Vitamins are essential nutrients that the body requires in small quantities daily from our diet, since the body can’t make them.  Vitamins are classified in two broad categories, namely fat soluble, such as vitamins A, D, E, and K, or water soluble, such as the rest of the vitamins (B complex and C).

Most of the vitamins have several important functions and are involved in diverse biochemical functions.  For example, vitamins A and D have hormone-like functions, while others such as Vitamin E and C have antioxidant functions, while the B group of vitamins functions primarily as enzyme helpers, called coenzymes, which are needed for enzymes to function.

B vitamins:

The B group of vitamins, also referred to as the B complex, are a group of eight essential nutrients obtained from our diets, which play roles in many organs and biochemical processes taking place in the body.  B vitamins work together in the body, although they also have their own unique functions.

The main functions of B vitamins are to assist with converting food into energy (metabolism), helping to create new blood cells, helping to make sure the cells in the body function properly, and helping to maintain healthy skin cells, brain cells, and other tissue in the body.

The eight essential nutrients that make up the B complex, with their main functions are:

  • Vitamin B1 (thiamin) – plays a role in metabolism as it helps to convert nutrients from food into energy.
  • Vitamin B2 (riboflavin) – also plays a role in converting nutrients into energy (metabolism), particularly to break down fats, and acts as antioxidant.
  • Vitamin B3 (niacin) – plays a role in metabolism, cellular signaling, maintaining healthy skin, as well as in DNA production and repair.
  • Vitamin B5 (pantothenic acid) – plays a role in metabolism, the production of hormones and cholesterol, and in the health of the brain and the nervous system.
  • Vitamin B6 (pyridoxine) – plays a role in amino acid metabolism, the production of red blood cells, supporting the immune system, and in creating neurotransmitters.
  • Vitamin B7 (biotin) – plays a role in metabolism of fat and carbohydrates, the regulation of gene expression, and is essential for healthy hair and nails.
  • Vitamin B9 (folate) – plays a role in amino acid metabolism, cell growth, the forming of red and white blood cells, and proper cell division.
  • Vitamin B12 (cobalamin) – plays a vital role in fat and protein metabolism, red blood cell development, DNA production, and in brain and neurological function.

Missing from this list are vitamins B4 (adenine), B8 (inositol), B10 (para-amino benzoic acid – PABA), and B11 (salicylic acid) as these nutrients were initially deemed to be vitamins, but later found to not really fit the definition of a vitamin.

B vitamins are numbered in the order in which they were discovered.  The most well-known of the vitamin B complex is vitamin B12.

The importance of vitamin B12:

Vitamin B12 is an essential vitamin that the body requires to function properly.  It is involved in a wide range of functions in the body:

  • It plays a role in the development and functioning of the brain, the nerves, and many other parts of the body,
  • Vitamin B12 plays an important role in the production of red blood cells.
  • It plays an important role in the production and regulation of DNA. 
  • As a water-soluble vitamin, B12 travels in the bloodstream throughout the body, and any unused or excess amounts are excreted in the urine.
  • Vitamin B12 plays a vital role in cell production and is important for maintaining healthy skin, hair, and nails, amongst others.
  • Vitamin B12 is needed for the normal metabolism of cells in the gastro-intestinal tract and bone marrow.
  • It assists with synthesizing and metabolizing the neurotransmitter serotonin in the brain.
  • Vitamin B12 supports bone health, as it is crucial for the development of healthy bones and a deficiency is linked to lower bone density.
  • Many older people experience the loss of neurons in the brain because of aging and sufficient levels of vitamin B12 can help to reduce the loss of neurons.
  • It plays a role in boosting energy levels, as fatigue can be one of the first signs of vitamin B12 deficiency.   As a matter of fact, all the B vitamins play a role in the production of energy.
  • As vitamin B12 is bound to the protein in the food that we eat, it must be released from the protein before it can be absorbed in the body.  Some vitamin B12 is released in the mouth when food is mixed with saliva, while more is released by the activity of hydrochloric acid and gastric protease in the stomach.  Gastric protease refers to the protease group of digestive enzymes that specifically targets and break down proteins into smaller building blocks (peptides and amino acid) to facilitate their absorption in the body.  The vitamin B12 freed by protease then combines with intrinsic factor – a transport and delivery protein, that is secreted by parietal cells located in the gastric glands of the stomach.  This complex is then absorbed in the distal ileum, which is the final section of the small intestine, whose main function is to absorb vitamin B 12 and bile salts.
  • As the vitamin B12 in supplements is not attached to protein, it does not need the action of the protease to free it, but still needs to be combined with intrinsic factor to be absorbed in the small intestine.
  • As vitamin B12 pays a part in the synthesis of fatty acids and energy production, the metabolism of every cell in the body depends on vitamin B12.

Implications of vitamin B12 deficiency:

The recommended daily amount of vitamin B12 for adults and children over the age of 14 is 2.4 micrograms (mcg) per day.  Overly high intake of vitamin B12 is not harmful and does not lead to toxic levels, as excess amounts of this water-soluble vitamin are excreted in the urine.  Most vitamin B12 deficiencies result from inadequate absorption and not poor intake.  Vitamin B12 deficiency have a wide range of effects on the body.

  • The hallmark symptoms of vitamin B12 deficiency are feeling tired or weak, while other symptoms may include loss of appetite, weight loss, pale skin, heart palpitations, or hands and feet becoming numb or tingly, which may indicate nerve problems
  • Anemia can occur when the red blood cell count drops and is a condition in which the body does not have enough healthy red blood cells.
  • The body produces millions of red blood cells every minute and these cells cannot multiply properly without vitamin B12.  Seeing that vitamin B12 is vital to produce red blood cells, which transports oxygen in the body, deficiency can cause reduced numbers of red blood cells, which means the body may not get enough oxygen.  Reduced numbers of red blood cells can result in a condition called megaloblastic anemia, in which the bone marrow produces larger than normal red blood cells and fewer in number.  These red blood cells are immature and structurally abnormal, all negatively affecting oxygen levels in the blood stream.  Fatigue and feeling tired and weak may indicate the presence of megaloblastic anemia.
  • Vitamin B12 deficiency results in low levels in the bloodstream, which may induce alterations or damage in DNA biosynthesis – when a cell divides to form two new daughter cells, a DNA related process called replication.  DNA replication refers to the process in which genetic information is duplicated to form two identical copies of the DNA during cell division.
  • Up to 40% of older adults can be affected by vitamin B12 deficiency as they do not have enough hydrochloric acid in their stomachs to help release this vitamin from the food that they eat.
  • Many older people suffer from loss of eyesight and deficiency in vitamin B12 can play a role in macular degeneration, while studies have shown that sufficient vitamin B12 intake is linked to a lower risk of macular degeneration.
  • Symptoms of fatigue and weakness may also be linked to pernicious anemia, a condition in which the blood is low in normal red blood cells through a lack of vitamin B12.  Pernicious anemia is the most common cause of clinically evident vitamin B12 deficiency and is thought to be an irreversible autoimmune disease that affects the stomach lining and may attack the parietal cells in the stomach, resulting in failure to produce intrinsic factor, or attack the actual intrinsic factor, all of which affects the body’s ability to absorb vitamin B12.
  • Vitamin B12 deficiency is not only linked to low counts of red blood cells, but also to low counts of white blood cells and platelets.
  • Neurological changes due to vitamin B12 deficiency may lead to symptoms such as tingling and numbness in the hands and feet.
  • A lack of vitamin B12 may result in damage to the myelin sheath that surrounds and protects nerves.  Without this protection, nerves may cease to function properly and even mild vitamin B12 deficiency may affect the nervous system and the proper functioning of the brain.  Signs and symptoms in this regard include pain and numbness as well as tingling in the hands and feet, sensory loss, lack of coordination, and generalized weakness of the legs.  Advanced neurological symptoms may include a creeping paralysis which starts with the extremities (hands and feet) and then creeps inwards and up along the spine.  Degeneration of certain areas of the spinal cord is associated with vitamin B12 deficiency.
  • As the body can store about 1 to 5 mg of vitamin B12, mainly in the liver, the symptoms of deficiency may take several years to appear.
  • People with disorders of the stomach or small intestines may be unable to absorb enough vitamin B12 from food, leading to vitamin B12 deficiency.
  • Vegans who consume no animal products and vegetarians who consume no meat have a higher risk of vitamin B12 deficiency, as natural food sources of vitamin B12 are found in animal foods.
  • Certain medication may potentially interfere with vitamin B12 absorption, such as gastric acid inhibitors or Metformin, which is used for the treatment of prediabetes and diabetes.
  • Conditions such as gastritis, inflammatory bowel disease, and celiac disease, or surgery that affects the area where intrinsic factor is made, can result in reduced absorption of nutrients and vitamin B12 deficiency.
  • The bodies of people with chronic alcoholism are unable to absorb nutrients efficiently, which may lead to vitamin B12 deficiency.
  • Some people, particularly those over 50, develop atrophic gastritis, which damages the cells of the stomach as the stomach mucus membrane (lining of the stomach) becomes inflamed, leading to a loss of important cells and diminishing production of hydrochloric acid and intrinsic factor.

Sources of vitamin B12:

Vitamin B12 does not typically appear in plant foods and is naturally found in animal foods, such as red meat (beef, pork, lamb), fish, shellfish, poultry, eggs, and dairy products, especially milk, cheese, and yoghurt.   Some of the sources containing the highest levels of vitamin B12 are liver, clams, salmon, and trout.

Vitamin B12 is also available in supplements and in certain fortified foods, such as fortified breakfast cereals.


Vitamin B12 plays a vital role in many processes in the body and deficiency in vitamin B12 is risky business, with dire consequences to one’s health.  The safest way to make sure that you are not at risk, is to measure vitamin B12 levels in the body.

According to scientists, measuring vitamin B12 levels in the blood is not the most accurate way to determine deficiency, as some people with deficiency can show normal vitamin B12 blood levels.  Measuring blood levels of a protein breakdown product called methylmalonic acid, and homocysteine levels, are deemed to be more accurate biomarkers for vitamin B12 activity.


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