Vitamin B12: what it’s for, deficiency and foods rich in it

Vitamin B12 is a vitamin fundamental in regulating various functions in the body, and a deficiency in it can lead to serious consequences. Learn more about it! Click To Tweet

Vitamin B12 is a vitamin fundamental in regulating various functions in the body, and a deficiency in it can lead to serious consequences. It is considered essential because the human body is unable to produce it, meaning it comes from the foods we consume. It is found in products of animal origin and fortified plant-based products of plant origin, such as dairy-free milks.

Importance of vitamin B12

Vitamin B12 is involved in various fundamental functions for the body to work correctly, being particularly relevant in synthesising deoxyribonucleic acid (DNA), and plays a fundamental part in energy metabolism.

It furthermore has an essential role in forming blood cell, especially erythrocytes – also known as red blood cells (responsible for transporting oxygen/carbon dioxide) – and in maintaining nervous-system cell integrity.

When it comes to absorbing this vitamin, a protein produced in the stomach – known as intrinsic factor – is needed, which binds to vitamin B12 allowing it to be absorbed in the intestine.

The daily recommended dose intake of vitamin B12 is varies according to life-cycle stage, independent of gender.

Food rich in vitamin B12

 Food products originating from cattle have a high content of this element, namely in the liver. However, it is also found in certain seaweedsThe 10 foods with the highest value of this vitamin per 100g are:

  • Cow’s liver
  • Cockle and clam
  • Pork kidney
  • Mackerel
  • Ousters
  • Sardines
  • Rabbit
  • Sea bream
  • Egg yoke
  • Prawns
  • Cheese

The majority of products of animal origin, such as eggs, milk and derivatives, as well as other types of meat and fish, also offer significant nutritional quantities of vitamin B12, able to meet the daily requirements of this micronutrient. With regard to products of plant origin, and similar to animals, plants do not product vitamin B12, meaning its presence in these products is practically non-existent.

There are nowadays products of plant origin on the market fortified with this nutrient. However, these do not always offer favourable bio-availability, meaning the body’s absorption of vitamin B12 is not as efficient.

Vitamin B12: what it’s for, deficiency and foods rich in it

Consequences of vitamin B12 deficiency

The importance of vitamin B12 for the body to function correctly is undisputed. However, vitamin B12 is stored in the liver for between 2 to 4 years, meaning if someone temporarily stops consuming food with this micronutrient, it is unlikely they will develop a deficiency.

A lack of this vitamin might bring about megaloblastic anaemia and become apparent through fatigue, weakness, difficulty concentrating, loss of appetite and, consequently, weight loss.

In a deficiency situation, it is also possible for disruptions to occur in the nervous system as well as neurological changes.

Which situations can lead to a lack of Vitamin B12?

This vitamin is more lacking in vegetarians than in omnivores. Vitamin B12 deficiency can be found in certain situations caused by decreased intake through good, genetic changes or when it comes to absorption issues, such as:

  • Restrictive diets are eating patterns based on plant-based products.
  • Surgery, such as for instance bariatric surgery and a bowel resection is performed.
  • Deficiency of intrinsic factor production in the stomach, essential for vitamin-B12 absorption.
  • Bowel illnesses, such as Crohn’s diseases and coeliac disease.
  • Prolonged presence of intestinal parasites.
  • High alcohol intake.
  • Age (>65 years) – a reduction in absorption capacity occurs alongside advancing age.
  • Pharmacological therapy.
Vitamin B12: what it’s for, deficiency and foods rich in it

Drugs reducing vitamin B12 absorption

Taking certain drugs that interact with vitamin B12 absorption may lead to this vitamin becoming less concentrated, with the most common being:

  • Proton pump inhibitors – used for treating gastroesophageal reflux disease and peptic ulcers;
  • H2 antihistamines – group of drugs used in treating gastrointestinal ulcers;
  • Metformin – oral antidiabetic, used for controlling diabetes.
  • High doses of folic acid supplements.

It if important to stress that before starting to use nutritional supplements, the deficiency in vitamin B12 must be properly diagnosed, reversed, the underlying cause understood and, if possible, stopped and relapses prevented.

What happens if we take too much vitamin B12?

There is insufficient scientific evidence to demonstrate what the adverse effects might be of continually taking doses of vitamin B12 above those recommended, nor for defining a dose limit, and it presents a low toxicity potential. However, a dose of supplement above that recommended by a qualified healthcare professional.

In healthy individuals, a suitable and balanced intake of foods containing vitamin B12 should be followed in order to maintain normal levels of this nutrient, which is sufficient for meeting the nutritional needs for this nutrient.


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