blood cells in the blood. Some anemias can cause blood cells to have a high volume and therefore die quickly, being called megaloblastic anemia.

However, not all anemia due to a lack of B12 causes changes in red blood cells, so the test should be complementary to the diagnosis of a lack of B12.

Dosage of B12

It is the most used test to measure the sufficiency of the vitamin in the body. There is no consensus on the ideal values ​​for the B12 exam. Laboratories stipulate as sufficient results between 211pg / mL and 900pg / mL, however, this figure is quite comprehensive.

Some researchers argue that patients with a result of 211pg / mL cannot be compared, in terms of health, to patients with 900pg / mL, as these are very distant values.

Therefore, there are professionals who indicate ideal results above 490pg / mL, as it would be a safe margin against vitamin deficiency.

Methylmalonic acid

When B12 is deficient, methylmalonic acid is elevated. The test can be done by collecting blood or urine.


Homocysteine ​​is also elevated when there is B12 deficiency, however, there are other factors that can alter the results, such as hypothyroidism , kidney disease or psoriasis , so the results must always be evaluated by a doctor.


Some conditions can develop due to the lack or deficiency of B12, among them:


Neuropathy is a disease that affects the nerves and can manifest pain, tingling, reduced sensitivity and numbness of the limbs.

Megaloblastic anemia

Without B12, the formation of red blood cells is impaired, causing a decrease in blood concentration. Red blood cells (red blood cells) are larger than normal and thinner membranes, making them more sensitive.

The result is that they die earlier and, therefore, the concentration of these cells in the blood decreases. Without red blood cells, the distribution of oxygen throughout the body is also affected, resulting in various dysfunctions and symptoms (such as tiredness, weakness and dizziness).

Accumulation of fatty plaques

The lack of B12 can cause the improper concentration of fatty or fibrous plaques on the blood vessel wall. Over time, the condition causes the diameter of the vessels to decrease and impairs blood flow, which can be completely blocked.

Permanent neuropsychiatric manifestations

Prolonged and severe B12 deficiency can result in permanent neuronal and psychological changes.

The frames of reduced memory and concentration can be aggravated, causing the condition not to recover even after cobalamin stabilization. Symptoms such as numbness in the limbs and tingling may also persist.

Malformation of the neural tube in babies

If the pregnant woman has B12 deficiency, the condition can impact the baby’s formation. This is because hypovitaminosis is able to alter the formation and closure of a structure called a neural plaque.

This plate, after properly formed, will compose the spine and the brain. Therefore, in the absence of nutrient B12, serious damage to the child can occur, such as paralysis of the lower limbs.


Psychological conditions may present or worsen in the absence of B12. Symptoms such as irritability, anxiety and constant mood swings are common among patients.

In these cases, depression is the psychological disorder that has the highest prevalence, with a marked degree of worsening.

Vitamin B12 and vegetarianism or veganism

Nutrient deficiency is strongly associated with dietary restrictions, especially vegetarian or vegan diets.

There are variations in vegetarian diet, such as ovolactovegetarian and lactovegetarian (in which only eggs and milk are also excluded), but in general it is meat that is no longer consumed. Vegans do not consume any products of animal origin (including leather clothing, cosmetics that test animals, for example).

As vitamin B12 is present mainly in meat and animal foods, such as eggs and milk, there is a concern about the adequate intake of the nutrient.

According to the SBV (Brazilian Society of Vegetarianism), people who choose to live a vegetarian or vegan life must be aware of nutritional deficiencies and, if necessary, carry out vitamin supplementation.

It should be noted that any dietary change must be accompanied by a nutritionist or nutrologist, in order to adapt meals and offer the necessary nutrients to the body.

Although vegan and vegetarian meals are more restricted in relation to B12, those who adopt this lifestyle are generally more attentive to food health. As the probability of vitamin insufficiency is already known, patients tend to undergo exams more frequently and, therefore, treat dietary deficiencies early.

The same is not always the case with people who do not have dietary restrictions, as many do not undergo medical monitoring or perform periodic examinations.

There are recommendations for vegetarians and vegans to increase their consumption of bean sprouts , fermented soybeans, peas, lettuce, peanuts, whole wheat, alfalfa, raw and fermented tubers, as they are usually in direct contact with the land and, therefore, have contamination by bacteria.

But the risk of infection by parasites is also high and the consumption of these products without the correct cleaning or cooking is not a consensus among professionals and adepts of veganism.

The most recommended for people adept at veganism is the use of supplementation, if necessary. For vegetarians, it is possible to increase the intake of milk and eggs, especially products that are enriched with vitamins.

Vitamin B12 replacement

You can reinforce the meal with the most adequate consumption of vitamin B12 or, if necessary, supplement it.

To maintain rates

If the amounts of B12 are adequate, feeding should be planned in order to keep rates stable. In this case, the reinforcement can be through food and it is indicated that you split the consumption, as the body is able to absorb only 1.5mcg of B12 every 4 or 6 hours.

This is because there are receptors in the intestine that block the vitamin from entering in larger quantities. That is, consuming a meal rich in cobalamin in one go is likely to be ineffective.

To give an estimate, 1 glass of milk reinforced with vitamins offers 1mcg for every 200mL. So it is necessary to ingest about 650mL of the product per day to reach the recommended amount of B12 (2.4mcg).

To raise levels

If the tests indicate a lack of vitamin B12, it is necessary to raise the rates, which is done through injectable or oral supplementation.

Treatment must take into account the test results and the patient’s symptoms. In general, oral treatment offers good responses from the body, as long as it is prescribed and followed correctly.

When the patient has very low levels of vitamin B12, the recommended dosages start with an attack application of 1,000mcg, intramuscularly, and a monthly reapplication until the values ​​are restored.

The oral dose is 1,000mcg to 2,000mcg daily.

But you may wonder how supplementation at high doses can work if the body cannot absorb large doses at each meal.

To understand how it works, think that the vitamin is absorbed up to approximately 1.5mcg without difficulty. After that, a barrier is formed that prevents higher doses from being absorbed.

If you take an overdose, it is as if a crowd of B12 forces the barrier, causing it to break and the high doses of vitamin to be absorbed.

Price and where to find B12 supplements

B12 replacement should be indicated by a doctor or nutritionist, because although there are no high risks of cobalamin intoxication, all nutritional intake must be monitored by professionals.

It is necessary to remember that vitamin injections need a prescription to be applied. Oral supplements, on the other hand, can be purchased at commercial or handling pharmacies, according to the instructions of your doctor and your preferences.

In general, the B12 can be found in the price range between R $ 15 and R $ 50 reais, including:

  • Citoneurin (especially indicated for the elderly);
  • Cronobê;
  • Calcitran B12.


NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

What foods contain vitamin b12?

Foods with B12 are great allies of balanced nutrition. They can meet the recommended daily needs of healthy people, reducing the need for supplements or multivitamins. Some have large sums and are part of the diet of many people. Among the richest options in B12 are:

  • Liver steak: 83.1mcg every 100g;
  • Mussels: 24mcg every 100g;
  • Lean steak: 8mcg every 100g;
  • Salmon: 2.8mcg for every 100g;
  • Egg: 2mcg per 100g (approximately 0.4mcg per unit);
  • White cheese: 1.8mcg for every 100;
  • Enriched rice milk: 1mcg every 200mL;
  • Skimmed milk: 0.75mcg every 200 mL;
  • Natural yogurt: 0.53mcg every 100g.
  • Chicken: 0.35mcg for every 100g.

But what is in the nutritional table is not always what we eat, as B12 is sensitive to heat. Therefore, if you use these products in preparations or recipes that require high temperatures (such as roasts or fried foods), the nutritional quantities can be considerably reduced.

It is pointed out that milk, eggs and derived products have a better absorption of the nutrient, because there may be a direct relationship between the ease of digestion of the meal and the absorption of B12.

That is, as meats tend to be processed and degraded more slowly, the vitamin can undergo changes in the use as well.

How to include food in meals?

Do you remember that there is a limit on the absorption of cobalamin every 4 or 6 hours? This amount is approximately 1.5mcg, causing the rest of the nutrient to be discarded.

So the ideal is to split the food and consume portions of these foods source of B12 at each meal.

People without vegetarian or vegan restrictions should plan their diet by inserting sources of B12 throughout the day. For example:

  • Breakfast: 2 eggs (0.8mcg of B12);
  • Lunch: 1 serving of meat (8mcg of B12);
  • Dinner: wholemeal bread sandwich with white cheese or 1 vitamin with milk enriched with B12 (approximately 1mcg each).

Vegans or vegetarians, on the other hand, can balance meals with foods suitable for the diet, adding to the supplementation with pills.

You can insert foods prepared with vegan milks enriched with B12 (soy, rice or almonds, for example), preparing meals such as vitamins, homemade pasta and vegan cheeses.

It is recommended to eat at least 3mcg of vitamin 2 twice a day. In addition, if the diet does not meet the ideal dosages or the person chooses to take formulations, nutrition can be supplemented with the use of supplements of 10mcg per day or 2,000mcg per week of B12.

Too much vitamin B12

In general, vitamin B12 presents hypervitaminosis only in patients who use supplementation at considerably high doses. Still, pictures are uncommon.

Among the consequences of high blood dosages may be:

  • Tingling in the hands and feet;
  • Muscle cramps and spasms;
  • Headache;
  • Sickness;
  • Increased blood pressure;
  • Excessive tiredness;
  • Change in respiratory rhythm;
  • Difficulty sleeping;
  • Vasodilation;
  • Allergic reactions, such as redness of the skin;
  • Mood swings.

In general, the suspension of supplementation is sufficient to reduce the rates and in a short time the patient is already able to notice the improvement of the symptoms.

Approximately 8% of patients undergoing cobalamin replacement may experience accumulation of the nutrient, and there is an association with the following causes:

  • Exaggerated vitamin supplementation;
  • Hepatocarcinoma (presence of cancer in the liver);
  • Chronic myeloid leukemia;
  • Hepatical cirrhosis;
  • Autoimmune lymphoproliferative syndrome.

Common questions

Why are there vegan people who do not suffer from B12 deficiency?

With regard to vitamin B12, our body can be quite economical, making the stock last for long periods. Even if a person does not ingest any cobalamin source products, they may never experience (or notice) drastic drops in the vitamin.

In addition to vitamin stores, our body can reuse the B12 present in bile secretions, which contains between 1mcg and 10mcg of the substance. In this case, the substance is absorbed again by the intestine.

It is important to remember that hypovitaminosis does not always trigger symptoms and as B12 participates in several functions of the organism, relatively low values ​​(but which are still not considered insufficient) can affect the proper organic functioning.

When should I replace vitamin B12?

All nutrients should only be supplemented with medical or nutritional guidance. Based on tests that indicate low vitamin levels, whether due to diet or other problems, or when there are other organic disorders, the use of supplements may be necessary.

Do algae, fermented foods and brewer’s yeast contain B12?

Contrary to what is spread, foods such as miso, shoyo, tempura, beer yeast and biologically fermented breads do not represent safe sources of B12 and should not be used as a nutritional resource of the vitamin, according to the Brazilian Vegetarian Society (SVB).

In addition, foods such as nori, chlorella, wakame, hiziki, kombu, spirulina and other algae do not contain B12, but they can produce a similar (analogous) form to the vitamin. Only this similar substance is inactive, that is, it is not processed by our organism.

Read more: Spirulina: what it is for, benefits and harms and how to use

There are studies that even indicate a harmful factor in the use of these products as sources of B12, since the analogous form of B12 can act as a competing component with the active vitamin. Thus, an even greater reduction in the vitamin rate may occur.

Although some products can be consumed without great risks, using them as B12 supplements requires a high intake. In that case, yes, there may be changes in the body.

Failure to wash or sanitize food can increase the amount of B12 in vegetables?

There are some beliefs that eating food without washing could increase the amount of B12, as it would be a process similar to the intake of the nutrient by animals. Since animals eat food directly from the soil, keeping them dirty could be beneficial and serve as a resource for obtaining B12.

However, the practice in addition to not increasing the concentration of cobalamin in the product (or increasing it very little), can be quite bad for the body and cause diseases or infections, such as cysticercosis.

Care with food is essential to maintain the body’s balance and prevent disease.

Vitamins are necessary nutrients for different functions and must be part of the daily diet. However, there are other factors that can alter the correct food absorption.

Therefore, it is necessary to carry out examinations, make food planning with a nutritionist and always be attentive to the body’s signs.

For more food tips, keep an eye on our blog!