Like the other B vitamins, Vitamin B12 is important for body metabolism. It aids in the formation of red blood cells and in maintaining the central nervous system. When your body is deficient in Vitamin B12, you may experience anemia, loss of balance, fatigue, weakness, lethargy, numbness or tingling in the arms and legs. Injections of the vitamin are sometimes to address anemia and by boosting energy. However, they will only give you an energy boost if you are already deficient in the vitamin.

Vitamin B12 is found in meat, poultry, shellfish, eggs, and dairy products. Most people get enough of the vitamin in their diet. If you are over 50, vegetarian or vegan, have had gastrointestinal surgery or digestive disorders, you may be more prone to a B12 deficiency.

Vitamin B12 Regulates Metabolism
Vitamin B12 is one of the eight members of the B complex vitamin family. B complex vitamins are water-soluble and B12 is the largest and most structurally complicated vitamin. It is normally involved in the metabolism within every cell of the human body, especially for DNA synthesis and regulation, but also fatty acid synthesis and energy production.

Since B12 is a water-soluble vitamin it dissolves in water. After the body has used what is needed, the excess amount leaves the body through the urine.

B12 is dependent upon the special gastric protein intrinsic factor to make its way from the gastrointestinal tract through the stomach and intestines and then into the rest of the body. The gastric intrinsic factor is a unique protein made in the stomach without which vitamin B12 cannot be absorbed.

Active Reagent in B12
In dietary supplements, vitamin B12 is usually present as cyanocobalamin. The body readily converts this form of B12 to methylcobalamin and 5-deoxyadenosylcobalamin which are the active forms. Dietary supplements can also contain methylcobalamin and other forms of vitamin B12.

In addition to oral dietary supplements, vitamin B12 is also available in sublingual forms as tablets or lozenges. These preparations are frequently marketed as having superior bioavailability, although the scientific evidence suggests that this is false marketing: there is no difference in efficacy between oral and sublingual forms.

How is B12 used in the Body?

  • Formation of red blood cells. Vitamin B12 is well known for its role in the development of red blood cells. As red blood cells mature, they require information provided by molecules of DNA. In the absence of B12, synthesis of DNA becomes defective, and so does the information needed for red blood cell formation. The blood cells become oversized and poorly shaped, and begin to function ineffectively, a condition called pernicious anemia.
  • Developing nerve cells. Vitamin B12 participates in the development of nerve cells. Myelin sheath is a coating which encloses the nerves, and it forms less successfully whenever B12 is deficient.
  • Protein cycling. Protein is required in the body for growth and repair of cells. Cycling of proteins through the body depends upon Vitamin B12. Low levels of B12 result in many of protein’s key components, especially amino acids, becoming unavailable for use within body.
  • Carbohydrate and fat processing: One of the steps in carbohydrate and fat processing requires B12 for its completion. Thus, insufficiency of the vitamin can affect the movement of carbohydrates and fats through the body.

When Might Vitamin B12 be Needed?

  • Vitamin B12 deficiency: Vitamin B12 deficiency can potentially cause severe and irreversible damage, especially to the brain and nervous system. Some of the symptoms include; fatigue, depression, and poor memory. Most people get sufficient vitamin B12 from their diet; however, there are several risk factors for a deficiency. These include:
  1. Age: Many people over age 50 lose the ability to absorb vitamin B12 from foods.
  2. Vegetarian or vegan: People who follow a strict vegetarian or vegan diet and do not consume eggs or dairy products may need vitamin B12 supplements.
  3. Gastrointestinal surgery: Those who have had gastrointestinal surgery, such as weight loss surgery, lose the ability to absorb vitamin B12.
  4. Digestive disorders: People who have digestive disorders, such as celiac disease or Crohn’s disease, may not absorb enough vitamin B12.
  • Pernicious anemia: Pernicious anemia is an autoimmune disease in which parietal cells of the stomach, which are responsible for secreting the protein intrinsic factor, are destroyed. Intrinsic factor is crucial for the normal absorption of Vitamin B12. In fact B12 was discovered because of its relationship to this disease. People with this disorder need to take B12 supplements to bolster levels of B12 in the body.
  • Cyanide poisoning: Vitamin B12 is used in the acute treatment of cyanide poisoning, administered intravenously and sometimes in combination with sodium thiosulfate. The mechanism of action is straightforward: the hydroxycobalamin hydroxide ligand is displaced by the toxic cyanide ion, and as a result, the harmless B12 complex is excreted through the urine.
  • Brain atrophy or shrinkage: Elderly people tend to suffer from brain atrophy or shrinkage. This is associated with Alzheimer’s disease and impaired cognitive function. High intake of vitamin B12 in elderly individuals may protect against this condition.

What Are the Side Effects?

In general, it is highly unlikely that you’ll experience any side effects from high doses of vitamin B12. Your body will just pee it out. However, in rare cases, people may experience the following side effects:

  • Dermatologic side effects: Some studies show that dermatologic side effects have occasionally included exacerbation or onset of inflammatory acne and folliculitis related to B12. When present, acne from eruptions usually occur on the facial area after the first or second injection, and typically disappear within 8 to 10 days after stopping therapy. It is suspected that sorbitol or iodine which is present in some ampoules of B12 may be the cause of at least some cases of skin eruptions associated with this drug.
  • Gastrointestinal side effects: In extreme cases, some people may experience gastrointestinal side effects associated with B12. These include dyspepsia, nausea, vomiting, and mild transient diarrhea.
  • Anaphylactic reactions: Anaphylactic reactions have been reported primarily with parenteral administration of B12. These reactions are thought to be the result of impurities during B12 preparations that are no longer manufactured. They may occur soon after a sensitizing dose, within a few weeks or months, or longer.
  • Nervous system side effects: Nervous system side effects associated with B12 have included abnormal gait, asthenia, anxiety, dizziness, hypoesthesia, nervousness, and coordination problems.

Vitamin B12 is often marketed as the vitamin that provides you energy. This is because a deficiency of this vitamin can cause tiredness, lethargy and numbness in the arms and legs. However, most people receive sufficient vitamin B12 in their diets. As noted, people prone to deficiencies include: persons over 50, vegetarians, vegans, and those with pernicious anemia, celiac disease, atrophic gastritis or Crohn’s disease. If applicable, you may consider supplementation and should talk to a healthcare professional regarding whether vitamin B12 can help.

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