Overview

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that is involved in many metabolic and neurological processes in the body. It is one of the eight B vitamins that are essential for human health. Vitamin B12 has a complex chemical structure that contains a metal ion, cobalt, and a corrin ring , it can found in different structures depending on the side groups attached to cobalt atom( the mostly used structure is cyanocobalamine ) as the photo below..

Symptoms

• Signs of deficiency may include: • Megaloblastic anemia—a condition of larger than normal sized red blood cells and a smaller than normal amount; this occurs because there is not enough vitamin B12 in the diet or poor absorption. • Pernicious anemia—a type of megaloblastic anemia caused by a lack of intrinsic factor so that vitamin B12 is not absorbed. • Fatigue, weakness • Nerve damage with numbness, tingling in the hands and legs. • Memory loss, confusion • Dementia • Depression • Seizures

Causes

• Factors that may cause vitamin B12 deficiency: • Avoiding animal products. People who do not eat meat, fish, poultry, or dairy are at risk of becoming deficient in vitamin B12, since it is only found naturally in animal products. Studies have shown that vegetarians have low vitamin B blood levels. For this reason, those who follow a vegetarian or vegan diet should include B12-fortified foods or a B12 supplement in their diets. This is particularly important for pregnant women, as the fetus requires adequate vitamin B12 for neurologic development and deficiency can lead to permanent neurological damage. • Lack of intrinsic factor. Pernicious anemia is an autoimmune disease that attacks and potentially destroys gut cells so that intrinsic factor is not present, which is crucial for vitamin B12 to be absorbed. If vitamin B12 deficiency ensues, other types of anemia and neurological damage may result. Even the use of a high-dose B12 supplement will not solve the problem, as intrinsic factor is not available to absorb it. • Inadequate stomach acid or medications that cause decreased stomach acid. A much more common cause of B12 deficiency, especially in older people, is a lack of stomach acid, because stomach acid is needed to liberate vitamin B12 from food. An estimated 10-30% of adults over the age of 50 have difficulty absorbing vitamin B12 from food. [1] People who regularly take medications that suppress stomach acid for conditions like gastroesophageal reflux disease (GERD) or peptic ulcer disease—such as proton-pump inhibitors, H2 blockers, or other antacids—may have difficulty absorbing vitamin B12 from food. These drugs can slow the release or decrease production of stomach acid. In theory this can prevent the vitamin from being released into its free usable form in the stomach; however, research has not shown an increased prevalence of a deficiency in people using these medications. Anyone using these medications for an extended time and who are at risk for a vitamin B12 deficiency for other reasons should be monitored closely by their physician. They may also choose to use fortified foods or supplements with vitamin B12, as these forms are typically absorbed well, and do not require stomach acid. • Intestinal surgeries or digestive disorders that cause malabsorption. Surgeries that affect the stomach where intrinsic factor is made, or the ileum (the last portion of the small intestine) where vitamin B12 is absorbed, can increase the risk of a deficiency. Certain diseases including Crohn’s and celiac disease that negatively impact the digestive tract also increase the risk of deficiency. • Medications that interfere with absorption. Long-term use of metformin, a drug commonly prescribed for type 2 diabetes, is strongly associated with vitamin B12 deficiency and lower folic acid levels as it can block absorption, which may lead to increased homocysteine levels and risk for cardiovascular disease. Proton pump inhibitors and histamine blockers prescribed to reduce stomach acid are also associated with lower vitamin B12 levels. • Lack of vitamin B12 in your diet: People who don't eat enough foods that naturally have vitamin B12 or don't eat foods fortified with vitamin B12 can develop vitamin B12 deficiency. • Gastritis: Gastritis is inflammation of the stomach lining, and it’s a common cause of vitamin B12 deficiency. It can cause vitamin B12 deficiency due to a lack of hydrochloric acid in your stomach, which is needed for vitamin B12 absorption. • Pernicious anemia: People who have pernicious anemia, a rare medical condition, are not able to make intrinsic factor, a protein made by your stomach. You need intrinsic factor so that your body can absorb B12 vitamin. People with pernicious anemia have a B12 vitamin deficiency

Risk factors

• What are the risk factors for vitamin B12 deficiency? A person is more likely to develop vitamin B12 deficiency if they have one or more of the following risk factors: • Being older than 75 years: Elderly people are more at risk for developing vitamin B12 deficiency because their bodies are often unable to fully absorb vitamin B12. • Having a digestive system disorder: Digestive disorders such as celiac disease and Crohn’s disease can make it more difficult for your body to absorb vitamin B12. • Following a strict vegan or vegetarian diet: Vitamin B12 is only naturally found in animal products such as meat and dairy. Because of this, people who eat a vegan or vegetarian diet are more likely to have a vitamin B12 deficiency if they aren't eating enough fortified foods with vitamin B12. • Taking certain medications: Certain medications can cause low levels of vitamin B12 in your body, including metformin (a drug used to manage diabetes), proton pump inhibitors (PPIs are used to treat GERD and peptic ulcers), histamine H2 blockers (a medicine used to reduce the amount of acid your stomach makes) and oral birth control pills (oral contraceptives). • Having Sjögren's syndrome. People with Sjögren's syndrome are over six times more likely to have vitamin B12 deficiency. • Drinking excessive amounts of alcohol: Chronic alcoholism can damage your digestive system and cause vitamin B12 deficiency.

Complications

• Can a vitamin B12 deficiency cause death? Untreated vitamin B12 deficiency can lead to severe neurological (nervous system) damage, which can put an individual at a higher risk of mortality. Pernicious anemia, a deficiency in the production of red blood cells due to a lack of vitamin B12, can cause permanent neurological damage that can lead to death if it is untreated.

Prevention

• How can I prevent vitamin B12 deficiency? Most people can prevent vitamin B12 deficiency by consuming foods and drinks that have vitamin B12. Options for consuming vitamin B12 include: • Animal food products: Red meat, fish, poultry, eggs, milk and other dairy products all contain vitamin B12. • Fortified foods: Fortified foods are foods that have certain vitamins and nutrients added to them that they don’t naturally have. Fortified foods include certain breakfast cereals, nutritional yeast, plant milk and certain bread. Be sure to check the food label (nutritional facts) to see if the food has been fortified with vitamin B12. • Vitamin B12 dietary supplements: Many multivitamins have vitamin B12. There are also supplements that only have vitamin B12. Ask your healthcare provider or pharmacist to help you choose which supplement is best for you. Other things you can do to help prevent vitamin B12 deficiency include: • Avoid alcohol: Frequent alcohol consumption can damage your digestive system and make it difficult for your body to absorb vitamin B12. • Do your best to manage your digestive disease: If you have a digestive disease such as Crohn’s disease or celiac disease, be sure to follow your healthcare provider’s instructions to stay healthy.

Extra Information

How is vitamin B12 deficiency treated?
Vitamin B12 deficiency can be treated with vitamin B12. It is often treated with cyanocobalamin, a man-made form of vitamin B12. Depending on the cause of the deficiency, the person may only have to be treated until their vitamin B12 levels are back to normal, or they may have to take vitamin B12 therapy for the rest of their life. Options for vitamin B12 treatment include:
• Vitamin B12 oral medication.
• Vitamin B12 intramuscular injections (a shot that goes into the muscle).
• Vitamin B12 nasal gel.
• Vitamin B12 nasal spray.