Vitamin B12 Guide – Benefits, Top Food Source, Deficiency Symptoms

Vitamin B12 benefits include better brain function, boosts energy, adverts depression, prevents cancer, etc. Even a minute decrease in vitamin B12 level in our body will produce an assortment of conditions like megaloblastic anemia (large, abnormal RBC), subacute combined degeneration (nerve damage), pins and needles sensation, dementia, etc.

While we can overcome anemia and fatigue by taking Vitamin B12 supplements, we cannot reverse certain problems like nerve damage and dementia.


Let’s learn more about this essential vitamin from different perspectives such as top foods, benefits, deficiency symptoms and cause.

What is Vitamin B12?

Vitamin B12 or Cobalamin is a water-soluble vitamin needed in trace amounts in our diet. Usually, bacteria that are present in our gut produce this vitamin.

This is the major source of Cobalamin along with other top vitamin B12 foods such as beef, pork, ham, lamb, poultry, dairy products, and eggs.

Vitamin B12 benefits

1. Improves brain function

A special type of fat called myelin provides insulation for the proper conduction of information in our nerves. B12 deficiency leads to the reduction of myelin production, and thus, nerve conduction is hindered. (1)

B12 keeps a check on homocysteine levels which is associated with the progression of Alzheimer’s disease (a type of dementia) and atherosclerosis (cardiovascular problem).

A link has been established between vitamin B12 deficiency and higher levels of cytokines (mediators of inflammation) leading to deterioration of Alzheimer’s. (2)

vitamin b12 benefits infographic

2. Averts depression

Certain neurotransmitters in the brain like Norepinephrine and Serotonin play a major role in elevating our mood. Research shows that vitamin B12 deficiency reduces the levels of these chemicals in the brain of laboratory rats. (3)

An epidemiological study on 700 disabled elderly women showed that lower B12 levels are directly correlated to depression. (4)

3. Increases red blood cell maturation

B12 enables another vitamin, folic acid, to produce the components of DNA. Red blood cells are created in the bone marrow as large, irregular cells and require Vitamin B9 (folic acid) and B12 (cobalamin) to mature into smaller, disc-like cells.

Mature RBCs have increased capacity to carry oxygen to tissues and hence, keep fatigue and dizziness at bay. Also, their smaller size prevents their breakage, consequently maintaining a steady pool of RBCs.

4. Boosts energy production

After a meal, most of our energy comes from carbohydrates. Three to four hours later, fat and protein become the primary source of energy.

B12 acts as an activator for the functioning of a critical enzyme (a protein which speeds up bodily reactions) in fat metabolism.

Research shows vitamin B12 deficiency is linked to reduced lipid metabolism, eventually leading to exhaustion and tiredness. (5)

5. Reduces the incidence of cancer

DNA or deoxyribonucleic acid is the control center of our cells. Any anomaly in their structure or function will lead to cellular dysfunction and even cancer.

Folic acid (vitamin B9) participates in DNA production, and B12 provides a continuous supply of folic acid in a usable form. Deficiency in either vitamin will cause DNA damage, and as this damage accumulates, cells will get triggered and become cancerous. (6)

Top vitamin B12 foods

1. Beef Liver

Beef liver is one of the most abundant sources of B12. Since it is also rich in vitamin B9 and iron, eating it daily in our diet protects us from nutritional anemia.

You must consume only high-quality beef produced from pasture-raised cows if you want to keep vitamin B12 deficiency at bay.

2. Lamb

Lamb is a rich source of not only vitamin B12 but also, iron, zinc, selenium, and protein. Selenium is an antioxidant and along with zinc, helps to boost our immune system.

Since lamb is not common in the households of the USA, its benefits are not well known.

3. Fish – Sardines, Atlantic Mackerel, wild-caught Salmon

You must keep in mind that Atlantic Mackerel, not King Mackerel and only wild-caught Salmon, not farmed Salmon is an excellent source of B12.

These fish are also rich in omega-3-fatty acids which are required to maintain a healthy heart and alleviate asthma. Salmon is one of the best sources of vitamin D needed to prevent fractures in older women over 65 years. (7)

4. Cheese – Cottage and Feta

Feta cheese is produced from either sheep milk or a mixture of sheep and goat milk. Both cottage and Feta cheeses are a rich source of protein, calcium and vitamin B12.

Feta cheese, having high vitamin B2 (riboflavin) content is also used in the treatment of a migraine. (8) Cottage cheese, along with flaxseed oil, is taken as a part of Budwig diet in cancer patients. (9)

5. Eggs

Eggs, apart from being a source of complete protein (egg white has all the essential amino acids), also contain reasonably high amounts of vitamin B12.

It also provides choline which is necessary for the proper functioning of the liver. However, raw eggs must not be consumed because they may lead to vitamin B7 deficiency in the long run. (10)

6. Nutritional yeast

Deactivated Saccharomyces cerevisiae, a species of yeast, is fortified with vitamin B complex and various essential amino acids; thus, making it an excellent source of these nutrients for vegans.

It’s robust and cheesy taste makes it a substitute for cheese for vegans.

Recommended daily allowance of vitamin B12

According to the National Institute of Health, following is the recommended amount of vitamin B12 to be taken daily. (11)

  • Children 4 to 8 years – 1.2 microgram
  • Children 9 to 13 years – 1.8 microgram
  • Teenagers and adults – 2.4 microgram
  • Pregnant women – 2.6 microgram
  • Lactating women – 2.8 microgram

Vitamin B12 deficiency – cause and symptoms

Causes of B12 deficiency

1.  Malabsorption

Medical conditions causing reduced acid production in the stomach and lower vitamin B12 binding factor production can reduce vitamin B12 absorption. Atrophic gastritis (thinned out gastric mucosa) and a leaky gut are other causes of vitamin B12 malabsorption.

2.  Pernicious anemia

Usually, our stomach releases some factors which bind to vitamin B12 in the food and enable its absorption in the small intestine. In pernicious anemia, the cells producing these factors get destroyed, and absorption of vitamin B12 does not occur.

3. Broad-spectrum antibiotics

Bacteria present in our gut constitute a significant source of vitamins B12, vitamin B7 and vitamin K in our body. Using broad-spectrum antibiotics (drugs that can kill a broad range of bacteria) for a long time will kill these friendly bacteria leading to deficiency of these vitamins.

Vitamin K plays a significant role in clot formation so; we will become more prone to a major blood loss following injury in case of its deficiency.

4. Autoimmune conditions

Inflammatory bowel diseases like Crohn’s disease and Ulcerative Colitis are autoimmune conditions which hinder absorption from the small intestine.

Other immune system disorders like SLE (systemic lupus erythematosus) and rheumatoid arthritis are also associated with vitamin B12 deficiency. (12)

5. Medications reducing vitamin B12 levels

Various medications alter vitamin B12 levels in our body –

  • Proton pump inhibitors like Nexium (esomeprazole) and Prilosec (omeprazole)
  • Oral hypoglycemic like Glucophage (metformin)
  • Anti-seizure medicines
  • Cancer chemotherapy (methotrexate)
  • Bile acid sequestrants

6.      Vegan diet

A diet devoid of animal products like milk, meat, cheese, and eggs will cause vitamin B12 deficiency as these are the primary sources of this vitamin.

Supplemental vitamin B12 in the form of tablets and injections (subcutaneous or intramuscular) can be taken to prevent nerve damage and anemia.

Deficiency symptoms

1. Anemia and fatigue

Lack of either vitamin B12 or folic acid or both will lead to the production of giant, irregular red blood cells, a condition known as megaloblastic anemia.

Being immature, they are not able to carry enough oxygen to tissues causing fatigue and weakness. Also, increased breakage of RBCs reduces their number, further diminishing their oxygen-carrying capacity giving the patient a pale look.

2. Jaundice

Increased lysis of red blood cells releases hemoglobin (oxygen carrier) into the bloodstream. Hemoglobin gets converted into a yellowish-brown pigment called bilirubin in the blood which is usually excreted by the liver in the form of bile juice.

However, excess bilirubin due to increased RBC breakage leads to its accumulation, giving a yellowish tinge to the person’s skin, nails and eyes.

3. Pins and needles sensation

Pins and needles sensation in arms and legs commonly arises due to sensory nerve damage supplying the area. Vitamin B12 plays a vital role in the production of myelin (nerve covering) as well as essential neurotransmitters.

Hence, nerve dysfunction ensues whenever the levels of vitamin B12 fall in our body.

4. Difficulty in movement and balance

Since myelin production diminishes in vitamin B12 deficiency, nerves lose their insulation and this leads to defective nerve conduction. A serious condition called Subacute Combined Degeneration may manifest in chronic vitamin B12 depleted states. (13)


The patient is unable to feel touch, pain, vibration, joint position and temperature changes in the affected areas. Movements become uncoordinated, and the patient is unable to maintain balance while walking.

5. Mood changes

Reduced vitamin B12 levels have been associated with depression (14) which can be attributed to many causes. Lower levels of Epinephrine and Serotonin neurotransmitters in brain destabilize our mood. (15)

Another research states increased homocysteine levels produces toxicity, eventually damaging the neurons in our mind and causing depression. (16)

Points to take home on Vitamin B12

Vitamin B12 has various benefits ranging from red cell maturation and improving brain function to minimizing the threat of cancer. We need it in minute quantities in our diet, and since it’s stored in our liver for several years, its deficiency takes a long time to manifest.

Vitamin B12 deficiency can have dangerous consequences in the form of megaloblastic anemia and nerve damage. Its commonly seen in malabsorption syndromes and with the use of certain medications. We can prevent vitamin B12 deficiency either by taking supplements or eating vitamin B12 rich foods.


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