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What makes vitamin B12 deficiency so dangerous

- and why is the problem so common?

 What makes vitamin B12 deficiency so dangerousLack of vitamin B12 can cause pernicious anemia, which WHO considers a global threat. Vitamin B12 is primarily known for its role in red blood cell formation, whereas its role in the brain and nervous system is often overlooked. A vitamin B12 deficiency can easily lead to disabling damage if it goes unnoticed. Pernicious anemia is an autoimmune disease that prevents people from absorbing vitamin B12 from food. The condition is potentially life-threatening but is difficult to diagnose and many people go untreated, according to Associate Professor Heidi Seage, who is affiliated with the Pernicious Anaemia Society. A worsening factor is the climate debate that has inspired an increasing number of people to turn to vegetarianism and veganism. Plant-based diets are known to cause vitamin B12 deficiency, and the problem is insidious and therefore not easy to detect. The use of diabetes medication (such as metformin) can also deplete the body’s levels of vitamin B12

Vitamin B12 is important for red blood cell formation, energy levels, the nervous system, the brain, the immune system, and cell division. Vitamin B12 is only found in animal food sources like meat, fish, eggs, and dairy products (there are very few plant sources). The vitamin is absorbed in our small intestine with help from a carrier called intrinsic factor. Although bacteria in our colon are able to synthesize small quantities of vitamin B12, we are unable to absorb the nutrient from the intestine. Vitamin B12 is stored in the liver. Months or even years may go by before any deficiency symptoms occur as a result of eating an entirely plant-based diet or due to other causes.
Pernicious anemia is when you are unable to absorb vitamin B12 from the diet. It is an autoimmune disease where the immune system produces antibodies that attack the gastric mucosa that produces intrinsic factor. If you lack intrinsic factor, it is virtually impossible for your body to absorb vitamin B12. Pernicious anemia may also be caused by chronic gastritis or occur in the wake of ulcer surgery that involves surgical removal of a large portion of the stomach, including the gastric mucosa that makes intrinsic factor.

Vitamin B12 deficiencies are common

  • 12 million people worldwide are believed to lack vitamin B12
  • An estimated 6 percent of people in the US and Great Britain are vitamin B12-deficient
  • One in eight adults older than 50 years of age lacks vitamin B12, according to an Irish study
  • 11 percent of vegetarians and vegans have subclinical or clinical vitamin B12 deficiency, according to a Spanish study
  • Around 20 percent of those taking metformin against type 2 diabetes are vitamin B12-deficient or have a borderline deficiency

Symptoms of vitamin B12 deficiency

There may be few or several symptoms that are caused by anemia or imbalances in the nervous system. The symptoms are typically insidious and with varying intensity.

  • Tiredness, memory problems, and mental fatigue
  • Shortness of breath, vertigo, headache, impaired immunity
  • Muscle weakness
  • Tingling sensation in fingers and toes (pins and needles)
  • Red and irritated tongue
  • Loss of taste
  • Digestive problems
  • Irreversible nerve damage
  • Anxiety and depression
  • Pregnancy problems
  • Children of vitamin B12-deficient mothers risk stunted growth, anemia, and mental retardation in worst case

Symptoms are often misdiagnosed

Wrong diet is often the root cause of a vitamin B12 deficiency. Globally, it is the most common cause of pernicious anemia. Pernicious anemia and lack of vitamin B12 can produce a variety of symptoms, and there is an underlying risk that they are misdiagnosed and interpreted as signs of stress, depression, dementia, or other conditions. It is therefore vital for the physician to look into the patient’s diet. Any suspicion of vitamin B12 deficiency should prompt a blood test.
The problem is that early signs of being vitamin B12-deficient, including pernicious anemia, make the diagnosis difficult. According to Associate Professor Heidi Seage, interviews of members of the Pernicious Anaemia Society showed that almost half of them were misdiagnosed, and around 20 percent had to wait two years or longer for a proper diagnosis.

Disabling symptoms

Being misdiagnosed or getting diagnosed too late may have serious consequences. If a vitamin B12 deficiency or pernicious anemia is not treated fast enough, it may result in disabling symptoms and any type of nerve damage may be irreversible.
Damage to the nerve system happens because vitamin B12 plays a key role in the production of myelin, which protects the nerve cells by forming a protective sheath around them. You can compare this sheath to the plastic coating on electric wiring. The most common disabling, neurological symptoms are fatigue, memory loss, and difficulty with concentrating.
“Pernicious” originates from Latin (it means death), and anemia means lack of blood. Through history, pernicious anemia has been known as a lethal condition.

Vitamin B12 therapy and the quality of supplements

If you have lost a large portion of your body’s vitamin B12 stores it is advisable to start with injections for fast relief of symptoms. If the vitamin B12 deficiency is linked to your diet you may need to change your diet and possibly take a vitamin B12 supplement. Lozenges are often much easier for the body to absorb, as vitamin B12 is absorbed directly by the oral mucosa.
Vitamin B12 supplements should contain at least 2.5 micrograms of vitamin B12, which corresponds with the daily reference intake (RI) level.
Pernicious anemia is a chronic condition that requires continuous vitamin B12 injections due to the lack of intrinsic factor, which the body needs in order to absorb the nutrient in the small intestine.

There is need for better guidelines and treatment

According to Associate Professor Heidi Seage, many patients in Great Britain get frequent vitamin B12 injections (every 8 or 12 weeks) yet find that their symptoms return because the treatment fails to work properly. When patients ask health professionals for more frequent injections, they are often met with a negative attitude. In some cases, the validity of their condition is questioned.
Heidi Seage believes that this stigmatization may affect the patients’ relation to their health professionals and possibly even result in increasing problems with anxiety and depression. It is therefore vital to pay attention to the symptoms that accompany a vitamin B12 deficiency so the problem can be addressed in time to prevent permanent damage.

  • Lack of folic acid may also cause anemia and many of the same symptoms as seen with a vitamin B12 deficiency
  • Folic acid supplementation is necessary during pregnancy
  • Folic acid supplements can prevent blood clots in patients on antihypertensive medication


Heidi Seage. Vitamin B12-mangel: Hvad er perniciøs anæmi, og hvorfor er det så farligt?: 2019

Ebba Nexø. Vegetarer risikerer at få for lidt B12-vitamin. marts 2018

Angélica Gallego-Narbon et al. Vitamin B12 and folate status in Spanish lacto-ovo vegetarians and vegans. J Nutr Sci. 2019

Trinity College Dublin. Many older adults are deficient in vitamin B12 and folate. ScienceDaily June 26, 2018

Vanita R Aroda et al. Long-Term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study. Endocrine Society 2016

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