Vitamin B12 101: Benefits, Sources causes of deficiency, & More.

Our content is not intended nor recommended as a substitute for medical advice by your doctor. Use for informational purposes only.

1. What is vitamin B12?

Vitamin B12 is an essential vitamin that humans cannot produce and must be obtained from outside sources.

Vitamin B12 is essential for many body functions. The three most important functions of vitamin B12 are:

  • Development and function of the nervous system
  • Healthy Red blood cells.
  • DNA synthesis.

Vitamin B12 malabsorption is the most common cause of vitamin B12 deficiency.

The process of vitamin B12 absorption is

2. Sources.

Vitamin B12 is found mainly in foods of animal origin. Most fruits and vegetables are deficient in vitamin B12.

Patients who are strict vegetarians are at higher risk of developing vitamin B12 deficiency. 

The following are the essential sources of vitamin B12:

  • Foods of animal origin: The highest concentrations are liver, calms, and tuna.
  • Dairy products: Like milk, yogurt, and cheese.
  • Eggs.
  • Fortified breakfast cereals and nutritional yeasts: Many brands in the United States add vitamin B12 to cereals and nutritional yeasts. The added vitamin B12 is readily available and better absorbed than food sources.
  • Supplements: available in oral, sublingual, nasal spray, and injection forms.

A balanced diet in healthy individuals will provide sufficient vitamin B12.

The below table includes selected sources of vitamin B12 and their content (reference).

The highest source of vitamin B12 is beef liver (it contains vitamin B12 amounts that are 29 times the recommended daily value).

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B12 SOURCEX of Recommended daily value.
Beef liver, cooked (3 ounces)29X
Clams, cooked (without shells), (3 ounces)7.1X
Tuna, bluefin (3 ounces)3.9X
Nutritional yeast, fortified (1/4 cup)3.5 to 10X
Salmon, Atlantic, cooked (3 ounces)1.1X
Beef (3 ounces)1X
Milk (2% fat), one cup0.5X
Yogurt (6-ounce container)0.4X
Fortified Breakfast cereals (with 25% of DV for one serving)0.25X
Egg, whole, cooked0.2X

3. Benefits of Vitamin B12:

The main three functions of vitamin B12 are:

  • Supports the development and normal function of nerve cells.
  • Needed for Red blood cell formation.
  • Required for DNA synthesis.

The major benefits of Vitamin B12 include:

  • Helps red blood cell formation and function. Its deficiency leads to anemia.
  • Necessary for a healthy pregnancy and prevents birth defects.
  • Supports brain and nerve function and prevents the loss of nerve cells.
  • May improve depression and mood.
  • May protect your eye against certain diseases such as macular degeneration.
  • May improve heart health.
  • May support healthy hair, nails, and skin.

Learn More.

4. Causes of Vitamin B12 deficiency.

In the United States and the United Kingdom:

  • About 6% of adults younger than 60 years have vitamin B12 deficiency.
  • About 20% of those older than 60 years have vitamin B12 deficiency.

Who is at higher risk of vitamin B12 deficiency:

  • Older adults: the elderly are at higher risk because of the high prevalence of conditions such as pernicious anemia, atrophic gastritis, and H. Pylori infection
  • Individuals with Pernicious anemia: A type of autoimmune disease that leads to atrophy of the gastric lining (stomach mucosa secrets the “intrinsic factor,” which is essential for absorbing vitamin B12).
  • Previous stomach or intestinal surgery: Such as people with gastric cancer surgery.
  • Vegetarians: The primary source of Vitamin B12 is animal protein. Strict vegetarians are at higher risk of vitamin B12 deficiency.
  • Infants born to vegetarian mothers.
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The leading cause includes:

  • Decreased intake (as with strict vegetarians).
  • A lack of the intrinsic factor (secreted by the stomach mucosa) as with pernicious anemia.
  • Lack of gastric acid (HCL) as with prolonged proton pump inhibitors).
  • Previous gastrointestinal surgery (especially those with the removal of parts of the stomach or the small intestine).
  • Prolonged use of medications such as metformin, omeprazole, pantoprazole, Esomeprazole, etc.

5. Symptoms and complications of deficiency.

Your body stores as much as 1000 to 2000 times the amount of vitamin B12 you need in a day. So, the symptoms of vitamin B12 deficiency can take several years to appear (reference).

Symptoms and complications of vitamin B12 deficiency include:

1 . Megaloblastic anemia (Rare, With extreme poverty).

A type of anemia characterized by large abnormal Red blood cells. Anemia causes symptoms such as:

  • Headache and dizziness.
  • Shortness of breath (especially with exertion).
  • A sense of fast heartbeats.
  • Lack of concentration.
  • Easy fatigue and generalized weakness.
  • Lightheadedness.
  • Chest pain.
  • Tongue pain and redness (glossitis).
  • Weight loss.
  • Numbness and tingling of the hands and feet.
  • Jaundice (yellowish skin and eye whites).

2. Neurological symptoms (with or without anemia) (Also rare).

  • Tingling and numbness of the hands and feet.
  • Dementia.
  • Depression.
  • Major neurological birth defects in infants born to vitamin B12 deficient mothers.
  • Impaired growth and development of the babies born to vitamin B12 deficient mothers.
  • Abnormal gait (walking).
  • Behavioral changes.

3. Others:

  • Heart failure due to anemia.
  • Risk of gastric (stomach) cancer.
  • Risk of autoimmune diseases such as Type 1 diabetes, Rheumatoid arthritis.

Treatment of Vitamin B12 Deficiency.

The following are the most important facts and tips about treating vitamin B12 deficiency.

  • Vitamin B12 is available in multiple formulas (oral supplement, sublingual tablets, oral patches, nasal spray, and injections).
  • The choice of which type of supplement you need depends on the cause of the deficiency.
  • For example, oral supplements are enough for strict vegetarians. In addition, injections and sublingual formulas are suitable for those who have conditions causing vitamin B12 malabsorption (such as pernicious anemia).
  • The dose and the duration of the vitamin B12 supplement depend on the severity and the cause of the deficiency.
  • For example, People who have malabsorption (intrinsic factor deficiency or pernicious anemia) will receive 1000 Micrograms (mcg) intramuscular every week in the first month, then once every month.
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